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Availability of data and materials: Not applicable. Copyright © The Author(s) 2022. Complement component 1q (C1q) is the recognition molecule of the classical pathway of the complement system that can bind to an array of closely spaced antigen-bound immunoglobulin G (IgG) and IgM antibodies. In addition to its involvement in defence against a range of pathogens and clearance of apoptotic and necrotic cells, C1q has also been implicated in immune and non-immune homeostasis. C1q is locally produced by immune cells such as monocytes, macrophages, and dendritic cells. C1q is also synthesized by decidual endothelial cells, thus acting as a link between decidual cells and trophoblasts, as well as contributing to the remodelling of spiral arteries. Furthermore, C1q is produced by the extravillous trophoblasts (EVTs) invading the decidua. As a pro-angiogenic molecule, C1q is also important for normal placentation processes as it favors the active angiogenesis in the developing decidua. These observations have been validated by C1q gene knock-out mice which showed pre-eclampsia (PE)-like symptoms, characterized by hypertension, proteinuria, glomerular endotheliosis, and increased soluble fms-like tyrosine kinase-1 (sFlt-1)/placental growth factor (PlGF) ratio, and increased oxidative stress. The role of C1q in normal and adverse human pregnancy is being studied extensively due to its absence or low level as a likely precipitating factor for the development of PE. Funding: Not applicable.

The omics era made possible the quest for efficient markers for cancer progression and revealed that macrophage populations are much more complex than just the M1/M2 dichotomy. Complement C1q pops up as a marker of a tolerogenic and immunosuppressive macrophage populations in both healthy and tumor tissues, but the specific role of C1q+ tumor-associated macrophages (TAM) is poorly understood. C1q is co-expressed in healthy and tumor macrophages with human leukocyte antigen DR (HLA-DR), Apolipoprotein E (APOE), and mannose receptor C-type 1 (MRC1) (CD206), suggesting a resident origin of this population. TAM expressing C1q correlate with T cell exhaustion and poor prognosis in numerous cancers. Herein, we discuss the plural roles of C1q in these macrophages and how it could drive cancer progression.

Glioblastoma (GBM) is the most aggressive and lethal form of brain tumor. Extracellular vesicles (EVs) released by tumor cells play a critical role in cellular communication in the tumor microenvironment promoting tumor progression and invasion. We hypothesized that GBM EVs possess unique characteristics which exert effects on endogenous CNS cells including neurons, producing dose-dependent neuronal cytotoxicity. We purified EVs from the plasma of 20 GBM patients, 20 meningioma patients, and 21 healthy controls, and characterized EV phenotypes by electron microscopy, nanoparticle tracking analysis, protein concentration, and proteomics. We evaluated GBM EV functions by determining their cytotoxicity in primary neurons and the neuroblastoma cell line SH-SY5Y. In addition, we determined levels of IgG antibodies in the plasma in GBM (n = 82), MMA (n = 83), and controls (non-tumor CNS disorders and healthy donors, n = 50) with capture ELISA. We discovered that GBM plasma EVs are smaller in size and had no relationship between size and concentration. Importantly, GBM EVs purified from both plasma and tumor cell lines produced IgG-mediated, complement-dependent apoptosis and necrosis in primary human neurons, mouse brain slices, and neuroblastoma cells. The unique phenotype of GBM EVs may contribute to its neuronal cytotoxicity, providing insight into its role in tumor pathogenesis.

The contribution of the complement system to non-specific host defence and maintenance of homeostasis is well appreciated. Many particulate systems trigger complement activation but the underlying mechanisms are still poorly understood. Activation of the complement cascade could lead to particle opsonisation by the cleavage products of the third complement protein and might promote inflammatory reactions. Antibody binding in a controlled manner and/or sensing of particles by the complement pattern-recognition molecules such as C1q and mannose-binding lectin can trigger complement activation. Particle curvature and spacing arrangement/periodicity of surface functional groups/ligands are two important parameters that modulate complement responses through multivalent engagement with and conformational regulation of surface-bound antibodies and complement pattern-recognition molecules. Thus, a better fundamental understanding of nanometer- and angstrom-scale parameters that modulate particle interaction with antibodies and complement proteins could portend new possibilities for engineering of particulate drug carriers and biomedical platforms with tuneable complement responses and is discussed here.

Recent studies have identified roles for complement in synaptic pruning, both physiological during development and pathological in Alzheimer’s disease (AD). These reports suggest that C1q initiates complement activation on synapses and C3 fragments then tag them for removal by microglia. There is an urgent need to characterise these processes in rodent AD models; this requires the development of reagents and methods for detection and quantification of rodent C1q in fluids and pathological tissues. These will enable better evaluation of the role of C1q in disease and its value as disease biomarker. We describe the generation in C1q-deficient mice of novel monoclonal antibodies against mouse and rat C1q that enabled development of a sensitive, specific, and quantitative ELISA for mouse and rat C1q capable of measuring C1q in biological fluids and tissue extracts. Serum C1q levels were measured in wild-type (WT), C1q knockout (KO), C3 KO, C7 KO, Crry KO, and 3xTg and APPNL-G-F AD model mice through ageing. C1q levels significantly decreased in WT, APPNL-G-F, and C7 KO mice with ageing. C1q levels were reduced in APPNL-G-F compared to WT at all ages and in 3xTg at 12 months; C3 KO and C7 KO, but not Crry KO mice, also demonstrated significantly lower C1q levels compared to matched WT. In brain homogenates, C1q levels increased with age in both WT and APPNL-G-F mice. This robust and adaptable assay for quantification of mouse and rat C1q provides a vital tool for investigating the expression of C1q in rodent models of AD and other complement-driven pathologies.

To combat infectious diseases, vaccines are considered the best prophylactic strategy for a wide range of the population, but even when vaccines are effective, the administration of therapeutic antibodies against viruses could provide further treatment options, particularly for vulnerable groups whose immunity against the viruses is compromised. Therapeutic antibodies against dengue are ideally engineered to abrogate binding to Fcγ receptors (FcγRs), which can induce antibody-dependent enhancement (ADE). However, the Fc effector functions of neutralizing antibodies against SARS-CoV-2 have recently been reported to improve post-exposure therapy, while they are dispensable when administered as prophylaxis. Hence, in this report, we investigated the influence of Fc engineering on anti-virus efficacy using the anti-dengue/Zika human antibody SIgN-3C and found it affected the viremia clearance efficacy against dengue in a mouse model. Furthermore, we demonstrated that complement activation through antibody binding to C1q could play a role in anti-dengue efficacy. We also generated a novel Fc variant, which displayed the ability for complement activation but showed very low FcγR binding and an undetectable level of the risk of ADE in a cell-based assay. This Fc engineering approach could make effective and safe anti-virus antibodies against dengue, Zika and other viruses.

Hanji Huang,1,2,* Manli Tan,1,* Li Zheng,1,3 Guohua Yan,1,2,4 Kanglu Li,1,2,4 Dejie Lu,1,2,4 Xiaofei Cui,1,2,4 Si He,1,2 Danqing Lei,5,6 Bo Zhu,1 Jinmin Zhao1– 4,7 1Guangxi Engineering Center in Biomedical Materials for Tissue and Organ Regeneration, The First Affiliated Hospital of Guangxi Medical University, Nanning, 530021, People’s Republic of China; 2Guangxi Collaborative Innovation Center for Biomedicine, Life Sciences Institute, Guangxi Medical University, Nanning, 530021, People’s Republic of China; 3International Joint Laboratory of Ministry of Education for Regeneration of Bone and Soft Tissues, The First Affiliated Hospital of Guangxi Medical University, Nanning, 530021, People’s Republic of China; 4Department of Orthopaedics Trauma and Hand Surgery, The First Affiliated Hospital of Guangxi Medical University, Nanning, 530021, People’s Republic of China; 5Pharmaceutical College, Guangxi Medical University, Nanning, 530021, People’s Republic of China; 6The Medical and Scientific Research Center, Life Sciences Institute, Guangxi Medical University, Nanning, 530021, People’s Republic of China; 7Guangxi Key Laboratory of Regenerative Medicine, The First Affiliated Hospital of Guangxi Medical University, Nanning, 530021, People’s Republic of China*These authors contributed equally to this workCorrespondence: Danqing LeiThe Medical and Scientific Research Center, Life Sciences Institute, Guangxi Medical University, Nanning, 530021, People’s Republic of ChinaTel +86-07715358549Email ldq0422@126.comBo ZhuGuangxi Engineering Center in Biomedical Materials for Tissue and Organ Regeneration, The First Affiliated Hospital of Guangxi Medical University, Nanning, 530021, People’s Republic of ChinaTel +86-07715540515Email gxzyxyzhubo@163.comBackground: Osteosarcoma (OS) is the most widespread bone tumour among childhood cancers, and distant metastasis is the dominant factor in poor prognosis for patients with OS. Therefore, it is necessary to identify new prognostic biomarkers for identifying patients with aggressive disease.Methods: Two OS datasets (GSE21257 and GSE33383) were downloaded from the Gene Expression Omnibus (GEO) and subsequently subjected to weighted gene co-expression network analysis (WGCNA) and differential gene expression analysis (DGE) to screen candidate genes. A prognostic model was constructed using OS data derived from the Therapeutically Applicable Research to Generate Effective Treatments (TARGET) program to further screen key genes and perform gene ontology (GO) analysis. The prognostic values of key genes were assessed using the Kaplan–Meier (KM) plotter. The GEO dataset was used for immune infiltration analysis and association analysis of key genes. In addition, quantitative real-time polymerase chain reaction (qRT-PCR) was employed to validate the expression levels of potentially crucial genes in OS cell lines.Results: In the present study, we found 114 genes with a highly significant correlation in the module and 44 downregulated genes; 25 candidate genes overlapped in the two parts of the genes. Among these, three key genes, C1QA, C1QB, and C1QC, were the most significant hub genes, which had the highest node degrees, were clustered into one group, and implicated in most significant biological processes (regulation of immune effector process). Moreover, these three key genes were negatively associated with the prognosis of OS and positively associated with three immune cells (follicular helper T cells, memory B cells, and CD8 T cells). Additionally, compared to non-metastatic OS cell lines, the expression of three key genes was significantly downregulated in metastatic OS cell lines.Conclusion: Our results revealed that three key genes (C1QA, C1QB, and C1QC) were implicated in tumour immune infiltration and may be promising biomarkers for predicting metastasis and prognosis of patients with OS.Keywords: osteosarcoma, immune infiltrates, complement protein, C1Q, metastasis

Psoriasis vulgaris (PsV) is an immune-mediated inflammatory disorder with devastating psychosocial consequences. Expression of immunoregulator molecules on leukocytes in PsV remains unclear. Leukocyte-associated Ig-like receptor-1 (LAIR-1) and complement receptor-1 (CR-1) are immunoregulator receptors reported to bind complement component 1q involved in phagocytosis. We aimed to explore if altered leukocyte expression of LAIR-1 and CR-1 is associated with PsV. This case–control study included 36 PsV patients and 36 healthy controls. Neutrophils, monocytes and B and T cells were examined by flow cytometry for LAIR-1 and CR-1 mean fluorescence intensity (MFI) and positive cell percentage. Comparison between both groups revealed a significant decrease in LAIR-1 MFI on neutrophils and T cells ( P

RNA sequencing and DNA methylomic profiling were performed after differentiating monocytes for 6 days into moDCs with/without CXCL4 presence. We show that CXCL4 downregulates genes associated with tolerogenicity in DCs including C1Q. Expression profiles of C1Q genes were negatively correlated with their DNA methylation profiles and with immunogenic genes.

C1q is an important recognition protein in the complement system, which is a major protein cascade in the innate immune system. Upon recognition of a target by C1q, the target is marked for opsonization and destruction. C1q recognizes many pathogenic patterns directly, but an important target is the Fc domain of antibodies binding to their antigen. In this paper, the curvature-dependence of the interaction between IgG and C1q is studied by surface plasmon resonance and quartz crystal microbalance. IgG is organized in similar surface coverage densities on flat polystyrene surfaces and polystyrene nanoparticles of different sizes, and the amount of C1q binding to the IgG is investigated. Nanoparticles in solution were found to aggregate upon incubation with IgG, and therefore a new technique utilizing nanoparticles binding to antifouling polymer brush functionalized surfaces was used to prepare surfaces with nanoparticles for measurements with surface plasmon resonance. Interestingly antigen-bound IgG at the curved surface of nanoparticles showed 5.6 times lower binding of C1q compared to at matched flat surfaces. There was no significant difference between the binding at 100 and 200 nm polystyrene particles. These findings are important for designing drug delivery systems to evade the complement system.

OBJECTIVE: Inflammation and innate immune responses may contribute to development and progression of Osteoarthritis (OA). Chondrocytes are the sole cell type of the articular cartilage and produce extracellular-matrix molecules. How inflammatory mediators reach chondrocytes is incompletely understood. Previous studies have shown that chondrocytes express mRNA encoding complement proteins such as C1q, suggesting local protein production, which has not been demonstrated conclusively. The aim of this study is to explore C1q production at the protein level by chondrocytes. DESIGN: We analysed protein expression of C1q in freshly isolated and cultured human articular chondrocytes using Western blot, ELISA and flow cytometry. We examined changes in mRNA expression of collagen, MMP-1 and various complement genes upon stimulation with pro-inflammatory cytokines or C1q. mRNA expression of C1 genes was determined in articular mouse chondrocytes. RESULTS: Primary human articular chondrocytes express genes encoding C1q, C1QA, C1QB, C1QC, and secrete C1q to the extracellular medium. Stimulation of chondrocytes with pro-inflammatory cytokines upregulated C1QA, C1QB, C1QC mRNA expression, although this was not confirmed at the protein level. Extracellular C1q bound to the chondrocyte surface dose dependently. In a pilot study, binding of C1q to chondrocytes resulted in changes in the expression of collagens with a decrease in collagen type 2 and an increase in type 10. Mouse articular chondrocytes also expressed C1QA, C1QB, C1QC, C1R and C1S at the mRNA level. CONCLUSIONS: C1q protein can be expressed and secreted by human articular chondrocytes and is able to bind to chondrocytes influencing the relative collagen expression. ispartof: OSTEOARTHRITIS AND CARTILAGE vol:28 issue:5 pages:675-684 ispartof: location:England status: published

Significance Staphylococcus aureus invariably acquires resistance mechanisms against new antibiotics. The persistent colonization with S. aureus is the key risk factor for invasive disease and a driver for the evolution of antibiotic resistant isolates. Anti-S. aureus antibodies that could promote decolonization, prevent infection, or treat disease would alleviate the selection for drug resistance. The successful development of such antibodies is complicated by Staphylococcal protein A (SpA) in the envelope of S. aureus. SpA captures immunoglobulins via their constant region, preventing antibodies from initiating anti-staphylococcal activities. Here, we demonstrate that therapeutic anti-S. aureus antibodies can be engineered to avoid sequestration by SpA. Such antibodies display extended half-lives and improve bacterial uptake and killing by immune cells., Gram-positive organisms with their thick envelope cannot be lysed by complement alone. Nonetheless, antibody-binding on the surface can recruit complement and mark these invaders for uptake and killing by phagocytes, a process known as opsonophagocytosis. The crystallizable fragment of immunoglobulins (Fcγ) is key for complement recruitment. The cell surface of S. aureus is coated with Staphylococcal protein A (SpA). SpA captures the Fcγ domain of IgG and interferes with opsonization by anti-S. aureus antibodies. In principle, the Fcγ domain of therapeutic antibodies could be engineered to avoid the inhibitory activity of SpA. However, the SpA-binding site on Fcγ overlaps with that of the neonatal Fc receptor (FcRn), an interaction that is critical for prolonging the half-life of serum IgG. This evolutionary adaptation poses a challenge for the exploration of Fcγ mutants that can both weaken SpA–IgG interactions and retain stability. Here, we use both wild-type and transgenic human FcRn mice to identify antibodies with enhanced half-life and increased opsonophagocytic killing in models of S. aureus infection and demonstrate that antibody-based immunotherapy can be improved by modifying Fcγ. Our experiments also show that by competing for FcRn-binding, staphylococci effectively reduce the half-life of antibodies during infection. These observations may have profound impact in treating cancer, autoimmune, and asthma patients colonized or infected with S. aureus and undergoing monoclonal antibody treatment.

Tick-borne encephalitis (TBE) is one of the most prevalent viral central nervous system (CNS) infections in Eurasia and neurological sequelae are common. The immune responses are considered crucial for the pathogenesis. The aim of this study was to explore the activation of the complement system in TBE. The complement system is a part of the innate immune response in the CNS, which previously has been reported to be activated in other flavivirus infections. We analyzed complement factors in 44 paired cerebrospinal fluid (CSF) and serum samples from 20 cases of TBE in the acute and later stages, as well as in serum and CSF from 32 healthy controls. The concentrations of complement factors C1q, C3a, C3b, and C5a were determined with commercially available ELISA kits. Clinical data to categorize the severity of disease and outcome was retrieved from the medical records of the TBE patients. We found significantly higher concentrations of all of the analyzed complement factors in the CSF from TBE patients compared to the healthy controls. In particular, the marked increment of C1q concentrations in the CSF (p

Background C1q has been reported to reveal complement-independent roles in immune and non-immune cells. C1q binds to its specific receptors to regulate distinct functions that rely on the environment and cell types. Discoidin domain receptor 2 (DDR2) is activated by collagen and functions in wound healing by controlling matrix metalloproteinase (MMP) expression. Since C1q exhibits a collagen-like structure, we hypothesized that C1q might engage DDR2 to regulate wound healing and extracellular matrix (ECM) remodeling. Methods Cell-based assay, proximity ligation assay, ELISA, and surface plasmon analysis were utilized to investigate DDR2 and C1q binding. We also investigate the C1q-mediated in vitro wound healing ability using the human fibrosarcoma cell line, HT1080. Results C1q induced the phosphorylation of DDR2, p38 kinase, and ERK1/2. C1q and DDR2 binding improved cell migration and induced MMP2 and MMP9 expression. DDR2-specific shRNA reduced C1q-mediated cell migration for wound healing. Conclusions C1q is a new DDR2 ligand that promotes wound healing. These findings have therapeutic implications in wound healing-related diseases.

Background Pancreatic ductal adenocarcinoma (PDAC) is one of the most lethal cancers due to its high metastasis rate in the liver. However, little is known about the molecular features of hepatic metastases due to difficulty in obtaining fresh tissues and low tumor cellularity. Results We conduct exome sequencing and RNA sequencing for synchronous surgically resected primary tumors and the paired hepatic metastases from 17 hepatic oligometastatic pancreatic ductal adenocarcinoma and validate our findings in specimens from 35 of such cases. The comprehensive analysis of somatic mutations, copy number alterations, and gene expressions show high similarity between primary tumors and hepatic metastases. However, hepatic metastases also show unique characteristics, such as a higher degree of 3p21.1 loss, stronger abilities of proliferation, downregulation of epithelial to mesenchymal transition activity, and metabolic rewiring. More interesting, altered tumor microenvironments are observed in hepatic metastases, especially a higher proportion of tumor infiltrating M2 macrophage and upregulation of complement cascade. Further experiments demonstrate that expression of C1q increases in primary tumors and hepatic metastases, C1q is mainly produced by M2 macrophage, and C1q promotes migration and invasion of PDAC cells. Conclusion Taken together, we find potential factors that contribute to different stages of PDAC metastasis. Our study broadens the understanding of molecular mechanisms driving PDAC metastasis.

The complement system, an essential part of the innate immune system, is composed of a group of secreted and membrane proteins that collectively participate in maintaining the function of the healthy and diseased brain. However, an inappropriate activation of the complement system has been related to an inflammatory response in multiple diseases, such as stroke, traumatic brain injury, multiple sclerosis, and Alzheimer’s disease, as well as Zika infection and radiotherapy. In addition, C1q and C3 (initial activation components of the complement cascade) have been shown to play a key beneficial role in the refinement of synaptic circuits during developmental stages and adult plasticity. Nevertheless, excessive synaptic pruning in the adult brain can be detrimental and has been associated with synaptic loss in several pathological conditions. In this brief review, we will discuss the role of the complement system in synaptic pruning as well as its contribution to neurodegeneration and cognitive deficits. We also mention potential therapeutic approaches to target the complement system to treat several neuroinflammatory diseases and unintended consequences of radiotherapy.

The complement system, an essential part of the innate immune system, is composed of a group of secreted and membrane proteins that collectively participate in maintaining the function of the healthy and diseased brain. However, an inappropriate activation of the complement system has been related to an inflammatory response in multiple diseases, such as stroke, traumatic brain injury, multiple sclerosis, and Alzheimer's disease, as well as Zika infection and radiotherapy. In addition, C1q and C3 (initial activation components of the complement cascade) have been shown to play a key beneficial role in the refinement of synaptic circuits during developmental stages and adult plasticity. Nevertheless, excessive synaptic pruning in the adult brain can be detrimental and has been associated with synaptic loss in several pathological conditions. In this brief review, we will discuss the role of the complement system in synaptic pruning as well as its contribution to neurodegeneration and cognitive deficits. We also mention potential therapeutic approaches to target the complement system to treat several neuroinflammatory diseases and unintended consequences of radiotherapy.

Background and Objectives: Asymptomatic bacteriuria (ASB) appears to have a higher prevalence in diabetics and has been associated with various genetic polymorphisms of the innate immune system. Single nucleotide polymorphisms (SNPs) of the C1q gene that encodes for the trigger molecule of the classical complement pathway increase the risk of bacterial infections as well as other diseases. In the present study, we sought to investigate the association of C1q rs292001 (G > A) SNP with ASB in patients with type 2 diabetes (T2D). Materials and Methods: In this case-control study, performed at the University and the Venizeleion General Hospital of Heraklion, Crete, Greece, 75 adult male and female Cretan patients with T2D and ASB and 75 adult male and female Cretan patients with T2D but without ASB were enrolled and genotyped for rs292001 SNP of C1q gene. Genetic analysis was based on the polymerase chain reaction (PCR) and restriction fragment length polymorphisms (RLFPs) methods. Results: Τhe frequency of homozygotes for the G/G genotype of C1q rs292001 was significantly higher in patients with T2D and ASB than in the control group (p-value = 0.0480, OR = 2.952, 95% CI: 1.052–7.542). Conclusions: Τhe present study provides the first evidence of an association between the C1q rs292001 SNP and an increased susceptibility for ASB in an adult Cretan population with T2D, thus suggesting that this SNP can be encountered as a risk factor for the presence of ASB in patients with T2D.

The aim of this work was to design and test a vaccine regimen focusing the immune response on targets associated with infection prevention. We demonstrated that priming with a DNA vaccine expressing only the HIV Env V1V2 region induces Ab responses targeting the critical region in V2 associated with protection. This work shows that V1V2 scaffold DNA priming immunization provides a method to focus immune responses to the desired target region, in the absence of immune interference by other epitopes. This induced immune responses with improved recognition of epitopes important for protective immunity, namely, V2-specific humoral immune responses inversely correlating with HIV risk of infection in the RV144 trial., The RV144 vaccine trial revealed a correlation between reduced risk of HIV infection and the level of nonneutralizing-antibody (Ab) responses targeting specific epitopes in the second variable domain (V2) of the HIV gp120 envelope (Env) protein, suggesting this region as a target for vaccine development. To favor induction of V2-specific Abs, we developed a vaccine regimen that included priming with DNA expressing an HIV V1V2 trimeric scaffold immunogen followed by booster immunizations with a combination of DNA and protein in rhesus macaques. Priming vaccination with DNA expressing the HIV recombinant subtype CRF01_AE V1V2 scaffold induced higher and broader V2-specific Ab responses than vaccination with DNA expressing CRF01_AE gp145 Env. Abs recognizing the V2 peptide that was reported as a critical target in RV144 developed only after the priming immunization with V1V2 DNA. The V2-specific Abs showed several nonneutralizing Fc-mediated functions, including ADCP and C1q binding. Importantly, robust V2-specific Abs were maintained upon boosting with gp145 DNA and gp120 protein coimmunization. In conclusion, priming with DNA expressing the trimeric V1V2 scaffold alters the hierarchy of humoral immune responses to V2 region epitopes, providing a method for more efficient induction and maintenance of V2-specific Env Abs associated with reduced risk of HIV infection. IMPORTANCE The aim of this work was to design and test a vaccine regimen focusing the immune response on targets associated with infection prevention. We demonstrated that priming with a DNA vaccine expressing only the HIV Env V1V2 region induces Ab responses targeting the critical region in V2 associated with protection. This work shows that V1V2 scaffold DNA priming immunization provides a method to focus immune responses to the desired target region, in the absence of immune interference by other epitopes. This induced immune responses with improved recognition of epitopes important for protective immunity, namely, V2-specific humoral immune responses inversely correlating with HIV risk of infection in the RV144 trial.

The first months of life represent a crucial time period for an infant. Alongside establishing the early microbiome, the mucosal immunological homeostasis is being developed. Both processes may be perturbed in prematurely born infants. The glycoprotein SALSA plays a role in mucosal inflammation and microbial clearance. It is one of the most abundant molecules on the intestinal mucosal surfaces in early life. SALSA binds to many types of microbes and host defence molecules like IgA, C1q and collectin molecules. We here describe the development in faecal SALSA levels during the first three months of life. During these 90 days, the median SALSA level in full-term babies decreased from 1100 mu g/mL (range 49-17 000 mu g/mL) to 450 mu g/mL (range 33-1000 mu g/mL). Lower levels of SALSA were observed in prematurely born infants in the same time period. Our novel observation thus indicates an impact of prematurity on an important component of the infant intestinal immune system. Changes in SALSA in early life may have an effect on the early establishment of the human microbiome.

During development, neurons generate excess processes which are then eliminated in concert with circuit maturation. C1q is the initiating protein in the complement cascade and has been implicated in this process, but whether C1q-mediated elimination is targeted to particular neural compartments is unclear. Using the murine retina, we identify C1q as a specific regulator of horizontal cell neurite confinement. Subsets of horizontal cell dendritic and axonal neurites extend into the outer retina suggesting that complement achieves both cellular and subcellular selectivity. These alterations emerge as outer retina synapses become mature. C1q expression is restricted to retina microglia, and the loss of C1q results in decreased microglia activation. This pathway appears independent of the C3a receptor (C3aR) and complement receptor 3 (CR3), as horizontal cells are normal when either protein is absent. Together, these data identify a new role for C1q in cell and neurite-specific confinement and implicate microglia-mediated phagocytosis in this process.

Significance All currently licensed antibodies against bacteria target exotoxins. For most pathogens, neutralization of toxin(s) is not sufficient to prevent bacterial replication. Antibodies against surface determinants represent better candidates to enhance opsonophagocytic killing, but the mechanisms of action of such antibodies have not been systematically studied. Staphylococcal protein A is a conserved surface protein of Staphylococcus aureus and a crucial virulence determinant that manipulates B-cell responses and blocks deposition of opsonin. Monoclonal antibodies directed against SpA represent potential therapeutic agents as well as a formidable tool to identify and optimize effector functions of antibodies that can promote bacterial clearance., Antibodies may bind to bacterial pathogens or their toxins to control infections, and their effector activity is mediated through the recruitment of complement component C1q or the engagement with Fcγ receptors (FcγRs). For bacterial pathogens that rely on a single toxin to cause disease, immunity correlates with toxin neutralization. Most other bacterial pathogens, including Staphylococcus aureus, secrete numerous toxins and evolved multiple mechanisms to escape opsonization and complement killing. Several vaccine candidates targeting defined surface antigens of S. aureus have failed to meet clinical endpoints. It is unclear that such failures can be solely attributed to the poor selection of antibody targets. Thus far, studies to delineate antibody-mediated uptake and killing of Gram-positive pathogens remain extremely limited. Here, we exploit 3F6-hIgG1, a human monoclonal antibody that binds and neutralizes the abundant surface-exposed Staphylococcal protein A (SpA). We find that galactosylation of 3F6-hIgG1 that favors C1q recruitment is indispensable for opsonophagocytic killing of staphylococci and for protection against bloodstream infection in animals. However, the simple removal of fucosyl residues, which results in reduced C1q binding and increased engagement with FcγR, maintains the opsonophagocytic killing and protective attributes of the antibody. We confirm these results by engineering 3F6-hIgG1 variants with biased binding toward C1q or FcγRs. While the therapeutic benefit of monoclonal antibodies against infectious disease agents may be debatable, the functional characterization of such antibodies represents a powerful tool for the development of correlates of protection that may guide future vaccine trials.

BackgroundComplement C1q (C1q) has been confirmed to be related to obesity, metabolic syndrome (MetS), and its components. However, human data regarding the associations are relatively scarce. This study aimed to investigate associations of C1q with obesity as well as MetS in Chinese adolescents.MethodsA total of 1,191 Chinese adolescents aged 13–18 years were enrolled in this study. The biochemical and anthropometric variables of all the subjects were evaluated using standardized procedures. C1q was measured using the immunoturbidometric assay. The relationship between C1q and obesity or MetS was analyzed using multiple regression analyses.ResultsObesity was more prevalent among participants in the highest tertile than in the lowest tertile of C1q levels. The highest tertile of C1q was related to a greater effect on the risk of MetS, and its trend test was statistically significant. Except for hyperglycemia, the prevalence of other components of MetS significantly increased relative to an increase in C1q tertile. Receiver operating characteristic (ROC) curve analysis of C1q for predicting adolescents with MetS illustrated that the area under the curve (AUC) was 0.82 [95% confidence interval (CI): 0.76, 0.88; PConclusionsThis study observed a significantly higher prevalence of obesity and MetS features in adolescents with high C1q. The findings of the current study also reported a significant relationship between C1q levels and MetS components [except for fasting plasma glucose (FPG)] in Chinese adolescents. C1q may represent a biomarker for predicting obesity or MetS in adolescents.

Because of its capacity to increase a physiologic inflammatory response, to stimulate phagocytosis, to promote cell lysis and to enhance pathogen immunogenicity, the complement system is a crucial component of both the innate and adaptive immune responses. However, many infectious agents resist the activation of this system by expressing or secreting proteins with a role as complement regulatory, mainly inhibitory, proteins. Trypanosoma cruzi, the causal agent of Chagas disease, a reemerging microbial ailment, possesses several virulence factors with capacity to inhibit complement at different stages of activation. T. cruzi calreticulin (TcCalr) is a highly-conserved, endoplasmic reticulum-resident chaperone that the parasite translocates to the extracellular environment, where it exerts a variety of functions. Among these functions, TcCalr binds C1, MBL and ficolins, thus inhibiting the classical and lectin pathways of complement at their earliest stages of activation. Moreover, the TcCalr/C1 interaction also mediates infectivity by mimicking a strategy used by apoptotic cells for their removal. More recently, it has been determined that these Calr strategies are also used by a variety of other parasites. In addition, as reviewed elsewhere, TcCalr inhibits angiogenesis, promotes wound healing and reduces tumor growth. Complement C1 is also involved in some of these properties. Knowledge on the role of virulence factors, such as TcCalr, and their interactions with complement components in host–parasite interactions, may lead toward the description of new anti-parasite therapies and prophylaxis.

Genetic deficiency in C1q is a strong susceptibility factor for systemic lupus erythematosus (SLE). There are two major hypotheses that potentially explain the role of C1q in SLE. The first postulates that C1q deficiency abrogates apoptotic cell clearance, leading to persistently high loads of potentially immunogenic self-antigens that trigger autoimmune responses. While C1q undoubtedly plays an important role in apoptotic clearance, an essential biological process such as removal of self- waste is so critical for host survival that multiple ligand-receptor combinations do fortunately exist to ensure that proper disposal of apoptotic debris is accomplished even in the absence of C1q. The second hypothesis is based on the observation that locally synthesized C1q plays a critical role in regulating the earliest stages of monocyte to dendritic cell (DC) differentiation and function. Indeed, circulating C1q has been shown to keep monocytes in a pre-dendritic state by silencing key molecular players and ensuring that unwarranted DC-driven immune responses do not occur. Monocytes are also able to display macromolecular C1 on their surface, representing a novel mechanism for the recognition of circulating “danger.” Translation of this danger signal in turn, provides the requisite “license” to trigger a differentiation pathway that leads to adaptive immune response. Based on this evidence, the second hypothesis proposes that deficiency in C1q dysregulates monocyte-to-DC differentiation and causes inefficient or defective maintenance of self-tolerance. The fact that C1q receptors (cC1qR and gC1qR) are also expressed on the surface of both monocytes and DCs, suggests that C1q/C1qR may regulate DC differentiation and function through specific cell-signaling pathways. While their primary ligand is C1q, C1qRs can also independently recognize a vast array of plasma proteins as well as pathogen-associated molecular ligands, indicating that these molecules may collaborate in antigen recognition and processing, and thus regulate DC-differentiation. This review will therefore focus on the role of C1q and C1qRs in SLE and explore the gC1qR/C1q axis as a potential target for therapy.

Objectives To examine the relation between serum C1q levels and blood type‐1 interferon signature (type‐1 IFN signature) in active pulmonary tuberculosis (APTB) and to determine whether combined measurement of serum C1q and type‐1 IFN signature may add to the diagnosis of QuantiFERON‐positive (QFT+) patients with uveitis of unknown cause. Methods C1q was determined (ELISA) in serum from two distinct Indonesian cohorts, and in total, APTB (n = 72), QFT+ uveitis of unknown aetiology (n = 58), QFT− uveitis (n = 51) patients and healthy controls (HC; n = 73) were included. The type‐1 IFN signature scores were previously determined. Results Serum C1q was higher in APTB than HC (P, Serum C1q is elevated in active pulmonary tuberculosis, especially in those cases with uveitis. Serum C1q correlated inversely with type‐1 IFN signature scores in APTB (P = 0.0036, r 2 = 0.3526), revealing that these biomarkers for active TB disease can be mutually exclusive. We propose that combined measurement of blood type‐1 IFN signature and serum C1q may provide added value in the diagnosis of active TB disease, which might be especially beneficial in often hard‐to‐diagnose TB‐associated uveitis cases.

Antecedentes. La alorrespuesta humoral, particularmente la mediada por la presencia de anticuerpos frente a los antígenos leucocitarios humanos (HLA) del aloinjerto, se asocia a un incremento en la prevalencia de rechazo y a una reducción en la supervivencia del trasplante. La mayor sensibilidad de los ensayos de fase sólida, basados en el empleo de microesferas magnéticas recubiertas con un único antígeno HLA (single antigen beads o SAB), los consolidó como técnica gold-estándar para identificar estos anticuerpos anti- HLA, garantizando un mayor éxito en los programas de trasplante de órgano sólido. La intensidad de fluorescencia media (MFI) proporcionada por el ensayo estandarizado (SABpanIgG) es el valor que se usa habitualmente para estratificar el riesgo inmunológico, asumiendo que es una estimación semicuantitativa fiable del nivel de anticuerpos circulantes. Sin embargo, este valor se ve frecuentemente afectado por ciertos efectos inhibitorios, que enmascaran la concentración real a la que se encuentra el anticuerpo en sangre. Más allá del valor MFI, ciertas características intrínsecas, como su capacidad para activar la cascada del complemento (SAB-C1q) o el perfil de subclases de IgG1-4 que lo conforma (SAB-subclass), han sido estudiadas con el objetivo de elucidar sus propiedades funcionales y definir de forma más precisa la relevancia clínica de los anticuerpos, usados como biomarcadores de la evolución del trasplante. No obstante, todavía existen cuestiones por resolver. Objetivo. El objetivo de este trabajo de tesis doctoral fue esclarecer la relación entre las diferentes propiedades de los anticuerpos anti-HLA identificables por los métodos de detección disponibles (valor MFI, capacidad de activar la cascada del complemento y perfil de subclases de IgG1-4) y evaluar prospectivamente el impacto de dichas propiedades sobre la evolución del aloinjerto renal trasplantado. Métodos. Para estudiar la relación entre las diferentes propiedades de los anticuerpos anti-HLA utilizadas en la estratificación del riesgo inmunológico, se analizaron las muestras de suero de 20 pacientes HLA-sensibilizados en lista de espera de trasplante renal, utilizando los ensayos de fase sólida disponibles: SAB-panIgG (para detectar y definir las especificidades de anticuerpos anti-HLA panIgG), SAB-subclass (para identificar la presencia de subclases IgG1-4 que componen una determinada especificidad de anticuerpo anti-HLA) y SAB-C1q (para definir los anticuerpos capaces de fijar C1q, el primer componente de la cascada del complemento humano por la vía clásica). Los ensayos SAB-panIgG y SAB-subclass se realizaron sobre muestras de suero neto y previamente diluido 1:16. Además, en el ensayo SAB-panIgG, se evaluaron los pretratamientos con calor (56 ºC durante 30 minutos) y EDTA (25 mM) como métodos para eliminar el efecto inhibitorio. Por otra parte, para estudiar el impacto de las propiedades de los anticuerpos anti-HLA, se examinó la función, ocurrencia de eventos de rechazo y supervivencia temprana del aloinjerto renal en una cohorte de 14 pacientes hiperinmunizados trasplantados con DSA preformados no fijadores de C1q (DSA+), en relación a una cohorte control de 58 pacientes trasplantados con anticuerpos anti-HLA preformados no específicos de donante (DSA-). Asimismo, se exploraron los cambios producidos en el perfil del DSA, así como en sus propiedades intrínsecas (valor MFI, capacidad de activar la cascada del complemento y perfil de subclases IgG1-4). Resultados. Al analizar las muestras de suero de los 20 pacientes en lista de espera de trasplante, se identificaron 1.285 anticuerpos anti-HLA como positivos, 473 (36,8%) de los cuales resultaron ser fijadores de C1q. La dilución de las muestras de suero aumentó la correlación entre la fuerza de los anticuerpos, estimada como el valor MFI, y su capacidad de unir C1q (rneto = 0,248 vs. rdiluido = 0,817). Los pre-tratamientos con calor y EDTA también aumentaron dicha correlación (rcalor = 0,699 y rEDTA = 0,656), si bien, ésta no fue tan elevada como la obtenida tras la dilución. El ensayo SAB-subclass reveló al menos una subclase de IgG1-4 en 1.012 (78,8%) de los anticuerpos positivos predefinidos en el ensayo SAB-panIgG. Las subclases con fuerte capacidad de activar complemento, principalmente IgG1, fueron particularmente frecuentes (98,9%) y, de hecho, no se encontraron diferencias entre anticuerpos C1q-positivos y C1q-negativos en relación a su presencia (99,4 vs. 98,5 %; p = 0,193). Por el contrario, las subclases incapaces o débilmente capaces de activar el complemento (IgG4/IgG2) se detectaron con más frecuencia en anticuerpos fijadores de C1q (78,9 vs. 38,6%; p < 0,001). La correlación entre la capacidad de unir C1q y la fuerza de la subclase IgG1 resultó ser fuerte (rIgG1 = 0,796). Aunque menor, la correlación entre la fuerza de la subclase IgG2 y la capacidad de unir C1q también resultó ser fuerte (rIgG2 = 0,758), estando ambas subclases estrechamente relacionadas (rIgG1-IgG2 = 0,817). No se encontró ninguna correlación entre la capacidad de unir C1q y la fuerza de las subclases IgG3 e IgG4. Por otra parte, en relación al análisis de las muestras de suero de los 14 pacientes trasplantados con DSA preformados no fijadores de C1q (DSA+), se observó que el valor MFI del DSA disminuyó significativamente en el post-trasplante (4.467,28 ± 2.052,95 vs. 2.030,25 ± 1.979,36; p = 0,002) en 12 (85,7%) de los pacientes, mientras que en 2 (14,3%) de ellos aumentó. Ningún DSA modificó su estatus C1q. El valor MFI de las subclases del DSA también disminuyó significativamente, excepto el de la subclase IgG3, que permaneció invariable (IgG1: 5.443,36 ± 9.033,25 vs. 1.488,91 ± 2.035,98; p = 0,028; IgG2: 752,34 ± 1.958,23 vs. 17,24 ± 15,04; p = 0,022; IgG3: 88,50 ± 215,23 vs. 91,93 ± 140,22; p = 0,386 e IgG4: 257,89 ± 612,41 vs. 47,66 ± 63,39; p = 0,037). La proporción de pacientes que desarrollaron DSA de novo fue similar en el grupo DSA+ con respecto al grupo DSA- (7,1 vs. 5,2%; p = 1,000). Los valores de creatinina sérica (mg/dL), filtrado glomerular (mL/min/m2), proteínas en orina (mg/dL) y cociente creatinina/proteínas en orina (mg/mg) tampoco fueron significativamente diferentes (p > 0,05) en ninguno de los intervalos de tiempo analizados (15, 30, 90, 180 y 365 días post-trasplante). En el grupo DSA-, una proporción significativamente mayor de pacientes fue diagnosticada de rechazo celular (TCMR; 0 vs. 41,7%; p = 0,035), mientras que hubo una clara tendencia en la supervivencia renal similares unidos a la invariabilidad en las propiedades funcionales del DSA asociadas a su potencial patológico (principalmente su capacidad de unir C1q), durante el primer año de seguimiento, sugieren que el trasplante renal en presencia de DSA preformados no fijadores de C1q podría ser factible en aquellos pacientes altamente sensibilizados con pocas opciones de trasplante. Background. Humoral alloresponse, particularly that mediated by the presence of antibodies against allograft human leukocyte antigens (HLA), is associated with an increased prevalence of rejection and a reduced transplant survival. The higher sensitivity of solid phase assays, based on magnetic microbeads coated with single HLA antigens (single antigen beads or SAB), consolidated them as the gold-standard method to identify these anti-HLA antibodies, ensuring a greater succeed in solid-organ allograft allocation programs. Mean fluorescence intensity (MFI) value provided by the standardized assay (SAB-panIgG) is regularly used to stratify the immunological risk, assuming it as a reliable semiquantitative estimation of the circulating antibody-level. However, this value is often affected by several inhibitory effects, which mask the real concentration of antibodies in blood. Beyond MFI, certain intrinsic characteristics, such as the complement-binding ability (SAB-C1q) or the IgG1-4 subclass profile comprising a particular specificity (SABsubclass), have been examined to clarify their functional properties and more accurately define the clinical relevance of antibodies, used as biomarkers of transplant outcome. However, there are still unresolved issues. Aim. The aim of this study was to elucidate the relationship between the different properties of anti-HLA antibodies detectable with the available assays (the MFI value, the ability to activate the complement cascade and the IgG1-4 subclass profile) and prospectively evaluate the impact of those properties on kidney transplanted allograft outcome. Methods. In order to study the relationship between different anti-HLA antibody properties use to stratify the immunological risk, serum-samples from 20 HLA-sensitized patients awaiting kidney transplantation were analyzed by the available solid-phase assays: SAB-panIgG (to detect and define the specificities of panIgG anti-HLA antibodies), SAB-subclass (to identify the presence of IgG1-4 subclasses comprising a particular anti HLA antibody specificity) and SAB-C1q (to define those antibodies capable of binding C1q, the first component of human complement classical pathway). SAB-panIgG and SABsubclass were performed on neat and 1:16 pre-diluted serum-samples. Additionally, in SAB-panIgG, heat (56 ºC for 30 minutes) and EDTA (25 mM) pre-treatments were evaluated as methods to avoid the inhibitory effect. Furthermore, in order to study the impact of anti-HLA antibody properties, allograft function, the occurrence of rejection events and early allograft survival rate were evaluated in a cohort of 14 highly-sensitized transplanted patients with preformed non-C1q-binding DSA (DSA+) and contrasted with a control cohort of 58 transplanted patients with preformed non-DSA anti-HLA antibodies (DSA-). Changes produced in the profile and in the intrinsic properties (the MFI value, the ability to activate the complement cascade and the IgG1-4 subclass profile) of the DSA were also explored. Results. When analyzing serum samples belonging to the 20 patients awaiting kidney transplantation, a total of 1,285 anti-HLA antibodies were identified as positive, 473 (36.8%) of which were C1q-binding. Serum-dilution enhanced the correlation between the antibody-strength, measured as the MFI and the C1q-binding ability (rneat = 0.248 vs. rdiluted = 0.817). Even though the heat and EDTA pre-treatments also improved that correlation (rheat = 0,699 y rEDTA = 0,656), it was not as high as that obtained after serum-dilution. SAB-subclass assay revealed at least one IgG1-4 subclass in the 1,012 (78.8%) positive antibody-specificities predefined by SAB-panIgG. Strong complement-binding subclasses, mainly IgG1, were particularly frequent (98.9%) and no differences were found between C1q-positive and C1q-negative antibodies regarding their presence (99.4% vs. 98.5%; p=0.193). In contrast, non- or weak C1q-binding subclasses (IgG4/IgG2) were more commonly detected in C1q-binding antibodies (78.9% vs. 38.6%; p < 0.001). Interestingly, a strong association was found between the C1q-binding ability and the IgG1 strength (rIgG1dil = 0.796). Though lower, the correlation between the IgG2 strength and the C1q binding ability was also strong (rIgG2dil = 0.758), being both subclasses closely related (rIgG1- IgG2 = 0.817). No correlation was found with the C1q-binding ability and the strength of IgG3/IgG4 subclasses. Furthermore, regarding the analysis of serum samples belonging to the 14 patients transplanted with preformed non-C1q-binding DSA (DSA+), it was observed that in 12 (85.7%) patients, the DSA MFI value significantly decreased after transplantation (4,467.28 ± 2,052.95 vs. 2,030.25 ± 1,979.36; p = 0.002), whereas in 2 (14.3%) of them it increased. No DSA changed their C1q-binding status. The MFI value of IgG-DSA subclases significantly decreased as well, except that of the IgG3, which remained invariable (IgG1: 5,443.36 ± 9,033.25 vs. 1,488.91 ± 2,035.98; p = 0.028; IgG2: 752.34 ± 1,958.23 vs. 17.24 ± 15.04; p = 0.022; IgG3: 88.50 ± 215.23 vs. 91.93 ± 140.22; p = 0.386 and IgG4: 257.89 ± 612.41 vs. 47.66 ± 63.39; p = 0.037). The proportion of patients who developed de novo DSA was similar in the DSA+ with regard to the DSA- group (7.1 vs. 5.2%; p = 1.000). Neither the creatinine serum level (mg/dL), glomerular filtration rate (mL/min/m2), urine protein level (mg/dL) nor the urine creatinine/protein ratio (mg/mg) were significantly different (p < 0.05) between groups at any point throughout the follow-up time (15, 30, 90, 180 and 365 days after transplantation). While a significantly higher proportion of patients in the DSA- group were diagnosed with T-cell mediated rejection (TCMR; 0 vs. 41.7%; p = 0.035), a clear trend was found in the proportion of biopsies with C4d staining in the DSA+ group (75.0 vs. 33.3%; p =0.096). No significant differences were found in the occurrence of TCMR with humoral component (62.5 vs. 33.3%; p = 0.219) nor in the occurrence of antibody-mediated rejection without cellular component (ABMR; 12.5 vs. 8.3; p = 1.000). Early kidney allograft survival until the end of the follow-up time was similar between both groups (85.7 vs. 93.2%; p = 0,329). Conclusions. The different properties of anti-HLA antibodies used to define their pathological potential (the MFI value, the ability to bind C1q and the circulating IgG1-4 subclass profile) seem to be related, albeit in a distinct manner as it initially could be expected. Thus, a particular profile of IgG subclasses (IgG1/IgG3 or IgG2/IgG4) itself does not determine at all the ability to bind complement of anti-HLA antibodies, given that the first (IgG1/IgG3), which are potent complement activators, are present both in C1qpositive and C1q-negative antibodies and the second (IgG2/IgG4) are, paradoxically, more frequent in C1q-positive antibodies. It is the subclass strength (MFI), mainly that of the ubiquitous IgG1, which usually appears combined with IgG2, that best correlates with the ability to bind C1q. That real strength (MFI) is more exactly estimated when analyzing diluted serum-samples, which allows to avoid the prozone effect, a common artifact in highly HLA-sensitized patients. Under an immunosuppressant context, the MFI value of the DSA and the particular IgG subclasses comprising it decreases after transplantation, while its C1q-binding ability, a proven worse prognosis biomarker, uses to remain invariable. Despite the undeniable interaction between the DSA and the kidney endothelium, evinced by the presence of C4d staining, early allograft function and survival rate of patients transplanted with preformed non-C1q-binding DSA is similar with respect to those of patients transplanted without DSA. The similar functionality and renal survival together with the invariability of DSA functional properties associated with their pathological potential (mainly the ability to bind C1q), during the first year of follow-up, suggest that kidney transplantation with preformed non-C1q-binding DSA could be feasible in those highly-sensitized patients with scarce transplantation recourses.

Like in most fields in science, the complement system is also in a fast gear of self-evolution, with new discoveries of unanticipated pathways and functions capable of cross-talk with other biologic systems. An emerging area that has been gaining much attention recently is the role of locally synthesized complement proteins, which mediate a plethora of cellular functions thereby enhancing either health or disease. Prominent among the locally synthesized proteins is C1q, the first subcomponent of the complement classical pathway, which has been shown to regulate a wide range of immunological and pathological processes in autocrine or paracrine manners. Although the main source of the local synthesis of C1q has been attributed to the potent antigen presenting cells such as macrophages and dendritic cells, where it plays as a powerful molecular sensor of danger and regulator of self-tolerance, the list of the type of cells that locally synthesize C1q has been expanding over the years and now includes various types of proliferating and non-proliferating cells including malignant cells. The aim of the current “Frontiers Topic” is, therefore, to compile a comprehensive list of review and research articles by experts in the field, so that they can be a major source of information for researchers and clinicians alike. This work is supported by a Singapore National University Health System seed fund (R-182-000229-750), a Singapore Ministry of Education Tier 2 grant (MOE2012-T2-2-122), and a Singapore National Medical Research Council Open-funding Individual Research Grant (NMRC/OFIRG/0013/2016).

TYROBP/DAP12 forms complexes with ectodomains of immune receptors (TREM2, SIRPβ1, CR3) associated with Alzheimer's disease (AD) and is a network hub and driver in the complement subnetwork identified by multi-scale gene network studies of postmortem human AD brain. Using transgenic or viral approaches, we characterized in mice the effects of TYROBP deficiency on the phenotypic and pathological evolution of tauopathy. Biomarkers usually associated with worsening clinical phenotype (i.e., hyperphosphorylation and increased tauopathy spreading) were unexpectedly increased in MAPTP301S;Tyrobp-/- mice despite the improved learning behavior and synaptic function relative to controls with normal levels of TYROBP. Notably, levels of complement cascade initiator C1q were reduced in MAPTP301S;Tyrobp-/- mice, consistent with the prediction that C1q reduction exerts a neuroprotective effect. These observations suggest a model wherein TYROBP-KO-(knock-out)-associated reduction in C1q is associated with normalized learning behavior and electrophysiological properties in tauopathy model mice despite a paradoxical evolution of biomarker signatures usually associated with neurological decline.

Poly(2-methyl-2-oxazoline) (PMOXA) is an alternative promising polymer to poly(ethylene glycol) (PEG) for design and engineering of macrophage-evading nanoparticles (NPs). Although PMOXA-engineered NPs have shown comparable pharmacokinetics and in vivo performance to PEGylated stealth NPs in the murine model, its interaction with elements of the human innate immune system has not been studied. From a translational angle, we studied the interaction of fully characterized PMOXA-coated vinyltriethoxysilane-derived organically modified silica NPs (PMOXA-coated NPs) of approximately 100 nm in diameter with human complement system, blood leukocytes, and macrophages and compared their performance with PEGylated and uncoated NP counterparts. Through detailed immunological and proteomic profiling, we show that PMOXA-coated NPs extensively trigger complement activation in human sera exclusively through the classical pathway. Complement activation is initiated by the sensing molecule C1q, where C1q binds with high affinity (K(d) = 11 ± 1 nM) to NP surfaces independent of immunoglobulin binding. C1q-mediated complement activation accelerates PMOXA opsonization with the third complement protein (C3) through the amplification loop of the alternative pathway. This promoted NP recognition by human blood leukocytes and monocyte-derived macrophages. The macrophage capture of PMOXA-coated NPs correlates with sera donor variability in complement activation and opsonization but not with other major corona proteins, including clusterin and a wide range of apolipoproteins. In contrast to these observations, PMOXA-coated NPs poorly activated the murine complement system and were marginally recognized by mouse macrophages. These studies provide important insights into compatibility of engineered NPs with elements of the human innate immune system for translational steps. [Image: see text]

Background/Aims: Complement activation is important in post-transplantation renal injury, but data on its role as predictor of transplant outcome/complications when assessed in donor kidneys are lacking. Methods: In human renal transplant biopsies with delayed graft function (DGF, n=12), antibody mediated rejection (ABMR, n=8), T-cell mediated rejection (TCMR, n=11), 1 year protocol biopsies (control, n=10) and corresponding zero-biopsies we performed immunohistochemical analyses of 6 complement factors using FFPE sections and correlated the findings with kidney function, as assessed by serum creatinine, and morphological changes including interstitial fibrosis and tubular atrophy (IF/TA). Results: In DGF, TCMR and ABMR significant complement deposition was observed, which was less pronounced in corresponding zero-biopsies. Zero-biopsies with subsequent ABMR showed glomerular complement factor D and C3c expression. Moreover, glomerular C3c and C9 and tubular MASP-2 and Collectin-11 expression in zero-biopsies significantly correlated with serum creatinine at diagnosis of DGF, TCMR or ABMR. Glomerular C1q was significantly increased in ABMR, but not in DGF and TCMR. In contrast, peritubular C1q was significantly enhanced in DGF and TCMR compared to zero-biopsies. Using C3d as a surrogate marker for complement activity we could confirm that stained complement factors are frequently associated with complement activity. Conclusion: Complement deposition strongly correlated with histopathological changes observed in renal transplants. All 3 complement pathways were operational in biopsies with DGF, TCMR and ABMR albeit with differential abundance and localization. Since complement deposition in zero-biopsies correlated with graft function and morphological changes, early specific complement inhibition in renal transplantation may be a new therapeutic option to prevent graft loss.

Complement and coagulation are both key systems that defend the body from harm. They share multiple features and are similarly activated. They each play individual roles in the systemic circulation in physiology and pathophysiology, with significant crosstalk between them. Components from both systems are mapped to important structures in the central nervous system (CNS) and peripheral nervous system (PNS). Complement and coagulation participate in critical functions in neuronal development and synaptic plasticity. During pathophysiological states, complement and coagulation factors are upregulated and can modulate synaptic transmission and neuronal conduction. This review summarizes the current evidence regarding the roles of the complement system and the coagulation cascade in the CNS and PNS. Possible crosstalk between the two systems regarding neuroinflammatory-related effects on synaptic transmission and neuronal conduction is explored. Novel treatment based on the modulation of crosstalk between complement and coagulation may perhaps help to alleviate neuroinflammatory effects in diseased states of the CNS and PNS.

Antibodies capable of activating the complement system (CS) when bound with antigen are referred to as “complement-fixing antibodies” and are involved in protection against Flaviviruses. A complement-fixing antibody test has been used in the past to measure the ability of dengue virus (DENV)-specific serum antibodies to activate the CS. As originally developed, the test is time-consuming, cumbersome, and has limited sensitivity for DENV diagnosis. Here, we developed and characterized a novel multiplex anti-DENV complement-fixing assay based on the Luminex platform to quantitate serum antibodies against all four serotypes (DENV1-4) that activate the CS based on their ability to fix the complement component 1q (C1q). The assay demonstrated good reproducibility and showed equivalent performance to a DENV microneutralization assay that has been used to determine DENV serostatus. In non-human primates, antibodies produced in response to primary DENV1-4 infection induced C1q fixation on homologous and heterologous serotypes. Inter-serotype cross-reactivity was associated with homology of the envelope protein. Interestingly, the antibodies produced following vaccination against Zika virus fixed C1q on DENV. The anti-DENV complement fixing antibody assay represents an alternative approach to determine the quality of functional antibodies produced following DENV natural infection or vaccination and a biomarker for dengue serostatus, while providing insights about immunological cross-reactivity among different Flaviviruses.

Myalgic encephalomyelitis; Blood analytics; Diagnosis Encefalomielitis miálgica; Análisis de sangre; Diagnóstico Encefalomielitis miàlgica; Anàlisi de sang; Diagnòstic Background: Routine blood analytics are systematically used in the clinic to diagnose disease or confirm individuals’ healthy status. For myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS), a disease relying exclusively on clinical symptoms for its diagnosis, blood analytics only serve to rule out underlying conditions leading to exerting fatigue. However, studies evaluating complete and large blood datasets by combinatorial approaches to evidence ME/CFS condition or detect/identify case subgroups are still scarce. Methods: This study used unbiased hierarchical cluster analysis of a large cohort of 250 carefully phenotyped female ME/CFS cases toward exploring this possibility. Results: The results show three symptom-based clusters, classified as severe, moderate, and mild, presenting significant differences (p < 0.05) in five blood parameters. Unexpectedly the study also revealed high levels of circulating complement factor C1q in 107/250 (43%) of the participants, placing C1q as a key molecule to identify an ME/CFS subtype/subgroup with more apparent pain symptoms. Conclusions: The results obtained have important implications for the research of ME/CFS etiology and, most likely, for the implementation of future diagnosis methods and treatments of ME/CFS in the clinic. This research was partially funded by the Association of Patients with ME/CFS and Fibromyalgia in Catalonia, Spain (ACAF; www.fibromyalgia.cat (accessed on 23 March 2019) to J.C.-M. and J.A.-M., and by a UCV 2020-270-001 grant to E.O.

Complement-dependent cytotoxicity (CDC) is a potent effector mechanism, engaging both innate and adaptive immunity. Although strategies to improve the CDC activity of antibody therapeutics have primarily focused on enhancing the interaction between the antibody crystallizable fragment (Fc) and the first subcomponent of the C1 complement complex (C1q), the relative importance of intrinsic affinity and binding valency of an antibody to the target antigen is poorly understood. Here we show that antibody binding affinity to a cell surface target antigen evidently affects the extent and efficacy of antibody-mediated complement activation. We further report the fundamental role of antibody binding valency in the capacity to recruit C1q and regulate CDC. More specifically, an array of affinity-modulated variants and functionally monovalent bispecific derivatives of high-affinity anti-epidermal growth factor receptor (EGFR) and anti-human epidermal growth factor receptor 2 (HER2) therapeutic immunoglobulin Gs (IgGs), previously reported to be deficient in mediating complement activation, were tested for their ability to bind C1q by biolayer interferometry using antigen-loaded biosensors and to exert CDC against a panel of EGFR and HER2 tumor cells of various histological origins. Significantly, affinity-reduced variants or monovalent derivatives, but not their high-affinity bivalent IgG counterparts, induced near-complete cell cytotoxicity in tumor cell lines that had formerly been shown to be resistant to complement-mediated attack. Our findings suggest that monovalent target engagement may contribute to an optimal geometrical positioning of the antibody Fc to engage C1q and deploy the complement pathway.

It has been increasingly demonstrated that the tumor microenvironment plays an active role in neoplasia growth and metastasis. Through different pathways, tumor cells can efficiently recruit stromal, immune and endothelial cells by secreting stimulatory factors, chemokines and cytokines. In turn, these cells can alter the signaling properties of the microenvironment by releasing growth-promoting signals, metabolites and extracellular matrix components to sustain high proliferation and metastatic competence. In this context, we identify that the complement component C1q, highly expressed locally by a range of human malignant tumors, upon interacting with the extracellular matrix hyaluronic acid, strongly affects the behavior of primary cells isolated from human tumor specimens. Here, we describe a method to test how C1q bound to hyaluronic acid (HA) impacts tumor cell adhesion, underlying the fact that the biological properties of key components of the extracellular matrix (in this case HA) can be shaped by bioactive signals toward tumor progression. Video Link

Background: CD93 has originally been known as a C1q receptor, and many studies have demonstrated that CD93 is expressed on hematopoietic stem cells, B cell progenitors, myeloid and monocytic cells. Moreover, CD93 is shown to be expressed on long-lived plasma cells, and CD93 deficient-mice display an impairment in plasma cell development. Objective: To investigate the expression of CD93 on multiple myeloma (MM) cells. Methods: Human MM and B cell lines were cultured, and the expression of CD93 was examined on these cells by quantitative Reverse Transcription Polymerase Chain Reaction (qRT-PCR) and Fluorescence Activated Cell Sorting (FACS). In addition, CD19+ primary B cells and CD19-/CD138+ primary MM cells were isolated by MACS columns, and CD93 expression was further analyzed on these cells. Results: qRT-PCR data showed that CD93 expression at mRNA level was much higher in MM cell lines compared with B cell lines. In addition, MM cell lines expressed a higher amount of surface CD93 at protein level compared with B cell lines. More importantly, CD93 expression was significantly higher in CD19-/CD138+ primary MM cells than in CD19+ primary B cells isolated from the bone marrow of patients with MM. Conclusion: We demonstrated that CD93 is expressed on myeloma cells and, that CD93 could play a key role in the pathogenesis of MM. Further studies are necessary to explore this possible role.

C1q-domain-containing (C1qDC) proteins are rapidly emerging as key players in the innate immune response of bivalve mollusks. Growing experimental evidence suggests that these highly abundant secretory proteins are involved in the recognition of microbe-associated molecular patterns, serving as lectin-like molecules in the bivalve proto-complement system. While a large amount of functional data concerning the binding specificity of the globular head C1q domain and on the regulation of these molecules in response to infection are quickly accumulating, the genetic mechanisms that have led to the extraordinary lineage-specific expansion of the C1qDC gene family in bivalves are still largely unknown. The analysis of the chromosome-scale genome assembly of the Eastern oyster Crassostrea virginica revealed that the 476 oyster C1qDC genes, far from being uniformly distributed along the genome, are located in large clusters of tandemly duplicated paralogs, mostly found on chromosomes 7 and 8. Our observations point out that the evolutionary process behind the development of a large arsenal of C1qDC lectin-like molecules in marine bivalves is still ongoing and likely based on an unequal crossing over.

Complement activation contributes to inflammation in many diseases, yet it also supports physiologic apoptotic cells (AC) clearance and its downstream immunosuppressive effects. The roles of individual complement components in AC phagocytosis have been difficult to dissect with artificially depleted sera. Using human in vitro systems and the novel antibody complement C1s inhibitor TNT003, we uncoupled the role of the enzymatic activation of the classical pathway from the opsonizing role of C1q in mediating a) the phagocytosis of early and late AC, and b) the immunosuppressive capacity of early AC. We found that C1s inhibition had a small impact on the physiologic clearance of early AC, leaving their immunosuppressive properties entirely unaffected, while mainly inhibiting the phagocytosis of late apoptotic/secondary necrotic cells. Our data suggest that C1s inhibition may represent a valuable therapeutic strategy to control classical pathway activation without causing significant AC accumulation in diseases without defects in AC phagocytosis.

Trigeminal nerve injury causes a distinct time window of glial activation in the trigeminal spinal subnucleus caudalis (Vc), which are involved in the initiation and maintenance phases of orofacial neuropathic pain. Microglia-derived factors enable the activation of astrocytes. The complement component C1q, which promotes the activation of astrocytes, is known to be synthesized in microglia. However, it is unclear whether microglia&ndash, astrocyte communication via C1q is involved in orofacial neuropathic pain. Here, we analyzed microglia-astrocyte communication in a rat model with infraorbital nerve injury (IONI). The orofacial mechanical hypersensitivity induced by IONI was significantly attenuated by preemptive treatment with minocycline. Immunohistochemical analyses revealed that minocycline inhibited the increase in c-Fos immune-reactive (IR) cells and the fluorescence intensity of both Iba1 and glial fibrillary acidic protein (GFAP) in the Vc following IONI. Intracisternal administration of C1q caused orofacial mechanical hypersensitivity and an increase in the number of c-Fos-IR cells and fluorescence intensity of GFAP. C1q-induced orofacial mechanical hypersensitivity was completely abrogated by intracisternal administration of fluorocitrate. The present findings suggest that the enhancement in the excitability of Vc nociceptive neurons is produced by astrocytic activation via the signaling of C1q released from activated microglia in the Vc following IONI, resulting in persistent orofacial neuropathic pain.

International audience; Elevated amounts of atmospheric CO2 are causing ocean acidification (OA) that may affect marine organisms including fish species. While several studies carried out in fish revealed that OA induces short term dysfunction in sensory systems including regulation of neurons activity in olfactory epithelium, information on the effects of OA on other physiological processes and actors is scarcer. In the present study we focused our attention on a European sea bass (Dicentrarchus labrax) sghC1q gene, a member of the C1q-domain-containing (C1qDC) protein family. In vertebrates, C1qDC family includes actors involved in different physiological processes including immune response and synaptic organization. Our microsynteny analysis revealed that this sghC1q gene is the orthologous gene in European sea bass to zebrafish (Danio rerio) cbln11 gene. We cloned the full length cbln11 mRNA and identified the different domains (the signal peptide, the coiled coil region and the globular C1q domain) of the deduced protein sequence. Investigation of mRNA expression by qPCR and in situ hybridization revealed that cbln11 gene is especially expressed in the non-sensory epithelium of the olfactory rosette at larval and adult stages. The expression of cbln11 mRNA was analysed by qPCR in the first generation (FO) of European sea bass broodstock exposed since larval stages to water pH of 8.0 (control) or 7.6 (predicted for year 2100) and in their offspring (F1) maintained in the environmental conditions of their parents. Our results showed that cbln11 mRNA expression level was lower in larvae exposed to OA then up-regulated at adult stage in the olfactory rosette of F0 and that this up-regulation is maintained under OA at larval and juvenile stages in F1. Overall, this work provides evidence of a transgenerational inheritance of OA-induced up-regulation of cbln11 gene expression in European sea bass. Further studies will investigate the potential immune function of cbln11 gene and the consequences of these regulations, as well as the possible implications in terms of fitness and adaptation to OA in European sea bass.

BACKGROUND: ATTRV30M amyloidosis is a lethal autosomal dominant sensorimotor and autonomic neuropathy caused by amyloid deposition composed of aggregated misfolded TTR monomers with the V30M mutation. The age of onset in patients with ATTRV30M varies in different foci and the mechanism behind it is still unknown. METHODS: The tertiary neurology center following all ATTRV30M patients in Cyprus was used to collect demographic data to estimate; prevalence, incidence, penetrance, anticipation, time from disease onset to diagnosis and transplantation. Ocular, cardiac and leptomeningeal involvement in transplanted patients was explored. Correlation of C1q tagging SNPs with age of disease onset was carried out. RESULTS: Prevalence and incidence for ATTRV30M neuropathy in Cyprus are 5.4/100,000 and 0.3/100,000 respectively. Mean age of onset is 40.6 years and anticipation is 8.3 years. Penetrance reaches 51% and 75% by the ages of 50 and 80 years respectively. In liver transplanted patients rates of ocular, cardiac and leptomeningeal involvement were estimated to be 60%, 20% and 16%, respectively. C1q polymorphisms correlated with age of disease onset. CONCLUSIONS: ATTRV30M neuropathy has a rising prevalence in Cyprus due to improved survival of patients. Late onset complications are becoming a major problem. Complement C1q appears to be a modifier in this disease.

Agnathans (lamprey and hagfish) are a group of primitive jawless fish. Jawed vertebrates possess adaptive immunity including immunoglobulins, while agnathans lack immunoglobulins but have alternative adaptive immunity in which variable lymphocyte receptors (VLRs) function as antibodies. The complement system consists of many proteins involved in the elimination of pathogens. In mammals, it is activated via the three different pathways, resulting in the generation of C3b followed by the lytic pathway. Complement components including C3, mannose-binding lectin (MBL), and MBL-associated serine proteases (MASP) of the lectin pathway and factor B of the alternative pathway have been identified from lamprey and/or hagfish, while lytic pathway components have not been identified. In mammals, C1q binds to IgM/IgG-antigen complexes and activates the classical pathway in association with C1r and C1s. Lamprey also has C1q (LC1q), but its function differs from that of mammalian C1q. LC1q acts as a lectin and activates C3 in association with MASP via the lectin pathway. Furthermore, LC1q may interact with a secreted type of VLR (VLRB) in complex with antigens and mediate activation of C3, potentially via MASP, leading to cytolysis. Cytolysis is mediated by a newly identified serum protein named lamprey pore-forming protein (LPFP). In conclusion, lamprey has a complement activation pathway, which could be regarded as the classical pathway and also has a cytolytic system that is distinct from the mammalian lytic pathway. Thus, it appears that the complement system of agnathans is very unique and may have developed independently from jawed vertebrates.

While the mechanisms underlying the functions of the complement system in the central nervous system (CNS) and systemically, namely opsonization, chemotaxis, membrane lysis, and regulation of inflammation are the same, the plethora of functions that complement orchestrates in the central nervous system (CNS) is complex. Strictly controlled expression of complement effector molecules, regulators and receptors across the gamut of life stages (embryogenesis, development and maturation, aging and disease) dictate fascinating contributions for this ancient system. Furthermore, it is becoming apparent that complement functions differ widely across distinct brain regions. This review provides a comprehensive overview of the newly identified roles for complement in the brain, including its roles in CNS development and function, during ageing and in the processes of neurodegeneration. The diversity and selectively of beneficial and detrimental activities of complement, while challenging, should lead to precision targeting of specific components to provide disease modifying treatments for devastating psychiatric and neurodegenerative disorders that are still without effective treatment.

Complement component C1q plays an important recognition role in adaptive, and innate, immunity through its ability to interact, via its six globular head regions, with both immunoglobulin and non-immunoglobulin activators of the complement system, and also in the clearance of cell debris, and by playing a role in regulation of cellular events by interacting with a wide range of cell surface molecules. The presence of collagen-like triple-helical structures within C1q appears crucial to the presentation, and multivalent binding, of the globular heads of C1q to targets, and also to its association with the proenzyme complex of C1r2–C1s2, to yield the C1 complex. The possible role that movement of these collagen-like structures may play in the activation of the C1 complex is a controversial area, with there still being no definitive answer as to how the first C1r proenzyme molecule becomes activated within the C1 complex, thus allowing it to activate proenzyme C1s, and initiate and the consequent cascade of events in the activation of the classical pathway of complement. The globular heads of C1q are similar to domains found within the tumor necrosis factor (TNF) superfamily of proteins, and have been shown to bind to a very wide range of ligands. In addition to its well-defined roles in infection and immunity, a variety of other functions associated with C1q include possible roles, in the development of problems in the central nervous system, which occur with aging, and perhaps in the regulation of tumor growth.

Activation of the classical complement pathway occurs to varying degrees within strains of the Borrelia burgdorferi sensu lato complex, which contain a group of pathogenic spirochetes that cause tick-borne Lyme borreliosis, including the agent of Lyme disease in the United States, B. burgdorferi. Despite this information, details related to the control of B. burgdorferi by the classical pathway are not clear. To address this question, we infected C1qα−/− mice, which cannot assemble the C1 complex and thus fail to activate the classical pathway, with B. burgdorferi sensu stricto strain B31. Using bioluminescent in vivo imaging, we found that C1qα−/− mice harbored more B. burgdorferi following 10 days of infection relative to their isogenic C57BL/6 parent. Quantitative PCR (qPCR) demonstrated that C1qα−/− mice harbored significantly more B. burgdorferi than parent mice did within lymph nodes, skin, heart, and joints. The increased B. burgdorferi load in C1qα−/− mice was observed at 21 and 28 days of infection, consistent with the classical pathway promoting complement-dependent, antibody-mediated killing following the development of a B. burgdorferi-specific humoral immune response. In addition, circulating borrelial-specific IgM was higher in C1qα−/− mice relative to their parent mouse strain and did not decrease at 21 and 28 days post-infection, indicating that IgG class switching was delayed in C1qα−/− mice. At day 28, both Borrelia-specific IgG1 and IgG3 levels were higher in infected C1qα−/− mice, but that these antibodies were not sufficient to control borrelial infection in the absence of the classical pathway. Furthermore, the lack of C1q also altered the balance of the Th1/Th2 response, as both circulating Th1 (MIP-1α, IL-2, IL-12, and TNFα), Th2 (IL-4, IL-10, and MCP-1), and Th17 (IL-17) cytokines were elevated in infected C1qα−/− mice. These data imply that C1q and the classical pathway play important roles in controlling borrelial infection via antibody and complement-dependent killing, as well as altering both antibody maturation processes and the T cell response following exposure to infectious B. burgdorferi.

The complement system bridges innate and adaptive immunity against microbial infections, with viral infection being a major trigger. Activation of the classical, alternative, and lectin pathways have been reported in chronic hepatitis C virus (HCV) infection and/or cryoglobulinemia. HCV infection leads to dysregulation of complement-mediated immune responses. Clinical and experimental evidence support involvement of complement in intra- and extrahepatic manifestations of HCV infection, such as liver fibrosis and type II cryoglobulinemia. In this review, we summarize studies that have investigated the interplay between HCV and the complement system to establish chronic infection and autoimmunity, as well as the association between HCV pathogenesis and abnormal complement profiles. Several unanswered questions are highlighted which suggest additional informative lines of investigation.

Introducción. La consolidación del ensayo single antigen beads (SABpanIgG) como método para la detección de anticuerpos frente a antígenos leucocitarios humanos (HLA), sin duda ha mejorado las expectativas de éxito en el trasplante de órganos sólidos. Paradójicamente, su alta sensibilidad para la detección de anticuerpos ha limitado seriamente las opciones de trasplante de una importante parte de la población que se encuentra sensibilizada frente a moléculas HLA. La actual estratificación del riesgo inmunológico en base a la presencia de un anticuerpo detectado por el ensayo SAB-panIgG, hace difícil encontrar donantes idóneos para estos pacientes, hecho que prolonga excesivamente su tiempo de permanencia en lista de espera. Una reciente modificación del ensayo estándar SAB-panIgG nos permite detectar únicamente aquellos anticuerpos capaces de activar la vía del complemento (ensayo SAB-C1q), los cuales, a priori, son más relevantes desde el punto de vista clínico. No obstante, la utilidad del ensayo SAB-C1q para estratificar el riesgo inmunológico de un anticuerpo preformado es un tema que, a día de hoy, suscita debate entre la comunidad científica. Objetivo. El objetivo principal de este trabajo fue evaluar el impacto de la capacidad de unir C1q de los anticuerpos anti-HLA específicos de donante (DSA) sobre la supervivencia del aloinjerto renal. Materiales y Métodos. Evaluamos retrospectivamente en muestras de suero pre-trasplante, pertenecientes a 389 pacientes trasplantados de riñón en el Hospital Universitario Reina Sofía entre los años 1995-2009, la presencia de DSA y su capacidad de fijar C1q mediante los ensayos SABpanIgG y SAB-C1q, respectivamente. Analizamos la supervivencia del aloinjerto renal en la población a los 7 años post-trasplante en función de su estatus de anticuerpos. El fallo de aloinjerto, definido como retorno a diálisis, fue considerado como evento de interés. Evaluamos el valor predictivo de fallo renal de múltiples variables clínicas e inmunológicas y establecimos un modelo de regresión de Cox multivariante para determinar el riesgo ajustado de pérdida de injerto en presencia de DSA y de su capacidad de unión por C1q. Resultados. Nuestro estudio reveló que los pacientes con DSA preformados capaces de fijar C1q presentaron la tasa de supervivencia del aloinjerto renal más baja de la población estudiada (40,7%), siendo significativamente menor a la de pacientes con DSA incapaces de fijar C1q (73,4%; p=0,001) y a la de pacientes sin DSA previos al trasplante (79,1%; p

Inflammation plays a key role in the pathophysiology of Glioblastoma Multiforme (GBM). Here we focus on the contribution of the so far largely ignored complement system. ELISA and immunohistochemistry were combined to assess levels and localization of critical components of the initiation- and effector pathways of the complement cascade in sera and tumor tissue from GBM patients and matched controls. Serum levels of factor-B were decreased in GBM patients whereas C1q levels were increased. C1q and factor-B deposited in the tumor tissue. Deposition of C3 and C5b-9 suggests local complement activation. MBL deficiency, based on serum levels, was significantly less frequent among GBM patients compared to controls (14% vs. 33%). Therefore low levels of MBL may protect against the initiation/progression of GBM. (C) 2014 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/3.0/).

C1q is the first recognition subcomponent of the complement classical pathway, which acts towards the clearance of pathogens and apoptotic cells. C1q is also known to modulate a range of functions of immune and non-immune cells, including their involvement in placental development and sensorial synaptic pruning. We have recently shown that C1q can promote tumour by encouraging their adhesion, migration and proliferation in addition to angiogenesis and metastasis. In this study, we have examined the role of C1q in the microenvironment of malignant pleuric mesothelioma (MPM), a rare form of cancer commonly associated with exposure to asbestos. We found that C1q was highly expressed in all MPM histotypes, particularly in epithelioid rather than in sarcomatoid histotype. C1q avidly bound high and low molecular weight hyaluronic acid via its globular domain. C1q bound to hyaluronic acid was able to induce adhesion and proliferation of mesothelioma cells via enhancement of ERK1/2, SAPK/JNK and p38 phosphorylation; however, it did not activate the complement cascade. Consistent with the modular organisation of the globular domain, we demonstrated that C1q may bind to hyaluronic acid through ghA module, whereas it may interact with human mesothelioma cells through the ghC. In conclusion, C1q highly expressed in MPM binds to hyaluronic acid and enhances the tumour growth promoting cell adhesion and proliferation. These data can help develop novel diagnostic markers and molecular targets for MPM.