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A wide range of microbial pathogens is capable of entering the gastrointestinal tract, causing infectious diarrhea and colitis. A finely tuned balance between different cytokines is necessary to eradicate the microbial threat and to avoid infection complications. The current study identified IL-33 as a critical regulator of the immune response to the enteric pathogen Citrobacter rodentium. We observed that deficiency of the IL-33 signaling pathway attenuates bacterial-induced colitis. Conversely, boosting this pathway strongly aggravates the inflammatory response and makes the mice prone to systemic infection. Mechanistically, IL-33 mediates its detrimental effect by enhancing gut permeability and by limiting the induction of protective T helper 17 cells at the site of infection, thus impairing host defense mechanisms against the enteric pathogen. Importantly, IL-33-treated infected mice supplemented with IL-17A are able to resist the otherwise strong systemic spreading of the pathogen. These findings reveal a novel IL-33/IL-17A crosstalk that controls the pathogenesis of Citrobacter rodentium-driven infectious colitis. Manipulating the dynamics of cytokines may offer new therapeutic strategies to treat specific intestinal infections.

The incidence of gastrointestinal infections continues to increase, and infectious colitis contributes significantly to morbidity and mortality worldwide. Carcinoembryonic antigen-related cell adhesion molecule 1 (CEACAM1) has been discovered to be strongly involved in the intestinal homeostasis. However, whether intestinal CEACAM1 expression has an impact on the control of infectious colitis remains elusive. Citrobacter rodentium (C. rodentium) is a gram-negative enteric pathogen that induces colonic inflammation in mice, with a critical role for CD4(+) T cell but not CD8(+) T cell immunity to primary infection. Here, we show that Ceacam1(−/−) mice are much more susceptible to C. rodentium infection than wildtype mice, which is mediated by a defect in the intestinal barrier and, surprisingly, by a dysregulated CD8(+) T cell but not CD4(+) T cell response in the colon. CEACAM1 expression is essential for the control of CD8(+) T cell immunity, as CEACAM1 deficiency during C. rodentium infection inhibits CD8(+) T cell exhaustion. We conclude that CEACAM1 is an important regulator of CD8(+) T cell function in the colon, and blocking CEACAM1 signaling to activate CD8(+) T cells may have unforeseen side effects.

This paper aims to review data regarding two determinants of comorbidity between depression and obesity, i.e., the role of disturbed gut microbiome in their genesis and of diets in their treatment. Obesity and major depressive disorders (MDD) are highly comorbid, the “metabolic” (obese) subtype of MDD affects about one third of all individuals with MDD. There is an urgent need for better therapies strategies, which may include specific dietary measures. A diet low in carbohydrates (low-carb), effective in obesity, may be beneficial also in MDD. However, the underlying mechanisms have not yet been elucidated. Recent data suggest a key role of gut microbiota, neuroplasticity, and neuroinflammation in obesity and MDD. We will focus on the brain-derived neurotrophic factor (BDNF), and microglial fractalkine, a main modulator of neuroinflammation. BDNF and fractalkine may be involved in “metabolic” depression. Future studies may uncover specific pathophysiological pathways in affected patients towards more efficient causal therapies.

Primary and recurrent cytomegalovirus (CMV) infections frequently cause CMV colitis in immunocompromised as well as inflammatory bowel disease (IBD) patients. Additionally, colitis occasionally occurs upon primary CMV infection in patients who are apparently immunocompetent. In both cases, the underlying pathophysiologic mechanisms are largely elusive - in part due to the lack of adequate access to specimens. We employed the mouse cytomegalovirus (MCMV) model to probe into the association between CMV and colitis. During acute primary MCMV infection of immunocompetent mice, the gut microbial composition was affected within the first 5 days post-infection as manifested by an altered ratio of the Firmicutes to Bacteroidetes phyla. Interestingly, these microbial changes incited with high-titer MCMV replication in the colon, mild crypt necrosis and increased colonic pro-inflammatory cytokine levels. Further analyses revealed that murine and human intestinal epithelial cell line as well as primary intestinal crypt cells/ organoids represent direct targets of CMV accompanied by increased cell mortality upon infection. Accordingly, in vivo MCMV infection disrupted the intestinal epithelial barrier and increased apoptosis of intestinal epithelial cells. In summary, our data show that CMV induces colitis in immunocompetent hosts by altering the intestinal homeostasis.

Summary A reciprocal interaction exists between the gut microbiota and the immune system. Regulatory T (Treg) cells are important for controlling immune responses and for maintaining the intestinal homeostasis but their precise influence on the gut microbiota is unclear. We studied the effects of Treg cell depletion on inflammation of the intestinal mucosa and analysed the gut microbiota before and after depletion of Treg cells using the DEpletion of REGulatory T cells (DEREG) mouse model. DNA was extracted from stool samples of DEREG mice and wild‐type littermates at different time‐points before and after diphtheria toxin application to deplete Treg cells in DEREG mice. The V3/V4 region of the 16S rRNA gene was used for studying the gut microbiota with Illumina MiSeq paired ends sequencing. Multidimensional scaling separated the majority of gut microbiota samples from late time‐points after Treg cell depletion in DEREG mice from samples of early time‐points before Treg cell depletion in these mice and from gut microbiota samples of wild‐type mice. Treg cell depletion in DEREG mice was accompanied by an increase in the relative abundance of the phylum Firmicutes and by intestinal inflammation in DEREG mice 20 days after Treg cell depletion, indicating that Treg cells influence the gut microbiota composition. In addition, the variables cage, breeding and experiment number were associated with differences in the gut microbiota composition and these variables should be respected in murine studies., In this study we showed that temporal regulatory T (Treg) cell depletion in DEpletion of REGulatory T cells mice was accompanied by an increase of the relative abundance of the phylum Firmicutes of the gut microbiota, indicating that Treg cells affect the gut microbiota composition. In addition, Treg cell depletion was associated with intestinal inflammation. Furthermore, the variables cage, breeding and experiment number affected the gut microbiota composition and should be respected in murine gut microbiota studies

Despite significant efforts, vaccines are not yet available for every infectious pathogen, and the search for a protective approach to prevent the establishment of chronic infections, i.e., with HIV, continues. Immune checkpoint therapies targeting inhibitory receptors, such as PD-1, have shown impressive results against solid tumors., PD-1-targeted therapies have shown modest antiviral effects in preclinical models of chronic viral infection. Thus, novel therapy protocols are necessary to enhance T cell immunity and viral control to overcome T cell dysfunction and immunosuppression. Here, we demonstrate that nanoparticle-based therapeutic vaccination improved PD-1-targeted therapy during chronic infection with Friend retrovirus (FV). Prevention of inhibitory signals by blocking PD-L1 in combination with therapeutic vaccination with nanoparticles containing the microbial compound CpG and a CD8+ T cell Gag epitope peptide synergistically enhanced functional virus-specific CD8+ T cell responses and improved viral clearance. We characterized the CD8+ T cell populations that were affected by this combination therapy, demonstrating that new effector cells were generated and that exhausted CD8+ T cells were reactivated at the same time. While CD8+ T cells with high PD-1 (PD-1hi) expression turned into a large population of granzyme B-expressing CD8+ T cells after combination therapy, CXCR5-expressing follicular cytotoxic CD8+ T cells also expanded to a high degree. Thus, our study describes a very efficient approach to enhance virus control and may help us to understand the mechanisms of combination immunotherapy reactivating CD8+ T cell immunity. A better understanding of CD8+ T cell immunity during combination therapy will be important for developing efficient checkpoint therapies against chronic viral infections and cancer.

Epigenetic modifications play critical roles in regulating cell lineage differentiation, but the epigenetic mechanisms guiding specific differentiation steps within a cell lineage have rarely been investigated. To decipher such mechanisms, we used the defined transition from proliferating (PC) into hypertrophic chondrocytes (HC) during endochondral ossification as a model. We established a map of activating and repressive histone modifications for each cell type. ChromHMM state transition analysis and Pareto-based integration of differential levels of mRNA and epigenetic marks revealed that differentiation-associated gene repression is initiated by the addition of H3K27me3 to promoters still carrying substantial levels of activating marks. Moreover, the integrative analysis identified genes specifically expressed in cells undergoing the transition into hypertrophy. Investigation of enhancer profiles detected surprising differences in enhancer number, location, and transcription factor binding sites between the two closely related cell types. Furthermore, cell type-specific upregulation of gene expression was associated with increased numbers of H3K27ac peaks. Pathway analysis identified PC-specific enhancers associated with chondrogenic genes, whereas HC-specific enhancers mainly control metabolic pathways linking epigenetic signature to biological functions. Since HC-specific enhancers show a higher conservation in postnatal tissues, the switch to metabolic pathways seems to be a hallmark of differentiated tissues. Surprisingly, the analysis of H3K27ac levels at super-enhancers revealed a rapid adaption of H3K27ac occupancy to changes in gene expression, supporting the importance of enhancer modulation for acute alterations in gene expression. © 2021 The Authors. Journal of Bone and Mineral Research published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research (ASBMR).

Colorectal cancer is one of the most frequent malignancies worldwide. Despite considerable progress in early detection and treatment, there is still an unmet need for novel antitumor therapies, particularly in advanced colorectal cancer. Regulatory T cells (Treg) are increased in the peripheral blood and tumor tissue of patients with colorectal cancer. Recently, transient ablation of tumor-associated Tregs was shown to foster CD8+ T-cell–mediated antitumoral immunity in murine colorectal cancer models. However, before considering therapies on targeting Tregs in patients with cancer, detailed knowledge of the phenotype and features of tumor-associated Tregs is indispensable. Here, we demonstrate in a murine model of inflammation-induced colorectal cancer that tumor-associated Tregs are mainly of thymic origin and equipped with a specific set of molecules strongly associated with enhanced migratory properties. Particularly, a dense infiltration of Tregs in mouse and human colorectal cancer lesions correlated with increased expression of the orphan chemoattractant receptor GPR15 on these cells. Comprehensive gene expression analysis revealed that tumor-associated GPR15+ Tregs have a Th17-like phenotype, thereby producing IL17 and TNFα. Gpr15 deficiency repressed Treg infiltration in colorectal cancer, which paved the way for enhanced antitumoral CD8+ T-cell immunity and reduced tumorigenesis. In conclusion, GPR15 represents a promising novel target for modifying T-cell–mediated antitumoral immunity in colorectal cancer. Significance: The G protein–coupled receptor 15, an unconventional chemokine receptor, directs Tregs into the colon, thereby modifying the tumor microenvironment and promoting intestinal tumorigenesis. See related commentary by Chakraborty and Zappasodi, p. 2817

Neuropilin-1 (Nrp-1) is a well described marker molecule for CD4+Foxp3+ thymus-derived regulatory T cells (Tregs). In addition, a small population of CD4+Foxp3− conventional (conv) T cells expresses Nrp-1 in naive mice, and Nrp-1 expression has been described to be upregulated on activated CD4+ T cells. However, the function of Nrp-1 expression on CD4+ non-Tregs still remains elusive. In this study, we demonstrate that Nrp-1 expression was induced upon stimulation of CD4+Foxp3− T cells in vitro and during an ongoing immune response in vivo. This activation-induced Nrp-1+CD4+ T cell subset (iNrp-1+) showed a highly activated phenotype in terms of elevated CD25 and CD44 expression, enhanced production of proinflammatory cytokines, and increased proliferation compared with the Nrp-1−CD4+ counterpart. In contrast, Nrp-1+CD4+Foxp3− conv T cells from naive mice (nNrp-1+) were dysfunctional. nNrp-1+CD4+ conv T cells upregulated activation-associated molecules to a lesser extent, exhibited impaired proliferation and produced fewer proinflammatory cytokines than Nrp-1−CD4+ conv T cells upon stimulation in vitro. Moreover, the expression of PD-1 and CTLA-4 was significantly higher on nNrp-1+CD4+Foxp3− T cells compared with iNrp-1+CD4+Foxp3− T cells and Nrp-1−CD4+Foxp3− T cells after stimulation and under homeostatic conditions. Strikingly, transfer of Ag-specific iNrp-1+CD4+ conv T cells aggravated diabetes development, whereas Ag-specific nNrp-1+CD4+ conv T cells failed to induce disease in a T cell transfer model of diabetes. Overall, our results indicate that Nrp-1 expression has opposite functions in recently activated CD4+ non-Tregs compared with CD4+ non-Tregs from naive mice.

In hematopoietic cell transplantation (HCT), permissive HLA-DPB1 mismatches between patients and their unrelated donors are associated with improved outcomes compared with nonpermissive mismatches, but the underlying mechanism is incompletely understood. Here, we used mass spectrometry, T-cell receptor-β (TCRβ) deep sequencing, and cellular in vitro models of alloreactivity to interrogate the HLA-DP immunopeptidome and its role in alloreactive T-cell responses. We find that permissive HLA-DPB1 mismatches display significantly higher peptide repertoire overlaps compared with their nonpermissive counterparts, resulting in lower frequency and diversity of alloreactive TCRβ clonotypes in healthy individuals and transplanted patients. Permissiveness can be reversed by the absence of the peptide editor HLA-DM or the presence of its antagonist, HLA-DO, through significant broadening of the peptide repertoire. Our data establish the degree of immunopeptidome divergence between donor and recipient as the mechanistic basis for the clinically relevant permissive HLA-DPB1 mismatches in HCT and show that permissiveness is dependent on HLA-DM–mediated peptide editing. Its key role for harnessing T-cell alloreactivity to HLA-DP highlights HLA-DM as a potential novel target for cellular and immunotherapy of leukemia.

The pro-inflammatory cytokine TNF-α was silenced by treating MODE-K cells with triple-shell calcium phosphate nanoparticles. These consisted of a core of calcium phosphate, followed by a shell of siRNA, then a shell of calcium phosphate to protect the siRNA from nucleases and finally a shell of poly(ethyleneimine) for colloidal stabilization and to give the particles a positive charge. First, the gene silencing efficiency was demonstrated with HeLa-eGFP cells and determined by manually counting the green fluorescent cells, by quantitative FACS analysis of the green fluorescence per cell, and by qPCR at the RNA level. Cell counting gave the highest degrees of eGFP expression, but FACS and qPCR gave more accurate data as they are not probing the cell colour (green or not green) only as yes/no property. This was transposed to the inflammatory relevant mouse cell line MODE-K that was previously stimulated with LPS to induce the expression of TNF-α. By application of the nanoparticles, the TNF-α expression was reduced almost to the original level, as shown by qPCR. Thus, calcium phosphate nanoparticles are well suited to reduce inflammatory reactions by silencing the corresponding cytokines, e.g. TNF-α.

Avidin was covalently conjugated to the surface of calcium phosphate nanoparticles, coated with a thin silica shell and terminated by sulfhydryl groups (diameter of the solid core about 50 nm), with a bifunctional crosslinker connecting the amino groups of avidin to the sulfhydryl group on the nanoparticle surface. This led to a versatile nanoparticle system where all kinds of biotinylated (bio-)molecules can be easily attached to the surface by the non-covalent avidin-biotin-complex formation. It also permits the attachment of different biomolecules on the same nanoparticle (heteroavidity), creating a modular system for specific applications in medicine and biology. The variability of the binding to the nanoparticle surface of the was demonstrated with various biotinylated molecules, i.e. fluorescent dyes and antibodies. The accessibility of the conjugated avidin was demonstrated by a fluorescence-quenching assay. About 2.6 binding sites for biotin were accessible on each avidin tetramer. Together with a number of about 240 avidin tetramer units per nanoparticle, this offers about 600 binding sites for biotin on each nanoparticle. The uptake of fluorescently labelled avidin-conjugated calcium phosphate nanoparticles by HeLa cells showed the co-localization of fluorescent avidin and fluorescent biotin, indicating the stability of the complex under cell culture conditions. CD11c-antibody functionalized nanoparticles specifically targeted antigen-presenting immune cells (dendritic cells; DCs) in vitro and in vivo (mice) with high efficiency. Statement of significance Calcium phosphate nanoparticles have turned out to be very useful transporters for biomolecules into cells, both in vitro and in vivo. However, their covalent surface functionalization with antibodies, fluorescent dyes, or proteins requires a separate chemical synthesis for each kind of surface molecule. We have therefore developed avidin-terminated calcium phosphate nanoparticles to which all kinds of biotinylated molecules can be easily attached, also as a mixture of two or more molecules. This non-covalent bond is stable both in cell culture and after injection into mice in vivo. Thus, we have created a highly versatile system for many applications, from the delivery of biomolecules over the targeting of cells and tissue to in vivo imaging.

Closed circulatory systems underlie the function of vertebrate organs, but in long bones their structure is unclear although they constitute the exit route for bone marrow (BM) leukocytes. To understand neutrophil migration from BM, we studied the vascular system of murine long bones. Here, in a mouse model, we show that hundreds of capillaries originate in BM, traverse cortical bone perpendicularly along the shaft and connect to the periosteal circulation. Structures similar to these trans-cortical vessels (TCVs) also exist in human limb bones. TCVs express arterial or venous markers and transport neutrophils. Furthermore, over 80% of arterial and 59% of venous blood passes through TCVs. Genetic and drug-mediated modulation of osteoclast count and activity leads to substantial changes in TCV numbers. In a murine model of chronic arthritic bone inflammation, new TCVs develop within weeks. Our data indicate that TCVs are a central component of the closed circulatory system in long bones and may represent an important route for immune cell export from BM.

CA Hansen The enzyme acid sphingomyelinase (ASM) hydrolyzes sphingomyelin to ceramide and is thereby involved in several cellular processes such as differentiation, proliferation, and apoptosis in different cell types. However, the function of ASM in T cells is still not well characterized. Here, we used T cell-specific ASM overexpressing mice (t-ASM/CD4cre) to clarify the impact of cell-intrinsic ASM activity on T cell function in vitro and in vivo. We showed that t-ASM/CD4cre mice exhibit decreased frequencies of Foxp3(+) T regulatory cells (Tregs) within the spleen. Enforced T cell-specific ASM expression resulted in less efficient induction of Tregs and promoted differentiation of CD4(+)CD25(-) naive T cells into IFN-gamma producing Th1 cells in vitro. Further analysis revealed that ASM-overexpressing T cells from t-ASM/CD4cre mice show elevated T cell receptor (TCR) signaling activity accompanied with increased proliferation upon stimulation in vitro. Plasmodium yoelii infection of t-ASM/CD4cre mice resulted in enhanced T cell activation and was associated with reduced parasitemia in comparison to infected controlmice. Hence, our results provide evidence that ASM activity modulates T cell function in vitro and in vivo.

The composition of immune infiltrates strongly affects the prognosis of patients with colorectal cancer (CRC). Interleukin (IL)-33 and regulatory T cells (Tregs) in the tumor microenvironment have been separately implicated in CRC; however their contribution to intestinal carcinogenesis is still controversial. Here, we reveal that IL-33 signaling promotes CRC by changing the phenotype of Tregs. In mice with CRC, tumor-infiltrating Tregs preferentially upregulate IL-33 receptor (ST2), and IL-33/ST2 signaling positively correlates with tumor number and size. Transcriptomic and flow cytometry analyses demonstrate that ST2 expression induces a more activated and migratory phenotype in FOXP3+ Tregs, which favors their accumulation in the tumor environment. Consequently, genetic ablation of St2 reduces Treg infiltration and concomitantly enhances the frequencies of effector CD8+ T cells, thereby restraining CRC. Mechanistically, IL-33 curtails IL-17 production by FOXP3+ Tregs and inhibits Th17 differentiation. In humans, numbers of activated ST2-expressing Tregs are increased in blood and tumor lesions of CRC patients, suggesting a similar mode of regulation. Together, these data indicate a central role of IL-33/ST2 signaling in shaping an immunosuppressive environment during intestinal tumorigenesis. Blockade of this pathway may provide a strategy to modulate the composition of CRC immune infiltrates.

Clinical administration of Interferon α (IFNα) resulted in limited therapeutic success against some viral infections. Immune modulation of CD8+ T cell responses during IFNα therapy is believed to play a pivotal role in promoting viral clearance. However, these clinical studies primarily focused on IFNα subtype 2. To date, the immunomodulatory roles of the remaining 10-13 IFNα subtypes remains poorly understood, thereby precluding assessments of their potential for more effective treatments. Here, we report that virus-specific CD8+ T cell responses were influenced to various extents by individual IFNα subtypes. IFNα4, 6 and 9 had the strongest effects on CD8+ T cells, including antiproliferative effects, improved cytokine production and cytotoxicity. Interestingly, augmented cytokine responses were dependent on IFNα subtype stimulation of dendritic cells (DCs), while antiproliferative effects and cytotoxicity were mediated by IFNAR signaling in either CD8+ T cells or DCs. Thus, precise modulation of virus-specific CD8+ T cell responses may be feasible for specific antiviral immunotherapies through careful selection and administration of individual IFNα subtypes.

Radiation-induced pulmonary fibrosis is a severe side effect of thoracic irradiation, but its pathogenesis remains poorly understood and no effective treatment is available. In this study, we investigated the role of the extracellular adenosine as generated by the ecto-5′-nucleotidase CD73 in fibrosis development after thoracic irradiation. Exposure of wild-type C57BL/6 mice to a single dose (15 Gray) of whole thorax irradiation triggered a progressive increase in CD73 activity in the lung between 3 and 30 weeks postirradiation. In parallel, adenosine levels in bronchoalveolar lavage fluid (BALF) were increased by approximately 3-fold. Histologic evidence of lung fibrosis was observed by 25 weeks after irradiation. Conversely, CD73-deficient mice failed to accumulate adenosine in BALF and exhibited significantly less radiation-induced lung fibrosis (P < 0.010). Furthermore, treatment of wild-type mice with pegylated adenosine deaminase or CD73 antibodies also significantly reduced radiation-induced lung fibrosis. Taken together, our findings demonstrate that CD73 potentiates radiation-induced lung fibrosis, suggesting that existing pharmacologic strategies for modulating adenosine may be effective in limiting lung toxicities associated with the treatment of thoracic malignancies. Cancer Res; 76(10); 3045–56. ©2016 AACR.

Recently, we demonstrated elevated numbers of CD4(+) Foxp3(+) regulatory T (Treg) cells in Plasmodium yoelii-infected mice contributing to the regulation of anti-malarial immune response. However, it remains unclear whether this increase in Treg cells is due to thymus-derived Treg cell expansion or induction of Treg cells in the periphery. Here, we show that the frequency of Foxp3(+) Treg cells expressing neuropilin-1 (Nrp-1) decreased at early time-points during P. yoelii infection, whereas percentages of Helios(+) Foxp3(+) Treg cells remained unchanged. Both Foxp3(+) Nrp-1(+) and Foxp3(+) Nrp-1(-) Treg cells from P. yoelii-infected mice exhibited a similar T-cell receptor V beta chain usage and methylation pattern in the Treg-specific demethylation region within the foxp3 locus. Strikingly, we did not observe induction of Foxp3 expression in Foxp3(-) T cells adoptively transferred to P. yoelii-infected mice. Hence, our results suggest that P. yoelii infection triggered expansion of naturally occurring Treg cells rather than de novo induction of Foxp3(+) Treg cells.

The endocytotic c-type lectin receptor DEC-205 is highly expressed on immature dendritic cells. In previous studies, it was shown that antigen-targeting to DEC-205 is a useful tool for the induction of antigen-specific Foxp3(+) regulatory T cells and thereby can prevent inflammatory processes. However, whether this approach is sufficient to mediate tolerance in mucosal tissues like the gut is unknown. In this study, we established a new mouse model in which the adoptive transfer of naive hemagglutinin (HA)-specific CD4(+)Foxp3(-) T cells into VILLIN-HA transgenic mice leads to severe colitis. To analyze if antigen-targeting to DEC-205 could protect against inflammation of the gut, VILLIN-HA transgenic mice were injected with an antibody-antigen complex consisting of the immunogenic HA110-120 peptide coupled to an α-DEC-205 antibody (DEC-HA) before adoptive T cell transfer. DEC-HA-treated mice showed significantly less signs of intestinal inflammation as was demonstrated by reduced loss of body weight and histopathology in the gut. Strikingly, abrogated intestinal inflammation was mediated via the conversion of naive HA-specific CD4(+)Foxp3(-) T cells into HA-specific CD4(+)Foxp3(+) regulatory T cells. In this study, we provide evidence that antigen-targeting to DEC-205 can be utilized for the induction of tolerance in mucosal organs that are confronted with large numbers of exogenous antigens.

MircoRNAs (miRs) are small molecules that regulate gene expression at the posttranscriptional level. They have been proposed to be involved in the regulation of several immune responses including autoimmunity. Here, we identified miR-183 and miR-96 to be highly expressed in CD4+ T cells from peripheral blood of Graves' orbitopathy (GO) patients as well as in human and murine T cells upon activation in vitro. By using Luciferase-based binding assays, we identified EGR-1 as target for miR-183 and miR-96. Overexpression of miR-183 and miR-96 in murine CD4+ T cells by retroviral gene transfer resulted in decreased EGR-1 and PTEN expression, elevated Akt phosphorylation and enhanced proliferation. In contrast, treatment of murine CD4+ T cells with specific antagomiRs increased EGR-1 and PTEN expression and interfered with the proliferative activity upon stimulation in vitro. Strikingly, adoptive transfer of miR-183 and miR-96 overexpressing antigen-specific T cells into INS-HA/Rag2KO mice accelerated the development of autoimmune diabetes, whereas transfer of antagomiR-treated cells delayed the disease onset. These results indicate that miR-183 and miR-96 have the ability to regulate the strength of T cell activation and thereby the development and severity of T cell-dependent autoimmune diseases.

Due to their cytotoxic activities, many anticancer drugs cause extensive damage to the intestinal mucosa and have antibiotic activities. Here we show that cisplatin induces significant changes in the repertoire of intestinal commensal bacteria that exacerbate mucosal damage. Restoration of the microbiota through fecal-pellet gavage drives healing of cisplatin-induced intestinal damage. Bacterial translocation to the blood stream is correspondingly abrogated, resulting in a significant reduction in systemic inflammation, as evidenced by decreased serum IL-6 and reduced mobilization of granulocytes. Mechanistically, reversal of dysbiosis in response to fecal gavage results in the production of protective mucins and mobilization of CD11b(+) myeloid cells to the intestinal mucosa, which promotes angiogenesis. Administration of Ruminococcus gnavus, a bacterial strain selectively depleted by cisplatin treatment, could only partially restore the integrity of the intestinal mucosa and reduce systemic inflammation, without measurable increases in the accumulation of mucin proteins. Together, our results indicate that reconstitution of the full repertoire of intestinal bacteria altered by cisplatin treatment accelerates healing of the intestinal epithelium and ameliorates systemic inflammation. Therefore, fecal microbiota transplant could paradoxically prevent life-threatening bacteremia in cancer patients treated with chemotherapy.

A universal influenza vaccine must provide protection against antigenically divergent influenza viruses either through broadly neutralizing antibodies or cross-reactive T cells. Here, intranasal immunizations with recombinant adenoviral vectors (rAd) encoding hemagglutinin (HA) and nucleoprotein (NP) in combination with rAd-Interleukin-(IL)-1 beta or rAd-IL-18 were evaluated for their efficacy in BALB/c mice. Mucosal delivery of rAd-IL-1 beta enhanced HA-specific antibody responses including strain-specific neutralizing antibodies. Nevertheless, the beneficial effects on the local T cell responses were much more impressive reflected by increased numbers of CD103(+)CD69(+) tissue-resident memory T cells (T-RM). This increased immunogenicity translated into superior protection against infections with homologous and heterologous strains including H1N1, pH1N1, H3N2, and H7N7. Inhibition of the egress of circulating T cells out of the lymph nodes during the heterologous infection had no impact on the degree of protection underscoring the unique potential of T-RM for the local containment of mucosal infections. The local co-expression of IL-1 beta and antigen lead to the activation of critical checkpoints in the formation of T-RM including activation of epithelial cells, expression of chemokines and adhesion molecules, recruitment of lung-derived CD103(+) DCs, and finally local T-RM imprinting. Given the importance of T-RM-mediated protection at mucosal barriers, this study has major implications for vaccine development.

Background: Type I interferon (IFN-I) predisposes to bacterial superinfections, an important problem during viral infection or treatment with interferon-alpha (IFN-α). IFN-I-induced neutropenia is one reason for the impaired bacterial control; however there is evidence that more frequent bacterial infections during IFN-α-treatment occur independently of neutropenia. Methods: We analyzed in a mouse model, whether Pseudomonas aeruginosa control is influenced by co-infection with the lymphocytic choriomeningitis virus (LCMV). Bacterial titers, numbers of neutrophils and the gene-expression of liver-lysozyme-2 were determined during a 24 hours systemic infection with P. aeruginosa in wild-type and Ifnar-/- mice under the influence of LCMV or poly(I:C). Results: Virus-induced IFN-I impaired the control of Pseudomonas aeruginosa. This was associated with neutropenia and loss of lysozyme-2-expression in the liver, which had captured P. aeruginosa. A lower release of IFN-I by poly(I:C)-injection also impaired the bacterial control in the liver and reduced the expression of liver-lysozyme-2. Low concentration of IFN-I after infection with a virulent strain of P. aeruginosa alone impaired the bacterial control and reduced lysozyme-2-expression in the liver as well. Conclusion: We found that during systemic infection with P. aeruginosa Kupffer cells quickly controlled the bacteria in cooperation with neutrophils. Upon LCMV-infection this cooperation was disturbed.

Sepsis is the dysregulated response of the host to systemic, mostly bacterial infection, and is associated with an enhanced susceptibility to life-threatening opportunistic infections. During polymicrobial sepsis, dendritic cells (DCs) secrete enhanced levels of interleukin (IL) 10 due to an altered differentiation in the bone marrow and contribute to the development of immunosuppression. We investigated the origin of the altered DC differentiation using murine cecal ligation and puncture (CLP), a model for human polymicrobial sepsis. Bone marrow cells (BMC) were isolated after sham or CLP operation, the cellular composition was analyzed, and bone marrow-derived DCs (BMDCs) were generated in vitro. From 24 h on after CLP, BMC gave rise to BMDC that released enhanced levels of IL-10. In parallel, a population of CD11chiMHCII+CD4+ DCs expanded in the bone marrow in a MyD88-dependent manner. Prior depletion of the CD11chiMHCII+CD4+ DCs from BMC in vitro reversed the increased IL-10 secretion of subsequently differentiating BMDC. The expansion of the CD11chiMHCII+CD4+ DC population in the bone marrow after CLP required the function of sphingosine 1-phosphate receptors and C-C chemokine receptor (CCR) 2, the receptor for C-C chemokine ligand (CCL) 2, but was not associated with monocyte mobilization. CD11chiMHCII+CD4+ DCs were identified as plasmacytoid DCs (pDCs) that had acquired an activated phenotype according to their increased expression of MHC class II and CD86. A redistribution of CD4+ pDCs from MHC class II- to MHC class II+ cells concomitant with enhanced expression of CD11c finally led to the rise in the number of CD11chiMHCII+CD4+ DCs. Enhanced levels of CCL2 were found in the bone marrow of septic mice and the inhibition of CCR2 dampened the expression of CD86 on CD4+ pDCs after CLP in vitro. Depletion of pDCs reversed the bias of splenic DCs toward increased IL-10 synthesis after CLP in vivo. Thus, during polymicrobial sepsis, CD4+ pDCs are activated in the bone marrow and induce functional reprogramming of differentiating BMDC toward an immunosuppressive phenotype. CA Flohe

Inflammatory bowel diseases (IBD) are chronic inflammatory disorders of the gastrointestinal tract, strongly associated with an increased risk of colorectal cancer development. Parasitic infections caused by helminths have been shown to modulate the host’s immune response by releasing immunomodulatory molecules and inducing regulatory T cells (Tregs). This immunosuppressive state provoked in the host has been considered as a novel and promising approach to treat IBD patients and alleviate acute intestinal inflammation. On the contrary, specific parasite infections are well known to be directly linked to carcinogenesis. Whether a helminth infection interferes with the development of colitis-associated colon cancer (CAC) is not yet known. In the present study, we demonstrate that the treatment of mice with the intestinal helminth Heligmosomoides polygyrus at the onset of tumor progression in a mouse model of CAC does not alter tumor growth and distribution. In contrast, H. polygyrus infection in the early inflammatory phase of CAC strengthens the inflammatory response and significantly boosts tumor development. Here, H. polygyrus infection was accompanied by long-lasting alterations in the colonic immune cell compartment, with reduced frequencies of colonic CD8+ effector T cells. Moreover, H. polygyrus infection in the course of dextran sulfate sodium (DSS) mediated colitis significantly exacerbates intestinal inflammation by amplifying the release of colonic IL-6 and CXCL1. Thus, our findings indicate that the therapeutic application of helminths during CAC might have tumor-promoting effects and therefore should be well-considered., Author summary Evidence from epidemiological studies indicates an inverse correlation between the incidence of certain immune-mediated diseases, including inflammatory bowel diseases, and exposure to helminths. As a consequence, helminth parasites were tested for treating IBD patients, resulting in clinical amelioration of the disease due to the induction of an immunosuppressive microenvironment. However, some infection–related cancers can be attributed to helminth infection, probably due to the generation of a microenvironment that might be conductive to the initiation and development of cancer. In the present study, we aimed to unravel the apparently controversial function of helminths in a mouse model of colitis-associated colon cancer. We show that helminth infection in the onset of colitis and colitis-associated colon cancer does not ameliorate colonic inflammation but activates intestinal immune cells that further facilitate tumor development. Therefore, a better understanding of mechanisms by which helminths modulate host immune responses in the gut should be defined precisely before application of helminths in autoimmune diseases like IBD.

Melanoma treatment has been revolutionized by antibody-based immunotherapies. IFNγ secretion by CD8+ T cells is critical for therapy efficacy having anti-proliferative and pro-apoptotic effects on tumour cells. Our study demonstrates a genetic evolution of IFNγ resistance in different melanoma patient models. Chromosomal alterations and subsequent inactivating mutations in genes of the IFNγ signalling cascade, most often JAK1 or JAK2, protect melanoma cells from anti-tumour IFNγ activity. JAK1/2 mutants further evolve into T-cell-resistant HLA class I-negative lesions with genes involved in antigen presentation silenced and no longer inducible by IFNγ. Allelic JAK1/2 losses predisposing to IFNγ resistance development are frequent in melanoma. Subclones harbouring inactivating mutations emerge under various immunotherapies but are also detectable in pre-treatment biopsies. Our data demonstrate that JAK1/2 deficiency protects melanoma from anti-tumour IFNγ activity and results in T-cell-resistant HLA class I-negative lesions. Screening for mechanisms of IFNγ resistance should be considered in therapeutic decision-making., IFNγ secretion by CD8+ T cells is critical for immunotherapy efficacy. In this study, the authors show that melanoma patients can become resistant to immunotherapy by acquiring chromosomal alterations and subsequent inactivating mutations in genes of the IFNγ signalling cascade, most often JAK1 or JAK2.

Cytomegalovirus (CMV) establishes lifelong chronic infection in its host with mostly asymptomatic or only mild disease, but under immunosuppressive conditions the virus can reactivate and infection can cause life-threatening disease. CMV has evolved several mechanisms to escape from host's immunity, allowing persistence of the virus. Until now, it remains elusive whether regulatory T cells (Tregs) have an impact on insufficient host immune response against the virus in this context. In the present study, we provide evidence that CD4(+)Foxp3(+) naturally occurring Tregs (nTregs) as well as CD4(+)Foxp3(-)IL-10(+)-induced Tregs (iTregs) interfere with an effective anti-mouse CMV (mCMV) immune response. Depletion of Foxp3(+) Tregs by using DEREG mice resulted in enhanced T-cell activation as measured by the expression of CD62L, granzyme B and interferon (IFN)-γ and was associated with reduced viral titers in salivary glands, the organ where mCMV mainly persists. Moreover, we identified CD4(+)Foxp3(-) T cells to produce elevated levels of the immunosuppressive cytokine IL-10 at early time points during mCMV infection. Analysis of T-cell activation and viral replication in mCMV-infected IL-10(flox/flox) × CD4-cre mice and IL-10(flox/flox) × FIC mice revealed that T-cell-specific inactivation of IL-10, but not Foxp3(+) Treg-specific IL-10 ablation alone, resulted in elevated IFN-γ production by T cells associated with a significant decrease in viral loads in salivary glands. Thus, our data illustrate a crucial role for CD4(+)Foxp3(+) nTregs as well as IL-10-producing CD4(+)Foxp3(-) iTregs in the regulation of appropriate T-cell responses and viral clearance during mCMV infection.

For subunit vaccines, adjuvants play a key role in shaping the magnitude, persistence and form of targeted antigen-specific immune response. Flagellin is a potent immune activator by bridging innate inflammatory responses and adaptive immunity and an adjuvant candidate for clinical application. Calcium phosphate nanoparticles are efficient carriers for different biomolecules like DNA, RNA, peptides and proteins. Flagellin-functionalized calcium phosphate nanoparticles were prepared and their immunostimulatory effect on the innate immune system, i.e. the cytokine production, was studied. They induced the production of the proinflammatory cytokines IL-8 (Caco-2 cells) and IL-1β (bone marrow-derived macrophages; BMDM) in vitro and IL-6 in vivo after intraperitoneal injection in mice. The immunostimulation was more pronounced than with free flagellin.

The uptake of calcium phosphate nanoparticles (diameter 120nm) with different charge by HeLa cells was studied by flow cytometry. The amount of uptaken nanoparticles increased with increasing concentration of nanoparticles in the cell culture medium. Several inhibitors of endocytosis and macropinocytosis were applied to elucidate the uptake mechanism of nanoparticles into HeLa cells: wortmannin, LY294002, nocodazole, chlorpromazine and nystatin. Wortmannin and LY294002 strongly reduced the uptake of anionic nanoparticles, which indicates macropinocytosis as uptake mechanism. For cationic nanoparticles, the uptake was reduced to a lesser extent, indicating a different uptake mechanism. The localization of nanoparticles inside the cells was investigated by conjugating them with the pH-sensitive dye SNARF-1. The nanoparticles were localized in lysosomes after 3h of incubation.

The ability of vaccines to induce T cell responses is crucial for preventing diseases caused by viruses or bacteria. Nanoparticles (NPs) are considered an efficient tool for inducing potent immune responses. In this study, we describe a novel vaccination approach with biodegradable calcium phosphate (CaP) NPs that serve as carrier of immunoactive TLR9 ligand (CpG) combined with a viral Ag from the influenza A virus hemagglutinin. Functionalized CaP NPs were efficiently taken up by dendritic cells in vivo and elicited a potent T cell–mediated immune response in immunized mice with high numbers of IFN-γ–producing CD4+ and CD8+ effector T cells. Most importantly, both i.p. and intranasal immunization with these NPs offered protection in a mouse model of influenza virus infection. This study demonstrates the great potential of CaP NPs as a novel vaccination tool that offers substantial flexibility for several infection models.

Background/Aims: Hypoxia occurs in many pathological conditions, including inflammation and cancer. Within this context, hypoxia was shown to inhibit but also to promote T cell responses. Due to this controversial function, we aimed to explore whether an insufficient anti-tumour response during colitis-associated colon cancer could be ascribed to a hypoxic microenvironment. Methods: Colitis-associated colon cancer was induced in wildtype mice, and hypoxia as well as T cell immunity were analysed in the colonic tumour tissues. In addition, CD4+ effector T cells and regulatory T cells were cultured under normoxic and hypoxic conditions and examined regarding their phenotype and function. Results: We observed severe hypoxia in the colon of mice suffering from colitis-associated colon cancer that was accompanied by a reduced differentiation of CD4+ effector T cells and an enhanced number and suppressive activity of regulatory T cells. Complementary ex vivo and in vitro studies revealed that T cell stimulation under hypoxic conditions inhibited the differentiation, proliferation and IFN-γ production of TH1 cells and enhanced the suppressive capacity of regulatory T cells. Moreover, we identified an active role for HIF-1α in the modulation of CD4+ T cell functions under hypoxic conditions. Conclusion: Our data indicate that oxygen availability can function as a local modulator of CD4+ T cell responses and thus influences tumour immune surveillance in inflammation-associated colon cancer.

Background Regulatory T cells (Tregs) have been shown to limit anti-viral immunity during chronic retroviral infection and to restrict vaccine-induced T cell responses. The objective of the study was to assess whether a combinational therapy of nanoparticle-based therapeutic vaccination and concomitant transient ablation of Tregs augments anti-viral immunity and improves virus control in chronically retrovirus-infected mice. Therefore, chronically Friend retrovirus (FV)-infected mice were immunized with calcium phosphate (CaP) nanoparticles functionalized with TLR9 ligand CpG and CD8+ or CD4+ T cell epitope peptides (GagL85–93 or Env gp70123–141) of FV. In addition, Tregs were ablated during the immunization process. Reactivation of CD4+ and CD8+ effector T cells was analysed and the viral loads were determined. Results Therapeutic vaccination of chronically FV-infected mice with functionalized CaP nanoparticles transiently reactivated cytotoxic CD8+ T cells and significantly reduced the viral loads. Transient ablation of Tregs during nanoparticle-based therapeutic vaccination strongly enhanced anti-viral immunity and further decreased viral burden. Conclusion Our data illustrate a crucial role for CD4+ Foxp3+ Tregs in the suppression of anti-viral T cell responses during therapeutic vaccination against chronic retroviral infection. Thus, the combination of transient Treg ablation and therapeutic nanoparticle-based vaccination confers robust and sustained anti-viral immunity. Electronic supplementary material The online version of this article (doi:10.1186/s12977-016-0258-9) contains supplementary material, which is available to authorized users.

There is an increasing body of evidence that heroin addiction is associated with severe alterations in immune function, which might contribute to an increased risk to contract infectious diseases like hepatitis B and C or HIV. However, the impact of heroin consumption on the CD4(+) T cell compartment is not well understood. Therefore, we analyzed the frequency and functional phenotype of CD4(+) T cells as well as immune-suppressive CD4(+)CD25(high) regulatory T cells (Tregs) isolated from the peripheral blood of opiate addicts currently abusing heroin (n=27) in comparison to healthy controls (n=25) and opiate addicts currently in opioid maintenance treatment (OMT; n=27). Interestingly, we detected a significant increase in the percentage of CD4(+)CD25(high) Tregs in the peripheral blood of heroin addicted patients in contrast to patients in OMT. The proliferative response of CD4(+) T cells upon stimulation with anti-CD3 and anti-CD28 antibodies was significantly decreased in heroin users, but could be restored by depletion of CD25(high) regulatory T cells from CD4(+) T cells to similar values as observed from healthy controls and patients in OMT. These results suggest that impaired immune responses observed in heroin users are related to the expansion of CD4(+)CD25(high) Tregs and more importantly, can be restored by OMT.

Objective: The high-mobility group box-1 protein (HMGB1) serves as the prototypic damage-associated molecular pattern molecule, interacting with a variety of defined pattern recognition receptors in the microenvironment of damaged or necrotic tissue. As regulatory T cells (Treg) play a crucial role in autoimmune diseases and tumor immune escape, the previously unexamined role of HMGB1 on the function of Treg is of great interest. Methods: Human CD4 1 CD25 1 CD127 2 Treg and CD4 1 CD25 2 CD127 1 conventional T cells (Tcon) were phenotypically analyzed for their constitutive as well as HMGB1-modulated expression of Toll-like receptors (TLR) and the receptor for advanced glycation end products (RAGE). Furthermore, the influence of recombinant and complexed HMGB1 from necrotic cell supernatant on the function of Treg and Tcon was investigated. Results: Treg express significantly higher levels of RAGE on the cell surface than Tcon, while levels of TLR4 are similar. HMGB1 modulates Treg biology by inducing migration and prolonging survival. Furthermore, HMGB1 enhances IL-10 release and Treg suppressive capacity in a RAGE-dependent manner. In addition, HMGB1 directly suppresses IFNg release of Tcon and inhibits their proliferation via TLR4. Conclusion: HMGB1 directly enhances immune inhibitory functions of Treg via RAGE-mediated mechanisms and limits the number and activity of Tcon. HMGB1 effects on Treg may alter immune reactivity in the setting of chronic inflammatory states such as cancer.

Neuropilin 1 mediates anti-tumor control by promoting regulatory T cell infiltration., Infiltration of Foxp3+ regulatory T (T reg) cells is considered to be a critical step during tumor development and progression. T reg cells supposedly suppress locally an effective anti-tumor immune response within tumor tissues, although the precise mechanism by which T reg cells infiltrate the tumor is still unclear. We provide evidence that Neuropilin 1 (Nrp-1), highly expressed by Foxp3+ T reg cells, regulates the immunological anti-tumor control by guiding T reg cells into the tumor in response to tumor-derived vascular endothelial growth factor (VEGF). We demonstrate for the first time that T cell–specific ablation of Nrp-1 expression results in a significant breakdown in tumor immune escape in various transplantation models and in a spontaneous, endogenously driven melanoma model associated with strongly reduced tumor growth and prolonged tumor-free survival. Strikingly, numbers of tumor-infiltrating Foxp3+ T reg cells were significantly reduced accompanied by enhanced activation of CD8+ T cells within tumors of T cell–specific Nrp-1–deficient mice. This phenotype can be reversed by adoptive transfer of Nrp-1+ T reg cells from wild-type mice. Thus, our data strongly suggest that Nrp-1 acts as a key mediator of Foxp3+ T reg cell infiltration into the tumor site resulting in a dampened anti-tumor immune response and enhanced tumor progression.

Calcium phosphate nanoparticles were coated with a shell of silica and covalently functionalized by silanization, either with thiol or with amino groups. This permits the covalent attachment of molecules like dyes or antibodies. Between the calcium phosphate surface and the outer silica shell, biomolecules like nucleic acids (DNA or siRNA) can be incorporated as cargo. This leads to cell-specific carriers of biomolecules into cells, e.g. for transfection, gene silencing or cell activation. The cellular uptake of antibody-coated calcium phosphate nanoparticles was demonstrated on two cell lines: HeLa (epithelial cell line) and MG-63 (osteoblast-like cell line). Furthermore, the functionalization of calcium phosphate nanoparticles with a dendritic cell-specific antibody (CD11c) led to a cell-specific targeting as shown with primary murine splenocytes. Thus, the successful coating of calcium phosphate nanoparticles with cell-specific antibodies makes them suitable for many clinical applications.

The intestinal immune system is constantly challenged by foreign antigens and commensal bacteria. Therefore, proper control of the intestinal microenvironment is required. One important arm of this regulatory network consists of regulatory T cells. In contrast to CD4(+) Foxp3(+) regulatory T cells, which have been well characterized, immunomodulatory CD8(+) T cells that express Foxp3 are less well defined in terms of their generation and function. Failures of these regulatory mechanisms contribute to the development of inflammatory bowel disease. In this study we demonstrate that the frequency of CD8(+) Foxp3(+) T cells is reduced in the peripheral blood of patients with ulcerative colitis. As these cells might play a currently underestimated role in the maintenance of intestinal homeostasis, we have investigated human and murine CD8(+) Foxp3(+) T cells generated by stimulating naive CD8(+) T cells in the presence of transforming growth factor-β and retinoic acid, mediators that are abundantly produced in the intestinal mucosa. These CD8(+) Foxp3(+) fully competent regulatory T cells show strong expression of regulatory molecules CD25, Gpr83 and CTLA-4 and exhibit cell-cell contact-dependent immunosuppressive activity in vitro. Our study illustrates a previously unappreciated critical role of CD8(+) Foxp3(+) T cells in controlling potentially dangerous T cells and in the maintenance of intestinal homeostasis.

Treg are endowed with immunosuppressive activities and have been proposed as promising targets for the therapy of autoimmune diseases. As the suppressive capacity of Treg depends on their migration into the affected tissues, we tested here whether modulation of Treg homing would enhance their capacity to suppress inflammation in mouse models of inflammatory bowel disease. Retinoic acid (RA) was used to induce the gut-specific homing receptor α₄β ₇ efficiently and, to some extent, the chemokine receptor CCR9 on in vitro expanded Treg. Upon transfer, RA-treated Treg were indeed more potent suppressors in an acute, small intestinal inflammation model, compared with Treg stimulated without RA. By contrast, the efficacy of Treg to resolve an established, chronic inflammation of the colon in the transfer colitis model was not affected by RA-treatment. In the latter model, a rapid loss of RA-induced α₄β₇ expression and de novo induction of α₄β₇ on previously negative cells was observed on transferred Treg, which implies that Treg acquire gut-seeking properties in vivo under inflammatory and/or lymphopenic conditions. Together, our data show that the induction of appropriate homing properties prior to transfer increases the protective potential of adoptively transferred Treg in acute, but not in chronic, inflammatory disorders of the gut. © 2010 Wiley-VCH Verlag GmbH & Co. KGaA.

Since the discovery of T helper type 1 and type 2 effector T cell subsets 20 years ago, inducible regulatory T cells and interleukin 17 (IL-17)-producing T helper cells have been added to the 'portfolio' of helper T cells. It is unclear how many more effector T cell subsets there may be and to what degree their characteristics are fixed or flexible. Here we show that transforming growth factor-beta, a cytokine at the center of the differentiation of IL-17-producing T helper cells and inducible regulatory T cells, 'reprograms' T helper type 2 cells to lose their characteristic profile and switch to IL-9 secretion or, in combination with IL-4, drives the differentiation of 'T(H)-9' cells directly. Thus, transforming growth factor-beta constitutes a regulatory 'switch' that in combination with other cytokines can 'reprogram' effector T cell differentiation along different pathways.

Regulatory T cells (T(regs)) have potential anti-inflammatory effects and are likely to be important in the pathogenesis of chronic inflammatory bowel disease (IBD). However, the induction and expansion of T(regs) at sites of mucosal inflammation are not yet fully understood and may involve antigen presentation by local dendritic cells (DCs) and/or intestinal epithelial cells (IECs).To determine the unique ways in which the gut induces or expands T(regs), a transgenic mouse model that is based on the specific expression of a model autoantigen (influenza haemagglutinin (HA)) in the intestinal epithelium (VILLIN-HA) was used. Gut-associated DCs and IECs isolated from these mice were phenotypically and functionally characterised for the potential to interact with HA-specific T(regs) in vitro and in vivo.Intestinal self-antigen expression leads to peripheral expansion of antigen-specific CD4(+)Foxp3(+) T(regs). Although gut-associated DCs can induce antigen-specific CD4(+)Foxp3(+) T cell proliferation, in vivo depletion of DCs did not preclude proliferation of these cells. Interestingly, antigen presentation by primary IECs is sufficient to expand antigen-specific CD4(+)Foxp3(+) T(regs) efficiently. This is dependent on major histocompatibility complex class II, but, in contrast to DCs, is unlikely to require transforming growth factor beta and retinoic acid.This study provides experimental evidence for a new concept in mucosal immunity: in contrast to current thinking, expansion of T(regs) can be achieved independently of local DCs through antigen-specific IEC-T cell interactions.

The transmembrane protein CD83 has been initially described as a maturation marker for dendritic cells. Moreover, there is increasing evidence that CD83 also regulates B cell function, thymic T cell maturation, and peripheral T cell activation. Herein, we show that CD83 expression confers immunosuppressive function to CD4⁺ T cells. CD83 mRNA is differentially expressed in naturally occurring CD4⁺CD25⁺ regulatory T cells, and upon activation these cells rapidly express large amounts of surface CD83. Transduction of naive CD4⁺CD25⁻ T cells with CD83 encoding retroviruses induces a regulatory phenotype in vitro, which is accompanied by the induction of Foxp3. Functional analysis of CD83-transduced T cells in vivo demonstrates that these CD83⁺Foxp3⁺ T cells are able to interfere with the effector phase of severe contact hypersensitivity reaction of the skin. Moreover, adoptive transfer of these cells prevents the paralysis associated with experimental autoimmune encephalomyelitis, suppresses proinflammatory cytokines IFN-γ and IL-17, and increases antiinflammatory IL-10 in recipient mice. Taken together, our data provide the first evidence that CD83 expression can contribute to the immunosuppressive function of CD4⁺ T cells in vivo. Copyright © 2008 by The American Association of Immunologists, Inc.

The aryl hydrocarbon receptor (AHR) is a ligand-dependent transcription factor best known for mediating the toxicity of dioxin. Environmental factors are believed to contribute to the increased prevalence of autoimmune diseases, many of which are due to the activity of T(H)17 T cells, a new helper T-cell subset characterized by the production of the cytokine IL-17. Here we show that in the CD4+ T-cell lineage of mice AHR expression is restricted to the T(H)17 cell subset and its ligation results in the production of the T(H)17 cytokine interleukin (IL)-22. AHR is also expressed in human T(H)17 cells. Activation of AHR by a high-affinity ligand during T(H)17 cell development markedly increases the proportion of T(H)17 T cells and their production of cytokines. CD4+ T cells from AHR-deficient mice can develop T(H)17 cell responses, but when confronted with AHR ligand fail to produce IL-22 and do not show enhanced T(H)17 cell development. AHR activation during induction of experimental autoimmune encephalomyelitis causes accelerated onset and increased pathology in wild-type mice, but not AHR-deficient mice. AHR ligands may therefore represent co-factors in the development of autoimmune diseases.

Background/Aims: IL10 is a key inhibitor of effector T cell activation and a mediator of intestinal homeostasis. In addition, IL10 has emerged as a key immunoregulator during infection with various pathogens, ameliorating the excessive T-cell responses that are responsible for much of the immunopathology associated with the infection. Because IL10 plays an important role in both intestinal homeostasis and infection, we studied the function of IL10 in infection-associated intestinal inflammation. Methods: Wildtype mice and mice deficient in CD4+ T cell-derived or regulatory T cells-derived IL10 were infected with the enteric pathogen Citrobacter (C.) rodentium and analyzed for the specific immune response and pathogloy in the colon. Results: We found that IL10 expression is upregulated in colonic tissue after infection with C. rodentium, especially in CD4+ T cells, macrophages and dendritic cells. Whereas the deletion of IL10 in regulatory T cells had no effect on C. rodentium induced colitis, infection of mice deficient in CD4+ T cell-derived IL10 exhibited faster clearance of the bacterial burden but worse colitis, crypt hyperplasia, and pathology than did WT mice. In addition, the depletion of CD4+ T cell-derived IL10 in infected animals was accompanied by an accelerated IFNγ and IL17 response in the colon. Conclusion: Thus, we conclude that CD4+ T cell-derived IL10 is strongly involved in the control of C. rodentium-induced colitis. Interference with this network could have implications for the treatment of infection-associated intestinal inflammation.

Inflammatory bowel disease (IBD) is characterized by chronic, uncontrolled inflammation in the intestinal mucosa. Although the etiology is poorly understood, it is widely accepted that loss of tolerance is involved in the development of IBD. Therefore, re-establishing tolerance or gut homeostasis is one of the key features in the development of new therapeutic strategies. Here we show that antigen targeting to DEC-205 on dendritic cells leads to an interleukin (IL)-10-dependent downregulation of C-X-C chemokine receptor 3 (CXCR3) expression on differentiated antigen-specific T helper type 1 (Th1) cells in vivo. This downregulation interferes with the migration of Th1 cells into the gut and protects mice against severe acute and relapsing intestinal inflammation. Moreover, CD4(+)CXCR3(+) T cells are highly enriched in the inflamed mucosa of IBD patients. Interference with this pathway may therefore be a promising approach for the treatment of IBD. In conclusion, we propose a hitherto undescribed mechanism by which IL-10 can act on effector T cells and orchestrate intestinal immune responses.

B cells are essential for antiviral immune defence because they produce neutralizing antibodies, present antigen and maintain the lymphoid architecture. Here we show that intrinsic signalling of CEACAM1 is essential for generating efficient B-cell responses. Although CEACAM1 exerts limited influence on the proliferation of B cells, expression of CEACAM1 induces survival of proliferating B cells via the BTK/Syk/NF-κB-axis. The absence of this signalling cascade in naive Ceacam1−/− mice limits the survival of B cells. During systemic infection with cytopathic vesicular stomatitis virus, Ceacam1−/− mice can barely induce neutralizing antibody responses and die early after infection. We find, therefore, that CEACAM1 is a crucial regulator of B-cell survival, influencing B-cell numbers and protective antiviral antibody responses., Antibody responses are regulated by selective survival of B cells with proper antigen specificity. Here the authors show that CEACAM1 is critical for B-cell survival during homeostasis and antiviral responses.

The role of Foxp3(+) regulatory T (Treg) cells in the course of the early hyper-inflammatory and subsequent hypo-inflammatory phases of sepsis is ambiguous. Whereas Nrp1 expression has been reported to discriminate natural Treg cells from induced Treg cells, the Treg cell stability depends on the methylation status of foxp3-TSDR. To specifically evaluate the role of Foxp3(+) Treg cells in the early and late phases of sepsis, we induced sepsis by caecal ligation and puncture and subsequent Pseudomonas aeruginosa lung infection in a DEREG (DEpletion of REGulatory T cells) mouse model. We found an increase of Foxp3(+) Treg cells to all CD4(+) T cells during murine sepsis. Using a new methylation-sensitive quantitative RT-PCR method and deep amplicon sequencing, we demonstrated that natural (Nrp1(+) Foxp3(+) ) Treg cells and most induced (Nrp1(-) Foxp3(+) ) Treg cells are stable and exhibit unmethylated foxp3-TSDR, and that both Treg populations are functionally suppressive in healthy and septic mice. DEREG mice depleted of Foxp3(+) Treg cells exhibit higher disease scores, mortality rates and interleukin-6 expression levels than do non-depleted DEREG mice in early-phase sepsis, a finding indicating that Foxp3(+) Treg cells limit the hyper-inflammatory response and accelerate recovery. Treg cell depletion before secondary infection with P. aeruginosa 1 week after caecal ligation and puncture does not influence cytokine levels or the course of secondary infection. However, a moderate Treg cell recurrence, which we observed in DEREG mice during secondary infection, may interfere with these results. In summary, Treg cells contribute to a positive outcome after early-phase sepsis, but the data do not support a significant role of Treg cells in immune paralysis during late-phase sepsis.

Regulatory T cells play a crucial role in the control of immune responses in the intestinal mucosa and their absence may predispose to inflammatory bowel disease (IBD). However, the induction of regulatory T cells at sites of mucosal inflammation is not yet fully understood and may involve antigen presentation by local immature dendritic cells and/or intestinal epithelial cells (IECs). VILLIN-HA mice, which express the hemagglutinin (HA) from influenza virus A exclusively in enterocytes of the intestinal epithelium, were matched with T cell receptor (TCR)-HA mice expressing an alphabeta-TCR which recognizes a major histocompatibility complex (MHC) class II-restricted epitope of HA in order to determine the impact of antigen presentation by IECs on CD4(+) T cell immunity. In VILLIN-HA x TCR-HA mice, peripheral HA-specific lymphocytes showed an activated phenotype and increased infiltration into the intestinal mucosa without destruction of the intestinal epithelium. Mucosal lymphocytes from VILLIN-HA x TCR-HA mice secreted lower amounts of interferon-gamma (IFN-gamma) and interleukin-2 (IL-2) and exhibited an increased expression of interleukin-10 (IL-10), Nrp-1, and Foxp3, molecules published as markers for regulatory T cells. IECs can take up and process antigen but the antigen presentation capacity of these cells is often inefficient. Functional and molecular characterization of IECs from VILLIN-HA and VILLIN-HA x TCR-HA transgenic mice revealed a direct role in the induction of CD4(+) T cells with a regulatory phenotype that maintain intestinal homeostasis.

Treatment options for pancreatic cancer are limited and often ineffective. Immunotherapeutic approaches are one possible option that needs to be evaluated in appropriate animal models. The aim of the present study was to analyze tumor-specific immune responses in a mouse model of pancreatic cancer, which mimics the human disease closely. C57BL/6 EL-TGF-α × Trp53−/− mice, which develop spontaneous ductal pancreatic carcinoma, were generated. EL-TGF-α × Trp53−/− mice developed spontaneous pancreatic tumors with pathomorphologic features close to the human disease. Tumor-specific CD8+ T-cell responses and IgG responses were analyzed in EL-TGF-α × Trp53−/− mice during tumor development and compared with mice with s.c. growing pancreatic tumors. In contrast to spontaneous pancreatic tumors, cell lines generated from these tumors were rejected after s.c. injection into wild-type mice but not in nude or RAG knockout mice. Direct comparison of spontaneous and s.c. injected tumors revealed an impaired infiltration of CD8+ T cells in spontaneous pancreatic tumors, which was also evident after adoptive transfer of tumor-specific T cells. Intratumoral cytokine secretion of tumor necrosis factor-α, IFN-γ, IL-6, and MCP-1 was lower in spontaneous tumors as well as the number of adoptively transferred tumor-specific T cells. Our data provide clear evidence for tumor-specific immune responses in a genetic mouse model for pancreatic carcinoma. Comparative analysis of s.c. injected tumors and spontaneous tumors showed significant differences in tumor-specific immune responses, which will help in improving current immune-based cancer therapies against adenocarcinoma of the pancreas. (Cancer Res 2006; 66(1): 508-16)

The development of novel approaches that allow accurate targeting of therapeutics to the intestinal mucosa is a major task in the research on intestinal inflammation. For the first time, a live genetically modified bacterial strain has been approved by Dutch authorities as a therapeutic agent for experimental therapy of intestinal bowel disease (IBD) in humans. Genetically modified probiotics can very well be used as carriers for localized antigen delivery into the intestine. Therapeutic safety, however, of such a carrier organism, is crucial, especially when a specific probiotic strain has to be used under diseased conditions. In this study, we tested the potential of Escherichia coli NISSLE 1917 to serve as a safe carrier for targeted delivery of recombinant proteins to the intestinal mucosa. In a well-defined and very sensitive immunological system, we demonstrate that intestinal recombinant E. coli NISSLE 1917 has no effect on migration, clonal expansion and activation status of specific CD4+ T cells, neither in healthy mice nor in animals with acute colitis. Furthermore, recombinant E. coli NISSLE 1917 has no effect on the induction or breakdown of peripheral T-cell tolerance in an autoimmune environment. The excellent colonization properties of E. coli NISSLE 1917 render this strain an ideal candidate as carrier organism for gut-focused in situ synthesis of therapeutic molecules.