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The article presents the discussion on human immune system possessing two fundamental recognition mechanisms as part of acquired immunity to initiate antigen-specific responses against pathogens. Topics include providing insights into previous exposure to specific pathogens and the development of immune responses; and offering insights into existing protective immunity or vaccine efficacy assessment.

Purpose: Besides their developmental and neurological phenotype, most patients with MECP2/IRAK1 duplication syndrome present with recurrent and severe infections, accompanied by strong inflammation. Respiratory infections are the most common cause of death. Standardized pneumological diagnostics, targeted anti-infectious treatment, and knowledge of the underlying pathomechanism that triggers strong inflammation are unmet clinical needs. We investigated the influence of IRAK1 overexpression on the canonical NF-κB signaling as a possible cause for excessive inflammation in these patients. Methods: NF-κB signaling was examined by measuring the production of proinflammatory cytokines and evaluating the IRAK1 phosphorylation and degradation as well as the IκBα degradation upon stimulation with IL-1β and TLR agonists in SV40-immortalized fibroblasts, PBMCs, and whole blood of 9 patients with MECP2/IRAK1 duplication syndrome, respectively. Results: Both, MECP2/IRAK1-duplicated patients and healthy controls, showed similar production of IL-6 and IL-8 upon activation with IL-1β and TLR2/6 agonists in immortalized fibroblasts. In PBMCs and whole blood, both patients and controls had a similar response of cytokine production after stimulation with IL-1β and TLR4/2/6 agonists. Patients and controls had equivalent patterns of IRAK1 phosphorylation and degradation as well as IκBα degradation upon stimulation with IL-1β. Conclusion: Patients with MECP2/IRAK1 duplication syndrome do not show increased canonical NF-κB signaling in immortalized fibroblasts, PBMCs, and whole blood. Therefore, we assume that these patients do not benefit from a therapeutic suppression of this pathway. [ABSTRACT FROM AUTHOR]

Purpose: NEMO-deficient patients present with variable degrees of immunodeficiency. Accordingly, treatment ranges from antibiotic prophylaxis and/or IgG-substitution to allogenic hematopoietic stem cell transplantation (HSCT). The correct estimation of the immunodeficiency is essential to avoid over- as well as under-treatment. We compare the immunological phenotype of a NEMO-deficient patient with a newly-described splice site mutation that causes truncation of the NEMO zinc-finger (ZF) domain and a severe clinical course with the immunological phenotype of three NEMO-deficient patients with missense mutations and milder clinical courses and all previously published patients. Methods: Lymphocyte subsets, proliferation, and intracellular NEMO-expression were assessed by FACS. NF-κB signal transduction was determined by measuring IκBα-degradation and the production of cytokines upon stimulation with TNF-α, IL-1β, and TLR-agonists in immortalized fibroblasts and whole blood, respectively. Results: The patient with truncated ZF-domain of NEMO showed low levels of IgM and IgG, reduced class-switched memory B cells, almost complete skewing towards naïve CD45RA+ T cells, impaired T cell proliferation as well as cytokine production upon stimulation with TNF-α, IL-1β, and TLR-agonists. He suffered from severe infections (sepsis, pneumonia, osteomyelitis) during infancy. In contrast, three patients with missense mutations in IKBKG presented neither skewing of T cells towards naïvety nor impaired T cell proliferation. They are stable on prophylactic IgG-substitution or even off any prophylactic treatment. Conclusion: The loss of the ZF-domain and the impaired T cell proliferation accompanied by almost complete persistence of naïve T cells despite severe infections are suggestive for a profound immunodeficiency. Allogenic HSCT should be considered early for these patients before chronic sequelae occur. [ABSTRACT FROM AUTHOR]

MECP2 (methyl CpG binding protein 2) duplication causes syndromic intellectual disability. Patients often suffer from life-threatening infections, suggesting an additional immunodeficiency. We describe for the first time the detailed infectious and immunological phenotype of MECP2 duplication syndrome. 17/27 analyzed patients suffered from pneumonia, 5/27 from at least one episode of sepsis. Encapsulated bacteria ( S.pneumoniae, H.influenzae) were frequently isolated. T-cell immunity showed no gross abnormalities in 14/14 patients and IFNy-secretion upon ConA-stimulation was not decreased in 6/7 patients. In 6/21 patients IgG-deficiency was detected - in 4/21 patients accompanied by IgA-deficiency, 10/21 patients showed low antibody titers against pneumococci. Supra-normal IgG-levels were detected in 11/21 patients and supra-normal IgG-levels were seen in 8/21 patients - in 6 of the patients as combined elevation of IgG and IgG. Three of the four patients with IgA/IgG-deficiency developed multiple severe infections. Upon infections pronounced acute-phase responses were common: 7/10 patients showed CRP values above 200 mg/l. Our data for the first time show systematically that increased susceptibility to infections in MECP2 duplication syndrome is associated with IgA/IgG-deficiency, low antibody titers against pneumococci and elevated acute-phase responses. So patients with MECP2 duplication syndrome and low IgA/IgG may benefit from prophylactic substitution of sIgA and IgG. [ABSTRACT FROM AUTHOR]

The article presents a case study of a two year old boy with short swelling of the metacarpophalangeal joints. Topics discussed include growth of Streptococcus pneumoniae in a blood culture, pyogenic arthritis and osteomyelitis with adjacent arthritis of the right elbow but little inflammation. It mentions that his grand parents were having arthritis

Primary Immune thrombocytopenia (ITP) is an autoimmune disease. Secondary ITP occurs in patients with underlying diseases such as common variable immunodeficiency (CVID). CVID is one of the most common symptomatic primary immunodeficiencies in adults, characterised by infectious and non-infectious symptoms. Amongst CVID patients, ITP is the most frequent autoimmune manifestation. In this single-centre study, we performed a clinical and immunological characterisation of 20 patients with CVID-related ITP and 20 ITP patients without CVID to compare severity and remission rates. We found that patients with CVID-related ITP had a higher WHO Bleeding Scale at initial diagnosis yet showed higher remission rates and required less treatment. Patients with ITP needed up to seven therapy options and were often treated with second-line drug therapy, whilst only one CVID-related ITP patient required second-line drug therapy. Therefore, we show that the course of thrombocytopenia in patients with CVID-related ITP is milder. Furthermore, we show that soluble interleukin-2 receptor (sIL-2R, CD25) was higher in CVID-related ITP compared to ITP patients and could accurately classify patient cohorts with an Area Under the Receiver Operating Characteristic of 0.92. Whilst none of the ITP patients had a history of immunodeficiency, we found immunological abnormalities in 12 out of 18 patients. Therefore, we recommend screening ITP patients for CVID and other immunodeficiencies to detect immune abnormalities early, as we found patients with reduced immunoglobulin levels as well as severe lymphocytopenia in our ITP cohort. [ABSTRACT FROM AUTHOR]

The transmembrane adaptor molecule TRIM is strongly expressed within thymus and in peripheral CD4+ T cells. Previous studies suggested that TRIM is an integral component of the T-cell receptor (TCR)/CD3 complex and might be involved in regulating TCR cycling. To elucidate the in vivo function of TRIM, we generated TRIM-deficient mice by homologous recombination. TRIM-/- mice develop normally and are healthy and fertile. However, the animals show a mild reduction in body weight that appears to be due to a decrease in the size and/or cellularity of many organs. The morphology and anatomy of nonlymphoid as well as primary and secondary lymphoid organs is normal. The frequency of thymocyte and peripheral T-cell subsets does not differ from control littermates. In addition, a detailed analysis of lymphocyte development revealed that TRIM is not required for either positive or negative selection. Although TRIM-/- CD4+ T cells showed an augmented phosphorylation of the serine/threonine kinase Akt, the in vitro characterization of peripheral T cells indicated that proliferation, survival, activation-induced cell death, migration, adhesion, TCR internalization and recycling, TCR-mediated calcium fluxes, tyrosine phosphorylation, and mitogen-activated protein family kinase activation are not affected in the absence of TRIM. Similarly, the in vivo immune response to T-dependent and T-independent antigens as well as the clinical course of experimental autoimmune encephalomyelitis, a complex Th1-mediated autoimmune model, is comparable to that of wild-type animals. Collectively, these results demonstrate that TRIM is dispensable for T-cell development and peripheral immune functions. The lack of an evident phenotype could indicate that TRIM shares redundant functions with other transmembrane adaptors involved in regulating the immune response. [ABSTRACT FROM AUTHOR]

SIT is a transmembrane adapter protein that modulates signals emanating from the T-cell receptor (TCR). Here, we have used gene-targeted mice to assess the role of SIT for T-cell development and peripheral T-cell functions. SIT-/- double-positive thymocytes show an upregulation of the activation markers CD5 and CD69, suggesting that SIT negatively regulates TCR-mediated signals at the CD4+ CD8+ stage of thymic development. This assumption is further supported by the observation that in female H-Y TCR transgenic mice, positive selection is enhanced and even converted to negative selection. Similarly, mature peripheral T cells are hyperresponsive towards TCR-mediated stimuli and produce larger amounts of T-helper 1 (TH1) cytokines, and SIT-deficient mice show an increased susceptibility to develop experimental autoimmune encephalomyelitis, a mouse model of multiple sclerosis. These results demonstrate that SIT is a critical negative regulator of TCR-mediated signaling and finely tunes the signals required for thymic selection and peripheral T-cell activation. [ABSTRACT FROM AUTHOR]

Genetic predisposition and environmental factors modulate the expression of allergic phenotypes. The frequent allergic phenotype 'immediate cutaneous hypersensitivity' was established in mice as a model for atopy. Genetic dissection of this trait requires a robust procedure to assess the allergic phenotype. To this end, different mouse strains were immunized with birch pollen extract. Immediate cutaneous hypersensitivity reactions were induced through intradermal allergen exposure. Wheel formation was quantitated and expressed as a hypersensitivity score according to the bonitur method. This procedure identified A/J and C57BL/6 mice as high– and low–responder strains, respectively. Crosses of A/J and C57BL/6 mice should allow the characterization of mendelian factors responsible for the two extreme phenotypes identified here. [ABSTRACT FROM AUTHOR]

Autoantibodies against IFN-α and IFN-ω (type I IFNs) were recently reported as causative for severe COVID-19 in the general population. Autoantibodies against IFN-α and IFN-ω are present in almost all patients with autoimmune polyendocrine syndrome type 1 (APS-1) caused by biallelic deleterious or heterozygous dominant mutations in AIRE. We therefore hypothesized that autoantibodies against type I IFNs also predispose patients with APS-1 to severe COVID-19. We prospectively studied 6 patients with APS-1 between April 1, 2020 and April 1, 2021. Biobanked pre-COVID-19 sera of APS-1 subjects were tested for neutralizing autoantibodies against IFN-α and IFN-ω. The ability of the patients' sera to block recombinant human IFN-α and IFN-ω was assessed by assays quantifying phosphorylation of signal transducer and activator of transcription 1 (STAT1) as well as infection-based IFN-neutralization assays. We describe 4 patients with APS-1 and preexisting high titers of neutralizing autoantibodies against IFN-α and IFN-ω who contracted SARS-CoV-2, yet developed only mild symptoms of COVID-19. None of the patients developed dyspnea, oxygen requirement, or high temperature. All infected patients with APS-1 were females and younger than 26 years of age. Clinical penetrance of neutralizing autoantibodies against type I IFNs for severe COVID-19 is not complete. [ABSTRACT FROM AUTHOR]

Introduction: In 2015, 4062 unaccompanied minor refugees were registered in Berlin, Germany. According to national policies, basic clinical examination and tuberculosis (TB) screening is a prerequisite to admission to permanent accommodation and schooling for every refugee. This article evaluates the use of an interferon-γ-release-assay (IGRA) during the initial examination and TB screening of 970 unaccompanied minor refugees. Results: IGRA test were obtained during TB screening for 301 (31.0%) of 970 adolescents not previously screened for TB. Positive IGRA results were obtained in 13.9% (42/301). Most of the 42 IGRA-positive refugees originated from Afghanistan or Syria (n?20 and 10 respectively). Two IGRA-positive adolescents were lost to follow-up, 2 were diagnosed with TB and the remaining 38 diagnosed with latent TB infection (LTBI). Demographic features of the 40 patients with positive IGRA result were as follows: 39 male, median age 16.8 years (IQR 16.0–17.2y), none meeting underweight criteria (median BMI 21.3kg/m2). On initial chest X-ray 2/40 participants had signs of active TB, while in 38 active disease was excluded and the diagnosis of latent TB infection (LTBI) made. Active hepatitis B-co-infection was diagnosed in 3/38 patients. All patients with LTBI received Isoniazid and Rifampicin for 3 months without occurrence of severe adverse events. The most frequently observed side effect was transient upper abdominal pain (n = 5). Asymptomatic elevation of liver transaminases was seen in 2 patients. 29 patients completed treatment with no signs of TB disease at the end of chemoprevention and 9 were lost to follow up. Conclusion: Screening for TB infection in minor refugees was feasible in our setting with a relatively high rate of TB infection detected. Chemopreventive treatment was tolerated well regardless of underlying hepatitis-B-status. Minor refugees migrating to Germany should be screened for TB infection, instead of TB disease only, regardless of the background TB incidence. [ABSTRACT FROM AUTHOR]

In Germany community-acquired Legionnaires' disease is usually caused by the species Legionella pneumophila. Recurrent cases of Legionnaires' disease are rarely reported and are due either to a second infection (reinfection) or a relapse of a previous case. We report a case of recurrent Legionnaires' disease in an 86-year-old female patient infected with Legionella pneumophila serogroup 1, monoclonal antibody-subtype Knoxville, sequence type unknown. Between the two disease incidents the patient had completely recovered. Legionella pneumophila was detected with the monoclonal antibody-subtype Knoxville, sequence type 182, in the drinking water of the patient's apartment. Exposure to contaminated drinking water was interrupted after the first incident exposure through the application of point-of-use water filters. The filters were later removed due to low water pressure, and the second illness occurred thereafter. It is unclear if immunological predisposition has contributed to this case of probable reinfection of Legionnaires' disease. Clinical, microbiological and epidemiological information combined suggest this is a case of reinfection of Legionnaires' disease. In cases of recurrent Legionnaires' disease complete collection of patient and water samples is necessary to differentiate relapse from reinfection cases, to implicate the source of infection and to gain more evidence for the role of immunological predisposition. [ABSTRACT FROM AUTHOR]

Purpose: Since we described for the first time a patient with IgG autoantibodies to IFN-γ more than 10 years ago, many patients with IFN-γ IgG autoantibodies have been described, mostly in Mongolian/ Asian patients with a particular HLA background and in association with disseminated nontuberculous mycobacterial infections. Very recently, the first Caucasian US patient was reported and we now present the case of a 65-year old Caucasian woman with severe disseminated Mycobacterium avium infection, cerebral toxoplasmosis and salmonella sepsis who was tested positive for IFN-γ deficiency due to unusual anti-IFN-γ IgG autoantibodies. Methods: IFN-γ production after ex vivo ConA stimulation of the patient's whole blood and isolated peripheral blood mononuclear cells was assessed. Anti-human IFN-γ antibodies were measured by Ig/Ig-subclass-specific ELISA. In vitro physiologic relevance and blocking capacity of IFN-γ-stimulation by patient's serum was analysed by flow cytometric assessment of cytokine-induced phosphorylation of pSTAT1. Results: Severely impaired IFN-γ production in the patient's whole blood but normal production in peripheral blood mononuclear cells in the absence of autologous serum was observed. High titre anti-IFN-γ antibodies of the IgG subclass could be demonstrated in the patient's serum by ELISA. Further, the addition of patient's serum to IFN-γ-stimulated immune cells showed inhibition of STAT1 phosphorylation. Conclusions: IFN-γ autoantibodies of any IgG-isotype should be considered in patients with severe opportunistic infections independent of age at onset and ethnicity. [ABSTRACT FROM AUTHOR]

The autosomal recessive immunodeficiency-centromeric instability-facial anomalies syndrome (ICF) is characterized by immunodeficiency, developmental delay, and facial anomalies. ICF2, caused by biallelic ZBTB24 gene mutations, is acknowledged primarily as an isolated B-cell defect. Here, we extend the phenotype spectrum by describing, in particular, for the first time the development of a combined immune defect throughout the disease course as well as putative autoimmune phenomena such as granulomatous hepatitis and nephritis. We also demonstrate impaired cell-proliferation and increased cell death of immune and non-immune cells as well as data suggesting a chromosome separation defect in addition to the known chromosome condensation defect. [ABSTRACT FROM AUTHOR]

Glycosylphophatidylinositol (GPI)-anchored proteins play important roles in many biological processes, and mutations affecting proteins involved in the synthesis of the GPI anchor are reported to cause a wide spectrum of intellectual disabilities (IDs) with characteristic additional phenotypic features. Here, we describe a total of five individuals (from three unrelated families) in whom we identified mutations in PGAP3, encoding a protein that is involved in GPI-anchor maturation. Three siblings in a consanguineous Pakistani family presented with profound developmental delay, severe ID, no speech, psychomotor delay, and postnatal microcephaly. A combination of autozygosity mapping and exome sequencing identified a 13.8 Mb region harboring a homozygous c.275G>A (p.Gly92Asp) variant in PGAP3 region 17q11.2–q21.32. Subsequent testing showed elevated serum alkaline phosphatase (ALP), a GPI-anchored enzyme, in all three affected children. In two unrelated individuals in a cohort with developmental delay, ID, and elevated ALP, we identified compound-heterozygous variants c.439dupC (p.Leu147Profs∗16) and c.914A>G (p.Asp305Gly) and homozygous variant c.314C>G (p.Pro105Arg). The 1 bp duplication causes a frameshift and nonsense-mediated decay. Further evidence supporting pathogenicity of the missense mutations c.275G>A, c.314C>G, and c.914A>G was provided by the absence of the variants from ethnically matched controls, phylogenetic conservation, and functional studies on Chinese hamster ovary cell lines. Taken together with recent data on PGAP2, these results confirm the importance of the later GPI-anchor remodelling steps for normal neuronal development. Impairment of PGAP3 causes a subtype of hyperphosphatasia with ID, a congenital disorder of glycosylation that is also referred to as Mabry syndrome. [Copyright &y& Elsevier]

Research within the last 10 years has provided compelling evidence that adaptor proteins regulate the major pathways of lymphocyte activation. Based upon their differential subcellular localization, transmembrane adaptors and cytosolic adaptors can be distinguished. Here we review some of the most recent findings about both types of adaptor proteins which have facilitated our understanding how immunoreceptors control lymphocyte activation and differentiation. [Copyright &y& Elsevier]

Hyperphosphatasia mental retardation (HPMR) syndrome is an autosomal recessive form of mental retardation with distinct facial features and elevated serum alkaline phosphatase. We performed whole-exome sequencing in three siblings of a nonconsanguineous union with HPMR and performed computational inference of regions identical by descent in all siblings to establish PIGV, encoding a member of the GPI-anchor biosynthesis pathway, as the gene mutated in HPMR. We identified homozygous or compound heterozygous mutations in PIGV in three additional families. [ABSTRACT FROM AUTHOR]

Hypomorphic mutations in the gene encoding Bruton tyrosine kinase (BTK) may result in milder phenotypes and delayed diagnosis of B‐cell related immunodeficiencies due to residual BTK function. Newborn screening for kappa‐deleting‐recombination‐excision circles (KRECs) reliably identifies classical X‐linked agammaglobulinaemia (XLA) patients with profound B‐cell lymphopenia at birth but has not been evaluated in patients with residual BTK function. We aimed to evaluate clinical findings, BTK function and KREC copy numbers in three patients with BTK mutations presenting with impaired polysaccharide responsiveness without agammaglobulinaemia. One patient had an invasive pneumococcal infection at the age of 4 years. All three patients (two brothers) had visible tonsils, normal to slightly decreased immunoglobulin G levels, undetectable pneumococcal antibodies despite pneumococcal conjugate vaccinations, no antibody response after a diagnostic polysaccharide vaccination as well as profound B‐cell lymphopenia with residual B‐cell differentiation. BTK mutations were identified by Sanger sequencing. BTK staining and phosphorylation assays were performed on peripheral B cells. KREC copy numbers were determined from dried blood spots obtained within the first week of life as well as once at the age of 8, 6 and 3 years, respectively. BTK staining showed residual protein expression. Also, residual BTK activity could be demonstrated. KREC copy numbers from dried blood spots were above the threshold set for detection of patients with profound B‐cell lymphopenia. Male patients with impaired polysaccharide responsiveness should be evaluated for B‐cell lymphopenia followed by BTK analyses irrespective of immunoglobulin levels or tonsil size. [ABSTRACT FROM AUTHOR]

The autosomal recessive immunodeficiency-centromeric instability-facial anomalies syndrome (ICF) is characterized by immunodeficiency, developmental delay, and facial anomalies. ICF2, caused by biallelic ZBTB24 gene mutations, is acknowledged primarily as an isolated B-cell defect. Here, we extend the phenotype spectrum by describing, in particular, for the first time the development of a combined immune defect throughout the disease course as well as putative autoimmune phenomena such as granulomatous hepatitis and nephritis. We also demonstrate impaired cell-proliferation and increased cell death of immune and non-immune cells as well as data suggesting a chromosome separation defect in addition to the known chromosome condensation defect. [ABSTRACT FROM AUTHOR]