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Tangye and collaborators use a series of mutants to elucidate the pathways required to generate distinct subsets of human effector CD4+ T cells., Naive CD4+ T cells differentiate into specific effector subsets—Th1, Th2, Th17, and T follicular helper (Tfh)—that provide immunity against pathogen infection. The signaling pathways involved in generating these effector cells are partially known. However, the effects of mutations underlying human primary immunodeficiencies on these processes, and how they compromise specific immune responses, remain unresolved. By studying individuals with mutations in key signaling pathways, we identified nonredundant pathways regulating human CD4+ T cell differentiation in vitro. IL12Rβ1/TYK2 and IFN-γR/STAT1 function in a feed-forward loop to induce Th1 cells, whereas IL-21/IL-21R/STAT3 signaling is required for Th17, Tfh, and IL-10–secreting cells. IL12Rβ1/TYK2 and NEMO are also required for Th17 induction. Strikingly, gain-of-function STAT1 mutations recapitulated the impact of dominant-negative STAT3 mutations on Tfh and Th17 cells, revealing a putative inhibitory effect of hypermorphic STAT1 over STAT3. These findings provide mechanistic insight into the requirements for human T cell effector function, and explain clinical manifestations of these immunodeficient conditions. Furthermore, they identify molecules that could be targeted to modulate CD4+ T cell effector function in the settings of infection, vaccination, or immune dysregulation.

Systemic lupus erythematosus (SLE or lupus) (OMIM: 152700) is a chronic autoimmune disease with debilitating inflammation that affects multiple organ systems. The STAT1-STAT4 locus is one of the first and most highly replicated genetic loci associated with lupus risk. We performed a fine-mapping study to identify plausible causal variants within the STAT1-STAT4 locus associated with increased lupus disease risk. Using complementary frequentist and Bayesian approaches in trans-ancestral Discovery and Replication cohorts, we found one variant whose association with lupus risk is supported across ancestries in both the Discovery and Replication cohorts: rs11889341. In B cell lines from patients with lupus and healthy controls, the lupus risk allele of rs11889341 was associated with increased STAT1 expression. We demonstrated that the transcription factor HMGA1, a member of the HMG transcription factor family with an AT-hook DNA-binding domain, has enriched binding to the risk allele compared with the non-risk allele of rs11889341.We identified a genotype-dependent repressive element in the DNA within the intron of STAT4 surrounding rs11889341. Consistent with expression quantitative trait locus (eQTL) analysis, the lupus risk allele of rs11889341 decreased the activity of this putative repressor. Altogether, we present a plausible molecular mechanism for increased lupus risk at the STAT1-STAT4 locus in which the risk allele of rs11889341, the most probable causal variant, leads to elevated STAT1 expression in B cells due to decreased repressor activity mediated by increased binding of HMGA1. © The Author(s) 2018. Published by Oxford University Press. All rights reserved.

In this study we examined mechanisms that regulate T-helper lymphocyte 1 (Th1) commitment in Helicobacter pylori -infected human gastric mucosa. The levels of gamma interferon (IFN-γ), interleukin-4 (IL-4), and IL-12 in total extracts of gastric biopsies taken from H. pylori -infected and uninfected patients were determined by an enzyme-linked immunosorbent assay. The levels of signal transducer and activator of transcription 4 (STAT4), STAT6, and T-box expressed in T cells (T-bet) in total proteins extracted from gastric biopsies were determined by Western blotting. Finally, the effect of a neutralizing IL-12 antibody on expression of Th1 transcription factors and the levels of IFN-γ in organ cultures of H. pylori -infected biopsies was examined. Increased levels of IFN-γ and IL-12 were found in gastric biopsy samples of H. pylori -infected patients compared to the levels in uninfected patients. In addition, H. pylori -infected biopsies exhibited high levels of expression of phosphorylated STAT4 and T-bet. Higher levels of IFN-γ and expression of Th1 transcription factors were associated with greater infiltration of mononuclear cells in the gastric mucosa. By contrast, production of IL-4 and expression of phosphorylated STAT6 were not associated with the intensity of mononuclear cell infiltration. In ex vivo organ cultures of H. pylori -infected biopsies, neutralization of endogenous IL-12 down-regulated the expression of phosphorylated STAT4 and T-bet and reduced IFN-γ production. Our data indicated that IL-12 contributes to the Th1 cell commitment in H. pylori -infected human gastric mucosa.

Sjögren's syndrome is a common autoimmune disease (affecting ?0.7% of European Americans) that typically presents as keratoconjunctivitis sicca and xerostomia. Here we report results of a large-scale association study of Sjögren's syndrome. In addition to strong association within the human leukocyte antigen (HLA) region at 6p21 (P meta = 7.65 × 10 -114), we establish associations with IRF5-TNPO3 (P meta = 2.73 × 10 -19), STAT4 (P meta = 6.80 × 10 -15), IL12A (P meta = 1.17 × 10 -10), FAM167A-BLK (P meta = 4.97 × 10 -10), DDX6-CXCR5 (P meta = 1.10 × 10 -8) and TNIP1 (P meta = 3.30 × 10 -8). We also observed suggestive associations (P meta less than 5 × 10 -5) with variants in 29 other regions, including TNFAIP3, PTTG1, PRDM1, DGKQ, FCGR2A, IRAK1BP1, ITSN2 and PHIP, among others. These results highlight the importance of genes that are involved in both innate and adaptive immunity in Sjögren's syndrome. © 2013 Nature America, Inc. All rights reserved.

ObjectiveSystemic lupus erythematosus is a clinically heterogeneous autoimmune disease. A number of genetic loci that increase lupus susceptibility have been established. This study examines if these genetic loci also contribute to the clinical heterogeneity in lupus.Materials and methods4001 European-derived, 1547 Hispanic, 1590 African-American and 1191 Asian lupus patients were genotyped for 16 confirmed lupus susceptibility loci. Ancestry informative markers were genotyped to calculate and adjust for admixture. The association between the risk allele in each locus was determined and compared in patients with and without the various clinical manifestations included in the ACR criteria.ResultsRenal disorder was significantly correlated with the lupus risk allele in ITGAM (p=5.0×10−6, OR 1.25, 95% CI 1.12 to 1.35) and in TNFSF4 (p=0.0013, OR 1.14, 95% CI 1.07 to 1.25). Other significant findings include the association between risk alleles in FCGR2A and malar rash (p=0.0031, OR 1.11, 95% CI 1.17 to 1.33), ITGAM and discoid rash (p=0.0020, OR 1.20, 95% CI 1.06 to 1.33), STAT4 and protection from oral ulcers (p=0.0027, OR 0.89, 95% CI 0.83 to 0.96) and IL21 and haematological disorder (p=0.0027, OR 1.13, 95% CI 1.04 to 1.22). All these associations are significant with a false discovery rate of ConclusionSignifi cant associations were found between clinical manifestations and the FCGR2A, ITGAM, STAT4, TNSF4 and IL21 genes. The findings suggest that genetic profiling might be a useful tool to predict disease manifestations in lupus patients in the future.

Objective.To examine the influence ofSTAT4rs7574865 gene polymorphism on patients with primary Sjögren’s syndrome (SS).Methods.Two different cohorts were studied: 69 patients with primary SS and 296 controls from Colombia and 108 patients with primary SS and 227 controls from Germany. Samples were genotyped for theSTAT4rs7574865 single-nucleotide polymorphism with a predesigned TaqMan single-nucleotide polymorphism genotyping assay. We carried out a metaanalysis of our results combined with data published to date.Results.Although no significant differences were observed in the allele frequencies ofSTAT4rs7574865 gene polymorphism between patients and controls in Colombians (p = 0.28, OR 1.24, 95% CI 0.82–1.87) and Germans (p = 0.08, OR 1.40, 95% CI 0.96–2.02), the metaanalysis disclosed a significant effect of the T allele on disease (p = 4.7 × 10−6, OR 1.40, 95% CI 1.21–1.62).Conclusion.These data reinforce the influence ofSTAT4gene on primary SS and as a general autoimmune gene.

The aim of this study was to determine the influence of STAT4 (rs7574865) and TRAF1/C5 (rs10818488 and rs2900180) gene polymorphisms on the risk of developing rheumatoid arthritis (RA) and systemic lupus erythematosus (SLE) in a Colombian population. This was a case-control study in which 839 individuals with RA (N = 274) and SLE (N = 144) and matched healthy controls (N = 421) were included. Genotyping was performed by using a polymerase chain reaction system with pre-developed TaqMan allelic discrimination assay. STAT4 rs7574865T allele disclosed a significant influence on the risk of developing SLE (P = 0.0005; OR 1.62, 95% CI 1.22-2.16) and RA (P = 0.008; OR 1.36; 95% CI 1.08-1.71), whereas no effect on these autoimmune diseases was observed for the TRAF1/C5 polymorphisms examined. Our data strengthen STAT4 rs7574865 polymorphism as a susceptibility factor for RA and SLE and provide further evidence for a common origin of autoimmune diseases.

Background and aims: Cholera toxin B subunit (CT-B) is a powerful modulator of immune responses. The authors have previously demonstrated that oral administration of recombinant CT-B (rCT-B) is able to prevent and cure the Crohn’s disease (CD)-like trinitrobenzene sulfonic acid (TNBS) mediated colitis. In this study they extended their observations and examined if rCT-B interferes with the molecular signaling underlying the Th1 type response both in TNBS colitis and in ex vivo human CD explants. Methods: TNBS treated mice were fed with rCT-B, and IFN-γ and IL-12 production by colonic lamina propria mononuclear cells (LPMC) was examined by ELISA. In vitro culture of mucosal explants from CD patients and non-inflammatory bowel disease controls, pre-incubated with rCT-B, were examined for IFN-γ and IL-12 production by ELISA and semiquantitative reverse transcription polymerase chain reactions. STAT-1, -4, -6 activation and T-bet expression were examined following rCT-B treatment by western blotting both in TNBS treated mice and in human mucosal explants. Results: rCT-B significantly reduced IL-12 and IFN-γ secretion by LPMC from TNBS treated mice. Consistent with this, rCT-B inhibited both STAT-4 and STAT-1 activation and downregulated T-bet expression. Inhibition of Th1 signaling by CT-B associated with no change in IL-4 synthesis and expression of active STAT-6 indicating that rCT-B does not enhance Th2 cell responses. Moreover, in vitro treatment of CD mucosal explants with rCT-B resulted in reduced secretion of IL-12/IFN-γ and inhibition of STAT-4/STAT-1 activation and T-bet expression. Conclusions: These studies indicate that CT-B inhibits mucosal Th1 cell signaling and suggest that rCT-B may be a promising candidate for CD therapy.

Background: In coeliac disease (CD) mucosa, the histological lesion is associated with marked infiltration of T helper cell type 1 (Th1) cells. However, the molecular mechanisms which regulate Th1 cell differentiation in CD mucosa are unknown. Aims: To analyse expression of transcription factors which control the Th1 cell commitment in CD. Patients: Duodenal mucosal samples were taken from untreated CD patients and normal controls. Methods: Interferon γ (IFN-γ) and interleukin (IL)-4 RNA expression was examined in T lamina propria lymphocytes by quantitative reverse transcription-polymerase chain reaction. T-bet and STAT-4, two Th1 promoting transcription factors, and STAT-6 and GATA-3, transcription factors which govern T helper cell type 2 (Th2) cell polarisation, were examined in duodenal biopsies by western blotting. The effect of gliadin and IFN-γ on expression of T-bet was examined in an ex vivo culture of biopsies taken from normal and treated CD patients. Results: As expected, IFN-γ but not IL-4 RNA transcripts were increased in the mucosa of CD patients in comparison with controls. CD mucosal samples consistently exhibited higher levels of T-bet than controls. However, no difference in active STAT-4 expression was seen between CD patients and controls, suggesting that Th1 polarisation was not induced by local IL-12. GATA-3 and STAT-6 were also low in both CD and control mucosa. In normal duodenal biopsies, IFN-γ stimulated T-bet through a STAT-1 dependent mechanism. Challenge of treated CD but not control biopsies with gliadin enhanced T-bet and this effect was also inhibited by STAT-1 inhibition. Conclusions: This study shows that activation of STAT-1 by IFN-γ promotes T-bet in CD mucosa.

Transcription factors of the STAT family are required for cellular responses to multiple signaling molecules. After ligand binding-induced activation of cognate receptors, STAT proteins are phosphorylated, hetero- or homodimerize, and translocate to the nucleus. Subsequent STAT binding to specific DNA elements in the promoters of signal-responsive genes alters the transcriptional activity of these loci. STAT function has been implicated in the transduction of signals for growth, reproduction, viral defense, and immune regulation. We have isolated and characterized two STAT homologs from the zebrafish Danio rerio. The stat3 gene is expressed in a tissue-restricted manner during embryogenesis, and larval development with highest levels of transcript are detected in the anterior hypoblast, eyes, cranial sensory ganglia, gut, pharyngeal arches, cranial motor nuclei, and lateral line system. In contrast, the stat1 gene is not expressed during early development. The stat3 gene maps to a chromosomal position syntenic with the mouse and human STAT3 homologs, whereas the stat1 gene does not. Despite a higher rate of evolutionary change in stat1 relative to stat3, the stat1 protein rescues interferon-signaling functions in a STAT1-deficient human cell line, indicating that cytokine-signaling mechanisms are likely to be conserved between fish and tetrapods.