Trans-ancestral studies fine map the SLE-susceptibility locus TNFSF4.

We previously established an 80 kb haplotype upstream of TNFSF4 as a susceptibility locus in the autoimmune disease SLE. SLE-associated alleles at this locus are associated with inflammatory disorders, including atherosclerosis and ischaemic stroke. In Europeans, the TNFSF4 causal variants have remained elusive due to strong linkage disequilibrium exhibited by alleles spanning the region. Using a trans-ancestral approach to fine-map the locus, utilising 17,900 SLE and control subjects including Amerindian/Hispanics (1348 cases, 717 controls), African-Americans (AA) (1529, 2048) and better powered cohorts of Europeans and East Asians, we find strong association of risk alleles in all ethnicities; the AA association replicates in African-American Gullah (152,122). The best evidence of association comes from two adjacent markers: rs2205960-T (P=1.71 × 10(-34) , OR=1.43[1.26-1.60]) and rs1234317-T (P=1.16 × 10(-28) , OR=1.38[1.24-1.54]). Inference of fine-scale recombination rates for all populations tested finds the 80 kb risk and non-risk haplotypes in all except African-Americans. In this population the decay of recombination equates to an 11 kb risk haplotype, anchored in the 5' region proximal to TNFSF4 and tagged by rs2205960-T after 1000 Genomes phase 1 (v3) imputation. Conditional regression analyses delineate the 5' risk signal to rs2205960-T and the independent non-risk signal to rs1234314-C. Our case-only and SLE-control cohorts demonstrate robust association of rs2205960-T with autoantibody production. The rs2205960-T is predicted to form part of a decameric motif which binds NF-κBp65 with increased affinity compared to rs2205960-G. ChIP-seq data also indicate NF-κB interaction with the DNA sequence at this position in LCL cells. Our research suggests association of rs2205960-T with SLE across multiple groups and an independent non-risk signal at rs1234314-C. rs2205960-T is associated with autoantibody production and lymphopenia. Our data confirm a global signal at TNFSF4 and a role for the expressed product at multiple stages of lymphocyte dysregulation during SLE pathogenesis. We confirm the validity of trans-ancestral mapping in a complex trait.

Expansion of circulating T cells resembling follicular helper T cells is a fixed phenotype that identifies a subset of severe systemic lupus erythematosus.

OBJECTIVE: In the sanroque mouse model of lupus, pathologic germinal centers (GCs) arise due to increased numbers of follicular helper T (Tfh) cells, resulting in high-affinity anti-double-stranded DNA antibodies that cause end-organ inflammation, such as glomerulonephritis. The purpose of this study was to examine the hypothesis that this pathway could account for a subset of patients with systemic lupus erythematosus (SLE). METHODS: An expansion of Tfh cells is a causal, and therefore consistent, component of the sanroque mouse phenotype. We validated the enumeration of circulating T cells resembling Tfh cells as a biomarker of this expansion in sanroque mice, and we performed a comprehensive comparison of the surface phenotype of circulating and tonsillar Tfh cells in humans. This circulating biomarker was enumerated in SLE patients (n = 46), Sjögren's syndrome patients (n = 17), and healthy controls (n = 48) and was correlated with disease activity and end-organ involvement. RESULTS: In sanroque mice, circulating Tfh cells increased in proportion to their GC counterparts, making circulating Tfh cells a feasible human biomarker of this novel mechanism of breakdown in GC tolerance. In a subset of SLE patients (14 of 46), but in none of the controls, the levels of circulating Tfh cells (defined as circulating CXCR5+CD4+ cells with high expression of Tfh-associated molecules, such as inducible T cell costimulator or programmed death 1) were increased. This cellular phenotype did not vary with time, disease activity, or treatment, but it did correlate with the diversity and titers of autoantibodies and with the severity of end-organ involvement. CONCLUSION: These findings in SLE patients are consistent with the autoimmune mechanism in sanroque mice and identify Tfh effector molecules as possible therapeutic targets in a recognizable subset of patients with SLE.

Association of the co-stimulator OX40L with systemic lupus erythematosus.

The archetypal systemic autoimmune disease systemic lupus erythematosus (SLE) has incompletely understood pathogenesis, although evidence suggests a strong genetic component. Unlike organ-specific autoimmune diseases such as type 1 diabetes, the genetics of lupus are not as dominated by the effect of a single locus. Undoubtedly, the major histocompatibility complex is the greatest and most consistent genetic risk factor in SLE susceptibility; however, recent candidate gene and whole genome association (WGA) studies have identified several other genes that are likely to advance our understanding of this complex disease. One of these, the TNF superfamily member OX40L, interacts with its unique receptor OX40, to maintain T cell memory by providing a late-stage co-stimulatory signal to sustain the survival of activated T cells. The precise immunological consequences are yet to be determined; however, signalling through OX40-OX40L is bidirectional and the reverse signalling pathway via OX40L may quantitatively enhance B cell proliferation to augment the B cell hyperactivity found in SLE. Like OX40L, several genes recently identified in WGA studies are components of B cell pathways. Collectively, these genes will help us to unravel the mechanisms by which aberrant B cell signalling results in lupus pathogenesis.

Polymorphism at the TNF superfamily gene TNFSF4 confers susceptibility to systemic lupus erythematosus.

Systemic lupus erythematosus (SLE) is a multisystem complex autoimmune disease of uncertain etiology (OMIM 152700). Over recent years a genetic component to SLE susceptibility has been established. Recent successes with association studies in SLE have identified genes including IRF5 (refs. 4,5) and FCGR3B. Two tumor necrosis factor (TNF) superfamily members located within intervals showing genetic linkage with SLE are TNFSF4 (also known as OX40L; 1q25), which is expressed on activated antigen-presenting cells (APCs) and vascular endothelial cells, and also its unique receptor, TNFRSF4 (also known as OX40; 1p36), which is primarily expressed on activated CD4+ T cells. TNFSF4 produces a potent co-stimulatory signal for activated CD4+ T cells after engagement of TNFRSF4 (ref. 11). Using both a family-based and a case-control study design, we show that the upstream region of TNFSF4 contains a single risk haplotype for SLE, which is correlated with increased expression of both cell-surface TNFSF4 and the TNFSF4 transcript. We hypothesize that increased expression of TNFSF4 predisposes to SLE either by quantitatively augmenting T cell-APC interaction or by influencing the functional consequences of T cell activation via TNFRSF4.

Association of IRF5 in UK SLE families identifies a variant involved in polyadenylation.

Results from two studies have implicated the interferon regulatory gene IRF5 as a susceptibility gene in systemic lupus erythematosus (SLE). In this study, we conducted a family-based association analysis in 380 UK SLE nuclear families. Using a higher density of markers than has hitherto been screened, we show that there is association with two SNPs in the first intron, rs2004640 (P = 3.4 x 10(-4)) and rs3807306 (P = 4.9 x 10(-4)), and the association extends into the 3'-untranslated region (UTR). There is a single haplotype block encompassing IRF5 and we show for the first time that the gene comprises two over-transmitted haplotypes and a single under-transmitted haplotype. The strongest association is with a TCTAACT haplotype (T:U = 1.92, P = 5.8 x 10(-5)), which carries all the over-transmitted alleles from this study. Haplotypes carrying the T alleles of rs2004640 and rs2280714 and the A allele of rs10954213 are over-transmitted in SLE families. The TAT haplotype shows a dose-dependent relationship with mRNA expression. A differential expression pattern was seen between two expression probes located each side of rs10954213 in the 3'-UTR. rs10954213 shows the strongest association with RNA expression levels (P = 1 x 10(-14)). The A allele of rs10954213 creates a functional polyadenylation site and the A genotype correlates with increased expression of a transcript variant containing a shorter 3'-UTR. Expression levels of transcript variants with the shorter or longer 3'-UTRs are inversely correlated. Our data support a new mechanism by which an IRF5 polymorphism controls the expression of alternate transcript variants which may have different effects on interferon signalling.

The innate immune responses of colonic epithelial cells to Trichuris muris are similar in mouse strains that develop a type 1 or type 2 adaptive immune response.

Trichuris muris resides in intimate contact with its host, burrowing within cecal epithelial cells. However, whether the enterocyte itself responds innately to T. muris is unknown. This study investigated for the first time whether colonic intestinal epithelial cells (IEC) produce cytokines or chemokines following T. muris infection and whether divergence of the innate response could explain differentially polarized adaptive immune responses in resistant and susceptible mice. Increased expression of mRNA for the proinflammatory cytokines gamma interferon (IFN-gamma) and tumor necrosis factor and the chemokine CCL2 (MCP-1) were seen after infection of susceptible and resistant strains, with the only difference in expression being a delayed increase in CCL2 in BALB/c IEC. These increases were ablated in MyD88-/- mice, and NF-kappaB p65 was phosphorylated in response to T. muris excretory/secretory products in the epithelial cell line CMT-93, suggesting involvement of the MyD88-NF-kappaB signaling pathway in IEC cytokine expression. These data reveal that IEC respond innately to T. muris. However, the minor differences identified between resistant and susceptible mice are unlikely to underlie the subsequent development of a susceptible type 1 (IFN-gamma-dominated) or resistant type 2 (interleukin-4 [IL-4]/IL-13-dominated) adaptive immune response.