Rheumatoid arthritis (RA) is a heterogeneous syndrome of which a subset of patients develops vascular inflammation. The genetic determinants that confer risk for rheumatoid vasculitis are not known, but patients with vascular complications are known to have an expansion of CD4⁺CD28^null T cells, a cell population potentially involved in endothelial damage. CD4⁺CD28^null T cell clones isolated from RA patients with vasculitis were found to express killer cell immunoglobulin–like receptors (KIRs) with the stimulatory KIR2DS2 often present in the absence of opposing inhibitory receptors with related specificities. To test the hypothesis that the KIR2DS2 gene is involved in the development of vasculitis, association studies were performed. The KIR2DS2 gene was significantly enriched among patients with rheumatoid vasculitis compared with normal individuals (odds ratio 5.56, P = 0.001) and patients with RA but no vasculitis (odds ratio 7.96, P = 0.001). Also, the distribution of human histocompatibility leukocyte antigen (HLA)-C, the putative ligand for KIRs, was significantly different in patients with rheumatoid vasculitis in comparison with the control populations. These data suggest that HLA class I–recognizing receptors and HLA class I genes are genetic risk determinants that modulate the pattern of RA expression. Specifically, KIR2DS2 in conjunction with the appropriate HLA-C ligand may have a role in vascular damage by regulating CD4⁺CD28^null T cells.

Objective To evaluate the use of prospective screening for the HLA-B*58:01 allele to identify Taiwanese individuals at risk of severe cutaneous adverse reactions (SCARs) induced by allopurinol treatment. Design National prospective cohort study. Setting 15 medical centres in different regions of Taiwan, from July 2009 to August 2014. Participants 2926 people who had an indication for allopurinol treatment but had not taken allopurinol previously. Participants were excluded if they had undergone a bone marrow transplant, were not of Han Chinese descent, and had a history of allopurinol induced hypersensitivity. DNA purified from 2910 participants’ peripheral blood was used to assess the presence of HLA-B*58:01. Main outcome measures Incidence of allopurinol induced SCARs with and without screening. Results Participants who tested positive for HLA-B*58:01 (19.6%, n=571) were advised to avoid allopurinol, and were referred to an alternate drug treatment or advised to continue with their prestudy treatment. Participants who tested negative (80.4%, n=2339) were given allopurinol. Participants were interviewed once a week for two months to monitor symptoms. The historical incidence of allopurinol induced SCARs, estimated by the National Health Insurance research database of Taiwan, was used for comparison. Mild, transient rash without blisters developed in 97 (3%) participants during follow-up. None of the participants was admitted to hospital owing to adverse drug reactions. SCARs did not develop in any of the participants receiving allopurinol who screened negative for HLA-B*58:01. By contrast, seven cases of SCARs were expected, based on the estimated historical incidence of allopurinol induced SCARs nationwide (0.30% per year, 95% confidence interval 0.28% to 0.31%; P=0.0026; two side one sample binomial test). Conclusions Prospective screening of the HLA-B*58:01 allele, coupled with an alternative drug treatment for carriers, significantly decreased the incidence of allopurinol induced SCARs in Taiwanese medical centres.

Expansion of CD4⁺CD28^null T cells is a characteristic finding in patients with rheumatoid arthritis. Despite lacking CD28 molecules, these unusual CD4 T cells undergo clonal proliferation and form large and long-lived clonal populations. They produce high levels of IFN-γ, exhibit autoreactivity, and have cytolytic function. The mechanisms facilitating the expansion and longevity of CD4⁺CD28^null T cell clones in vivo are unknown. Here, we report that CD4⁺CD28^null, but not CD4⁺CD28⁺, T cells express MHC class I-recognizing receptors normally found on NK cells. CD4⁺CD28^null T cells preferentially expressed killer cell activating receptors (KAR), often in the absence of killer cell inhibitory receptors. Cross-linking of KAR molecules enhanced the proliferative response to TCR-mediated stimulation, but not the cytolytic function of CD4⁺CD28^null T cells, suggesting different signaling pathways in CD4 T cells and NK cells. Triggering of KAR signaling led to the phosphorylation of several cellular targets, although the pattern of phosphorylation differed from that induced by the TCR. Aberrant expression of KAR molecules in the absence of inhibitory receptors and in the appropriate HLA setting may lead to the clonal outgrowth of autoreactive CD4⁺CD28^null T cells commonly seen in rheumatoid arthritis.

Objective.: The expression of autoimmunity in mice deficient in programmed death 1 (PD‐1) suggests that PD‐1 is a candidate gene involved in the development of human autoimmune diseases such as systemic lupus erythematosus (SLE) and rheumatoid arthritis (RA). We therefore tested the potential association between PD‐1 and the development of SLE and RA by conducting case–control genetic‐association studies.Methods.: Ninety‐eight SLE patients, 84 RA patients, and sex‐matched control subjects for each disease group were recruited and genotyped for a single‐nucleotide polymorphism, C+872T, in the human PD‐1 gene. The significance of the association of the PD‐1 gene with SLE or with RA was analyzed by statistical tests for the difference in genotype distribution between disease and control groups.Results.: The human PD‐1 gene was found to be significantly associated with disease development in RA patients, but not SLE patients. The risk of RA development appeared to be significantly increased by carriage of the T allele (odds ratio 3.32, P < 0.0001) or the C/T genotype (odds ratio 3.52, P < 0.00005).Conclusion.: The PD‐1 gene is significantly associated with RA susceptibility, suggesting the possibility that PD‐1 may contribute to the pathogenesis of RA.