It really is tempting to speculate that this maybe the case with T-bet and remains an interesting question to be explored in future studies
September 28, 2021
It really is tempting to speculate that this maybe the case with T-bet and remains an interesting question to be explored in future studies. The mechanism by which this intronic SNP rs2281808 regulates SIRP expression on T-cells remains unknown. potential mechanisms by which SIRP might regulate human immune responses. Introduction Genome-wide association studies have been instrumental in identifying genetic risk variants in autoimmune diseases. However, in most cases, the biological interpretation of how the reported risk variants potentiate autoimmunity remains unknown. Multiple GWAS studies have shown that the SNP rs2281808 TT variant is associated with type 1 diabetes (T1D)1C3. Rs2281808 TT is an intronic SNP present between exons 5 and 6 of the Signal Regulatory Protein (gene can interfere with transcription factors important in T-cell development7. Further, Differential expression of has also been reported in Systemic Lupus Erythematosus (SLE) patients, suggesting that SIRP might be pathologically relevant in multiple autoimmune diseases. Since polymorphism in gene is associated with the development of T1D, we hypothesized that the rs2281808 genotype might modulate SIRP-mediated regulation of T-cell effector responses. We provide the first evidence that rs2281808 T variant is associated with a reduction in SIRP expression on human T-cells and that this can have potentially pathogenic consequences since SIRPlow CD8 T-cells were characterized by exaggerated effector responses. Results SNP rs2281808 TT is associated with the reduction of SIRP expression on T cells To determine whether the rs2281808 TT variant regulates SIRP expression on T-cells, 79 healthy donors (HD) were genotyped for SNP rs2281808 and assessed for SIRP expression. We found that 45 and 31 HD showed the CC and CT Rabbit Polyclonal to NPHP4 genotypes, respectively, whereas the TT variant was present in 3 HD. Flow cytometry revealed that the CC ARN 077 genotype was associated with robust SIRP expression on the majority of CD4 and CD8 T-cells. In contrast, CD4 (Fig.?1A,B) and CD8 (Fig.?1C,D) T-cells from rs2281808 TT carriers had significantly reduced surface expression of SIRP, whereas the CT genotype was associated with an ARN 077 intermediate SIRP expression that was significantly lower than CC cells (SIRP-MFI on CD4 T-cells in TT vs. CT vs CC: 203??10.8 vs. 350??123 vs 526??244, CC vs. CT & CT vs. TT, p?0.05; CC vs. TT, p?0.01, p?0.05 and SIRP-MFI on CD8 T-cells in TT vs. CT vs. CC: 160??7.9 vs. 275??93 vs. 439??170; CC vs. CT & CT vs. TT, p?0.05; CC vs. TT, p?0.01). Open in a separate window Figure 1 Autoimmune disease risk SNP rs2281808 causes low of SIRP expression on human T-cells. All the 79 PBMC samples from HD were subjected to flow cytometry staining and genotyping for rs2281808 using TaqMan chemistry. SIRP expression relative to rs2281808 genotyping status was analyzed on gated CD3 CD4 and CD3 CD8 T-cells (ACE). Representative histograms (A,C) and cumulative MFI data (B,D) are shown. CD8 T-cells showed a bimodal expression of SIRP, which was used to determine the frequency of SIRPhigh and SIRPlow cells. The frequency of SIRPlow CD8 T-cells is shown in (E). Isotype staining is shown in grey. Gates are shown for SIRPlow cells. One-way ANOVA with Tukeys posthoc test was performed and p?0.05 was considered significant. We also noted that, in contrast to ARN 077 the unimodal distribution of SIRP on CD4 T-cells, it showed a bimodal distribution on CD8 T-cells, which was particularly pronounced in CT carriers (Fig.?1C), who showed significantly greater frequencies of SIRPlow CD8 T-cells as compared to CC carriers (21.8%??12 vs. 37.4%??11, p?0.05; Fig.?1E). In keeping with the MFI, the majority of CD8 T-cells (80%) in TT carriers were SIRPlow (Fig.?1C,E). Unlike CT/TT carriers, SIRPlow CD8 T-cells in CC carriers are absent from the na?ve pool We also noted that 6/42 (14%) of CC individuals in HD showed relatively higher frequencies of SIRPlow CD8 T-cells compared to the rest of the CC donors. Similarly, there were 7/32 (22%) of CT individuals who showed a relatively low fraction of SIRPlow CD8 T-cells (Fig.?1E, outliers). In this regard, the CC individuals exhibited a CT pattern of staining and vice versa. We hypothesized that the SIRPlow cells from CC individuals may represent downregulation of SIRP during effector/memory differentiation (as opposed to having a SIRPlow fraction in na?ve CD8 T-cells). To test.