Reduced function of the adaptor SH2B3 promotes T1D via altered cytokine-regulated, T cell intrinsic immune tolerance

Genome-wide association studies have identified SH2B3 as an important non-MHC gene for islet autoimmunity and type 1 diabetes (T1D). In this study, we found a single SH2B3 haplotype significantly associated with increased risk for human T1D. Fine mapping has demonstrated the most credible causative variant is the single nucleotide rs3184504*T polymorphism in SH2B3. To better characterize the role of SH2B3 in T1D, we used mouse modeling and found a T cell-intrinsic role for SH2B3 regulating peripheral tolerance. SH2B3 deficiency had minimal effect on TCR signaling or proliferation across antigen doses, yet enhanced cell survival and cytokine signaling including common gamma chain-dependent and interferon-gamma receptor signaling. SH2B3 deficient naïve CD8⁺ T cells showed augmented STAT5-MYC and effector-related gene expression partially reversed with blocking autocrine IL-2 in culture. Using the RIP-mOVA model, we found CD8⁺ T cells lacking SH2B3 promoted early islet destruction and diabetes without requiring CD4⁺ T cell help. SH2B3-deficient cells demonstrated increased survival and reduced activation-induced cell death. Lastly, we created a spontaneous NOD.Sh2b3^-/- mouse model and found markedly increased incidence and accelerated T1D across sexes. Collectively, these studies identify SH2B3 as a critical mediator of peripheral T cell tolerance limiting the T cell response to self-antigens.