Diabetogenic CD8 Tcells are highly adaptive in beta-cell antigen recognition 2258433

Introduction Type 1 diabetes (T1D) is an autoimmune disease in which cytotoxic CD8+ T cells destroy insulin-producing β cells through TCR recognition of β-cell antigens presented by MHC class I. Yet, how CD8 T cells recognize these self-antigens and bypass self-tolerance remains unclear. We used ultrasensitive two-dimensional (2D) assays to quantify TCR affinity and bond lifetime, aiming to reveal how antigen recognition dynamics drive diabetogenic CD8 T cell activation. Methods We focused on two diabetogenic TCR transgenic systems–G9C8 and NY8.3–which recognize distinct β-cell autoantigens, an insulin epitope and an IGRP epitope, respectively. Using 2D kinetic measurements, we assessed TCR affinity and bond lifetime during thymocyte selection and after diabetes onset. To test generality, we further performed single-cell RNA sequencing (scRNA-seq) combined with TCR V(D)J sequencing on T cells from IGRP/insulin peptide-immunized mice, selected a panel of TCRs specific to each peptide, generated corresponding TCR retrogenic mice, and repeated the same 2D measurements. Results Our data show that CD8 T cells form weak bonds with β-cell antigens during thymocyte selection but greatly increase bond strength after activation upon diabetes onset. This adaptive self-reactivity occurs at the single TCR clonal level and is mediated by the CD8 coreceptor rather than by changes in the TCR itself. Notably, this phenomenon was not observed for foreign antigen recognition. The follow-up experiments with newly generated TCRs of the same specificities confirmed the highly adaptive self-reactivity of diabetogenic CD8 T cells. Conclusion These findings support a model in which, during autoimmune diabetes, CD8 T cells fundamentally alter self-antigen recognition by modulating TCR binding kinetics. This enables them to evade thymic negative selection while acquiring heightened self-reactivity in the periphery, ultimately mediating β-cell destruction and disease onset.