Immune dysregulation and stem-like CD8+ T cell enrichment in type 1 diabetes pancreatic lymph nodes.

Effector CD8+ T cells are key drivers of type 1 diabetes (T1D) pathogenesis, yet questions remain regarding the molecular defects leading to altered cytotoxicity, peripheral tissue phenotype, and receptor specificity. We analyzed human pancreatic lymph nodes (pLNs) using mass cytometry and single-cell RNA-seq (scRNA-seq) with combined T cell receptor (TCR) profiling. Cytometric analysis revealed enrichment of T stem cell memory-like (TSCM-like) cells (CD8+CD45RA+CD27+CD28+CCR7+CXCR3+) in T1D pLNs. scRNA-seq indicated an elevated inflammatory cytokine gene signature (IFITM3, LTB) along with regulators of terminal differentiation (BCL6, BCL3), coupled with downregulation of exhaustion-associated genes (DUSP2, NR4A2, TSC22D3) in CD8+ T cells in T1D pLNs. Immune response enrichment analysis (IREA) indicated IL-15 signaling as a significant driver of these phenotypes. Integrated TCR and transcriptomics analysis revealed a cluster of diverse naive-like CD8+ T cell clones in T1D pLNs. Comparison of pLNs and pancreatic tissue slice isolates indicated sharing of effector CD8+ T cells, with enhanced terminal effector signatures within the pancreas relative to paired pLNs. Multiplex imaging revealed differential localization of T cell factor 1 (TCF1)- and thymocyte selection-associated high mobility group box protein (TOX)-expressing T cells in the pancreas, with islet-proximal TCF1+TOX+ cells displaying a mixture of activation and exhaustion-associated phenotypes. Thus, we provide multimodal cellular profiles enriched in T1D tissues for consideration in therapeutic targeting.