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 (pLN) using mass cytometry and single-cell RNA sequencing (scRNAseq) with combined T cell receptor (TCR) profiling. Cytometric analysis revealed enrichment of T stem-cell memory (TSCM)-like cells (CD8+CD45RA+CD27+CD28+CCR7+CXCR3+) in T1D pLNs. scRNAseq 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 pLN. Immune Response Enrichment Analysis (IREA) indicated IL-15 signaling as a significant driver of these phenotypes. Integrated TCR and transcriptomic analysis revealed a cluster of diverse naïve-like CD8+ T cell clones in T1D pLN. Comparison of pLN and pancreatic slice isolates supported sharing of effector CD8+ T cells, with enhanced terminal effector signatures within the pancreas relative to paired pLN. Multiplex imaging revealed differential localization of TCF1 and 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.