Epitope Hierarchy in Type 1 Diabetes Pathogenesis

Type 1 diabetes (T1D) is an autoimmune disease mediated by T cells destroying insulin-producing β cells. Identifying the antigenic epitopes targeted by autoreactive T cells is crucial for understanding pathogenesis, detecting biomarkers, and developing immunotherapies. This paper covers T-cell epitopes in T1D, focusing on pre-proinsulin and hybrid insulin peptides (HIPs) as major autoantigens. Substantial evidence highlights epitopes in the insulin B-chain and C-peptide as dominant targets for pathogenic CD4 and CD8 T cells infiltrating the islets. HIPs, formed by proinsulin fragments ligated to other peptides, constitute a novel class of epitopes detected in human and mouse islets. In addition, the paper also examines neoepitopes arising from posttranslational modifications, splice variants, and defective ribosomal products. A key challenge is differentiating genuinely pathogenic epitopes driving disease from nonpathogenic mimotopes. Identifying any essential, indispensable epitopes among this array could enable the development of antigen-specific immunotherapies targeting the root causative factors underlying T1D.