Analysis of islet antigen-specific autoreactive T cells from Japanese patients with slowly progressive insulin-dependent diabetes mellitus.

Pancreatic islet antigen-specific autoreactive T cells are involved in inflammation in slowly progressive insulin-dependent diabetes mellitus (SPIDDM). Pancreatic islet antigens, such as glutamic acid decarboxylase 65 (GAD), insulinoma-associated protein 2 (IA-2), and insulin, are associated with SPIDDM. However, the association between pancreatic islet antigen-specific T cells and SPIDDM incidence remains unclear. We aimed to identify the characteristics of pancreatic islet antigen autoreactive T cells in Japanese patients with SPIDDM. Peripheral blood mononuclear cells were obtained from Japanese patients with type 1 diabetes mellitus (T1DM) enrolled in our diabetic cohort study. An ex vivo cytokine assay using overlapping peptides of GAD, IA-2, and insulin was performed. The production of tumor necrosis factor-alpha (TNF-α) by CD4⁺ T cells and the fractions of TNF-α⁺ CD4⁺ T cell fractions were measured by fluorescence-activated cell sorting. The %parent of TNF-α⁺ CD4⁺ T cells and the effector memory TNF-α⁺ CD4⁺ T cells increased after stimulation with overlapping GAD and IA-2 peptides. The response to overlapping peptides was varied among individual SPIDDM case. Response to overlapping peptides of GAD, IA-2, and insulin were observed in each group of T1DM. Islet antigen-specific autoreactive TNF-α⁺ CD4+ T cells from Japanese patients with SPIDDM were activated by overlapping GAD and IA-2 peptides.