T-Lymphocyte Lines Specific for Glutamic Acid Decarboxylase (GAD) the 64K β-Cell Antigen of IDDM

Insulin-dependent diabetes mellitus (IDDM) is viewed as a thymus-dependent autoimmune disease, although the specific β-cell autoantigen or autoantigens remain unknown. The recent identification of the β-cell 64K antigen as the enzyme glutamic acid decarboxylase (GAD) permits investigation of GAD as a candidate for the autoantigen associated with β-cell destruction, mediated by T-lymphocytes, in susceptible individuals. In this study, we describe the isolation of GAD-specific T-lymphocyte lines from BB rats, an animal model of IDDM. GAD (Escherichia coli) was inoculated into the footpads of diabetes-resistant BB rats, and after 10 days, a popliteal lymph node cell culture suspension was prepared. GAD-specific T lymphocytes were obtained by culture with interleukin 2 and repeated stimulation with GAD in the presence of BB rat thymic antigen-presenting cells. Four stable, CD4⁺, MHC (RT1^u)-restricted T-lymphocyte lines were isolated. They proliferate selectively in the presence of GAD and secrete interleukin 2 and interferon-γ. T-lymphocyte lines such as these could be important in the definition of pathogenetic epitopes associated with GAD.