Peptide-specific cytotoxicity of T lymphocytes against glutamic acid decarboxylase and insulin in type I diabetes mellitus

Cytotoxic T lymphocytes (CTL) against pancreatic p-cells probably play a ma jor role in the etiology of type 1 diabetes mellitus (DM). CTLs recognize a complex formed between MHC class 1 acid antigenic peptides fragments deriv ed from intracellular processing of proteins. However, the exogenous peptid es, which show strong affinities to MHC class I, can be presented. In this study, we focused on the cytotoxic activity of peripheral lymphocytes in pa tients with type 1 DM against the peptides of glutamic acid decarboxylase ( GAD) and insulin, which can bind MHC class 1 A24. Lymphocytes were isolated from peripheral blood of 12 type 1 DM patients and eight healthy control s ubjects. The effector cells were cultured with peptides, IL-2 and IL-7, res timulated weekly by autologous antigen presenting cells, which were culture d with IL-4 and GM-CSF. On day 21, CTL activities: of cultured effector cel ls were tested against autologous EB-blast cells as target cells pulsed wit h the stimulating peptides using Cr-51 release assay. The results showed th at cytotoxicity against insulin peptide binding to MHC class I A24 was obse rved in lymphocytes of four out of ten patients with type 1 DM. The mean cy totoxicity was 46.0% of the maximum release. The antibody against HLA-class I inhibited this effect. Cytotoxicity against GAD peptide which bind MHC c lass 1 A24 was not observed in seven patients. None of healthy controls sho wed cytotoxicity against GAD or insulin peptides was observed. This is the first report describing the cytotoxic activity of CD8(+) T lymphocytes: aga inst insulin in type 1 DM. (C) 2001 Elsevier Science Ireland Ltd. All right s reserved.