Identification of cells responsible for the suppression of anti-beta-cell cytotoxicity in type I (insulin-dependent) diabetes mellitus.

Peripheral blood mononuclear cells (PBMC) from newly diagnosed type I diabetic patients induced a significantly higher cytotoxic insulin leakage from isolated rat islets during a 20-h incubation. compared with PBMC from healthy controls (13.9 +/- 7.7 versus 2.6 +/- 3.2 ng insulin/islet/20 h). The addition of PBMC from healthy subjects in a ratio of 1:4 suppressed the cytotoxic effect (13.9 +/- 7.7 to 6.7 +/- 4.4 ng insulin/islet/20 h). Depletion of CD8+ T lymphocytes from the PBMC of healthy subjects abolished their suppressive capacity, while depletion of CD4+ T lymphocytes and pre-incubation with CD3 monoclonal antibodies had no effect.