Cell-mediated immune reactions against B cells and defect of suppressor cell activity in type 1 (insulin-dependent) diabetes mellitus.

A cytotoxic effect of peripheral blood mononuclear cells from 22 out of 23 newly diagnosed Type 1 (insulin-dependent) diabetic patients against B cells of isolated rat islets was demonstrated. The addition of peripheral blood mononuclear cells from healthy subjects reduced the cytotoxic effect in 9 out of 10 patients. The addition of peripheral blood mononuclear cells from other diabetic patients was without significant effect in 14 out of 16 cases. The results indicate functional abnormalities of peripheral blood mononuclear cells in newly diagnosed Type 1 diabetes. Beside cytotoxic effects against B cells, a defect in the suppressor function seems to exist. The activation of T-lymphocytes might be a consequence of such a defect.