The effect of azathioprine, cyclosporine A and insulin on the in vitro lymphocyte-mediated cytotoxicity in type I diabetic patients.

Previously both specific and nonspecific immune reactions have been reported in patients with type I diabetes mellitus. In this study the effect of various immunosuppressive drugs and insulin was studied on in vitro lymphocyte-mediated cytotoxicity in 20 type I diabetic patients. Twenty sex- and age-matched healthy subjects served as controls. Human pancreas-extract (300 micrograms/ml protein)-coated, 51-Chromium labeled chicken erythrocytes were used as target cells and separated T-lymphocytes as effector cells with and without azathioprine 50 micrograms/50 microliters (Wellcome), Cyclosporine A 5 ng/50 microliters (Sandoz) and MC Actrapid insulin 0.1 IU/50 microliters (Novo). The degree of cytotoxicity was expressed with cytotoxic capacity: the number of maximal killed target cells. Simultaneously islet cell antibodies (ICA) in sera and the number of activated T-lymphocytes were assessed. Significant lymphocyte-mediated cytotoxicity was observed in the majority of type I diabetic patients (18/20), while no cytotoxicity was found in the control cases. The cytotoxicity decreased in all 16 patients using azathioprine or insulin, independently of ICA and HLA-DR positivity. The number of killed target cells was lowered considerably by Cyclosporine A in all 18 patients having cytotoxicity against pancreas-extract. Our observations reveal that Cyclosporine A proved to be the most effective immunosuppressive agent in vitro. It decreases not only the leucocyte migration inhibition as previously observed, but also the lymphocyte-mediated cytotoxicity, which represents the late stage of cellular immune reactions against pancreatic tissue.