Detection of lymphocytotoxic antibodies in relatives of patients with type I diabetes.

Concentrations of lymphocytotoxic antibodies were measured in serum samples from 19 patients recently diagnosed as having type I diabetes and 43 healthy relatives (33 consanguineous and 10 non-consanguineous). The specificity of the reaction was tested at 15 degrees C and 37 degrees C against T lymphocytes and purified helper/inducer and cytotoxic/suppressor subsets. The concentrations of lymphocytotoxic antibodies in each of the three test groups were significantly higher than those in controls (type I patients, p less than 0.005; consanguineous relatives, p less than 0.001; and non-consanguineous relatives, p less than 0.002). The frequency of detection of the antibodies was also greater in each of the study groups (p less than 0.01, p less than 0.01, and p less than 0.05, respectively). Cytotoxicity affected both subsets at 15 degrees C but only cytotoxic/suppressor cells at 37 degrees C. The findings of lymphocytotoxic antibodies in healthy relatives of type I diabetics, irrespective of consanguinity, suggests that an environmental agent such as a virus is at least partially responsible for this lymphocytotoxic effect. Furthermore, the residual cytotoxic/suppressor cell killing at 37 degrees C could explain the defect of suppressor cells observed in these patients.