Defective suppressor cell generation in juvenile onset diabetes.

Lymphocytes of juvenile onset, insulin-dependent diabetics failed to generate suppressor cell activity after preincubation with concanavalin A (Con A). The mean suppression of the autologous proliferative response to phytohemagglutinin (PHA) was 6.1 +/- 7.8% (mean +/- SEM) in the diabetics and 34.0 +/- 4.9% in 9 age-matched healthy controls (p less than 0.01). Cell mixing experiments identified the defect to be in the generation of suppressor cells rather than in the responses to their action. Plasma of insulin-dependent diabetics had no effect on the generation of suppressor activity. In contrast to our findings in insulin-dependent diabetics, Con A preincubation of lymphocytes from 4 maturity onset diabetics induced normal suppression of PHA responses. Defective immunoregulation is present in insulin-dependent diabetes and may underlie autoimmunity.