Maturational impairment of thymic lymphocytes in streptozotocin-induced diabetes in rats.

Streptozotocin (STZ)-induced diabetes in rats was associated with marked decreases in thymus weight and the number of thymic lymphocytes. Histologically, the cortical lymphocytes which were present near the cortico-medullary junction in the thymus seemed to be reduced selectively in the STZ-induced diabetes. Rosette-forming cells, which bind to guinea pig erythrocytes in the presence of fetal calf serum, were also significantly decreased. Insulin treatment allayed these intrathymic changes. Preincubation of thymic lymphocytes from diabetic rats with thymosin fraction 5 significantly enhanced the percentage of rosette-forming cells to near the control level. These results suggest that a maturational impairment of thymus cortical lymphocytes may be caused in STZ-induced diabetes with hypoinsulinemia and it may be intimately related to reductions in thymus weight and the number of thymic lymphocytes.