INDUCTION OF THYMIC HYPERPLASIA AND SUPPRESSION OF SPLENIC T-CELLS BYLESIONING OF THE ANTERIOR HYPOTHALAMUS IN AGING WISTAR RATS

The effect of destruction of the anterior hypothalamus (AHT) on the im mune system was examined in rats 4-50 weeks after the treatment. The t hymic weight significantly increased in the experimental group regardl ess of age, while a significant decrease was observed in the percentag e of splenic T cells as well as their proliferative response to phytoh emagglutinin (PHA). The increase of thymic weight was observed as long as 24 weeks and the decrease of splenic T cell number was observed as long as 50 weeks after the operation. Hypophysectomy gave rise to atr ophy of both thymus and spleen, while either adrenalectomy or gonadect omy resulted in hypertrophy of both thymus and spleen. The results tak en together suggest that development and aging of the immune system ar e under the balance of positive and negative signals from AHT. (C) 199 7 Elsevier Science B.V.