Effect of aging on the autoimmune response to rat male accessory glands: deficit of I-E-positive peritoneal cells capable of inducing suppression.

The present report analyzes the ability to induce suppression to rat male accessory gland (RAG) autoantigens and the characteristics of T suppressor (Ts)-inducer peritoneal cells (PC) in old rats which show increased autoimmune responses. The injection of young rats with a purified fraction (FI) of RAG 10 and 3 days prior to immunization with chemically modified RAG (MRAG) markedly reduced the immune response to RAG autoantigens when compared with young rats which had only been immunized (controls), while the pretreatment of old rats did not block the delayed-type hypersensitivity reaction to MRAG when compared with control old rats. The study of cell surface markers on PC from rats injected i.p. 2 h previously with FI of RAG (FI-PC) showed an increase of OX-6 (I-A) and a decrease of OX-17 (I-E) in FI-PC of old rats with respect to FI-PC of young animals, which showed a selective increase of I-E+ Ts-inducer PC. The i.p. injection of FI-PC from old rats into young recipients, 10 and 3 days prior to immunization with MRAG in complete Freund's adjuvant, did not modify the autoimmune response when compared with controls. By contrast, the injection of young and old rats with FI-PC from young animals induced a significant suppression of the autoimmune response. The reduced percentage of I-E+ suppressor-inducer PC provides an explanation for the diminished ability to induce suppression to RAG autoantigens in old rats.