REGULATION OF IMMUNE-RESPONSE IN AUTO-IMMUNE NZB-NZW F1 MICE .2. AGE-DEPENDENT RELEASE OF SUPPRESSIVE FACTORS FROM SPLEEN-CELLS

Abstract

Suppressor cells in the spleens of overtly autoimmune NZB .times. NZW (B/W) mice, but not age matched normal strain mice, released a small, < 20,000 Dalton factor which inhibited early events in the anti-SRBC [sheep red blood cell] PFC [plaque-forming cell] response and the mitogenic response. This splenic inhibitory factor (SIF) had the following properties: it was stable on heating (56.degree., 30 min) and freezing (-70.degree.); it was non-specific for antigen; it was absorbed and/or inactivated by target cells in young B/W spleen cell cultures; and it was released gradually into the culture medium by metabolically active cells. SIF also blocked the T [thymus-derived] cell replacing effect of allogeneic factors (TRF) in the anti-SRBC response. SIF may lead to the immunodepressed state in overtly autoimmune B/W mice by preventing the activation or differentiation of lymphocytes responding to exogenous antigen.