Corticosteroids inhibit murine macrophage Ia expression and interleukin 1 production.

Corticosteroids have profound effects on functions of the macrophage associated with antigen presentation to T cells. The drugs inhibited the expression of surface I-region-associated (Ia) antigens by peritoneal macrophages both in vitro and in vivo, reduced the production of IL 1, and inhibited antigen presentation for T cell proliferation by macrophages. The doses of hydrocortisone and prednisolone that inhibited by 50% Ia expression in cultured macrophages ranged around 2 to 5 x 10(-8) M. These results could explain one mechanism by which corticosteroids suppress the induction of immune responses.