Immune complex effects on murine macrophages. II. Immune complex effects on activated macrophages cytotoxicity,...

We investigated the effects of immune complexes on macrophage functions in vitro. Immune complexes inhibit lymphokine induction of both I-Ak expression and cytotoxic activity by fetal calf serum elicited macrophages during long-term (7 days) culture. In addition, induction of antigen presentation was significantly inhibited by immune complexes. Expression of membrane interleukin 1 (IL-1) (a membrane-bound bound form of the T cell mitogen required for antigen presentation by fixed cells) was minimally inhibited by immune complexes. Therefore, inhibition of antigen presentation was primarily due to effects on Ia expression rather than membrane IL 1 expression. The inhibitory effect of immune complexes was not found during short-term culture (4 to 48 hr) when activated macrophages (bearing high levels of Ia) from mice infected with Listeria monocytogenes were examined. Immune complexes maintained or even increased levels of both I-Ak and cytotoxicity in activated macrophages. The implications of these findings for immune complex modulation of the immune response are discussed.