Cytokine regulation of complement receptor-mediated ingestion by mouse peritoneal macrophages. M-CSF and IL-4 activate phagocytosis by a common mechanism requiring autostimulation by IFN-beta

Macrophage CSF (M-CSF, CSF-1) and IL-4 are two cytokines known to have effects on mature monocytic phagocytes in vitro. In this report we show that M-CSF and IL-4 activate resident mouse peritoneal macrophages to ingest particles via their C3b and C3bi receptors, which are not capable of mediating ingestion in resting cells. IgG-mediated ingestion was also increased by IL-4 and M-CSF. IL-1, IL-2, TNF-alpha, and IFN-gamma were not able to stimulate C receptor-mediated ingestion. Stimulation by IL-4 and M-CSF is dependent upon high cell density and greater than 24-h exposure to the cytokine. Interestingly, antibody to IFN-alpha/beta and mAb to IFN-beta inhibited the enhanced ingestion caused by both M-CSF and IL-4. However, neither IFN-alpha nor IFN-beta alone stimulated C receptor-mediated ingestion. M-CSF did not affect the ligand-independent distribution of CR3 on the macrophage surface. We conclude that two apparently unrelated cytokines, M-CSF and IL-4, both enhance macrophage phagocytosis of C and IgG-coated targets via a common pathway in which autocrine stimulation with IFN-alpha/beta is necessary but not sufficient.