Quantifying complement-mediated phagocytosis by human monocyte-derived macrophages

The present study demonstrates that SRBC can be opsonized with untreated hu man serum such that lysis by active complement components is minimal but su fficient opsonization occurs to permit high rates of complement-mediated ph agocytosis. Phagocytosis of SRBC opsonized with 2% whole human serum by hum an monocyte-derived macrophages was quantified in a colourimetric assay. In gestion of SRBC was shown to occur solely via complement receptors because no phagocytosis was observed when SRBC were coated with heat- inactivated h uman serum, phagocytosis was augmented by the phorbol ester, PMA, and phago cytosis was inhibited by a protein kinase C (PKC)-specific inhibitor RO 31- 8220. This method was used to demonstrate directly that HIV-1 infection of human monocyte-derived macrophages inhibits complement-mediated phagocytosi s and will provide a useful tool for pharmacological investigations on comp lement-mediated phagocytosis by adherent macrophages.