Measurement of Fcγ Receptor–Mediated Binding and Phagocytosis

Abstract Macrophages are perhaps best recognized for their ability to phagocytose foreign particles. Phagocytosis can be nonspecific, but is often dramatically augmented with the aid of receptors that recognize the Fc portion of antibodies bound to the intruder. Macrophages utilize receptors that recognize IgG (FcγR), which is a major opsonic mediator of phagocytosis. This unit describes two functional assays that quantify macrophage FcγR surface expression. In each assay, IgG‐opsonized sheep red blood cells (SRBC) labeled with Na 2 51 CrO 4 are used to detect interaction with macrophages. The is used to measure phagocytosis of target cells. The is used to measure FcγR‐mediated binding of target cells to macrophages. A choice of opsonin in both methods allows for some discrimination between subclasses of FcγRs that are responsible for the observed results.