Ratiometric Analysis of Subcellular Recruitment of Fc Receptors During Phagocytosis

Numerous immune receptors have the ability to mediate phagocytosis of large particles by triggering dynamic local rearrangement of the cytoskeleton and cell membrane. Different receptors can be differentially recruited to sites of particle binding, which in turn can have important functional consequences with respect to engulfment and downstream signaling. Using Fcγ receptor-mediated phagocytosis of IgG-coated particles as a model, we describe a method for analyzing nascent phagocytic cups and quantifying relative receptor levels at sites of phagocytosis. This technique is based on a ratiometric analysis of subcellular localization of exogenously expressed receptors carrying different fluorescent protein tags. This approach could be applied more generally to the analysis of surface membrane protein localization in the context of any dynamic cellular process.