Figure 5.

FcγRI is necessary and sufficient for IgG-mediated phagocytosis. BMDM from wild type (CD57BL/6), FcγRIIb knockout mice (CD32^−/−) or mice expressing only FcγRI (FcγRI only) were transduced with virus encoding PKC-ε-GFP (to visualize internalization) and phagocytosis followed by live imaging as detailed in Methods. Compared to CD57BL/6 (A); phagocytosis was unaffected by removal of CD32 (B). Adding α-CD16/32 (C) or α-CD16.2 (D) to CD32^−/− cells did not affect internalization. Blocking FcγRI with α-CD64 reduced internalization (E) but not target binding (inset), supporting a role for FcγRI in IgG-mediated phagocytosis. (F–H) Internalization by C57BL/6 and FcγRI only macrophages is similar. Quantitation of phagocytic rate from movies reveal that uptake by FcγRI only cells is equivalent to controls, arguing that FcγRI is necessary and sufficient for IgG-mediated phagocytosis. (H) Each dot represents data from one cell, statistical significance was tested using an unpaired t-test.