Fcγ receptors exhibit different phagocytosis potential in human neutrophils

In neutrophils, two receptors for IgG antibodies, namely Fc gamma RIIA and Fc gamma RIIIB are constitutively expressed, and a third one, Fc gamma RI, can be upregulated by interferon-gamma. Whether Fc gamma RIIIB is capable of triggering phagocytosis by itself is still controversial. The main role of Fc gamma RI has not been clearly established in these cells. To address this problem, neutrophils were treated with interferon-gamma, and then phagocytosis mediated by each type of Fc gamma receptor was evaluated by flow cytometry. Fc gamma RIIA was the most efficient receptor for phagocytosis. Fc gamma RIIIB could mediate phagocytosis but much less efficiently than Fc gamma RIIA. Both Fc gamma RIIA- and Fc gamma RIIIB-mediated phagocytosis were blocked by inhibitors of Src family kinases, Syk, PI 3-K, and ERK. In contrast, interferon-gamma-induced Fc gamma RI was not able to mediate phagocytosis. Also, Fc gamma RI did not activate ERK in the nucleus, but was however able to stimulate an efficient calcium rise. These data show that different neutrophil Fc gamma receptors possess different phagocytosis capabilities: Fc gamma RIIA and Fc gamma RIIIB, but not Fc gamma RI, promote phagocytosis. (C) 2010 Elsevier Inc. All rights reserved.