Macrophage Polarization Modulates FcγR- and cD13-Mediated Phagocytosis and reactive Oxygen species Production, independently of receptor Membrane expression

In response to microenvironmental cues, macrophages undergo a profound phenotypic transformation acquiring distinct activation phenotypes ranging from pro-inflammatory (M1) to anti-inflammatory (M2). To study how activation phenotype influences phagocytosis and production of reactive oxygen species (ROS) mediated by receptors for IgG antibodies (Fc gamma receptors) and by CD13, human monocyte-derived macrophages were polarized to distinct phenotypes using IFN-gamma (M phi-IFN-gamma), IL-4 ( M phi-IL-4), or IL-10 (M phi-IL-10). Phenotypically, M phi-IFN-gamma were characterized as CD14(+)CD80(+)CD86(+) cells, M phi-IL-4 as CD209(high)CD206(+)CD11b(+)CD14(low), and M phi-IL-10 as CD16(+)CD163(+) cells. Compared to non-polarized macrophages, Fc gamma RI expression increased in M phi-IFN-gamma and M phi-IL-10 and Fc gamma RIII expression increased in M phi-IL-10. None of the polarizing cytokines modified Fc gamma RII or CD13 expression. Functionally, we found that cytokine-mediated activation significantly and distinctively affected Fc gamma R- and CD13-mediated phagocytosis and ROS generation. Compared to non-polarized macrophages, Fc gamma RI-, Fc gamma RII-, and CD13-mediated phagocytosis was significantly increased in M phi-IL-10 and decreased in M phi-IFN-gamma.,although both cytokines significantly upregulated Fc gamma RI expression. IL-10 also increased phagocytosis of Escherichia coli, showing that the effect of IL-10 on macrophage phagocytosis is not specific for a particular receptor. Interestingly, M phi-IL-4, which showed poor Fc gamma R- and CD13-mediated phagocytosis, showed very high phagocytosis of E. coli and zymosan. Coupled with phagocytosis, macrophages produce ROS that contribute to microbial killing. As expected, M phi-IFN-gamma showed significant production of ROS after Fc gamma RI-, Fc gamma RII-, or CD13-mediated phagocytosis. Unexpectedly, we found that M phi-IL-10 can also produce ROS after simultaneous stimulation through several phagocytic receptors, as coaggregation of Fc gamma RI/Fc gamma RII/CD13 induced a belated but significant ROS production. Together, these results demonstrate that activation of macrophages by each cytokine distinctly modulates expression of phagocytic receptors, Fc gamma R- and CD13-mediated phagocytosis, and ROS production.