Fc Receptor-Mediated Phagocytosis Makes a Significant Contribution to Clearance of Influenza Virus Infections

Top Cited Papers
Open Access
Publisher Website
Google Scholar
Abstract
Fc receptors for IgG expressed on macrophages and NK cells are important mediators of opsonophagocytosis and Ab-dependent cell-mediated cytotoxicity. Phagocyte-mediated opsonophagocytosis is pivotal for protection against bacteria, but its importance in recovery from infection with intracellular pathogens is unclear. We have now investigated the role of opsonophagocytosis in protection against lethal influenza virus infection by using FcR γ−/− mice. Absence of the FcR γ-chain did not affect the expression of IFN-γ and IL-10 in the lungs and spleens after intranasal immunization with an influenza subunit vaccine. Titers of serum and respiratory Abs of the IgM, IgG1, IgG2a, and IgA isotypes in FcR γ−/− mice were similar to levels seen in FcR γ+/+ mice. Nevertheless, FcR γ−/− mice were highly susceptible to influenza infection, even in the presence of anti-influenza Abs from immune FcR γ+/+ mice. NK cells were not necessary for the observed Ab-mediated viral clearance, but macrophages were found to be capable of actively ingesting opsonized virus particles. We conclude that Fc receptor-mediated phagocytosis plays a pivotal role in clearance of respiratory virus infections.