IgA-mediated phagocytosis by mouse alveolar macrophages

Ingestion of antibody-opsonized sheep red blood cells by murine alveolar and peritoneal exudate macrophages was studied. Alveolar macrophages or peritoneal macrophages were isolated by lavage and incubated with TNP-SRBC, which had been preincubated with anti-DNP IgG, IgA, and IgE. Significant enhancement of phagocytosis by alveolar macrophages of TNP-SRBC was mediated by all classes of antibody examined, most markedly with IgG and less so with IgA and IgE. Enhancement of phagocytosis by peritoneal macrophages was mediated by IgG and IgE, but not by IgA. These results suggest that the interaction of IgA and Fc receptors for IgA on alveolar macrophages may increase the level of this cell's function in the mammalian lung to clear pathogens and immune complexes from the alveolar spaces.