SIGNAL TRANSDUCTION MECHANISMS THROUGH FC-GAMMA RECEPTORS ON THE MOUSE MACROPHAGE SURFACE

Mouse macrophages and macrophage cell lines such as P388D1 or J774 carry at least two distinct Fc-gamma receptors (Fc-gamma-R): one specific for the Fc portion of IgG2a (Fc-gamma-2aR, also classified as Fc-gamma-RI) and another for IgG2b (Fc-gamma-2bR, also classified as Fc-gamma-RII-beta). These Fc-gamma-Rs should transmit, upon binding of an appropriate ligand, a specific signal that leads to the regulation of macrophage functions, as the interaction of immune complex with cell surface receptor has been shown to lead to suppression of the humoral immune response or B cell differentiation, to the destruction of target cells by antibody-dependent cell-mediated cytotoxicity, to activiation of arachidonic acid metabolic cascade, to the phagocytosis of opsonized particles, or to the generation of superoxide anion. In this review, we first describe evidence that Fc-gamma-2aR and Fc-gamma-2bR are associated with casein kinase II and phospholipase A2 activity, respectively. We will then discuss a potential role for these enzymatic activities in signal transduction pathways that leads to the activation of the arachidonic acid metabolic cascade and adenylate cyclase, to the regulation of phagocytosis, and to the suppression of interferon-gamma action to induce Ia antigens.