Early biochemical events in leukocyte activation through receptors for IgG

Membrane receptors for the Fc portion of IgG antibodies (FcγR) are expressed by most cells of the immune system. Recent research has revealed that, besides their role in effector functions mediated by leukocytes, FcγR also participate in the antibody-mediated regulation of many phenomena in the afferent phase of immune responses and in the homeostasis of the immune system. Here, we review recent findings on the mechanisms of signal transduction by these receptors as well as on the modulation of FcγR signaling by signal regulators and/or by the activation state of the cell.