Human IgG Fc receptors.

Human IgG receptors constitute a family of glycoprotein complexes consisting of ligand-binding, and associated signaling chains. Three leukocyte classes (FCγRI, II, and III) and one separate endothelial FcγR class (FcRB) are defined which are expressed on hematopoietic and endothelial cells. Upon interaction with IgG, FcγR initiate a plethora of signaling cascades involving receptor signaling motifs, and protein tyrosine kinases and phosphatases. These cascades ultimately culminate in activation or deactivation of effector cells, resulting in initiation or down-modulation of cellular processes. Recent evidence points to a crucial in vivo role of FcγR in both initiation and regulation of inflammatory and cytotoxic responses. These FcγR-mediated immune responses can be exploited to develop novel immunotherapies.