Opsonin receptors

Opsonin receptors are a functional class of leukocyte surface proteins that recognize and bind to opsonins, which are host-derived molecules like antibodies (IgG) and complement fragments (C3b, iC3b) that coat pathogens or apoptotic cells. This group primarily includes Fc receptors (FcRs) and complement receptors (CRs), such as CR1, CR3 (Mac-1), and CR4, which are expressed on neutrophils, macrophages, and other myeloid cells. Upon ligation with opsonized targets, these receptors initiate intracellular signaling cascades—often involving Src-family kinases and Syk—that lead to phagocytosis, the release of reactive oxygen species, and the secretion of inflammatory cytokines. They are essential for the clearance of infectious agents and the maintenance of immune homeostasis, but their dysregulation is a key driver in autoimmune diseases and chronic inflammatory conditions. Therapeutic modulation of these receptors includes the use of intravenous immunoglobulin (IVIG) to block Fc receptors or monoclonal antibodies designed to enhance or inhibit opsonin-mediated cell clearance in cancer and inflammatory disorders.

Other names

Fc receptorsComplement receptorsPhagocytic receptorsOpsonin-binding receptors