Complement Receptors

The complement system comprises an assembly of liver-manufactured, soluble and cell-bound proteins that participate in innate and adaptive immunity. Activation of the complement cascade by protease cleavage leads to chemotaxis (C5a), inflammation and increased capillary permeability (C3a, C5a), opsonization (C3b), and cytolysis.

 Fc receptors  Immune Cytokines  Immunoglobulins  Interferons

receptor	ligands	functions
CR1 (CD35)	C3b, C3bi, C4b, C4bi	opsonization and antigen clearance (phagocytes), antigen persistence (FDC), immune complex clearance (RBC), complement regulation
C1qR	C1q	immune complex binding to phagocytes(macrophages, neutrophils)
CR2 (CD21)	C3d, C3dg, C3bi, EBV	B cell activation ( B cells, FDC)
CR3 (MAC-1, CD11b/CD18)	C3bi	adhesion, extravasation, phagocytosis of macrophages and neutrophils
CR4 (p150.95, CD11c/CD18)	C3bi	adhesion, extravasation, phagocytosis of macrophages and neutrophils
C5aR	C5a	adherence, phagocytosis, CR1 and CR3 expression (macrophages, neutrophils)
C3aR, C4aR, C5aR	C3a, C4a, C5a	granule release from mast cells, contraction of smooth muscle

 Fc receptors  Immune Cytokines  Immunoglobulins  Interferons