Complement Receptors

Complement Receptors of Complement System List

Receptor Ligand CD number Protein superfamily Function
CR1 C3b CD35 Regulators of complement
Promotion of phagocytosis, immune complex (IC) clearance, processing of IC-bound C3b
CR2 C3dg (iC3b) CD21 Regulators of complement activation B-cell proliferation, alternative pathway activation
CR3 iC3b CD11b/CD18 β2 integrin reactive oxygen metabolites/nitric oxide (ROM/NO) synthesis, degranulation
CR4 iC3b CD11c/CD18 β2 integrin Phagocytosis, leucocyte migration
C3aR C3a - G protein-coupled receptors NO synthesis
C5aR C5a; C5a-desarg CD88 G protein-coupled receptors Leucocyte chemoattraction, degranulation
cC1qR C1q, MBL, SPA - - Chemotaxis, promotion of phagocytosis, ROM
C1qRp C1q, MBL, SPA CD93 - Synthesis, platelet aggregation, leucocyte migration
gC1qR C1q - - Regulation of B-cell activity

Complement Receptors of Complement System Background

Complement receptors are membrane proteins expressed on the surface of immune cells. They interact specifically with complement factors leading to the removal of antigen from the circulation.

In addition to promoting microorganism destruction by memebrane attack complex (MAC), the complement system exerts a wide-ranging influence on the activities of cells involved in the immune response. Thus, complement is instrumental in the direction of blood leucocytes to a site of inflammation; the induction of granule release and synthesis of cytotoxic oxygen- and nitrogen-containing compounds by leucocytes of the myeloid lineage; the promotion of particle phagocytosis by these cells; the clearance of soluble immune complexes (ICs) from the circulation; and the induction of a primary B-cell response to antigen. These effects are exerted through interaction of the activation products of complement factors C1, C3 or C5 with specific receptors on the responding cells. The receptors can be divided into three categories: (1) those recognizing the anaphylotoxic polypeptides, C3a, C5a and C5a-desarg, (2) those binding the active C3 fragment, C3b, and its degradation products, iC3b and C3dg, and (3) receptors for C1q and related collagenous lectins.

Complement Receptors of Complement System References

1. Leslie R G Q, et al. (2009). Complement receptors. eLS.
2. Brown E J. (1992). Complement receptors, adhesion, and phagocytosis. Infectious agents and disease, 1(2), 63.
3. Nielsen C H, et al. (1997). The roles of complement receptors type 1 (CR1, CD35) and type 3 (CR3, CD11b/CD18) in the regulation of the immune complex‐elicited respiratory burst of polymorphonuclear leukocytes in whole blood. European journal of immunology, 27(11), 2914-2919.
4. Ahearn J M, et al. (1989). Structure and function of the complement receptors, CR1 (CD35) and CR2 (CD21). Advances in immunology, 46, 183-21