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Complement receptor | |
---|---|
Identifiers | |
Symbol | Complement receptor |
Membranome | 116 |
A complement receptor is a membrane-bound receptor belonging to the complement system, which is part of the innate immune system. Complement receptors bind effector protein fragments that are produced in response to antigen-antibody complexes or damage-associated molecules. [1] Complement receptor activation contributes to the regulation of inflammation, leukocyte extravasation, and phagocytosis; it also contributes to the adaptive immune response. [2] [3] Different complement receptors can participate in either the classical complement pathway, the alternative complement pathway, or both. [4]
White blood cells, particularly monocytes and macrophages, express complement receptors on their surface. All four complement receptors can bind to fragments of complement component 3 or complement component 4 coated on pathogen surface, but the receptors trigger different downstream activities. [1] Complement receptor (CR) 1, 3, and 4 function as opsonins which stimulate phagocytosis, whereas CR2 is expressed only on B cells as a co-receptor.
Red blood cells (RBCs) also express CR1, which enables RBCs to carry complement-bound antigen-antibody complexes to the liver and spleen for degradation. [5]
CR # | Name | Molecular weight (Da, approx.) [1] | Ligand [4] | CD | Major cell types [4] a | Major activities [1] |
---|---|---|---|---|---|---|
CR1 | Complement receptor 1 | 190,000–250,000 | C3b, C4b, iC3b | CD35 | B, E, FDC, Mac, M0, PMN | Immune complex transport (E); phagocytosis (PMN, Mac); immune adhesion (E); cofactor and decay-acceleration; secondary Epstein-Barr virus receptor |
CR2 | Complement receptor 2 | 145,000 | C3d, iC3b, C3dg, Epstein-Barr virus | CD21 | B, FDC | B cell coactivator, primary Epstein-Barr virus receptor, CD23 receptor |
CR3 | Macrophage-1 antigen or "integrin αMβ2" | 170,000 α chain + common 95,000 β chain | iC3b | CD11b+ CD18 | FDC, Mac, M0, PMN | Leukocyte adherence, phagocytosis of iC3b-bound particles |
CR4 | Integrin alphaXbeta2 or "p150,95" | 150,000 α chain + common 95,000 β chain | iC3b | CD11c+ CD18 | D, Mac, M0, PMN | Leukocyte adhesion |
C3AR1 | C3a receptor | 75,000 | C3a | – | Endo, MC, Pha | Cell activation |
C5AR1 | C5a receptor | 50,000 | C5a | CD88 | Endo, MC, Pha | Cell activation, immune polarization, chemotaxis |
C5AR2 | C5a receptor 2 | 36,000 | C5a | – | Chemotaxis |
Deficits in complement receptor expression can cause disease. [6] Mutations in complement receptors which alter receptor function can also increase risk of certain diseases. [1]
This article needs additional citations for
verification. (September 2008) |
Complement receptor | |
---|---|
Identifiers | |
Symbol | Complement receptor |
Membranome | 116 |
A complement receptor is a membrane-bound receptor belonging to the complement system, which is part of the innate immune system. Complement receptors bind effector protein fragments that are produced in response to antigen-antibody complexes or damage-associated molecules. [1] Complement receptor activation contributes to the regulation of inflammation, leukocyte extravasation, and phagocytosis; it also contributes to the adaptive immune response. [2] [3] Different complement receptors can participate in either the classical complement pathway, the alternative complement pathway, or both. [4]
White blood cells, particularly monocytes and macrophages, express complement receptors on their surface. All four complement receptors can bind to fragments of complement component 3 or complement component 4 coated on pathogen surface, but the receptors trigger different downstream activities. [1] Complement receptor (CR) 1, 3, and 4 function as opsonins which stimulate phagocytosis, whereas CR2 is expressed only on B cells as a co-receptor.
Red blood cells (RBCs) also express CR1, which enables RBCs to carry complement-bound antigen-antibody complexes to the liver and spleen for degradation. [5]
CR # | Name | Molecular weight (Da, approx.) [1] | Ligand [4] | CD | Major cell types [4] a | Major activities [1] |
---|---|---|---|---|---|---|
CR1 | Complement receptor 1 | 190,000–250,000 | C3b, C4b, iC3b | CD35 | B, E, FDC, Mac, M0, PMN | Immune complex transport (E); phagocytosis (PMN, Mac); immune adhesion (E); cofactor and decay-acceleration; secondary Epstein-Barr virus receptor |
CR2 | Complement receptor 2 | 145,000 | C3d, iC3b, C3dg, Epstein-Barr virus | CD21 | B, FDC | B cell coactivator, primary Epstein-Barr virus receptor, CD23 receptor |
CR3 | Macrophage-1 antigen or "integrin αMβ2" | 170,000 α chain + common 95,000 β chain | iC3b | CD11b+ CD18 | FDC, Mac, M0, PMN | Leukocyte adherence, phagocytosis of iC3b-bound particles |
CR4 | Integrin alphaXbeta2 or "p150,95" | 150,000 α chain + common 95,000 β chain | iC3b | CD11c+ CD18 | D, Mac, M0, PMN | Leukocyte adhesion |
C3AR1 | C3a receptor | 75,000 | C3a | – | Endo, MC, Pha | Cell activation |
C5AR1 | C5a receptor | 50,000 | C5a | CD88 | Endo, MC, Pha | Cell activation, immune polarization, chemotaxis |
C5AR2 | C5a receptor 2 | 36,000 | C5a | – | Chemotaxis |
Deficits in complement receptor expression can cause disease. [6] Mutations in complement receptors which alter receptor function can also increase risk of certain diseases. [1]