Complement receptor

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Complement receptor
SymbolComplement receptor

A complement receptor is a receptor of the complement system, part of the innate immune system. Complement receptors bind proteins of the complement system, and can thus detect pathogens without mediation by antibodies.[1] Complement activity can be triggered by specific antigen-antibody complexes, sugars or pathogens directly.

Complement receptors[edit]

Many white blood cells express complement receptors on their surface, particularly monocytes and macrophages. All four complement receptors bind to fragments of complement component 3 or complement component 4 coated on pathogen surface, but the receptors have different functions. Complement receptor (CR) 1, 3, and 4 work as opsonins (stimulate phagocytosis), whereas CR2 is expressed only on B cells as a co-receptor.

Red blood cells (RBCs) also express CR1. With these receptors, RBCs bring antigen-antibody complexes bound to complement fragments in the blood to the liver and spleen for degradation.[2]

CR # Name Ligand[1] CD
CR1 - C3b, C4b, iC3b CD35
CR2 - C3d, iC3b, C3dg, Epstein-Barr virus CD21
CR3 Macrophage-1 antigen or "integrin αMβ2" iC3b CD11b+CD18
CR4 Integrin alphaXbeta2 or "p150,95" iC3b CD11c+CD18
- C3a receptor C3a -
- C5a receptor C5a CD88

Clinical significance[edit]

Defects in these receptors can be associated with disease.[3]

See also[edit]


  1. ^ a b Janeway, CA Jr; Travers P; Walport M; et al. (2001). "The complement system and innate immunity". Immunobiology: The Immune System in Health and Disease. New York: Garland Science. Retrieved 29 December 2017.
  2. ^ Peter Parham, The Immune System (2nd ed.), Taylor&Francis
  3. ^ "Complement Receptor Deficiency: eMedicine Dermatology". Retrieved 7 December 2010.

External links[edit]