Complement receptor

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title: "Complement receptor" type: doc version: 1 created: 2026-02-28 author: "Wikipedia contributors" status: active scope: public tags: ["complement-system", "single-pass-transmembrane-proteins"] topic_path: "general/complement-system" source: "https://en.wikipedia.org/wiki/Complement_receptor" license: "CC BY-SA 4.0" wikipedia_page_id: 0 wikipedia_revision_id: 0

| Symbol = Complement receptor | Name = Complement receptor | image = | width = | caption = | InterPro= | SMART= | PROSITE = | SCOP = | TCDB = | OPM family= | OPM protein= | Pfam= | PDB= | Membranome family= 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. Complement receptor activation contributes to the regulation of inflammation, leukocyte extravasation, and phagocytosis; it also contributes to the adaptive immune response. Different complement receptors can participate in either the classical complement pathway, the alternative complement pathway, or both.

Expression and function

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. 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.

::data[format=table] | CR # || Name || Molecular weight (Da, approx.) || Ligand || CD || Major cell types || Major activities | |---| | CR1 | | CR2 | | CR3 | | CR4 | | C3AR1 | | C5AR1 | | C5AR2 | ::

:a.B: B cell. E: erythrocyte. Endo: endothelial cell. D: dendritic cell. FDC: follicular dendritic cell. Mac: macrophage. MC: mast cell. M0: monocyte. Pha: phagocyte. PMN: polymorphonuclear leukocyte.

Clinical significance

Main article: Complement system#Role in disease, Classical complement pathway#Clinical significance, Alternative complement pathway#Role in disease

Deficits in complement receptor expression can cause disease. Mutations in complement receptors which alter receptor function can also increase risk of certain diseases.

References

References

  1. (29 January 2014). "Complement and its receptors: new insights into human disease". Annual Review of Immunology.
  2. (15 September 2017). "Encyclopedia of Life Sciences".
  3. (December 2008). "Complement and humoral immunity". Vaccine.
  4. (2001). "Immunobiology: The Immune System in Health and Disease". Garland Science.
  5. Parham, Peter. (2005). "The Immune System". Garland Science.
  6. "Complement Receptor Deficiency: eMedicine Dermatology".

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