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Complement receptor
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<h2 id="expression-and-function">Expression and function</h2> <p><a href="/facts/White_blood_cell/vsDunUK0">White blood cells</a>, particularly <a href="/facts/Monocyte/FW4NNMKM">monocytes</a> and <a href="/facts/Macrophage/z7hkQu3o">macrophages</a>, <a href="/facts/Gene_expression/alCPohLR">express</a> complement receptors on their surface. All four complement receptors can bind to fragments of <a href="/facts/Complement_component_3/pqsRthBP">complement component 3</a> or <a href="/facts/Complement_component_4/nqX5xhav">complement component 4</a> coated on pathogen surface, but the receptors trigger different downstream activities.<a class="footnote-ref" id="fnref:5" href="#fn:5"><sup>5</sup></a> Complement receptor (CR) 1, 3, and 4 function as <a href="/facts/Opsonin/wKPBjS1t">opsonins</a> which stimulate <a href="/facts/Phagocytosis/eBrv2XKV">phagocytosis</a>, whereas CR2 is expressed only on <a href="/facts/B_cell/6Y1tgwwp">B cells</a> as a <a href="/facts/Co-receptor/eJsUxd3F">co-receptor</a>. </p><p><a href="/facts/Red_blood_cell/Kggpq8Jh">Red blood cells</a> (RBCs) also express CR1, which enables RBCs to carry complement-bound <a href="/facts/Antigen-antibody_complex/s4kKT3lc">antigen-antibody complexes</a> to the <a href="/facts/Liver/Rtp4Fk2b">liver</a> and <a href="/facts/Spleen/6NKn9d8s">spleen</a> for degradation.<a class="footnote-ref" id="fnref:6" href="#fn:6"><sup>6</sup></a> </p> <table><tbody><tr><th>CR #</th><th>Name</th><th>Molecular weight (Da, approx.)<a class="footnote-ref" id="fnref:7" href="#fn:7"><sup>7</sup></a></th><th><a href="/facts/Ligand_(biochemistry)/44QLL4eU">Ligand</a><a class="footnote-ref" id="fnref:8" href="#fn:8"><sup>8</sup></a></th><th><a href="/facts/Cluster_of_differentiation/cLEuDQId">CD</a></th><th>Major cell types<a class="footnote-ref" id="fnref:9" href="#fn:9"><sup>9</sup></a>a</th><th>Major activities<a class="footnote-ref" id="fnref:10" href="#fn:10"><sup>10</sup></a></th></tr><tr><td>CR1</td><td><a href="/facts/Complement_receptor_1/ShQaxyLT">Complement receptor 1</a></td><td>190,000–250,000</td><td>C3b, C4b, iC3b</td><td>CD35</td><td>B, E, FDC, Mac, M0, PMN</td><td>Immune complex transport (E); phagocytosis (PMN, Mac); immune adhesion (E); cofactor and decay-acceleration; secondary Epstein-Barr virus receptor</td></tr><tr><td>CR2</td><td><a href="/facts/Complement_receptor_2/Y2IaYELw">Complement receptor 2</a></td><td>145,000</td><td>C3d, iC3b, C3dg, Epstein-Barr virus</td><td>CD21</td><td>B, FDC</td><td>B cell coactivator, primary Epstein-Barr virus receptor, CD23 receptor</td></tr><tr><td>CR3</td><td><a href="/facts/Macrophage-1_antigen/ft7kK5a7">Macrophage-1 antigen</a> or "integrin αMβ2"</td><td>170,000 α chain + common 95,000 β chain</td><td>iC3b</td><td><a href="/facts/CD11b/SDNFWgNB">CD11b</a>+<a href="/facts/CD18/gCr14tJd">CD18</a></td><td>FDC, Mac, M0, PMN</td><td>Leukocyte adherence, phagocytosis of iC3b-bound particles</td></tr><tr><td>CR4</td><td><a href="/facts/Integrin_alphaXbeta2/VWm3qwGo">Integrin alphaXbeta2</a> or "p150,95"</td><td>150,000 α chain + common 95,000 β chain</td><td>iC3b</td><td><a href="/facts/CD11c/8uvVMAeE">CD11c</a>+<a href="/facts/CD18/gCr14tJd">CD18</a></td><td>D, Mac, M0, PMN</td><td>Leukocyte adhesion</td></tr><tr><td>C3AR1</td><td><a href="/facts/C3a_receptor/Df35uIC3">C3a receptor</a></td><td>75,000</td><td>C3a</td><td>–</td><td>Endo, MC, Pha</td><td>Cell activation</td></tr><tr><td>C5AR1</td><td><a href="/facts/C5a_receptor/YM83g3TT">C5a receptor</a></td><td>50,000</td><td>C5a</td><td>CD88</td><td>Endo, MC, Pha</td><td>Cell activation, immune polarization, chemotaxis</td></tr><tr><td>C5AR2</td><td><a href="/facts/C5AR2/7ngEr9Ru">C5a receptor 2</a></td><td>36,000</td><td>C5a</td><td>–</td><td></td><td>Chemotaxis</td></tr></tbody></table> a.^ B: <a href="/facts/B_cell/6Y1tgwwp">B cell</a>. E: <a href="/facts/Erythrocyte/Kggpq8Jh">erythrocyte</a>. Endo: <a href="/facts/Endothelial_cell/L4ENFVnw">endothelial cell</a>. D: <a href="/facts/Dendritic_cell/19KBuKFK">dendritic cell</a>. FDC: <a href="/facts/Follicular_dendritic_cell/lfvX5GcT">follicular dendritic cell</a>. Mac: <a href="/facts/Macrophage/z7hkQu3o">macrophage</a>. MC: <a href="/facts/Mast_cell/szfXss5q">mast cell</a>. M0: <a href="/facts/Monocyte/FW4NNMKM">monocyte</a>. Pha: <a href="/facts/Phagocyte/1vbsR9er">phagocyte</a>. PMN: <a href="/facts/Polymorphonuclear_leukocyte/zsE3ldLb">polymorphonuclear leukocyte</a>. <h2 id="clinical-significance">Clinical significance</h2> <p class="note">Main articles: <a href="/facts/Complement_system/vRSrQDUv">Complement system § Role in disease</a>, <a href="/facts/Classical_complement_pathway/wtB1DPJn">Classical complement pathway § Clinical significance</a>, and <a href="/facts/Alternative_complement_pathway/eN5PARpC">Alternative complement pathway § Role in disease</a></p> <p>Deficits in complement receptor expression can cause disease.<a class="footnote-ref" id="fnref:11" href="#fn:11"><sup>11</sup></a> Mutations in complement receptors which alter receptor function can also increase risk of certain diseases.<a class="footnote-ref" id="fnref:12" href="#fn:12"><sup>12</sup></a> </p> <h2 id="see-also">See also</h2> <ul><li><a href="/facts/Complement_system/vRSrQDUv">Complement system</a></li> <li><a href="/facts/Humoral_immunity/qG9I4pGf">Humoral immunity</a></li> <li><a href="/facts/Immune_system/HRCTf1pb">Immune system</a></li></ul> <h2 id="external-links">External links</h2> <ul><li><a href="https://meshb.nlm.nih.gov/record/ui?name=Complement+receptors">Complement+receptors</a> at the U.S. National Library of Medicine <a href="/facts/Medical_Subject_Headings/C57g2JuF">Medical Subject Headings</a> (MeSH)</li></ul> <h2 id="references">References</h2> <ol> <li id="fn:1"><p>Holers VM (29 January 2014). "Complement and its receptors: new insights into human disease". Annual Review of Immunology. 32: 433–59. doi:10.1146/annurev-immunol-032713-120154. PMID 24499275. <a href="https://doi.org/10.1146%2Fannurev-immunol-032713-120154" target="_blank">https://doi.org/10.1146%2Fannurev-immunol-032713-120154</a> <a href="#fnref:1" class="footnote-back-ref">↩</a></p></li> <li id="fn:2"><p>Verschoor A, Kemper C, Köhl J (15 September 2017). "Complement Receptors". eLS: 1–17. doi:10.1002/9780470015902.a0000512.pub3. ISBN 9780470015902. <a href="9780470015902" target="_blank">9780470015902</a> <a href="#fnref:2" class="footnote-back-ref">↩</a></p></li> <li id="fn:3"><p>Carroll MC (December 2008). "Complement and humoral immunity". Vaccine. 26 (Suppl 8): I28-33. doi:10.1016/j.vaccine.2008.11.022. PMC 4018718. PMID 19388161. <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4018718" target="_blank">https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4018718</a> <a href="#fnref:3" class="footnote-back-ref">↩</a></p></li> <li id="fn:4"><p>Janeway Jr CA, Travers P, Walport M, Shlomchik MJ (2001). "The complement system and innate immunity". Immunobiology: The Immune System in Health and Disease (5th ed.). New York: Garland Science. Retrieved 17 June 2020. <a href="https://www.ncbi.nlm.nih.gov/books/NBK27100" target="_blank">https://www.ncbi.nlm.nih.gov/books/NBK27100</a> <a href="#fnref:4" class="footnote-back-ref">↩</a></p></li> <li id="fn:5"><p>Holers VM (29 January 2014). "Complement and its receptors: new insights into human disease". Annual Review of Immunology. 32: 433–59. doi:10.1146/annurev-immunol-032713-120154. PMID 24499275. <a href="https://doi.org/10.1146%2Fannurev-immunol-032713-120154" target="_blank">https://doi.org/10.1146%2Fannurev-immunol-032713-120154</a> <a href="#fnref:5" class="footnote-back-ref">↩</a></p></li> <li id="fn:6"><p>Parham P (2005). The Immune System (2nd ed.). Garland Science. ISBN 9780815340935. <a href="9780815340935" target="_blank">9780815340935</a> <a href="#fnref:6" class="footnote-back-ref">↩</a></p></li> <li id="fn:7"><p>Holers VM (29 January 2014). "Complement and its receptors: new insights into human disease". Annual Review of Immunology. 32: 433–59. doi:10.1146/annurev-immunol-032713-120154. PMID 24499275. <a href="https://doi.org/10.1146%2Fannurev-immunol-032713-120154" target="_blank">https://doi.org/10.1146%2Fannurev-immunol-032713-120154</a> <a href="#fnref:7" class="footnote-back-ref">↩</a></p></li> <li id="fn:8"><p>Janeway Jr CA, Travers P, Walport M, Shlomchik MJ (2001). "The complement system and innate immunity". Immunobiology: The Immune System in Health and Disease (5th ed.). New York: Garland Science. Retrieved 17 June 2020. <a href="https://www.ncbi.nlm.nih.gov/books/NBK27100" target="_blank">https://www.ncbi.nlm.nih.gov/books/NBK27100</a> <a href="#fnref:8" class="footnote-back-ref">↩</a></p></li> <li id="fn:9"><p>Janeway Jr CA, Travers P, Walport M, Shlomchik MJ (2001). "The complement system and innate immunity". Immunobiology: The Immune System in Health and Disease (5th ed.). New York: Garland Science. Retrieved 17 June 2020. <a href="https://www.ncbi.nlm.nih.gov/books/NBK27100" target="_blank">https://www.ncbi.nlm.nih.gov/books/NBK27100</a> <a href="#fnref:9" class="footnote-back-ref">↩</a></p></li> <li id="fn:10"><p>Holers VM (29 January 2014). "Complement and its receptors: new insights into human disease". Annual Review of Immunology. 32: 433–59. doi:10.1146/annurev-immunol-032713-120154. PMID 24499275. <a href="https://doi.org/10.1146%2Fannurev-immunol-032713-120154" target="_blank">https://doi.org/10.1146%2Fannurev-immunol-032713-120154</a> <a href="#fnref:10" class="footnote-back-ref">↩</a></p></li> <li id="fn:11"><p>Schwartz RA, Thomas I. "Complement Receptor Deficiency: eMedicine Dermatology". Medscape. Retrieved 7 December 2010. <a href="http://emedicine.medscape.com/article/1051238-overview" target="_blank">http://emedicine.medscape.com/article/1051238-overview</a> <a href="#fnref:11" class="footnote-back-ref">↩</a></p></li> <li id="fn:12"><p>Holers VM (29 January 2014). "Complement and its receptors: new insights into human disease". Annual Review of Immunology. 32: 433–59. doi:10.1146/annurev-immunol-032713-120154. PMID 24499275. <a href="https://doi.org/10.1146%2Fannurev-immunol-032713-120154" target="_blank">https://doi.org/10.1146%2Fannurev-immunol-032713-120154</a> <a href="#fnref:12" class="footnote-back-ref">↩</a></p></li> </ol>