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Complement receptor type 1 (CR1) also known as C3b/C4b receptor or CD35 (cluster of differentiation 35) is a protein that in humans is encoded by the CR1 gene.〔(【引用サイトリンク】 url = http://www.ncbi.nlm.nih.gov/sites/entrez?Db=gene&Cmd=ShowDetailView&TermToSearch=1378 )〕 This gene is a member of the regulators of complement activation (RCA) family and is located in the 'cluster RCA' region of chromosome 1. The gene encodes a monomeric single-pass type I membrane glycoprotein found on erythrocytes, leukocytes, glomerular podocytes, hyalocytes, and splenic follicular dendritic cells. The Knops blood group system is a system of antigens located on this protein. The protein mediates cellular binding to particles and immune complexes that have activated complement. Decreases in expression of this protein and/or mutations in its gene have been associated with gallbladder carcinomas, mesangiocapillary glomerulonephritis, systemic lupus erythematosus and sarcoidosis. Mutations in this gene have also been associated with a reduction in ''Plasmodium falciparum'' rosetting, conferring protection against severe malaria. Alternate allele-specific splice variants, encoding different isoforms, have been characterized. Additional allele specific isoforms, including a secreted form, have been described but have not been fully characterized.〔 In primates, CR1 serves as the main system for processing and clearance of complement opsonized immune complexes. It has been shown that CR1 can act as a negative regulator of the complement cascade, mediate immune adherence and phagocytosis and inhibit both the classic and alternative pathways. The number of CR1 molecules decreases with aging of erythrocytes in normal individuals and is also decreased in pathological conditions such as systemic lupus erythematosus (SLE), HIV infection, some s and other conditions featuring immune complexes. In mice, CR1 is an alternatively spliced variant of the complement receptor 2 (CR2) gene. Certain alleles of this gene have been statistically associated with an increased risk of developing late-onset Alzheimer's Disease. ==1q32 region== In humans, the ''CR1'' gene is located at on the long arm of chromosome 1 at band 32 (1q32) and lies within a complex of immunoregulatory genes. In 5’-3’ order the genes in this region are: membrane cofactor protein - CR1- complement receptor type 2 - decay-accelerating factor - C4-binding protein. * Membrane cofactor protein is a widely distributed C3b/C4b binding regulatory glycoprotein of the complement system; * decay-accelerating factor (DAF: CD55: Cromer antigen) protects host cells from complement-mediated damage by regulating the activation of C3 convertases on host cell surfaces; * complement receptor 2 is the C3d receptor. Factor H, another immunoregulatory protein, also maps to this location. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Complement receptor 1」の詳細全文を読む スポンサード リンク
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