Complement component 4B (Chido blood group) is a protein that in humans is encoded by the C4B gene.
This gene encodes the basic form of complement factor 4, part of the classical activation pathway. The protein is expressed as a single chain precursor which is proteolytically cleaved into a trimer of alpha, beta, and gamma chains prior to secretion. The trimer provides a surface for interaction between the antigen-antibody complex and other complement components. The alpha chain may be cleaved to release C4 anaphylatoxin, a mediator of local inflammation. Deficiency of this protein is associated with systemic lupus erythematosus. This gene localizes to the major histocompatibility complex (MHC) class III region on chromosome 6. Varying haplotypes of this gene cluster exist, such that individuals may have 1, 2, or 3 copies of this gene. In addition, this gene exists as a long form and a short form due to the presence or absence of a 6.4 kb endogenous HERV-K retrovirus in intron 9. [provided by RefSeq, Jul 2008].
Yu CY (1998). "Molecular genetics of the human MHC complement gene cluster". Experimental and Clinical Immunogenetics. 15 (4): 213–30. doi:10.1159/000019075. PMID10072631.
Yang Z, Mendoza AR, Welch TR, Zipf WB, Yu CY (Apr 1999). "Modular variations of the human major histocompatibility complex class III genes for serine/threonine kinase RP, complement component C4, steroid 21-hydroxylase CYP21, and tenascin TNX (the RCCX module). A mechanism for gene deletions and disease associations". The Journal of Biological Chemistry. 274 (17): 12147–56. doi:10.1074/jbc.274.17.12147. PMID10207042.
Blom AM, Webb J, Villoutreix BO, Dahlbäck B (Jul 1999). "A cluster of positively charged amino acids in the C4BP alpha-chain is crucial for C4b binding and factor I cofactor function". The Journal of Biological Chemistry. 274 (27): 19237–45. doi:10.1074/jbc.274.27.19237. PMID10383431.
Tas SW, Klickstein LB, Barbashov SF, Nicholson-Weller A (Nov 1999). "C1q and C4b bind simultaneously to CR1 and additively support erythrocyte adhesion". Journal of Immunology. 163 (9): 5056–63. PMID10528211.
Aoki H, Takizawa F, Tsuji S, Nagasawa S (Jul 2000). "Elongation factor-1alpha as a homologous complement activator of Jurkat cells". International Journal of Molecular Medicine. 6 (1): 87–92. doi:10.3892/ijmm.6.1.87. PMID10851272.
Teisberg P, Akesson I, Olaisen B, Gedde-Dahl T, Thorsby E (Nov 1976). "Genetic polymorphism of C4 in man and localisation of a structural C4 locus to the HLA gene complex of chromosome 6". Nature. 264 (5583): 253–4. doi:10.1038/264253a0. PMID1088823.
Pan Q, Ebanks RO, Isenman DE (Sep 2000). "Two clusters of acidic amino acids near the NH2 terminus of complement component C4 alpha'-chain are important for C2 binding". Journal of Immunology. 165 (5): 2518–27. doi:10.4049/jimmunol.165.5.2518. PMID10946278.
Kramer J, Harcos P, Prohászka Z, Horváth L, Karádi I, Singh M, Császár A, Romics L, Füst G (Nov 2000). "Frequencies of certain complement protein alleles and serum levels of anti-heat-shock protein antibodies in cerebrovascular diseases". Stroke: A Journal of Cerebral Circulation. 31 (11): 2648–52. doi:10.1161/01.STR.31.11.2648. PMID11062289.