C4B
C4B encodes the basic form of complement factor 4, a component of the classical complement activation pathway that is secreted as a processed trimer of alpha, beta and gamma chains. It is also known as CPAMD3, C4F, CO4, C4B1, C4B3 and CH. Browse Assay Genie's current range of C4B research reagents below, or read on for the biology behind the target.
Complement C4-B, the product of the C4B gene, works together with the C4A gene product in the classical activation pathway of complement. The protein is expressed as a single-chain precursor that is proteolytically cleaved into a trimer of alpha, beta and gamma chains before secretion. This trimer provides a surface for interaction between the antigen-antibody complex and other complement components. Cleavage by complement proteases, namely C1S, MASP2 or GZMK depending on the complement pathway, releases a putative humoral mediator from the alpha chain, the C4 anaphylatoxin.
The C4 anaphylatoxin is strongly similar to other anaphylatoxins, but its role is unclear. It was reported to act as a mediator of local inflammation, although those effects were probably due to contamination with C3a and C5a anaphylatoxins in biological assays. UniProt records the protein as secreted and also at the cell surface, the synapse, and in axon and dendrite projections. Researchers studying C4B should take the anaphylatoxin caveat into account when interpreting older functional reports.
The C4B gene lies in the major histocompatibility complex (MHC) class III region on chromosome 6. Haplotypes of this gene cluster vary, so individuals may carry one, two or three copies of the gene. The gene also exists as a long form and a short form, depending on the presence or absence of a 6.4 kb endogenous HERV-K retrovirus in intron 9. Deficiency of this protein is associated with systemic lupus erythematosus. HGNC places it among blood group antigens, as reflected in the Chido/Rodgers name, and among complement system activation components. Earlier names include complement component 4B.
C4B is part of the classical activation pathway, providing a surface for interaction between antigen-antibody complexes and other complement components.
Deficiency of this protein is associated with systemic lupus erythematosus, making C4B relevant to studies of autoimmune disease.
The alpha chain may release C4 anaphylatoxin, reported as a mediator of local inflammation, though its role remains unclear.
Gene copy number varies between one and three, and long and short forms exist through a HERV-K insertion in the MHC class III region.
C4B encodes the basic form of complement factor 4, part of the classical activation pathway. The secreted trimer of alpha, beta and gamma chains provides a surface for interaction between antigen-antibody complexes and other complement components. The alpha chain may release C4 anaphylatoxin, whose role is unclear.
C4B is also called CPAMD3, C4F, CO4, C4B1, C4B3 and CH. HGNC lists the full name as complement C4B (Chido/Rodgers blood group), and previous names include complement component 4B and complement component 4B (Chido blood group). UniProt names the protein Complement C4-B.
Deficiency of C4B is associated with systemic lupus erythematosus. A mouse ortholog, C4b, exists; check the datasheet of any product for its validated reactivity. The human gene sits in the MHC class III region, where copy number varies between individuals.
Other complement components, anaphylatoxins and complement-activating proteases with products at Assay Genie.
Gene and protein annotations from HGNC, NCBI Gene and UniProt P0C0L5; product specifications from Assay Genie datasheets.