Anti-C1QB / Complement C1q B-Chain Monoclonal Antibody (Clone: C1QB/2965)

C1q, a subcomponent of the classical complement pathway, is composed of nine subunits that mediate classical complement activation and thereby play an important role in the immune response. Six of these subunits are disulfide-linked dimers of chains A and B, while three of these subunits, designated C1q-A throµgh C1q-C, are disulfide-linked dimers of chain C. Each chain contains an N-terminal collagen-like region and a C-terminal C1q globular domain. The presence of receptors for C1q on effector cells modulates its activity, which may be antibody-dependent or independent. Macrophages are the primary source of C1q, while anti-inflammatory drµgs as well as cytokines differentially regulate expression of the mRNA as well as the protein. C1q deficiency is associated with lupus erythematosus and glomerulonephritis. Protein function: C1q associates with the proenzymes C1r and C1s to yield C1, the first component of the serum complement system. The collagen-like regions of C1q interact with the Ca(2+)-dependent C1r(2)C1s(2) proenzyme complex, and efficient activation of C1 takes place on interaction of the globular heads of C1q with the Fc regions of IgG or IgM antibody present in immune complexes. [The UniProt Consortium]