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C4A isotype is accountable for effective binding to form amide bonds with resistant aggregates or protein antigens, while C4B isotype catalyzes the transacylation of the thioester carbonyl group to form ester bonds with carbohydrate antigens. .
|Sequence:||6; NC_000006.12 (32014795..32035418)|
Complement component C4 is expressed at highest levels in the liver, at moderate levels in the adrenal cortex, adrenal medulla, thyroid gland,and the kidney, and at lowest levels in the heart, ovary, small intestine, thymus, pancreas and spleen. The extra-hepatic sites of expression may be important for the local protection and inflammatory response.
Secreted. Cell junction, synapse. Cell projection, axon. Cell projection, dendrite.