The complement factor C3 consists of an alpha and a beta chain. C3 is a central factor in the complement cascade. It is central to the alternative pathway that leads to the C3 convertase C3bBb. The classical mannose binding lectin activation pathway leads to the C3 convertase C4b2a. These convertases cleave C3 resulting in C3a and C3b. Further degradation leads to the formation of the alpha chain products C3d, C3g and C3c. C3 is an acute phase protein that is produced by a wide range of tissues, including renal epithelial cells and hepatocytes.
