Complement factor C8

The complement system is a part of the larger immune system and three biochemical pathways are present: the classical complement pathway, the alternative pathway, and the mannose-binding lectin pathway. Human complement factor C8 is one of five components (C5b, C6, C7, C8, and C9) that interact to form the cytolytic membrane attack complex (MAC) which is the cytolytic end product of the complement cascade. MAC is typically formed on the surface of intruding pathogenic bacterial as a result of the activation of the complement system, and it is one of the ultimate weapons of the immune system. C8 is composed of an α (64 kDa), β (64 kDa), and γ (22 kDa) subunit. Within C8, the subunits are arranged as a disulfide-linked C8 α-γ heterodimer that is noncovalently associated with C8 β. During MAC formation, C8 α mediates binding and self-polymerization of C9 to form a pore-like structure on the membrane of target cells.