C8 is a constituent of the membrane attack complex. C8 binds to the C5B-7 complex, forming the C5B-8 complex. C5-B8 binds C9 and acts as a catalyst in the polymerization of C9. The gamma subunit seems to be able to bind retinol (By similarity). C8 is composed of three chains: alpha, beta and gamma. The alpha and gamma chains are disulfide bonded (By similarity). Belongs to the calycin superfamily. Lipocalin family.