Complement component C8 is a constituent of the membrane attack complex, C8 alpha, C8 beta and C8G. C8G is a secreted protein and comsists a disulfide-linked C8 alpha-gamma heterodimer and a non-covalently associated C8 beta chain. C8 alpha and C8 beta play an important role in complement-mediated bacterial killing together.C8 is involved in the formation of Membrane Attack Complex on bacterial cell membranes. 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. Patients lacking C8 are susceptible to certain bacterial infections.