C5 and autoimmune disease: OmCI binds directly to C5 and thus inhibits cleavage into anaphylatoxin C5a and C5b, a subunit of the membrane attack complex (MAC; C5b-9) and prevents MAC-mediated lysis and destruction of red blood cells in paroxysmal nocturnal hemoglobinuria (PNH) and tissue destruction in various other complement-mediated inflammatory and autoimmune diseases (Hepburn et al., 2007; Fredslund et al., 2008).