Decreased circulating complement C8 concentration 2008-03-18T09:53:00Z UMLS:C3151082 The eighth component of complement (C8) plays an important role in the function of membrane attack complex (MAC) that is generated on target cells upon activation of the complement system. MAC is generated by sequential addition of C5b, C6, C7, C8, and C9 molecules, which results in the transmembrane pore and eventual cell lysis. Individuals with C8 deficiency tend to have recurrent neisserial infections. C8 deficiency Concentration of the complement component C8 in the blood circulation below the lower limit of normal. Decreased serum complement C8 HP:0004434 Decreased circulating terminal complement component concentration