The principal function of activated components of the complement system include production of inflammatory and chemotactic proteins (C3a and C5a), cell lysis through the formation of the membrane attack complex (complex of C5b-9 proteins), and most importantly in the context of SLE, recognition and clearance of immune complexes and apoptotic cells (C1–C4) [6–8, 44]. Here, C4A is linked to systemic lupus erythematosus.