C3/C5-Depleted Serum is normal human serum in which C3 and C5 have been removed by immunoaffinity chromatography. The product is tested for the absence of C3 and C5 activity by testing classical and alternative pathway function and for the absence of C3 and C5 proteins by double immunodiffusion. The C3/C5-depleted serum is certified to exhibit less than 5% classical pathway and alternative pathway activities. Functional classical and alternative pathways can be reconstituted by addition of purified C3 protein (1.3 mg/mL) and C5 protein (75 ug/mL) indicating that all other complement components necessary for classical and alternative pathway activation are present. After reconstitution with C3 (1.3 mg C3/mL) and C5 (0.75 mg/mL), the C3/C5-Depleted Serum is certified to possess a functional classical and alternative pathway for complement activation (Morgan, B.P. (2000); Dodds, A.W. and Sim, R.B. (1997)). Although a functional lectin pathway should also be reconstituted by the addition of similar concentrations of C3 and C5, the function of this pathway is not tested.