Quantitation of C2 by rocket immunoelectrophoresis in 120 pathological sera

A potent monospecific anti-C2 was used for quantitation of serum C2 by rocket immunoelectrophoresis (RIE). This ready procedure was compared to the one-step hemolytic titration utilizing C2-deficient human serum. RIE detected 4 nanograms C2 in 5 microliters samples. Using highly purified C2 as a reference, C2 concentration in pooled normal human sera was estimated around 50 micrograms/ml by both test systems. The reliability of RIE was assessed when immunochemical and hemolytic determinations were comparatively performed in 120 pathological sera. The correlation coefficient was significant (r = 0.69) and only 8 sera were found outside the expected range, exhibiting an abnormally high C2 protein. They were obtained from 6 patients with cryoglobulinemia associated connective tissue disease and 2 with acute glomerulonephritis. These occasional findings suggested the possibility of an activation of C2 hemolytic activity without simultaneous loss of C2 protein. In 16 sera of individuals with familial C2 deficiency (r = 0.83) and 29 sera of patients with angioneurotic edema (r = 0.72), RIE provided an extremely simple and reliable alternative to the time consuming hemolytic titration of C2.