Alternative Pathway-Hemolytic Complement Titer (ACH50) of Porgy Pagrus major Serum

Alternative complement pathway activity (ACH50) of porgy serum was measured by incubating the serum with rabbit red blood cells (RaRBC) in the presence of 10 Mm Egta. It was confirmed that the concentration of EGTA (10 Mm) Is enough to prevent the activation of the classical pathway of porgy complement, and that among red blood cells from several animals, RaRBC is the most effective activator of the alternative pathway of porgy complement. Optimum conditions for the hemolytic reaction were: reaction temperature, 15°C; reaction time, 120 min; pH 7.8; concentration of Mg²⁺, 10 mM. When determined under these conditions, the ACH 50 values of the sera from 33 porgy, weighing 23–31 g, were remarkably high (143 ± 81 units/ml) as compared with those reported for mammalian sera.