ANTIBODY-DEPENDENT HEMOLYSIN, COMPLEMENT AND OPSONIN IN SERA OF A MAJOR CARP, CIRRHINA-MRIGALA AND CATFISH, CLARIAS-BATRACHUS AND HETEROPNEUSTES-FOSSILIS

The present communication is a continuation of our earlier study on th e natural serum haemagglutinin/lectins of Cirrhina mrigala, Clarias ba trachus and Heteropneustes fossilis. Sera of Cirrhina mrigala, belongi ng to the major carp family, could not only agglutinate heterologous r abbit erythrocytes, but also lyse them spontaneously. This lysis of ra bbit RBC by Cirrhina mrigala sera was calcium ion dependent and heat s ensitive, indicating thereby that the haemolysis was mediated by the f ish serum complement system via the classical pathway. Quantification of CH50 and APCH50 levels in the sera of Clarias batrachus and Heterop neustes fossilis as well as in the sera of amphibia, aves and mammals showed that lower vertebrates predominantly possessed an alternative p athway of the complement system, while on the other hand, in the highe r vertebrates the major pathway of complement activation was classical . Furthermore sera of Clarias batrachus and Heteropneustes fossilis ha d opsonins, which could stimulate heterologous rat peritoneal macropha ges to engulf Staphylococcus aureus with the production of superoxide anion. From this study we concluded that fishes have been armed with v arious powerful natural humoral defense systems for their protection a gainst environmental pathogens.