Alternative pathway fof bovine complement Immunochemical studies on factor B-like serum protein and its conversion product B gamma 2.

Rabbits produced antibodies to a factor B-like serum protein (factor Bbov), its conversion product B gamma 2 and some other bovine serum proteins after repeated immunization with zymosan which previously had been incubated with fresh bovine serum. Such antisera were used to monitor purification of B gamma 2 from fresh bovine sera incubated with zxymosan. Subsequently, antisera specific for factor Bbov and B gamma 2 were produced. Antiserum produced against B gamma 2 cross-reacted with factor Bbov. Functional assays for factor Bbov were carried out in a hemolytic system with guinea pig erythrocytes in EGTA buffer. Heat inactivation (56 degrees C/5 min) of bovine serum destroyed the antigenicity of factor Bbov but not that of B gamma 2. Factor Bbov had an apparent molecular weight of 95,000 and B gamma 2 a molecular weight of 40,000 daltons. Conversion of factor Bbov to B gamma 2 was determined qualitatively by immunoelectrophoresis and quantitatively by radial immunodiffusion. Conversion of factor Bbov to B gamma 2 in bovine serum, in the presence of zymosan or cobra venom factor (CoVF) required Mg++ but not Ca++, did not occur in heat inactivated (56 degrees C/5 min) serum and was maximal, but not complete, when fresh bovine serum was incubated with zymosan (20 mg/mL) at 37 for two hours.