The haemolytic plaque assay in carp (Cyprinus carpio).

A haemolytic plaque assay for the enumeration of antibody forming cells in the carp (Cyprinus carpio) is described. Serum of bream (Abramis brama) turned out to be a more reliable complement source than allogeneic carp serum. The addition of 3--5% bream serum to a mixture of immune lymphoid carp cells and xenogeneic erythrocytes gave optimal results. Higher amounts of bream complement inhibited plaque formation. Plaque formation was also suppressed when inactive or heat-inactivated bream or carp serum was added to a mixture containing normal bream complement.