Cross-reactivity of human leukocyte differentiation antigen monoclonal antibodies on carp and rainbow trout cells

Three hundred and seventy-seven monoclonal antibodies (mabs) directed against human CD antigens and non-classified human leukocyte surface antigens were assayed for their reactivity with common carp (Cyprinus carpio L.) and rainbow trout (Oncorhynchus mykiss) peripheral blood leukocytes (PBL) and thymocytes within the animal homologue section of the 8th International Workshop on Human Leukocyte Differentiation Antigens (HLDA8). Four of the mabs clearly reacted with rainbow trout PBL and two with carp PBL. Positive mabs were investigated further by two-colour flow cytometry with established mabs directed against carp and rainbow trout leukocyte subpopulations. None of these mabs were suitable for Western blotting and immunoprecipitation. Three mabs were found to stain cells in fixed cryostate sections of the lymphatic organs thymus, pronephros and spleen. In this study, for the first time an anti-CD14 mab was found to cross-react with fish cells. This mab could be a valuable tool complementing the limited toolbox of population-specific mabs in fish. The low number of cross-reactive mabs analyzed in this workshop is another indication for the great phylogenetic difference between mammals and osteichthyes.