In vivo priming of TNP-reactive effector cells in carp

In a study of immune mechanisms in fish, specific cell-mediated cytotoxic activity against trinitrophenyl (TNP)-modified autologous peripheral blood leucocytes (PBL) was successfully induced in in vivo primed carp Cyprinus carpio. The cytotoxic activity increased in proportion to the number of immunizations. The cytotoxic activity was shown to be gradually reduced with time after in vivo sensitization, and was finally lost. In addition, cytotoxic activities against TNP-modified allogeneic PBLs (T-ALLO-PBL) in carp immunized with TNP-modified autologous PBLs (T-AUTO-PBL) were not detected and effector cells from carp immunized with T-ALLO-PBL were not significantly cytotoxic against T-AUTO-PBL. Thus, the occurrence of a genetic restriction in carp was shown using the in vivo priming model. These results suggest that specific cell-mediated cytotoxicity of in vivo primed carp in some respects resembles mammalian cytotoxic T cells.