DRUG-INDUCED MODULATION OF IMMUNE FUNCTION IN THE RAINBOW-TROUT, ONCORHYNCHUS-MYKISS

Trouts were injected with triamcinolone (TMC) or methotrexate (MTX) at various times after primary immunization with Vibrio bacterin, and subsequently evaluated for effects on selected immunologic parameters. There was a leucopenia at the expense of lymphocytes in the MTC-treated animals, whereas lymphocytes, granulocytes and monocytes were accountable for leucopenia in the MTX-treated. The thymus, spleen and head kidney displayed reduced cellularity in the former, and, not so much, in the latter. Phagocytic ability was ameliorated in the immunized controls, while diminished in the two groups of drug-injected trout. Antibody production was detectable in the controls, as well as the TMC-treated fish but not in the MTX-treated. Challenging with virulent Vibrio indicated that actual protection has been obtained in immunized controls, while all the TMC- and MTX-treated fish died.