Correlation of transforming growth factor-beta messenger RNA (TGF-beta mRNA) expression with cellular immunoassays in triamcinolone-treated captive hybrid striped bass

Assessing fish immune status with molecular markers has been hampered by a lack of specific reagents. A quantitative polymerase chain reaction (PCR) m ethod (reverse transcription quantitative-competitive PCR, RT-qcPCR) for me asuring transforming growth factor-beta (TGF-beta) transcription from a bro ad range of teleost fish has recently been developed. The quantitative PCR now permits monitoring production of this important immunosuppressive cytok ine in response to immunomodulating agents and conditions. We examined ante rior kidney and spleen mononuclear cells from hybrid striped bass (female s triped bass Morone saxatilis x male white bass M. chrysops) for production of TGF-beta messenger RNA (mRNA) in response to administration of the synth etic glucocorticoid triamcinolone. We also compared TGF-beta transcription with anterior kidney macrophage bactericidal activity and splenic lymphocyt e blastogenesis. Anterior kidney mononuclear cell TGF-beta mRNA levels decr eased, whereas bactericidal activity increased. Spleen TGF-beta mRNA levels did not change significantly, and splenic lymphocyte pokeweed mitogen stim ulation index increased in triamcinolone-treated fish. Since triamcinolone is used therapeutically as a suppressive immunomodulator, the enhanced immu ne functions indicated by the cellular immunoassays were unexpected; howeve r, the inverse response of TGF-beta production and macrophage bactericidal activity was consistent with the known relationship between TGF-beta and ma crophage activation in mammals. Induced immunomodulation in hybrid striped bass was detectable by both traditional cellular immunoassays and the new R T-qcPCR for TGF-beta.