Suppression of the Primary Immune Response in Rainbow Trout, Salmo gairdneri, Sublethally Exposed to Tritiated Water During Embryogenesis

Abstract

Antibody synthesis, in response to vaccination with a 0.1-ml (1.8 × 108 cells/ml) intraperitoneally injected, heat-killed strain of Flexibacter columnaris, was employed to investigate the effect of tritium irradiation (0, 0.04, 0.4, 4.0, 40 rads total dose for 20 days during embryogenesis) on development of the primary immune response in 5-mo rainbow trout, Salmo gairdneri, reared under essentially pathogen-free conditions. Specific agglutinins to F. columnaris, determined 1-wk pre vaccination, and 3, 5, 7, 9, and 11 wk postvaccination increased rapidly in both control and irradiated fish following vaccination. Agglutinin levels in irradiated fish were suppressed to 50% of control levels at 40 rads during the 9th wk, and 50% of control levels at 4.0 rads during the 11th wk. Electrophoretic separation of serum proteins of both control and irradiated–vaccinated fish demonstrated four major protein fractions. Densitometry analyses demonstrated that fraction IV increased significantly in percent of total protein following antigenic stimulation, suggesting that fraction IV represents the specific humoral antibody to F. columnaris. The relative percent of total protein contained in fraction IV was significantly reduced in irradiated–vaccinated fish. Key words: antibody synthesis, agglutination assay, vaccination, Flexibacter columnaris, tritium, Salmo gairdneri, electrophoresis, serum protein, densitometry, primary immune response