Induction of antibody‐producing cells in rainbow trout, Salmo gairdneri Richardson; by flush exposure

Splenic antibody‐producing cells were produced by rainbow trout that had been exposed to O‐antigens extracted from Yersinia ruckeri and Aeromonas salmonicida by adding the concentrated antigen preparation directly into the water of the tank holding the fish for a flush exposure. This method was compared with the proven techniques of exposure: intraperitoneal injection or a 2 minute immersion of the fish in the antigen preparation. Dosage experiments showed that the production of antibody‐producing cells was induced by the immersion of trout for 2 minutes in water with 5.0 μg/ml‐1 (or more) with the Y. ruckeri O‐antigen, or 500 μg ml‐1 (or more) of the A. salmonicida O‐antigen. Similar differences were evident when the respective antigens were added directly to the water.