Salmonid spleen and anterior kidney harbor populations of lymphocytes with different B cell repertoires.

An O-antigen extract of the fish pathogen Vibrio anguillarum was used to stimulate plaque-forming cells (PFC) in coho salmon. The kinetics of the response demonstrates peak PFC per organ on day 16 post immunization for the spleen and anterior kidney. Significant PFC were also seen in thymic tissue. PFC responses were shown to be immunoglobulin mediated and antigen specific. Inhibition profiles of responding PFC populations demonstrate that the cells of the anterior kidney are more restricted in their recognition of antigen than those of the spleen. These data lend functional support to the concept of the hematopoietic nature of the anterior kidney of teleosts.