Demonstration of an antibody response of the anterior kidney following intestinal administration of a soluble protein antigen in trout

The humoral antibody response following anal intubation of a soluble antigenic protein to trout was investigated. The transfer of human immunoglobulin G (IgGh) to the plasma was demonstrated by ELISA assays. The participation of the anterior kidney in plasma clearance of the antigen was shown by an immunofluorescence study. The anterior kidney displayed a proliferation of specific B lymphocytes and differentiation into plasma cells producing anti-IgGh IgM. The peak of plasma specific antibody concentration occurred 30 days after intubation and a second intubation led to another peak 20 days later, whose amplitude was close to that of the primary response.