Immune response of rainbow trout (Oncorhynchus mykiss, Walbaum) to Aeromonas hydrophila

Rainbow trout ( Oncorhynchus mykiss Walbaum), immunised by injection, immersion and orally with killed and live cells of Aeromonas hydrophila , produced antibodies in the serum, bile, skin and gut mucus, and skin and muscle extracts. The antibodies were of a low affinity macroglobulin class, sensitive to 2-mercaptoethanol, and of a structure comprising heavy and light chains. These antibodies reacted maximally with formalised cells and lipopolysaccharide (LPS), and to a lesser extent with exopolysaccharide (EPS), flagella, S-layer protein and a haemolytic component of the extracellular products (ECP) of A. hydrophila .