The Nature of Antibodies and the Immune Response in Rainbow Trout (Salmo Gairdneri)

Abstract

Rainbow trout were immunized with three purified soluble proteins of different molecular sizes: BSA, BGG and KLH. Passive hemagglutinating antibodies were detected in a few of the trout anti-BSA sera on the 31st day and precipitins on the 73rd day after the initial injection of antigen. Only a small number of BSA-injected trout developed detectable antibodies at any interval. No detectable antibodies to BGG were produced by rainbow trout during a 5-month period of immunization. Specific anti-KLH precipitating antibodies were detected by the 22nd day after initial injection of antigen and were eventually produced by all surviving KLH-injected trout. Rainbow trout isoimmune hemagglutinating antibodies resided in a serum fraction which contained 10.5 S and 13.5 S components. They migrated as β-globulins in immunoelectrophoresis. No large- to small-molecule production shift analogous to the 19 S to 7 S production-shift in mammals was observed with either rainbow trout isoimmune hemagglutinating or immune precipitating antibody. Specific natural anti-rabbit RBC hemagglutinins of rainbow trout sera consisted of both large and small molecules. These natural hemagglutinins represent distinctly different molecular species than immune isohemagglutinins. The natural hemolytic activity of rainbow trout serum was in some respects similar to that of the antibody-complement systems of other species. However, it differed in that heat-inactivated trout sera could not be reactivated by various complements and sera, that heterologous or homologous antibody or guinea pig complement did not increase serum titers and that ammonium hydroxide did not significantly affect hemolysis by trout serum.