Immune Response To Bacterial Immunization Of Channel Catfish Maintained In A Recirculating Water-Reuse System

摘要

Intraperitoneal immunization of channel catfish, Ictalurus punctatus, with the Gram-negative bacterium Salmonella paratyphi in Freund's complete adjuvant produced persistant serum agglutinating antibody titers of hundreds of thousands during an immune response of about one year. Bactericidal activity of two high-titered sera averaged 30% and 20%. Post-immunization bactericidal activity varied little and remained within 10% of pre-immunization activity. The enzyme lysozyme, active against Gram-positive bacteria, was present at 1.8 micrograms/ml serum or 34 ng lysozyme/mg protein. Channel catfish serum can therefore provide protection against both Gram-positive and Gram-negative bacteria that the catfish may come in contact with in its aquatic environment. Channel catfish (Ictalurus punctatus) skin mucus also demonstrated an immunological function. Agglutinating antibody (titer of 1:80) and a bactericidal response to Salmonella paratyphi were found in the mucus after intraperitoneal injection of bacteria. By immunodiffusion in gel, the catfish skin mucus gave a precipitin line of identity with catfish 14S serum macroglobulin against rabbit anticatfish 14S serum indicating the presence of secretory IgM in the mucus. Parenteral immunization (intraperitoneally) can thus yield specific IgM antibody in the mucus. Lysozyme at a concentration of 183 micrograms/ml was demonstrated in the mucus. 8% of skin mucus cells from Wright-stained smears were lymphocytes which are immunocompetent cells in fish.