The immune response of the brown trout Salmo trutta to lipopolysaccharide

Brown trout produced high molecular weight, thermostable, dithiothreitol sensitive, non‐precipitating, complement‐fixing antibodies and agglutinins to lipopolysaccharides after intramuscular injection with adjuvant. Antibodies were first detected on Day 14 and reached maximum titres after 56 to 63 days when a single injection was given. When either a second or a third injection was administered maximum titres occurred 34 to 40 days after the injection. After each injection the titres increased significantly, and the protein concentration of the sera was significantly decreased. In cellulose acetate electrophoresis experiments those bands which migrated in the β‐ to γ‐globulin regions were increased. Antibody‐secreting and antigen‐binding cells were detected on Days 8 and 4 respectively and maxima were reached between Day 16 and Day 18. The number of cells per 106 lymphoid cells was higher in the spleen than in the kidney.