The goldfish immune response. I. Characterization of the humoral response to particulate antigens

Anti-red blood cells (RBC) and anti-hapten antibody synthesis were studied in the goldfish, Carassius auratus. Spontaneous haemagglutination titres were found against all the antigens tested. A weak secondary response was observed in RBC-primed fish boosted during the end-phase of the primary antibody production. However, when the second antigenic challenge was performed during the early exponential phase of a primary stimulation, an important amplified response was obtained. The antibody production and immunological memory can be dissociated: no antibody synthesis occurred in glutaraldehyde-fixed RBC (F-RBC) primed was obtained when untreated or F-RBC were given to F-RBC primed animals. The amplified response to sheep red blood cells (SRBC) was significantly inhibited when fish were primed with a mixture of SRBC and Xenopus red blood cells (XRBC), demonstrating an antigenic competition phenomenon. Studies on anti-trinitrobenzene responses confirm the efficiency of E. coli lipopolysaccharide as a carrier for fish anti-hapten immunization. The kinetics and regulation of antibody synthesis in fish are discussed in relation to the described results.