Preferential expression of catfish light chain immunoglobulin isotypes in anti-dinitrophenyl antibodies

Previous studies indicated that immunoglobulins of the channel catfish, Ictalurus punctatus, contained two distinct isotypes of light chains. These different light chains, designated F and G, are reminiscent of kappa and lambda light chains of higher animals. This study was undertaken to establish whether or not there was preferential expression of one of the light chains in antibodies induced to the dinitrophenyl moiety during the course of the catfish humoral antibody response. The results indicated that, although antibody produced very early (1-2 weeks) after primary immunization contained significant amounts (approximately 20%) of G light chains, the vast majority (approximately 90%) of antibody produced later (3 weeks through 1 year) was of the F isotype. Thus fish, as well as higher vertebrates, can express different isotypes of antibody during the immune response.