Development of immunological memory in rainbow trout ( Oncorhynchus mykiss). I. An immunochemical and cellular analysis of the B cell response

Abstract

In vivo and in vitro analyses of the antibody responses of rainbow trout ( Oncorhynchus mykiss) confirmed the existence of immunological memory in this species. An enhanced in vitro secondary antibody response was found to be due strictly to an expansion of the antigen-sensitive precursor pool without a concomitant increase in clone size. In contrast to the development of immunological memory in mammalian species, there was no evidence for affinity maturation during the primary or secondary response. A distinct shift in the fine specificity profiles of the antibodies, however, did occur during the generation of the secondary response. Additionally, more than a single injection of the priming antigen, TNP-KLH was required to produce an enhanced in vitro response to this T-dependent antigen. However, a second priming injection was not required to produce an enhanced secondary response to the T-independent form of antigen, TNP-LPS. These results indicate that memory in trout may be due to a simple expansion of the antigen-specific precursor pool without many of the qualitative changes in antibody or B cell function associated with the expression of memory in mammals.