Immunogenetics of disease resistance in fish

Wiegertjes, G.F.


The aim of the work described in this thesis is to investigate the possibility to select for immune responsiveness, and subsequently produce isogenic carp ( Cyprinus carpio L.) lines, via gynogenesis, that express the trait under selection. If possible, this would allow the repeated production of numerous isogenic fish lines, all selected for different immune parameters, that can be used for immunogenetic studies on disease resistance. As a model, we chose a defined antigenic determinant (dinitrophenyl: DNP), coupled to a carrier molecule (keyhole limpet haemocyanin: KLH) in combination with a reliable read-out system (enzymelinked immunosorbent assay: ELISA), to divergently select carp for the magnitude of their primary antibody response. The possibility to reproduce both homozygous gynogenetic females and functional males with a high or a low antibody response, resulted in the establishment of a number of F 1 hybrid crosses with high or low immune responsiveness to DNP-KLH. Typically, these isogenic lines showed no within-line genetic variation. Between-line genetic variation in susceptibility to infection with Trypanoplasma borreli, a haemoflagellate parasite of carp, was dependent upon the immune response type of the carp lines. Major histocompatibility complex (Mhc) class II β-chain polymorphism could be associated with the immune response types described and, in retrospect, may have contributed to the observed differences in magnitude of immune responsiveness to DNP-KLH, and possibly T.borreli.