Publication details

A link between variability of MHC IIB genes and metazoan parasites in the selected populations of the chub ( Leuciscus cephalus Linnaeus, 1758 )



Year of publication 2005
Type Appeared in Conference without Proceedings
MU Faculty or unit

Faculty of Science

Description The genes of the MHC (major histocompatibility complex) play a central role in mediating a vertebrate’s immune response to diseases and parasites. The MHC family is divided into two major subfamilies, class I and class II. In the teleost fishes, the class I and II genes are not localized on the same linkage group. The MHC loci are characterized by high levels of polymorphism, and the products of these genes are the sign of individuality. The allelic lineages of MHC are often shared by related species (this feature is called as trans-species polymorphism). Variability of MHC loci is maintained by two main types of mechanisms: the pathogen-driven balancing selection and reproductive mechanisms. There are two basic types of the hypothesis of the pathogen-driven balancing selection: (1) overdominance hypothesis based on the advantage being heterozygotes at MHC alleles, which permits to recognize wider range of antigens derived from the pathogens than in the case of homozygotes, (2) negative frequency dependent selection hypothesis (or rare-allele advantage) proposing that the individuals with a rare MHC allele respond better to new pathogens. The hypothesis of MHC dependent mating preferences proposes that selection of MHC alleles contributing to the immune recognition of pathogens or parasites could be connected with sexual selection which may provide a choice of “good genes” in order to increase the offspring resistance. Considering the class IIB the polymorphism is concentrated in exon 2 corresponding to ß1 domain of this class which includes the peptide binding regions (PBR). The PBR should interact with the parasitic antigens or parasites, the source of the antigen, are likely the selective agents. The goal of this study was to investigate the variability in exon 2 of class II beta-encoding genes (DAB genes) in four populations of the chub (Leuciscus cephalus L.) collected from the different water basins not historically connected, and evaluate the potential role of the metazoan parasites on the MHC genes differentiation. The results indicate the relationship between MHC allelic diversity and parasites.
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