Antigen Presentation and Aquaculture: why studying Major Histocompatibility gene function can lead to enhanced fish health

Major Histocompatibility Complex (MHC) receptors are central to the initiation of immune responses through binding of peptide fragments of pathogens and presenting them to T cells (antigen presentation), which start immune responses to the specific pathogens. There are several accessory molecules required to perform this task, all of which are the same as those used in antigen presentation in mammals. The discovery and characterization of Major Histocompatibility Complex genes, and the genes encoding their accessory molecules, in teleost fish has revealed some startling differences in the regulation of the immune response between fish and mammals, as well as between the different orders of fish. The function of these molecules under normal conditions and at non-physiological temperatures will be discussed.

MHC genes have hundreds of variants (alleles) in most species and specific alleles have been link to susceptibility to or resistance against many pathogens in many species of animals. The exact number of genes on animal can possess also varies and can impact individual fish health. This is due to variant haplotypes and may present challenges for common strategies used for aquaculture, such as triploidization as the presence of too many MHC genes may end up causing immunosuppression. An investigation of the function of these genes may assist in understanding the problems with triploidy and allowing it's use as a strategy to mitigate ecological impact.

The results of these lines of research will enhance our understanding of MHC function and genetics in fish, enabling the production of effective vaccines, the implementation of better husbandry techniques and enhancing fish health.