The impact of MHC diversity on cattle T cell responses

Major histocompatibility complex (MHC) genes play a key role in immunity to infectious pathogens. Their high level of diversity is a functionally important characteristic. In cattle our knowledge of MHC diversity and the functional distinction between genes is limited. Recent studies in commercially important dairy cattle populations reveal that MHC class I diversity is relatively low, although it does not appear to be declining. The presence and frequency of some genes and alleles was markedly different between geographically distinct populations, and trait selection was implicated as an influential force. Functional studies suggest that some alleles may have a disproportionally high impact on T cell responses, thus it may be important to consider their role in both disease resistance and vaccine efficacy. It is clear that increasing our knowledge of the functional capabilities of different cattle MHC class I genes is essential to maintain healthy populations in the future.