Tissue transplant experiments have revealed a cluster of genes responsible for graft rejection, the major histocompatibility complex (MHC). The MHC is a region dense in immune genes with a role in antigen presentation. Porcine MHC genes are highly polymorphic, varying amongst breeds. Unlike other species, such as mouse, cattle, and human, serological approaches to derive MHC haplotypes have been unsuccessful. To identify porcine haplotypes it is essential to utilize DNA typing approaches. In humans and swine (who have 85% homology in MHC class II), exon 2 of MHC class II genes encodes the first domain of the beta- chain and this domain is in direct contact with the processed peptide and/or the T- cell receptor during antigen presentation. Specific polymorphisms in these class II genes leads to an increase in susceptibility to diseases such as pneumoconiosis, autoimmune diseases, and allo/xeno- graft rejection. In an effort to understand polymorphisms and tissue expression of MHC class II genes (DQB and DRB) DNA from divergent breeds of unrelated pig was analyzed. Primers targeting exon 2 of DQB and DRB were shown to be locus specific, and amplified all alleles. Expression of exon 2 PCR amplicons was verified through sequence analysis revealing over 35 different alleles among the 12 breeds with an average of 7 animals per breed represented. Preliminary data reveals breed specific polymorphisms within both genes. A subsequent analysis was done to analyze expression in various tissue samples. These tissue samples were analyzed through RT- PCR to quantitate RNA expression in each.
Research also presented at the Annual Meeting of the American Association of Immunologists, May 12-16, 2006, Boston, MA.