Novel SLA-DR alleles of three Chinese pig strains and the related function in human T cell response

To elucidate the structures of SLA-DR (swine leukocyte antigen DR) genes of three Chinese pig strains (Gz, Bm and Yn), the SLA-DRA and SLA-DRB cDNA were amplified by RT-PCR and subjected to determine the sequences. The whole structures of SLA-DRA alleles are identical among three strains, consisting of 759 nucleotides including an open reading frame (ORF), and are shared with those reported from NIH minipigs SLA-DRA(c) and SLA-DRA(d). The same length of the ORF-containing SLA-DRB genes of three Chinese pig strains was also identified. They are composed of 801 nucleotides encoding a xenogeneic antigen molecule of 266 amino acid residues. The nucleotide sequences of the SLA-DRB genes, however, are different when compared either among the three strains or with the published data of SLA-DRB sequences, which allowed our novel SLA-DRB alleles receiving their accession numbers AY102479, AY102480 and AY102481 from the GenBank. This study further reveals that the phylogenic homologies of MHC DR or DR-like genes in structures of nucleotides and deduced amino acids between Chinese pigs (SLA) and human (HLA-DRB1*0901) are better than those between pigs and mice (H-2(b)Ebeta). High similarities were also found for DRalpha-DRbeta heterodimers between Chinese pigs and human in terms of amino acids sequences critical for binding with human CD4 coreceptor molecule, which are better than those between SLA-DR and H-2 I-E molecules. A functional test indicated that, by cotransfection with Bm-DRA and Bm-DRB genes, the Bm-DR molecule-expressed L929 cells could stimulate human T cells quite well in a xenogeneic reaction in presence of human APCs.