To elucidate the structures of SLA-DR(swine leukocyte antigen DR)genes of three Chinese pig strains (Gz,Bmand Yn),the SLA-DRA and SLA-DRB cDNA were amplified by RT-PCR and subjected to determine thesequences.The whole structures of SLA-DRA alleles are identical among three strains,consisting of 759nucleotides including an open reading frame(ORF),and are shared with those reported from NIH minipigsSLA-DRA~c and SLA-DRA~d.The same length of the ORF-containing SLA-DRB genes of three Chinese pigstrains was also identified.They are composed of 801 nucleotides encoding a xenogeneic antigen molecule of266 amino acid residues.The nucleotide sequences of the SLA-DRB genes,however,are different whencompared either among the three strains or with the published data of SLA-DRB sequences,which allowed ournovel SLA-DRB alleles receiving their accession numbers AY102479,AY102480 and AY102481 from theGenBank.This study further reveals that the phylogenic homologies of MHC DR or DR-like genes in structuresof nucleotides and deduced amino acids between Chinese pigs(SLA)and human(HLA-DRB1*0901)are betterthan those between pigs and mice (H-2~b Eβ).High similarities were also found for DRα-DRβ heterodimersbetween Chinese pigs and human in terms of amino acids sequences critical for binding with human CD4coreceptor molecule,which are better than those between SLA-DR and H-2 I-E molecules.A functional testindicated that,by cotransfection with Bm-DRA and Bm-DRB genes,the Bm-DR molecule-expressed L929 cellscould stimulate human T cells quite well in a xenogeneic reaction in presence of human APCs.Cellular &Molecular Immunology.2004;1 (3):212-218. To elucidate the structures of SLA-DR (swine leukocyte antigen DR) genes of three Chinese pig strains (Gz, Bmand Yn), the SLA-DRA and SLA-DRB cDNA were amplified by RT-PCR and subjected to thesequences. Whole structures of SLA-DRA alleles are identical among three tumors, consisting of 759 nucleotides including an open reading frame (ORF), and are shared with those reported from NIH minipigsSLA-DRA-c and SLA-DRA-d. the same length of the ORF -containing SLA-DRB genes of three Chinese pigstrains was also identified. These are composed of 801 nucleotides encoding a xenogeneic antigen molecule of266 amino acid residues. The nucleotide sequences of the SLA-DRB genes, however, are different whencompared either among the three strains or with the published data of SLA-DRB sequences which allowed ournovel 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 struct uresof nucleotides and deduced amino acids between Chinese pigs (SLA) and human (HLA-DRB1 * 0901) are betterthan those between pigs and mice (H-2 ~ b Eβ) .High similarities were also found for DRα-DRβ heterodimersbetween 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 IE molecules. A functional testindicated that, by cotransfection with Bm-DRA and Bm-DRB genes, the Bm -DR molecule-expressed L929 cells can stimulate human T cells quite well in a Xenogeneic reaction in presence of human APCs. Cellular & Molecular Immunology. 2004; 1 (3): 212-218.