ANALYSIS ON ALLELIC VARIATION OF THE HLA-DMB GENE IN JAPANESE BY PCR-RFLP AS WELL AS DIRECT DNA-SEQUENCING AND IDENTIFICATION OF A NEW DMB ALLELE, DMB-ASTERISK-0105

In the HLA-D region, one of the class II genes, DMA and DMB have been identified between the DQ and DP genes, acid four allelic polymorphism s in each of the DMA (DMA0101 similar to 0104) and DMB (DMB*0101 simi lar to 0104) genes have been so far recognized. Several recent studies suggested that the DM molecule is required for class II antigen prese ntation pathway especially by promoting the binding of antigenic pepti des to the classical HLA class Ii molecule. In this study, we have ana lyzed genetic polymorphism and allelic variation of the DMB gene in a Japanese population by the direct DNA sequencing technique and also by the polymerase chain reaction - restriction fragment length polymorph ism (PCR-RFLP) method, and could recognize DMB0101 (49.3%), DMB*0102 (23.2%), DMB0103 (23.2%), and DMB*0104 (0.4%). Further, a new DMB all ele, DMB0105 characterized by the presence of Val and Ile at two poly morphic sites, codons 144 and 179, respectively was identified. Strong linkage disequilibria were found between DMB0101 and DRB1*0101, DPB1 0402 and DRB1*1502, and also between DMB*0103 and DRB1*1501 and DQB1* 0602. HLA-DMB genotyping using the PCR-RFLP method established here wi ll provide accurate evaluation of the effects of sequence allelism in the DME: gene on the HLA class II disease associations.