COMBINATIONS OF HLA-DPB1 AND HLA-DQB1 ALLELES DETERMINE SUSCEPTIBILITY TO EARLY-ONSET MYASTHENIA-GRAVIS IN JAPAN

HLA class II alleles in the DQA1, DQB1, DRB1, and DPB1 genes were inve stigated in Japanese patients with myasthenia gravis (MG) by digestion of polymerase chain reaction amplified DNAs with allele specific rest riction endonucleases (PCR-RFLP). A significantly higher frequency of DQB103, which includes *0301, *0302, *0303 and determines the serolog ical DQ3 specificity, was observed in feamle patients less than 30 yea rs in age at onset of disease compared with healthy controls (90.5 vs. 53.2%). This study also confirms the high incidence of DPB10201 in e arly-onset female patients compared to the controls (85.7 vs. 40.3%). Moreover, 81.0% of the early onset female patients were found to carry both DQB103 and DPB1*0201, compared to 17.7% of the controls. Since DQB103 and DPB1*0201 are not in linkage disequilibrium, both these al leles are supposed to be synergistically involved in disease developme nt in early-onset female MG. In contrast, no obvious association of HL A-DQA1, DQB1, DRB1 and DPB1 alleles with either late-onset patients or patients with thymoma was observed. Clearly, the genetic background o f Japanese females with early onset MG is different from that of other patients with MG.