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The HLA—B8 antigen is one of the characteristic antigens associated with organ specific autoimmune diseases among Caucasians. Among the Japanese, HLA—B8 positives have been assumed to be extremely rare. By using some HLA-B8 typing sera, a new HLA-B antigen, HLA-Bw4 positive, was found in the Japanese. This new HLA-B antigen, tentatively called HOK-1, showed a phenotype frequency of 3.7% and a gene frequency of 1.9 ± 0.6%. This antigen has a strong linkage disequilibrium with HLA-Cw1 among the Japanese.

To elucidate the immunogenetic background of idiopathic inflammatory myopathies (IIM) such as polymyositis (PM), dermatomyositis (DM) and any overlapping subsets, with other collagen vascular diseases, HLA class I antigens and class II alleles were determined and compared from individuals with various clinical and serological features of IIM, including pulmonary interstitial lesions (PI). Seventy-three Japanese patients with myositis (32PM, 18DM, 23 overlapped subsets) and 62 healthy unrelated controls were enrolled onto the study. Statistical differences between groups were determined by the Fisher's exact probability test. Serum fluorescent antinuclear antibody, rheumatoid factor (RF), anti-SS-A/Ro antibody, anti-Jol antibody and anti-Ul RNP antibody were examined using routine methods. PI was detected by chest X-ray and/or computed tomography. In patients with DM, the frequency of the HLA-DRB1 * 1302-DQA1 * 0102-DQB1 * 0604 haplotype was significantly higher than in the healthy controls (42.1% vs 17.7%), and in the patients with PM (42.1% vs 9.4%). Furthermore, the frequency of the HLA-DRB1 * 0405-DQA1 * 03-DQB1 * 0401 haplotype was higher in the PM patients with PI than in the controls (50.0% vs 17.7%), and PM without PI (50.0% vs 5.5%). These results suggest that in terms of HLA class II association, Japanese DM and PM, and PM with and without PI, belong to different clinical groups.

To elucidate the clinical characteristics and pathogenesis of scleroderma-rheumatoid arthritis (SSc-RA) overlap syndrome, we analyzed the clinical features of 5 patients with SSc-RA overlap. Their HLA phenotypes and genotypes were also determined. Generalized skin sclerosis, severe seropositive polyarthritis, pulmonary fibrosis, anti-topoisomerase I antibodies, and HLA-DR4,53;DQA1*0301;DBQ1*04 haplotype were observed in all of the patients. Similar clinical features were recognized in most of the 10 cases reported previously. Our case studies indicate that SSc-RA overlap may be a distinct entity.