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Patients with pulmonary Mycobacterium avium complex (MAC) infection occasionally have neither past histories of pulmonary diseases nor underlying immunodeficiency conditions. Therefore, we hypothesized that MAC may be linked with a disease-susceptibility gene and determined human leukocyte-associated antigens (HLA) in patients with pulmonary MAC infection. HLA phenotypes were tested in 59 patients with pulmonary MAC infection, and diagnosed according to the criteria of the American Thoracic Society. Data of a Japanese population reported at the Tenth Japan HLA Workshop were used as a control. HLA-A33 (28.8% versus 12.5%, p = 5 x 10(-)(4)) and HLA-DR6 (50.8% versus 20.2%, p = 5 x 10(-)(8)) antigen frequencies in patients with MAC were significantly increased compared with those of the control population. Frequency of a haplotype A33-B44-DR6 in the MAC patients was also significantly increased compared with those of the control population (23.7% versus 4.2%; p = 3 x 10(-)(9)). These data suggest that development of pulmonary MAC infection is associated with specific HLA in a Japanese population.

The distribution of HLA-A, B, C, DR and DRB1, DQB1, DPB1 alleles was studied in 60 Japanese patients with clinically definite multiple sclerosis (MS) using serologic and genomic analysis. We found significant associations with HLA-Cw3 (p = 0.002, pc = 0.012, RR = 3.2), DR2 (p = 0.007, RR = 2.6), and DQB1*0602 (p = 0.04, RR = 4.0) in Japanese patients for the first time. The combined presence of Cw3 and DR2 gave a higher risk than each antigen alone. The reported increase in the frequency of DPw4 in Japanese MS patients [12] could not be confirmed by our genomic study. The frequencies of all of the residues in each variable region of the amino acid sequences of DQ beta and DP beta chains were not different between the MS patients and the controls. These results suggest that MS susceptibility may result from polygenic influences and from the presence of environmental factors.