[Molecular biological analysis of HLA class II gene in autoimmune hepatitis among Japanese]

The frequencies of HLA B54, DR4, DR53 and DQ4 were significantly higher in patients with autoimmune hepatitis than in healthy controls. HLA-DR4 was most frequently associated with autoimmune hepatitis. To define the HLA class II gene which has the susceptibility or resistance to autoimmune hepatitis, we performed HLA class II genotyping using polymerase chain reaction-restriction fragment length polymorphisms (PCR-RFLP) method. The frequency of DRB1*0405 was significantly higher in autoimmune hepatitis than in controls. However, there was no significant difference in the frequency of the DR4 associated Dw-allele between the patients and the controls who were DR4-positive. Six DR4-negative patients had DR2, but there was no significant difference in the frequency of the DR2-associated Dw-alleles compared with the DR2-positive controls. Comparison of the amino acid residues of DRB1 chain suggested that the basic amino acid at position 13, which is present only on the DR2 and DR4 B1 molecules (Arg on DR2 and His on DR4), contributes to the susceptibility to autoimmune hepatitis among Japanese.