HLA Class II influences humoral autoimmunity in patients with type 2 autoimmune hepatitis

Background/Aims Type 2 autoimmune hepatitis (AIH) is characterized by the presence of anti-liver kidney microsome (anti-LKM-1) and/or anti-liver cytosol type 1 (anti-LC1) autoantibodies. However, the correlation between these autoantibodies and the genetic background has not been studied. Methods Frequencies of HLA class II alleles were compared between the 60 Caucasian children with type 2 AIH and 313 control subjects. The anti-LKM1 antibody reactivity directed against antigenic sites of CYP2D6 was analysed by ELISA. Results HLA-DQB1*0201 allele was found to be the primary genetic determinant of susceptibility to type 2 AIH by conferring the highest odd-ratio (OR = 6.4). HLA-DRB1*03 allele was significantly increased (P < 0.0001) among patients with both anti-LKM1 and anti-LC1 autoantibodies as well as in those with only anti-LC1+ compared to those with anti-LKM1+ alone. In contrast, HLA-DRB1*07 allele was significantly associated (P < 0.0001) with anti-LKM1+ alone compared to groups with both anti-LKM and anti-LC1 or with LC1+ alone. Children with the DRB1*07 allele develop anti-LKM1 autoantibodies having a more restricted specificity (2 epitopes) than to those having HLA-DRB1*03 allele (5 epitopes). Conclusions The HLA-DR locus is involved in autoantibody expression, while the DQ locus appears to be a critical determinant for the development of type 2 AIH.