CHARACTERIZATION OF ANTIHISTONE ANTIBODIES IN PATIENTS WITH TYPE-1 AUTOIMMUNE HEPATITIS

We have recently found that antibodies to total histones are common in a group of American patients with type 1 autoimmune hepatitis (AIH). In an attempt to determine the profile and clinical association of ant i-histone antibody (AHA), 45 Japanese AIH patients were studied for se rum isotypic reactivity with individual histones (H1, H2A, H2B, H3, H4 ) by enzyme-linked immunosorbent assay and western blotting. The resul ts revealed that 40% of sera had reactivities with at least one of ind ividual histones and that the antibodies were detected in all three cl asses of immunoglobulins (IgG, IgM, IgA). Immunoglobulin G type anti-H 3 showed the dominant reactivity and it characterized 72% of sera with AHA. The titre of anti-H3 decreased significantly (P < 0.0075) after steroid therapy and the index of decrease for anti-H3 was correlated i n individuals with that for serum aminotransferase. In general, patien ts with AHA showed higher serum level of alanine aminotransferase (P < 0.05), immunoglobulin G (P < 0.025), and higher frequency of A2-DR4-h aplotype (53 vs 17%) than their seronegative counterparts. However, th e titre of AHA was low in this disease condition and histone class-spe cific antibodies did not distinguish patients with distinctive clinica l features, although patients with anti-H3 tended to be younger than t hose without AHA.