Antibodies to P450IID6, SLA, PDH-E2 and BCKD-E2 in Japanese patients with chronic hepatitis

ABSTRACT Auto‐antibodies specific to various antigens in chronic hepatitis (CH) have been detected but their specificities and implications were uncertain. The aims of the present study were to investigate the frequency and the significance of seropositivity of antibodies to P450IID6 or liver/kidney microsome 1 (LKM1), soluble liver antigen (SLA), pyruvate dehydrogenase (PDH) and branched‐chain keto acid dehydrogenase (BCKD) in 188 Japanese patients with different forms of CH by western blot or enzyme immunoassay (EIA). Anti‐LKM1 was also measured by indirect immunofluorescent test. Anti‐P450IID6 was found in 6/188 (3.2%) CH patients including 5/104 (4.8%) with hepatitis C virus (C) infection and 1/12 (8.3%) CH‐C patients with antibodies to nuclear and smooth muscle antigens and hypergammaglobulinaemia (> 2.5 g/dL). This patient was the only one diagnosed with autoimmune hepatitis (AIH). All CH patients with hepatitis B (B), hepatitis non‐B non‐C (NBNC) and AIH were seronegative for anti‐LKM1. Antibodies to soluble liver antigen were found in two of 188 (1%) patients, one with AIH and one with CH‐B. Anti‐BCKD‐E2 but not anti‐PDH‐E2 was found in four patients (2.5%), one with AIH, two with CH‐C, and one with NBNC. There was no obvious difference in age, sex ratio and laboratory findings in patients with or without anti‐SLA and anti‐BCKD‐E2. Antibodies to P450IID6, SLA, PDH‐E2 and BCKD‐E2 are uncommon in adult CH‐C, CH‐B, CH‐NBNC and AIH patients in Japan. Some of these patients positive for auto‐antibodies appear to have autoimmune features and might require a careful follow up. The heterogeneity of these antibodies in CH preclude further justification for subtyping of AIH by the presence of the distinct auto‐antibodies.