Anti‐smooth muscle antibodies (ASMAs) and anti‐cytoskeleton antibodies (ACTAs) in liver diseases: a comparison of classical indirect immunofluorescence with ELISA

摘要

In the diagnosis of autoimmune hepatitis type I (AIH‐I), the routine assay of indirect immunofluorescence (IFL), used for the detection of anti‐smooth muscle antibodies (ASMAs), has a low predictive value. On the other hand, the enzyme‐linked immunosorbent assay (ELISA), which detects anti‐cytoskeleton antibodies (ACTAs), presents contradictory results concerning their specific antigenic target. In this study, we first looked for the immunological properties (isotypes and antigenic targets) of autoantibodies in AIH‐I and two other control liver diseases: primary biliary cirrhosis (PBC) and viral hepatitis (VH), using ELISA based on cytoskeleton proteins: F‐actin, G‐actin, myosin, tropomyosin, troponin, desmin, vimentin, keratin, and an extract of HEp‐2 carcinoma cells. We also compared the diagnostic value of IFL and ELISA. In contrast to previous studies, we found that actin was not specific for AIH‐I. No autoantigen and no antibody class or subclass discriminated AIH‐I from the control diseases. IFL is more suitable for AIH‐I diagnosis, as 97% of AIH‐I sera but only 22% of PBC sera were ASMA‐positive. Additionally, 96% of ASMA‐positive, and all ASMA‐negative sera from all three liver diseases were ACTA‐positive. ASMA were mainly IgG, while >50% of ACTA also contained IgA and IgM. These data suggest that ACTAs recognize additional epitopes as compared to ASMAs, and they frequently occur in all liver diseases. © 2002 Wiley‐Liss, Inc.