Pathophysiological significance of autoantibody to liver plasma membrane-bound cytoskeleton-related proteins in liver diseases.

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In this study, we found the autoantibody to calmodulin (CaM) which had never been described, and concentrated on clarification of clinical and pathophysiological significance of this autoantibody. The autoantibody to CaM (CaM antibody) was assayed by enzyme-linked immunosorbent assay (ELISA). Immunoglobulin bound to bovine brain CaM fixed to immunoplate was determined using HRP-conjugated antihuman IgG, IgM ad IgA. CaM antibody was decreased by absorption of serum with bovine brain CaM or human erythrocyte CaM, not with actin, tropnin C or DNA. The presence of CaM antiobody was also confirmed by immunoblotting method. IgG class antibody was found in the sera from the patients with collagen diseases as well as those with chronic liver diseases, whereas IgM class antiobody was detected more frequently in the pationts with chronic liver diseases than in those with collagen diseases, In some serum samples, the antibody titres were higher in the presence of free Ca^<++> than in its absence, suggesting that they recognized conformations of CaM. Using CaM-conjugated agarose column, we found that there were three types of antibody : antibodies that bound to Ca^<++>-bound CaM, Ca^<++>-free CaM and both of these. CaM antiobody inhibited phosphodiesterase activity. However it remained for future study whether CaM antibody was involved in the liver cell injury or not.