IMMUNOLOGICAL STUDY OF ANTI-M2 IN ANTIMITOCHONDRIAL ANTIBODY-NEGATIVEPRIMARY BILIARY-CIRRHOSIS

We investigated the specificity of various autoantibodies in antimitoc hondrial antibody (AMA)-negative patients with primary biliary cirrhos is (PBC), We examined sera from 144 patients with PBC, 17 of whom were AMA negative by indirect immunofluorescence. The AMA-negative group s howed a significantly higher positivity for smooth muscle antibody, bu t not for antinuclear antibody, as compared with the AMA-positive grou p, IgG class anti-PDH by enzyme-linked immunosorbent assay (ELISA) mer e detected in 13 % of the AMA-negative group, However, all PBC patient s showed positive IgG, IgA, and/or IgM class anti-M2 to the four M2 pr oteins by immunoblotting. These results suggest that the detection of IgG and IgM class anti-PDH and that of antibodies to the four M2 prote ins increases the positivity of this ELISA method, and that detection of IgG, IgA, and IgM class anti-M2 to the four M2 proteins by immunobl otting is useful in diagnosing AMA-negative patients with PBC.