IDENTIFICATION AND CHARACTERIZATION OF ANTIMITOCHONDRIAL AUTOANTIBODIES IN SERA OF PATIENTS WITH MONOCLONAL GAMMOPATHIES

Monoclonal gammopathies (MG) are defined by the accumulation of monocl onal immunoglobulins, a result of monoclonal B lymphocytes or plasma c ell proliferative disorder. Only rarely do these antibodies cause an o vert disease by binding to a specific autoantigen (e.g., factor VIII). In the present study, sera from 100 patients with MG were screened fo r the presence of antibodies against the mitochondrial pyruvate dehydr ogenase complex (PDH) - autoantibodies that are the hallmark of primar y biliary cirrhosis (PBC). Anti-PDH antibodies were found in 6 patient s, all asymptomatic. Using ELISA and immunoblotting methods, it was fo und that the titre of the anti-PDH antibodies was relatively low (aver age OD +/- SD: 0.744 +/- 0.529; PBC patients: 1.225 +/- 0.291; P = 0.0 2). In each patient the autoantibodies were of both kappa and lambda c hains, suggesting that they are of polyclonal origin and implying that in MG there is a significant production of polyclonal autoantibodies, in addition to monoclonal proliferation. Furthermore, in 5 of the 6 p atients (83%) the anti-PDH antibodies did not recognize the E2 compone nt of PDH (which is the major autoantigen in PBC) and did not inhibit the activity of PDH (which was inhibited by PBC autoantibodies). This is in concert with the fact that none of the patients developed liver disease and emphasizes the specificity of the anti-PDH autoantibodies associated with PBC.