SELECTIVE IMPAIRMENT OF SERUM ANTIBODY REPERTOIRES TOWARD MUSCLE AND THYMUS ANTIGENS IN PATIENTS WITH SERONEGATIVE AND SEROPOSITIVE MYASTHENIA-GRAVIS

We analyzed the antibody (Ab) repertoires of IgM and IgG of patients w ith seropositive and patients with seronegative myasthenia gravis (MG) toward self antigens by means of a quantitative immunoblotting techni que using normal human tissue extracts as sources of self antigens. Re pertoires of reactivities of IgG and IgM with liver, kidney and stomac h antigens were conserved between myasthenic patients and controls. Ig G and IgM Ab repertoires toward muscle antigens differed significantly between patients with seropositive MG and healthy donors, as assessed by multiparametric statistical analysis. Patterns of Ab reactivities to muscle antigens were similar in patients with seronegative MG and h ealthy controls. Antibody repertoires of IgG and IgM toward thymus ant igens of both seropositive and seronegative MG patients, differed sign ificantly from those of healthy individuals. Our results indicate that MG is characterized by a selective impairment of self-reactive Ab rep ertoires toward muscle and thymus antigens. The observation that self- reactive Ab repertoires toward thymus antigens are similar in patients with seropositive and seronegative MG suggests that both forms of MG share common immunopathological features.