AbstractD‐Penicillamine added to lymphocyte cultures from myasthenia gravis patients infrequently and inconsistently stimulated anti‐AChR production. This usually occurred in the presence of pokeweed mitogen (PWM), and often only at a single concentration ofD‐penicillamine which varied among patients. The change was typically paralleled by an increase in total IgG production of similar magnitude, suggesting that the effect was nonspecific.D‐penicillamine did not affect AChR expression in cultured thymic adherent cells. These data provide no evidence that penicillamine induces myasthenia gravis by direct stimulation of anti‐AChR antibody‐prod