Immune Responses to Hydralazine and Nuclear Antigens in Hydralazine-Induced Lupus Erythematosus

Immune responses to hydralazine were detected in patients with hydralazine-induced lupus but not in patients taking hydralazine without developing toxicity, patients with systemic lupus erythematosus, or normal persons. Patients with active hydralazine lupus had circulating antibodies to hydralazine; in vitro their lymphocytes transformed to hydralazine. These responses were not detectable in the other groups. Circulating antibodies to native DNA, characteristic of systemic lupus, were found in patients with hydralazine lupus. Serial studies in a woman who developed two episodes of hydralazine lupus showed that antibodies against hydralazine appeared during the symptomatic periods and disappeared during the asymptomatic interval; lymphocyte transformation and antibodies to native DNA appeared only during the asymptomatic period and signaled the onset of the second episode. These data suggest that hydralazine lupus may represent a unique hypersensitivity reaction in which antibodies to native DNA occur. These antibodies may account for the clinical similarities between hydralazine lupus and systemic lupus.