SULFONAMIDE-REACTIVE LYMPHOCYTES DETECTED AT VERY-LOW FREQUENCY IN THE PERIPHERAL-BLOOD OF PATIENTS WITH DRUG-INDUCED ERUPTIONS

Background: The role of T lymphocytes in mediating drug eruptions is uncertain. Methods: Twenty-four patients with eruptions induced by sulfonamide-related drugs were studied to detect lymphocyte reactivity to drugs. Both the lymphocyte transformation test and limiting dilution analysis were used as assays for drug-reactive lymphocytes. Peripheral blood lymphocytes were expanded in interleukin-2 and tested for reactivity to sulfamethoxazole and furosemide. Results: The lymphocyte transformation test results to sulfamethoxazole, sulfisoxazole, and furosemide were found to be generally unreliable with a high rate of false-negative and false-positive results. However, as determined by limiting dilution analysis, sulfamethoxazole-reactive lymphocytes were detected in the peripheral blood of one patient at a frequency of 1/172,000. This is within the lower range of frequencies of urushiol-reactive T cells in the peripheral blood of patients with allergic contact dermatitis to urushiol (poison ivy). Two sulfonamide-reactive lymphocyte lines were cultured from two patients. Both lines proliferated in response to sulfamethoxazole but not in response to furosemide, suggesting that furosemide does not cross-react with the sulfonamides. Conclusions: Lymphocytes reactive to sulfamethoxazole were detected at low frequencies in the peripheral blood of three patients with drug eruptions secondary to administration of sulfamethoxazole.