@article {Farrell229, author = {John Farrell and Dean J. Naisbitt and Nicola S. Drummond and Jan P. H. Depta and F. Javier Vilar and Munir Pirmohamed and B. Kevin Park}, title = {Characterization of Sulfamethoxazole and Sulfamethoxazole Metabolite-Specific T-Cell Responses in Animals and Humans}, volume = {306}, number = {1}, pages = {229--237}, year = {2003}, doi = {10.1124/jpet.103.050112}, publisher = {American Society for Pharmacology and Experimental Therapeutics}, abstract = {Sulfamethoxazole (SMX) is associated with hypersensitivity reactions. Identification of drug-specific lymphocytes from hypersensitive patients suggests involvement of the immune system. Lymphocytes from humans recognize SMX and nitroso-SMX (SMX-NO), whereas cells from sensitized rats recognize only SMX-NO. In this investigation, we study the nature of SMX-specific T cells in four species. Male rats, mice, and rabbits were immunized with SMX (50 mg kg{\textendash}1) or SMX-NO (1 mg kg{\textendash}1). Lymphocytes and/or splenocytes were isolated and incubated with SMX, SMX-hydroxylamine or SMX-NO and proliferation were measured. Lymphocytes were also isolated from SMX-hypersensitive patients (n = 3) and drug-specific proliferation was measured. In addition, rabbits were bled fortnightly for 4 months to determine whether SMX-NO-specific T cells cross-react with SMX. To confirm that SMX-NO responses were due to covalent binding and not cross-reactivity, cells were pulsed with SMX-NO and/or coincubated with glutathione. Splenocytes from mice, rats, and rabbits proliferated when stimulated with SMX-NO, but not SMX. A 2-h pulse with SMX-NO was sufficient for proliferation, whereas cells coincubated with SMX-NO and glutathione did not proliferate. Rabbit lymphocytes proliferated in the presence of SMX-NO and SMX-hydroxylamine, but not SMX. SMX-hydroxylamine was converted to SMX-NO in culture. The SMXNO-specific response of rabbit lymphocytes was maintained for at least 4 months and the cells did not cross-react with SMX. Human lymphocytes from hypersensitive patients proliferated in the presence of SMX and both metabolites. These results highlight important differences in T-cell recognition of drug (metabolite) antigens in animals that have been sensitized against a drug metabolite and patients with hypersensitivity to the drug. The American Society for Pharmacology and Experimental Therapeutics}, issn = {0022-3565}, URL = {https://jpet.aspetjournals.org/content/306/1/229}, eprint = {https://jpet.aspetjournals.org/content/306/1/229.full.pdf}, journal = {Journal of Pharmacology and Experimental Therapeutics} }