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–1) or SMX-NO (1 mg kg–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.
Footnotes
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These studies were supported by the Wellcome Trust. D.J.N. is a Wellcome Trust Research Career Development Fellow. Data were presented in part as a poster communication to be published [Farrell J, Naisbitt DJ, Depta JPH, Pichler WJ, Pirmohamed M, and Park BK (2003) Characterization of sulfamethoxazole and sulfamethoxazole metabolite-specific T-cell responses in animals and man Toxicology, in press] at the British Toxicology Society meeting, Manchester, UK, September 2002.
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DOI: 10.1124/jpet.103.050112.
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ABBREVIATIONS: SMX, sulfamethoxazole; HIV, human immunodeficiency virus; SMX-NO, nitroso sulfamethoxazole; MHC, major histocompatibility complex; DMSO, dimethyl sulfoxide; HBSS, Hanks' balanced salt solution; SI, stimulation indices.
- Received February 5, 2003.
- Accepted April 3, 2003.
- The American Society for Pharmacology and Experimental Therapeutics
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