Enhanced antigenicity leads to altered immunogenicity in sulfamethoxazole-hypersensitive patients with cystic fibrosis

Background: Exposure of patients with cystic fibrosis to sulfonamides is associated with a high incidence of hypersensitivity reactions. Objective: To compare mechanisms of antigen presentation and characterize the phenotype and function of T cells from sulfamethoxazole-hypersensitive patients with and without cystic fibrosis. Methods: T cells were cloned from 6 patients and characterized in terms of phenotype and function. Antigen specificity and mechanisms of antigen presentation to specific clones were then explored. Antigen-presenting cell metabolism of sulfamethoxazole was quantified by ELISA. The involvement of metabolism in antigen presentation was evaluated by using enzyme inhibitors. Results: Enzyme inhibitable sulfamethoxazole-derived protein adducts were detected in antigen-presenting cells from patients with and without cystic fibrosis. A significantly higher quantity of adducts were detected with cells from patients with cystic fibrosis. Over 500 CD4⁺ or CD8 ⁺ T-cell clones were generated and shown to proliferate and kill target cells. Three patterns of MHC-restricted reactivity (sulfamethoxazole- responsive, sulfamethoxazole metabolite-responsive, and cross-reactive) were observed with clones from patients without cystic fibrosis. From patients with cystic fibrosis, sulfamethoxazole metabolite-responsive and cross-reactive, but not sulfamethoxazole-responsive, clones were observed. The response of the cross-reactive clones to sulfamethoxazole was dependent on adduct formation and was blocked by glutathione and enzyme inhibitors. Antigen-stimulated clones from patients with cystic fibrosis secreted higher levels of IFN-γ, IL-6, and IL-10, but lower levels of IL-17. Conclusion: Sulfamethoxazole metabolism and protein adduct formation is critical for the stimulation of T cells from patients with cystic fibrosis. T cells from patients with cystic fibrosis secrete high levels of IFN-γ, IL-6, and IL-10.