Dapsone and Nitroso Dapsone Activation of Naı̈ve T‑Cells from Healthy Donors

Dapsone (DDS) causes hypersensitivity reactions in 0.5–3.6% of patients. Although clinical diagnosis is indicative of a hypersensitivity reaction, studies have not been performed to define whether dapsone or a metabolite activates specific T-cells. Thus, the aims of this study were to explore the immunogenicity DDS and nitroso DDS (DDS-NO) using peripheral blood mononuclear cells from healthy donors and splenocytes from mice and generate human T-cell clones to characterize mechanisms of T-cell activation. DDS-NO was synthesized from DDS-hydroxylamine and shown to bind to the thiol group of glutathione and human and mouse albumin through sulfonamide and <i>N</i>-hydroxyl sulphonamide adducts. Naïve T-cell priming to DDS and DDS-NO was successful in three human donors. DDS-specific CD4+ T-cell clones were stimulated to proliferate in response to drug via a MHC class II restricted direct binding interaction. Cross reactivity with DDS-NO, DDS-analogues, and sulfonamides was not observed. DDS-NO clones were CD4+ and CD8+, MHC class II and I restricted, respectively, and activated via a pathway dependent on covalent binding and antigen processing. DDS and DDS-NO-specific clones secreted a mixture of Th1 and Th2 cytokines, but not granzyme-B. Splenocytes from mice immunized with DDS-NO were stimulated to proliferate <i>in vitro</i> with the nitroso metabolite, but not DDS. In contrast, immunization with DDS did not activate T-cells. These data show that DDS- and DDS-NO-specific T-cell responses are readily detectable