BACKGROUND: The activation of T lymphocytes is implicated in delayed-onset drug hypersensitivity. However, currently defined cellular and genetic risk factors are not sufficient for the development of comprehensive predictive tools, translatable across conventional drug classes, new modalities, and diverse reaction phenotypes. OBJECTIVE: We sought to assess the frequency of interactions between drugs, HLA proteins, and T-cell receptors within human populations and the role of TNF-alpha as a critical regulator. METHODS: To study the frequency and functionality of T-cell responses, a novel in vitro culture system was used to mimic the inflammatory microenvironment, achieved through 6-day culture of PBMCs from drug-naive and drug-tolerant individuals with a panel of drugs(metabolites) commonly associated with hypersensitivity, and TNF-alpha. T-cell proliferation was measured through [(3)H]-thymidine incorporation, and cytokine analysis was performed using the ELISpot assay. RESULTS: T-cell responses to antibiotics were frequently detectable in drug-tolerant and drug-naive individuals following the addition of TNF-alpha. Ninety percent and 60% of drug-naive individuals produced detectable T-cell responses to vancomycin and piperacillin, respectively. Similarly, T-cell responses to dapsone, sulfamethoxazole, and/or reactive nitroso metabolites were present at high frequencies (>65%). Drug immunogenicity was inhibited by the introduction of TNF-alpha antagonists and HLA-blocking antibodies. Assays performed using PBMC components (CD3(+), CD4(+), CD8(+), CD45RO(+), and CD45RA(+)) show that drugs readily prime and activate naive T cells, with CD4(+)CD45RA(+) T cells preferentially activated. CONCLUSIONS: We challenge the central dogma that tolerant individuals do not express the correct immunologic receptors to mount a drug-specific T-cell response and that the cellular machinery for response elicitation is not limited to hypersensitive patients.
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