In vitro drug allergy detection system incorporating human liver microsomes in chlorazepate-induced skin rash: drug-specific proliferation associatedwith interleukin-5 secretion

Background Chlorazepate is a benzodiazepine often used for pre-operative an xiolysis, The central metabolite responsible for the pharmacological and pr obably for the adverse effects of most benzodiazepines, including chlorazep ate, is N-desmethyldiazepam. We report a woman who developed a generalized exanthem 1 day after receiving chlorazepate and four other drugs related to anaesthesia for surgery of the larynx, Patch tests pointed to chlorazepate as the culprit drug for the skin rash. Objectives The purpose of this study was to detect drug allergy to chloraze pate or a metabolite in vitro by means of the lymphocyte transformation tes t (LTT), and to determine the concentrations of the T-helper (Th) 2-type cy tokine interleukin (IL) -5 and the Th1-type cytokine interferon (IFN) -gamm a in the culture supernatants. Methods We performed an LTT with peripheral blood mononuclear cells from th e patient and a control, employing human liver microsomes containing cytoch rome P450 enzymes as a metabolizing system, in parallel cultures. IL-5 and IFN-gamma concentrations in the culture supernatants were assessed by enzym e-linked immunosorbent assay. Results In the LTT, no T-cell reactivity was observed to the parent compoun d chlorazepate, whereas coincubation of the drug with human liver microsome s yielded proliferative T-cell reactivity, which was associated with secret ion of IL-5 but not of IFN-gamma, Conclusions We conclude that addition of a metabolizing system may be advan tageous for in vitro detection of T-cell reactivity to drug metabolites in the LTT.