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

Background Chlorazepate is a benzodiazepine often used for pre-operative anxiolysis, The central metabolite responsible for the pharmacological and probably for the adverse effects of most benzodiazepines, including chlorazepate, 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 chlorazepate or a metabolite in vitro by means of the lymphocyte transformation test (LTT), and to determine the concentrations of the T-helper (Th) 2-type cytokine interleukin (IL) -5 and the Th1-type cytokine interferon (IFN) -gamma in the culture supernatants. Methods We performed an LTT with peripheral blood mononuclear cells from the patient and a control, employing human liver microsomes containing cytochrome P450 enzymes as a metabolizing system, in parallel cultures. IL-5 and IFN-gamma concentrations in the culture supernatants were assessed by enzyme-linked immunosorbent assay. Results In the LTT, no T-cell reactivity was observed to the parent compound chlorazepate, whereas coincubation of the drug with human liver microsomes yielded proliferative T-cell reactivity, which was associated with secretion of IL-5 but not of IFN-gamma, Conclusions We conclude that addition of a metabolizing system may be advantageous for in vitro detection of T-cell reactivity to drug metabolites in the LTT.