Drug-specific CD4 + T-cell immune responses are responsible for antituberculosis drug-induced maculopapular exanthema and drug reaction with eosinophilia and systemic symptoms syndrome.

Background A multidrug regimen including isoniazid, rifampicin, pyrazinamide and ethambutol is commonly used as first-line treatment for tuberculosis. However, this regimen can occasionally result in severe adverse drug reactions, such as drug reaction with eosinophilia and systemic symptoms (DRESS) syndrome and drug-induced liver injury. The culprit drug and mechanistic basis for the hypersensitive reaction are unknown. Objectives To investigate drug-specific T-cell responses in patients with anti-tuberculosis drug (ATD)-induced cutaneous hypersensitivity and its underlying mechanism. Methods We enrolled eight patients with ATD-induced maculopapular exanthema and DRESS and performed a lymphocyte transformation test. Subsequently, drug-specific T-cell clones were generated from four of the patients who showed proliferation in response to ATDs. We measured the drug-specific proliferative responses and counted the drug-specific interferon (IFN)-gamma/granzyme B-producing cells after drug stimulation. Antihuman leukocyte antigen (HLA) class I and class II blocking antibodies were used to analyse human leukocyte antigenrestricted T-cell responses. Results Positive proliferative responses to ATDs were mostly found in patients with cutaneous hypersensitivity. Furthermore, we isolated isoniazid/rifampicin-specific T cells from patients, which consisted primarily of CD4+ T cells. Drug-specific CD4+ T cells proliferated and secreted IFN-gamma/granzyme B when stimulated with isoniazid or rifampicin, respectively. Isoniazid-responsive T-cell clones did not proliferate in the presence of rifampicin and vice versa. Drug-specific T-cell responses were blocked in the presence of anti-HLA class II antibodies. Conclusions This study identifies the presence of isoniazid/rifampicin-specific T cells in patients with ATD-induced maculopapular exanthema and DRESS. Furthermore, it highlights the important role of drug-specific T-cell immune responses in the pathogenesis of these reactions.