Culprit drugs induce specific IL-36 overexpression in Acute Generalized Exanthematous Pustulosis.

Acute generalized exanthematous pustulosis (AGEP) is a severe adverse cutaneous drug reaction. Although an involvement of drug-specific T cells has been reported, the physiopathology of AGEP and mechanism of neutrophilic skin inflammation remains incompletely understood. Recently, mutations in IL-36RN, the gene encoding the IL-36 receptor antagonist, have been reported to be more frequent in AGEP patients and pustular psoriasis. Here, we show that IL-36 cytokines, in particular IL-36γ, is highly expressed in lesional skin of AGEP patients, keratinocytes and macrophages being a major source of IL-36γ. Such an IL-36γ overexpression could not be observed in patients with drug-induced maculo-papular rash (MPR). In vitro, the causative drug specifically induced IL-36γ release either directly by peripheral blood monocytes from AGEP patients, or indirectly by keratinocytes in presence of autologous peripheral blood mononuclear cells. Such culprit drug induction of IL-36γ secretion in vitro was specific for AGEP and involved the sensing of drug/albumin complex as danger signal by Toll-like receptor 4. Our results suggest that IL-36γ secretion by monocytes/macrophages and keratinocytes in response to culprit drug exposure likely plays a key role in the pathogenesis of AGEP