Helper T (T(H)) cells are an important part of the adaptive immune system. It is hypothesized that one type of helper T-cell, T(H)17 cells, play an important role in idiosyncratic drug-induced liver failure, and it was found that interleukin (IL)-17, the signature cytokine of T(H)17 cells, was elevated in most patients with idiosyncratic drug-induced liver failure. However, it was also found that IL-17 was elevated in some patients with acetaminophen (APAP)-induced liver failure. It is unlikely that APAP-induced liver failure is mediated by the adaptive immune system, but there are other cells such as macrophages and natural killer (NK) cells that also produce IL-17. Therefore, the phenotype of cells that produce IL-17 was studied in a mouse model of APAP-induced liver toxicity. To the authors' surprise, it was found that most of the IL-17 producing cells in the liver were T(H)17 cells, and they were increased within hours of APAP treatment. This is too fast for a response of the adaptive immune system. These data suggest that T(H)17 cells can be part of the innate immune response; however, it is unclear what role they play in the pathogenesis of APAP-induced hepatotoxicity