Although MAIT cells have both cytotoxic activity37 and the ability to rapidly produce pro-inflammatory cytokines including IL-17A, TNF and IFN-γ10, the protective effect of MAIT cells against Legionella infection was not dependent on TNF or IL-17A, but instead relied upon the capacity of MAIT cells to secrete IFN-γ and GM-CSF. The gene discussed is IL17A; the disease is legionellosis.