IL-17+ CD8+ T cells are mostly characterised as non-cytotoxic in mice , , , ,  and humans ,  thus distinguishing these cells from IFN-γ+ CD8+ T cells. However, there are data implicating the cytotoxic function of IL-17+ CD8+ T cells in both mice  and humans . Additionally, IL-12-converted mouse IL-17+ IFN-γ+ CD8+ T cells possessed more cytotoxic activity than IL-17-expressing CD8+ T cells ,  and like IFN-γ+ CD8+ T cells, possessed anti-tumour functions . Thus, variability in cytotoxicity may indicate functional differences of IL-17-expressing CD8+ T cells; however it remains to be determined whether and how (lack of) cytotoxic activity contributes to human inflammatory disease.