Although the ability of Th9 cells to directly trigger cancer cell death remains unclear, Purwar et al. showed that Th9 cells derived from OT-II transgenic mice effectively killed OVA-expressing tumor cells [122] and noted that Th9 cells expressed high levels of granzyme B. Down-regulating granzyme B in Th9 cells reduced their anti-tumor effects against melanoma cells. The gene discussed is GZMB; the disease is cancer.