IL‐17 production by γδ T cells is important for the antitumor effect of <i>Mycobacterium bovis</i> bacillus Calmette‐Guérin treatment against bladder cancer

Abstract

Abstract Intravesical inoculation of Mycobacterium bovis bacillus Calmette‐Guérin (BCG) has been used for the treatment of bladder cancer. Recent studies implied the requirement of neutrophil infiltration for the antitumor effect. In this study, we found that IL‐17 was produced in the bladder after BCG treatment, preceding the infiltration of neutrophils. Neutrophils in the bladder after BCG treatment were reduced in IL‐17‐deficient mice, in which BCG‐induced antitumor effect against intravesically inoculated bladder cancer was abolished. Notably, the level of IL‐17 production and the number of neutrophils in BCG‐treated bladder was reduced in γδ T‐cell‐deficient mice but not in CD4‐depleted mice. Survival of bladder cancer‐inoculated γδ T‐cell‐deficient mice was not improved by BCG treatment. These results suggest that IL‐17‐producing γδ T cells play a key role in the BCG‐induced recruitment of neutrophils to the bladder, which is essential for the antitumor activity against bladder cancer.