CCR9 and cancer: The clinical responses of cancer patients to immune checkpoint inhibitors were closely correlated with the relative abundance of A. muciniphila, and oral supplementation with A. muciniphila after fecal microbiota transplantation with non-responder feces restored the efficacy of the PD-1 blockade in an interleukin-12-dependent manner by increasing the recruitment of CCR9+CXCR3+CD4+ T lymphocytes into mouse tumor beds (Routy et al., 2018).