Oral gavages with A. muciniphila and E. hirae increased the efficacy of PD-1 blockade with respect to tumor growth and A. muciniphila and E. hirae induced dendritic cells to secrete IL-12, a Th1 cytokine involved in the immunogenicity of PD-1 blockade in eubiotic conditions. Oral supplementation with A. muciniphila after FMT with nonresponder feces restored the efficacy of PD-1 blockade in an interleukin-12-dependent manner by increasing the recruitment of CCR9+CXCR3+CD4+ T lymphocytes into mouse tumor beds. The gene discussed is CD4; the disease is neoplasm.