Specific to the antitumor activity of immune checkpoint inhibitors, a growing body of evidence now posits that the gut microbiota may enhance the function of DCs with more potent tumor antigen presentation and cytokine production, increase trafficking of CD4+ memory T-cells from mesenteric and draining lymph nodes to the TME, decrease Tregs and MDSCs, and increase recruitment and activation of IFN-γ-producing tumor-antigen-specific effector T-cells that altogether contribute to the modulation of the antitumor immune response (Fig. 2) [29]. This evidence concerns the gene CD4 and neoplasm.