CD4 and neoplasm: With respect to the role of the microbiome in the antitumor activity of ICI, a growing body of evidence indicates that certain gut microbiota compositions can enhance the function of dendritic cells (DCs) with more potent tumor antigen presentation and cytokine production, increase trafficking of CD4+ memory T cells from intestinal lymph nodes to the TME, decrease Tregs and MDSC numbers, and increase recruitment and activation of interferon-γ-producing tumor-specific effector T cells [4, 5, 11, 18, 30].