Mice treated with synergistic B. bifidum strains (B. bif_K57) and anti-PD-1 manifested an increase in cytokine-producing IL-2+CD4+ and IFN-γ+CD8+ tumor-infiltrating T cells, anti-tumor lymphocytes CD4+ T, CD8+ T, NK cells, CD8+ T/Treg cells and effector CD8+ T/Treg cell ratios in the tumor and the spleen [65]. Here, CD4 is linked to neoplasm.