CD4 and cancer: Beyond myeloid cells, crosstalk between cancer cells that have undergone EMT and immune cells can induce CD4+ T cell differentiation to an immunosuppressive T regulatory cell subtype [51], inhibit proliferation and infiltration of B cells, NK cells and CD4+ and CD8+ T cells [51,52], and render cancer cells less sensitive to cytotoxic T cell killing (Box 2) [53].