CD4 and neoplasm: Reduce the killing function of CD8+T lymphocytes and CD4+T lymphocytes to tumor cells; it can also inhibit T cell activation through PD-1/PD-L1 pathway, induce T cell apoptosis, and then immune escape, promote tumor progression and metastasis.[11] With the progression of tumor, the immunosuppressive cytokines IL-4, IL-10, and IL-13 in TME induce the polarization of macrophages towards M2 phenotype, and induce the gradual polarization of M1-TAM into M2-TAM, which will eventually promote the proliferation and invasion of tumor cells, induce immune suppression and enhance tumor drug resistance.