CD4 and neoplasm: Moreover, the TME can be enriched in CD4+ Tregs, which secrete additional immunosuppressive cytokines such as IL-10 and TGF-β, as well as myeloid-derived suppressor cells (MDSCs) and M2-polarized TAMs (tumor-associated macrophages), all of which are skewed towards an immunosuppressive phenotype known to promote tumor proliferation.