CD4 and neoplasm: In the PDAC microenvironment, the prevalent immune cells tending to promote tumor progression via immunosuppression include T regulatory cells (Treg), Myeloid Derived Suppressor Cells and Type 2 Tumor Associated Macrophages, while dampening immune effector cells (mainly CD8+ and CD4+ T cells, Dendritic Cells (DCs) and Natural Killer Cells) (37).