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. 2021 May 20;11:672490. doi: 10.3389/fonc.2021.672490

Figure 3.

Figure 3

Immune responses in the tumor microenvironment. In the initiation of tumorigenesis, activated Tc and NK cells suppress tumor proliferation. While in the immune evasion, Th2 recruits MDSC and promotes macrophages polarization (M1 to M2). Finally, survived tumor cells exhaust Tc cells by some immune checkpoints. DC, Dendritic cell; MCH-1, Major histocompatibility complex class I; MCH-II, Major histocompatibility complex class II; TCR, T cell receptor; Th, T helper cell; Th1, T helper 1 cell; Th2, T helper 2 cell; Tc, Cytotoxic T cell; IFN-γ, Interferon-gamma; Treg, Regulatory T cell; Foxp3, Forkhead box Protein 3; MDSC, Myeloid-derived suppressor cell; NOS2, Nitric Oxide Synthase 2; TNFα, Tumor necrosis factor-alpha; IL-2, Interleukin 2; IL-6, Interleukin 6; iNOS, Inducible nitric oxide synthase; M1, Macrophage 1; M2, Macrophage 2; PD-1, Programmed cell death protein 1; PD-L1, Programmed cell death protein ligand 1; CTLA-4, Cytotoxic T-lymphocyte antigen 4; NK, Natureal kill cell; TGF-β, Transforming growth factor-beta; MMP-9, Matrix metallo proteinase-9; VEGF, Vascular endothelial growth factor; ┤,Inhibition; →, Promotion.