Figure 2.

Mechanisms of the microenvironment of lung cancer modulates NK cells. Tumor cells downregulate the expression of active receptors of NK cells (yellow arrow). Tumor cells and some immune cells in the TME secrete immunosuppressive factors which alter the phenotype and metabolism of NK cells (green arrow). The physical and chemical conditions of the TME impair NK cell function (blue arrow). Tumor cells upregulate the expression of inhibitory receptors of NK cells (red arrow). NK, natural killer; TME, tumor microenvironment; HLA, human leukocyte antigen; IDO, indoleamine 2,3-dioxygenase; IL, interleukin; ILT, Ig-like transcript; KIR, killer cell immunoglobulin-like receptor; MDSC, myeloid-derived suppressor cell; MICA/B, MHC class I chain-related protein A/B; NKG2A, natural killer group 2 member A; PVR, poliovirus receptor; TAMC, tumor-associated myeloid cell; TGF-β, transforming growth factor-β; TIGIT, T-cell immunoglobulin and ITIM domain; Treg, regulatory T cell.