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. 2018 Jun 26;9:1483. doi: 10.3389/fimmu.2018.01483

Figure 2.

Figure 2

The roles played by γδ T cells at different stages of colorectal cancer development. (1) During chronic inflammation, γδ T cells can limit excessive inflammatory response and maintain homeostasis by (a) removal of impaired epithelial cells; (b) secretion of protective IL-17; (c) enhancement of Gr-1+CD11b+ suppressor cell infiltration; and (d) regulation of αβ T cell functions. (2) At the initiation of tumor formation, circulating γδ T cells can recognize and kill cancer cells, but they are reprogrammed with cancer development. (3) At stages of tumor progression, IL-17 and granulocyte macrophage colony-stimulating factor (GM-CSF), produced by γδ T cells in response to IL-23 and transforming growth factor beta 1 (TGF-β1) from inflammatory dendritic cells (inf-DCs) and cancer cells, are essential for the recruitment of polymorphonuclear myeloid-derived suppressor cells (PMN-MDSCs), consequently inducing a cascade of suppressive immune responses. CTLA4, cytotoxic T lymphocyte-associated protein-4; PD-1, programmed cell death protein 1; TNF-α, tumor necrosis factor α; IL-17, interleukin-17.