Institut Curie Collection,
components of tumoral microenvironment
- Access to: Natural Killer Cell Map
Natural killers (NK) are big granular lymphocytes which can be cytotoxic for tumor cells. The markers of this cell type are specific NK-receptors as NKp30, NKp46, NKG2D, etc. The main role of NK cells in innate immunity is elimination of cells lacking MHC1 molecules that therefore cannot be recognized by T-cells. NK are stimulated by the target cells expressing NK receptors activating ligands such as MICA, MICB, etc. The activity of NK cells is modulated by inflammatory cytokines as IL15, IL12, produced by macrophages and dendritic cells. NK cells secrete granules contains lytic enzymes (granzymes, perforin, granulysin, etc) and express apoptosis inducers TRAIL and FASL. Presence of active NK cells in cancer is correlated with good prognosis. To escape NK control, tumor cells express immunosuppressive ligands as MIF, IL10, TGFB and downregulation of NK ligands expression that collectively inhibit cytotoxic activity of NK cells. Pro-tumor polarization of NK cells is not described in the literature, however suppressed NK cells are incapable to reject tumor cells and therefore indirectly promote cancer progression.