Natural killer (NK) cells are defined as large granular lymphocytes and play a critical role in the innate immune system. They often lack antigen-specific cell surface receptors. Instead of acting via antigen-specific receptors, like T-cells, lysis of tumor cells by NK cells involves exocytosis of cytoplasmic granules from the NK cell towards cancer cells; this process can directly occur in the proximity of cancer cells or after engagement of alternative receptor members of the TNF superfamily (FasL/TNF) and their corresponding ligands (Fas/TNFR).
NK cell mediated lysis of cancer cells
NK cells can mediate cancer cell killing through the release of granules/granzymes. This occurs:
- in a direct manner or after activation of receptors on the NK cell's surface that bind ligands on the cancer cell's surface.
- Upon this activation, the cytotoxic granules released by the NK cells are vectorially secreted into the intercellular space formed during conjugation of the NK cell and the cancer cell.
- The granules contain a number of proteins, including perforin, that induce the formation of membrane lesions on the cancer cell, resulting in NK cell mediated lysis of cancer cells.
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