natural killer (NK) cells

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  • cells of the inate immune system
  • are mononuclear and have lymphocyte morphology
    • their different surface characteristics however prevent them from being classified as either B or T cells.
  • also known as “large granular lymphocytes” (LGLs)
  • mainly found in the circulation
  • comprise between 5-11% of the total lymphocyte fraction
  • possess receptors for immunoglobulin type G (IgG)
  • also contain two unique cell surface receptors known as killer activation receptor and killer inhibition receptor
    • activation of killer activation receptor initiates cytokine (“communication”) molecules from the cell
    • activation of the killer inhibition receptor inhibits the cytokines
  • have an important role in attacking virally-infected cells in addition to certain tumour cells
  • destruction of infected cells is achieved through the release of perforins and granyzymes from its granules, which induce apoptosis (programmed cell death)
  • able to secrete interferon-alpha
    • interferon alpha prevents healthy host cells from becoming infected by a virus; and augments the T cell response to other virally infected cells
  • cells lyse antibody-coated cells in the absence of complement by attaching to the Fc potion of the antibody molecule

Last reviewed 01/2018

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