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Natural Killer Cell
Aka: Natural Killer Cell, NK cell, Large Granular Lymphocyte
- See Also
- Major Histocompatibility Complex 1 (MHC-1)
- White Blood Cell (Leukocyte)
- Lymphocyte
- Immune System
- B-Lymphocyte (B Cell)
- T-Lymphocyte (T-Cell)
- Physiology
- Background
- Lymphocytes providing protection against Intracellular Bacteria and viruses, as well as cancer cells
- Respond to intracellular viral infections within first 3 days
- Part of Innate Immunity in which response is not based on prior exposure to pathogen
- Contrast with B-Cells and T-Cells which have a learned pathogen response (Adaptive Immunity)
- Natural Killer Cell Markers
- CD56 positive
- CD3 negative
- Activation of Natural Killer Cells
- Macrophage and dendritic cell derived Cytokines (e.g. Interleukin 12, type 1 Interferons)
- Deactivation of Natural Killer Cells
- Natural Killer Cells bind Major Histocompatibility Complex 1 (MHC-1)
- MHC-1 is present on normal cells and it inactivates NK cells
- MHC-1 is NOT expressed by infected cells
- NK activating receptor Ligand is expressed
- NK cells bind infected cells and destroy them
- NK cell mechanisms of infected cell destruction
- Cytoplasmic granules released, resulting in Target Cell lysis
- Perforin
- Generates pores on cells targeted for destruction
- Granzyme
- Induces programmed cell death (apoptosis) on entry into Target Cells
- Cytokines
- Tumor Necrosis Factor A (TNFa)
- Granulocyte Macrophage Colony Stimulating Factor (GM-CSF)
- Chemokines (CCL1-5 and CCL-8)
- Interferon-Gamma (IFN-g)
- Activates Macrophages for Phagocytosis
- Image: NKC Mediated Destruction of Infected Host Cells

- References
- Guyton and Hall (2006) Medical Physiology, p. 419-50
- Mahmoudi (2014) Immunology Made Ridiculously Simple, MedMaster, Miami, FL