Lymphoma and plasma cell neoplasms
Lymph nodes
Normal lymphocyte development - NK cells

Topic Completed: 1 December 2010

Minor changes: 16 March 2020

Revised: 1 January 2019, last major update December 2010

Copyright: (c) 2001-2020,, Inc.

PubMed Search: nk cells lymphocyte development

Nikhil Sangle, M.D.
Page views in 2019: 2,047
Page views in 2020 to date: 814
Cite this page: Sangle N. NK cells. website. Accessed May 27th, 2020.
Definition / general
  • Distinct group of non T, non B lymphocytes (5 - 10% of peripheral blood lymphocytes) with large granular lymphocyte morphology on Wright-Giemsa stains
  • NK cells derive from a common lymphoid progenitor with T cells
  • First line of defense against various infections, by recognizing and killing target cells and producing cytokines, particularly interferon-gamma, which enhance the innate immune response
  • Capable of lysing certain target cells (virally infected and tumor cells) without prior activation or major histocompatibility complex restriction (hence named "natural killers" that are part of "innate" immune system, Wikipedia)
  • Do not rearrange their receptor genes, as B / T cells do, but rely on a fixed number of NK cell receptors (inhibitory and activating) that recognize MHC class I and class I-like molecules and other ligands
  • Appear to have capability for memory-like responses (EMBO Rep 2009;10:1103)
  • Important for immunomodulation and regulation of hematopoiesis
Diagrams / tables

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How NK cells kill tumor cells

Microscopic (histologic) images

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NK cell lymphocytosis

Positive stains
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