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Lymphoma - B cell neoplasms

Lymph nodes

Normal lymphocyte development - NK cells

Reviewer: Nikhil Sangle, M.D., University of Utah and ARUP Laboratories (see Reviewers page)
Revised: 31 January 2012, last major update December 2010
Copyright: (c) 2001-2010, PathologyOutlines.com, Inc.

General
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● Distinct group of non-T, non-B lymphocytes (5-10% of peripheral blood lymphocytes) with large granular lymphocyte morphology on Wright-Giemsa stains

Development
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● NK cells derive from a common lymphoid progenitor with T cells

Physiology
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● 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
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How NK cells kill tumor cells

Animations of NK cells:
Normal cell, virally infected or mutated cell, apopotosis

Micro images
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NK cell lymphocytosis

Positive stains
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● CD56, CD57, CD16
● Also cytoplasmic (not surface) CD3, CD2, CD7, CD8, perforin, granzyme B, TIA-1
● >90% are CD16+/CD56+
● Up to 80% express CD8

EM images
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NK cells

NK cell (yellow) attacks tumor cell (red)

End of Lymphoma - B cell neoplasms > Lymph nodes > Normal lymphocyte development - NK cells

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