Natural killer cells (NK cells)

Author: V. Dimov, M.D., Allergist/Immunologist and Assistant Professor at University of Chicago
Reviewer: S. Randhawa, M.D., Allergist/Immunologist and Assistant Professor at LSU (Shreveport) Department of Allergy and Immunology

Immune System has 2 arms:

- Innate immune system
- Adaptive immune system


The 2 arms of the immune system: innate immunity and adaptive immunity (click to enlarge the image).

NK Cells

NK
Natural Killers, "born to kill"
Not lymphocytes

NK cells are CD45+ CD3- CD16+ or CD56+.

NKT cells are CD45+ CD3+ CD16+ or CD56+.

NK are "born to kill," they are natural killers because they do not need a stimulus to kill affected cells. In a sense, NK are "hyperactive" and potenially, the most dangerous cells in the human body.

MHC I
I
Inhibits cell killing by NK

Viruses inhibit MHC I expression which leads to killing by NK cells.

IL 15
Increases number of NK cells
IL 12 stimulation
INF gamma stimulation of NK cells

NK cells (not T-lymphocytes) are different from NKT cells. NKT cells are T-lymphocytes.

NK cells are CD45+ CD3- CD16+ or CD56+.

NKT cells are CD45+ CD3+ CD16+ or CD56+.

The mnemonic for different T-cell subtypes is FERMNN G ("pheromon G"):

Four, CD4, helper cells (Th1 and Th2)
Eight, CD8, killer cells
Regulatory, formerly known as suppressors
Memory
Naïve T cells
Natural Killer T cells (NKT)

Gamma/delta T cells (γδ)


Mind map of the 7 different T-cell subtypes remembered by the mnemonic FERMNN G (click to enlarge the image).

Published: 12/05/2007
Updated: 09/05/2010

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