# data[].attributes.body
The following diagram illustrates the process of how CD8 T Cells are primed

# data[].attributes.body
The following diagram illustrates how CD8 T Cells kill infected cells.

# data[].attributes.body
The following diagram helps illustrate the mechanism of a NK cell and its interaction with different target cells.
- Luqman J

# data[].attributes.headline
Functional similarities between Tc and NK

# data[].attributes.subject
Functional similarities between Tc and NK

# data[].attributes.body
Natural killer cells and cytotoxic T lymphocytes  perform complementary roles in immune responses directed against viruses and tumours. CTLs are antigen specific and recognize peptides derived from virus and tumour antigens presented by major histocompatibility complex (MHC) class I molecules. Not surprisingly, the cell surface expression of MHC class I is often down-regulated by tumours and virus-infected cells, enabling these cells to escape CTL killing.

However, NK cells can recognize and kill cells that have down-regulated MHC class I molecules from their cell surface. Therefore NK cells are a faster acting innate cell response more effective at getting rid of the antigen.

# data[].attributes.body
• NK cells are found in:
-- Peripheral blood
– Secondary lymphoid organs: bone marrow, spleen, activated lymph nodes
– Peripheral tissue: liver, lung and the decidual lining of the uterus

•  Key cytokines: – Interleukin-15: required for NK cell development – IL-12, IL-18: promote activation, cytotoxicity, IFN-γ production

• Key surface markers:
– CD16 (FcγRIII), binds IgG and promotes the antibody-dependent cytotoxicity (ADCC) of NK cells
– CD56 (adhesion molecule),
– Killer cell Immunoglobulin-like Receptor (KIR): recognize MHC class I molecules (HLA-A, B, C). A specific allele (KIR3DS1) can recognize HIV peptide in HLABw4 and is associated with slow progression to AIDS.

# data[].attributes.headline
Cytotoxin release by NK cells and CD8 T cells

# data[].attributes.subject
Cytotoxin release by NK cells and CD8 T cells

# data[].attributes.body
1) Perforin -  it binds to the target cell's plasma membrane, and oligomerises in a Ca2+ dependent manner to form pores on the target cell. The pores allow granzymes to enter the infected cell

2) Granzymes -   serine proteases that are released by cytoplasmic granules.  They induce programmed cell death in the target cell, thus eliminating cells that have become cancerous or are infected with viruses or bacteria.

3) Granulysin -  It create holes in the target cell membrane and destroy it. Granulysin also able to induce apoptosis in target cell and has antimicrobial action.

# data[].attributes.body
Differences

CD8 T cell

• Express CD8 (potentiates interaction with class I MHC molecule)

• Each T cell expresses a unique

receptor, within a highly diverse

repertoire generated by V(D)J

recombination

• Scan MHC class I-peptide complexes, searching for pathogen or tumor encoded antigens

• Preactivation and differentiation
Required Natural killer cells

• Invariant activating and inhibitory receptors
• Recognize ‘missing self’: the absence of class I MHC on the cell surface triggers NK attack (viral or tumor strategy to evade immune surveillance by CD8+ T cells)

• No preactivation required, but significantly potentiated by cytokines

Similarities
-Both are cytotoxic
-The granules are perforin,granzymes,granulysin

# data[].attributes.headline
-NK cells posses receptors which are differentiated based on the functions. NK cells activation depends on inhibitory receptor  and activation receptor. 

# data[].attributes.subject
-NK cells posses receptors which are differentiated based on the functions. NK cells activation depends on inhibitory receptor  and activation receptor. 

# data[].attributes.body
-Prominent inhibitory receptor signals will inhibit the NK cell activity, however if activation receptor signal is dominant NK cell will be activate.
ACTIVATING RECEPTORS:
1. LY49
2. Natural Cytotoxicity  Receptor
3. CD94
4. CD16
INHIBITORY RECEPTORS:
1. KIR (killer cell immunoglobulin-like receptor)
2. ILT or LIR (leukocytes inhibitory receptors)
3.LY49

# data[].attributes.body
- Involve in adaptive immune system
- Specific antigen
- Kills cancer cell, infected cell (particularly viruses) and damaged cells
- Recognized peptides presented by MHC Class I molecules that found on all nucleated cells.
- Recognized antigens and become activated

# data[].attributes.body
- Bind and kill certain tumour cells without recognition of MHC antigen on target cell.
-Defense against viral infection
-secretes cytokines, gamma interferon, TNF, GM-CSF.

# data[].attributes.body
-involves in innate immunity as first body defense
-not requires recognition of MHC antigen
-Non antigen specificity
-Do not acquires immune memory after an initial exposure to a virus infected cell

# data[].attributes.headline
Introduction to Natural Killer Cells: Origin and function

# data[].attributes.subject
Introduction to Natural Killer Cells: Origin and function

# data[].attributes.body
Innate immune cells with two functional properties (when activated):
1. To kill the altered self cell: cytolytic granule mediated
2. To produce cytokines that induces adaptive responses- Antibody dependent cellular cytotoxicity