NK Cells

• NK cell activity is regulated by the interaction of receptors on the cell surface with their corresponding target ligands without the stimulation of specific antigens.
• A normal cell will display peptides from normal cellular protein turnover on its class I MHC, and CTLs will not be activated in response to them due to central and peripheral tolerance mechanisms. When a cell expresses foreign proteins, such as after viral infection, a fraction of the class I MHC will display these peptides on the cell surface. Consequently, CTLs specific for the MHC: peptide complex will recognize and kill presenting cells.
  Alternatively, class I MHC itself can serve as an inhibitory ligand for natural killer cells (NKs). Reduction in the normal levels of surface class I MHC, a mechanism employed by some viruses and certain tumors to evade CTL responses, activates NK cell killing.

• Activated NK cells synthesize various granular materials (perforin and granzyme) and secrete them from the cells to destroy the abnormal cells. Also, they secrete cytokine and chemokine such as IFN-gamma and TNF-alpha to work directly on the cells that carry the antigens and to control or activate the acquired immune cells.

Attack and remove cancer cell directly

Recognize abnormal cells including cancer cells and remove them directly without a specific antigen.

1. Cancer cell recognition by receptor
2. Cytotoxic enzyme secretion
3. Cancer cell removal
4. Necrosis, Apoptosis

Regulate immune and inflammatory

responses-key role in regulating immune and inflammatory responses. (Nat Immunol. 2008 May;9(5):503-10, J. Immunol 2009; 182:3530-9.)

1. INF-γ, TNF-α Cytokine Secretion (activator)
2. Cancer cell antigen passed on to T cell
3. Cancer cell removal
4. B cell activation induced (Antibody production)

Inhibition of proliferation/ relapse/ metastasis of cancer cells

CSC/CTC removal which are important for cancer recurrence. (Nat Immunol. 2008 May;9(5):503-10, J. Immunol 2009; 182:3530-9.)

In our body, there are more than 5,000 abnormal cells such as cancer cells, growing and dying every day. NK cell is the only cell that recognizes and attacks cancer cells. It can inhibit proliferation of cancer cells and prevent recurrence. The importance of NK Cells and the correlation between them and cancer has been widely documented since the early 1980s. It has since been proven that the activity of NK cells is more significant than the number of NK cells in our immune system’s fight against cancer cells. As a result, research about NK cell activity is being conducted world-wide.