NK cells

Definition

Natural Killer (NK) cells are a type of lymphocyte that play a crucial role in the innate immune system by targeting and destroying virally infected cells and tumor cells. They do not require prior sensitization to specific antigens.

5 Must Know Facts For Your Next Test

1. NK cells can recognize stressed cells in the absence of antibodies and MHC, allowing for a faster immune reaction.
2. They release cytotoxic granules containing perforin and granzymes to induce apoptosis in target cells.
3. NK cell activity is regulated by a balance between activating and inhibitory receptors on their surface.
4. They produce cytokines such as IFN-γ which help in modulating the adaptive immune response.
5. NK cells can also participate in antibody-dependent cellular cytotoxicity (ADCC) where they lyse antibody-coated target cells.

Review Questions

• What mechanisms do NK cells use to induce apoptosis in target cells?
• How do NK cells distinguish between healthy and stressed or infected cells?
• What role do cytokines produced by NK cells play in immunity?

Related terms

Cytotoxic T Lymphocytes (CTLs): A type of T cell that kills cancerous, infected, or damaged cells through antigen-specific recognition.

Perforin:

A protein released by NK cells and CTLs that forms pores in the membranes of target cells, leading to cell death.

Antibody-Dependent Cellular Cytotoxicity (ADCC): An immune response where effector cells actively lyse a target cell whose membrane-surface antigens have been bound by specific antibodies.