Natural killer (NK) cells

Definition

Natural killer (NK) cells are a type of lymphocyte in the innate immune system that can destroy virus-infected cells and tumor cells. They recognize stressed cells in the absence of antibodies, allowing for a faster immune reaction.

5 Must Know Facts For Your Next Test

1. NK cells do not require prior sensitization to respond to infected or abnormal cells.
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 play a crucial role in early defense against viral infections and cancer.
5. Cytokines such as interleukin-2 (IL-2) and interferon-gamma (IFN-γ) can enhance NK cell activity.

Review Questions

• What is the primary function of natural killer (NK) cells?
• How do NK cells distinguish between healthy and abnormal cells?
• Which cytokines are known to enhance the activity of NK cells?

Related terms

Lymphocyte: A type of white blood cell that is part of the immune system, including B cells, T cells, and NK cells.

Apoptosis: The process of programmed cell death that occurs in multicellular organisms.

Cytokine: A broad category of small proteins important in cell signaling, especially in immune responses.