Natural killer cells (NK cells)

Definition

Natural killer (NK) cells are a type of lymphocyte that plays a critical role in the body's innate immune response by targeting and destroying virus-infected cells and cancerous cells. They do not require prior activation or recognition of specific antigens to act.

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 play a significant role in early defense against viral infections before adaptive immunity kicks in.
5. Cytokines such as interleukin-2 (IL-2) can enhance NK cell activity, making them more effective at killing target cells.

Review Questions

Related terms

Cytotoxic T Cells:

A type of lymphocyte that kills cancer cells, cells that are infected with viruses, or damaged cells.

Perforin:

A protein released by NK cells and cytotoxic T lymphocytes that creates pores in the plasma membrane of target cells.

Granzymes:

Serine proteases released by cytotoxic T cells and NK cells that enter target cells through perforin-created pores to induce apoptosis.