Written by the Fiveable Content Team • Last updated September 2025
Written by the Fiveable Content Team • Last updated September 2025
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
NK cells can recognize stressed cells in the absence of antibodies and MHC, allowing for a faster immune reaction.
They release cytotoxic granules containing perforin and granzymes to induce apoptosis in target cells.
NK cell activity is regulated by a balance between activating and inhibitory receptors on their surface.
They produce cytokines such as IFN-γ which help in modulating the adaptive immune response.
NK cells can also participate in antibody-dependent cellular cytotoxicity (ADCC) where they lyse antibody-coated target cells.
Review Questions
Related terms
Cytotoxic T Lymphocytes (CTLs): A type of T cell that kills cancerous, infected, or damaged cells through antigen-specific recognition.
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.