Natural Killer Cells

Definition

Natural killer (NK) cells are a type of lymphocyte in the immune system that play a critical role in the body's defense against tumors and viral infections. They are known for their ability to recognize and destroy abnormal cells without prior sensitization, making them essential in the early response to cancerous growths and pathogens.

5 Must Know Facts For Your Next Test

1. Natural killer cells are characterized by their ability to identify stressed cells in the absence of antibodies and major histocompatibility complex (MHC) molecules.
2. These cells release cytotoxic granules containing perforin and granzymes to induce apoptosis in target cells, such as tumor or virus-infected cells.
3. NK cells play a vital role in immunosurveillance, monitoring for cancerous transformations in cells and responding quickly to eliminate them.
4. They are activated by various cytokines, including interleukin-2 (IL-2) and interleukin-15 (IL-15), which enhance their proliferation and cytotoxicity.
5. Research shows that NK cell activity can be influenced by tumor microenvironments, which may help or hinder their ability to combat cancer effectively.

Review Questions

• How do natural killer cells distinguish between healthy and abnormal cells?
  • Natural killer cells distinguish between healthy and abnormal cells through specific receptors that recognize stress signals typically associated with infected or transformed cells. They can detect changes in surface markers on these abnormal cells, such as reduced levels of MHC class I molecules. This allows NK cells to act swiftly against tumor or virus-infected cells without needing prior exposure or sensitization.
• What role do cytokines play in the function and activation of natural killer cells during cancer progression?
  • Cytokines play a crucial role in activating natural killer cells and enhancing their cytotoxic functions. For instance, interleukin-2 (IL-2) and interleukin-15 (IL-15) promote NK cell proliferation, survival, and overall activity. During cancer progression, tumor microenvironments often produce various cytokines that can either activate NK cell responses or create immunosuppressive conditions that inhibit their effectiveness against tumors.
• Evaluate how immunotherapy strategies targeting natural killer cells might improve outcomes in cancer treatment.
  • Immunotherapy strategies aimed at enhancing natural killer cell activity have shown promise in improving cancer treatment outcomes. By using agents that stimulate NK cell proliferation or function, such as checkpoint inhibitors or cytokine therapies, these approaches can increase the body's ability to target and eliminate tumors. Moreover, engineering NK cells with chimeric antigen receptors (CAR-NK) allows for more precise targeting of cancer antigens, potentially leading to better therapeutic efficacy and reduced side effects compared to traditional treatments.

Related terms

Lymphocytes:

A subtype of white blood cells that are key players in the immune response, including B cells, T cells, and natural killer cells.

Cytokines: Signaling proteins released by cells that affect the behavior of other cells, particularly during immune responses, including the activation and proliferation of NK cells.

Immunotherapy:

A treatment strategy that uses the body’s immune system to fight diseases, particularly cancer, which often involves enhancing the activity of natural killer cells.