Natural Killer Cells

Definition

Natural killer cells (NK cells) are a type of lymphocyte in the immune system that play a crucial role in the body's defense against tumors and viral infections. They are part of the innate immune response and can recognize and destroy compromised cells without prior sensitization, making them essential in identifying and eliminating early-stage cancerous cells.

5 Must Know Facts For Your Next Test

1. Natural killer cells can recognize stressed, infected, or transformed cells by detecting changes in surface molecules, such as decreased expression of MHC class I molecules.
2. They release cytotoxic granules containing perforin and granzymes that create pores in target cell membranes and trigger apoptosis.
3. NK cells also secrete cytokines like interferon-gamma, which helps to enhance the immune response and activate other immune cells.
4. The effectiveness of natural killer cells can be influenced by various factors including the presence of tumor microenvironments that can inhibit their function.
5. Natural killer cells are important in the context of cancer immunotherapy, as they can be harnessed or enhanced to improve the body’s ability to fight tumors.

Review Questions

• How do natural killer cells recognize and target compromised cells in the body?
  • Natural killer cells recognize compromised cells by detecting alterations in surface molecules, particularly a reduction in MHC class I molecules, which are commonly downregulated by infected or cancerous cells. This recognition allows NK cells to distinguish between healthy and unhealthy cells, leading them to selectively target and eliminate those that pose a threat. Their ability to act without prior sensitization also makes them a first line of defense against early-stage malignancies.
• Discuss the role of natural killer cells in the context of tumor surveillance and how they contribute to preventing cancer development.
  • Natural killer cells play a vital role in tumor surveillance by actively monitoring for abnormal or transformed cells within the body. Upon recognition of such cells, NK cells initiate cytotoxic actions that lead to cell death, effectively preventing the progression of potential tumors. Additionally, by secreting cytokines like interferon-gamma, NK cells not only directly kill tumor cells but also enhance the overall immune response, helping to mobilize other immune components to further protect against cancer development.
• Evaluate the implications of natural killer cell activity in cancer therapy and how they can be manipulated to improve treatment outcomes.
  • The activity of natural killer cells has significant implications for cancer therapy as they can be manipulated through various approaches such as cytokine therapy, adoptive transfer of activated NK cells, or use of checkpoint inhibitors. These strategies aim to enhance NK cell function and restore their ability to detect and kill tumor cells effectively. Understanding the mechanisms by which tumors evade NK cell detection is crucial for developing innovative therapies that boost NK cell responses and improve patient outcomes in cancer treatment.

Related terms

Cytotoxic T Cells: A subtype of T lymphocytes that directly kill infected or cancerous cells by recognizing specific antigens presented on their surface.

Apoptosis: A form of programmed cell death that is triggered in response to cellular stress or damage, which natural killer cells can induce in their target cells.

Immunoediting: The process through which the immune system interacts with tumor cells, leading to the selection of less immunogenic variants that can evade immune detection.