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 virally infected cells. They are part of the innate immune response and are unique because they can recognize and eliminate abnormal cells without prior sensitization, making them essential in early host defense mechanisms.

5 Must Know Facts For Your Next Test

1. Natural killer cells are distinguished from other lymphocytes by their ability to respond quickly to viral infections and tumor formation, often acting within hours.
2. These cells utilize various receptors to detect stressed or infected cells, leading to their activation and subsequent release of cytotoxic granules that induce apoptosis in target cells.
3. NK cells also produce cytokines like interferon-gamma (IFN-γ), which help shape the immune response and enhance the activity of other immune cells.
4. They have a unique ability to differentiate between healthy and abnormal cells through a balance of activating and inhibitory signals received from surface receptors.
5. Research is ongoing into enhancing NK cell function for therapeutic purposes, particularly in developing more effective cell-based immunotherapies for cancer treatment.

Review Questions

• How do natural killer cells distinguish between healthy and abnormal cells?
  • Natural killer cells distinguish between healthy and abnormal cells through a complex system of activating and inhibitory receptors on their surface. When NK cells encounter a potential target cell, these receptors assess the presence of specific ligands. If an abnormal cell has reduced levels of 'self' markers, such as MHC molecules, or displays stress-induced ligands, NK cells receive activating signals to initiate a response. This mechanism enables NK cells to effectively target virally infected or tumorigenic cells while sparing normal healthy tissues.
• Discuss the role of natural killer cells in the context of immunotherapy for cancer treatment.
  • Natural killer cells play a pivotal role in immunotherapy as they can be harnessed to enhance anti-tumor responses. Immunotherapies often aim to boost NK cell activity or incorporate engineered NK cells capable of specifically targeting cancer cells. By increasing the number or potency of these immune cells, therapies can improve outcomes in patients with malignancies. Ongoing research focuses on utilizing NK cells as a powerful tool for directly combating cancer through various strategies such as checkpoint inhibition or genetic modification.
• Evaluate the significance of cytokine production by natural killer cells in modulating the immune response.
  • The significance of cytokine production by natural killer cells lies in their ability to modulate the overall immune response during infection or tumor development. By releasing cytokines such as interferon-gamma (IFN-γ), NK cells can not only enhance their own cytotoxic functions but also stimulate other immune components like macrophages and T lymphocytes. This cross-talk among immune cells amplifies the body’s defense mechanisms against pathogens and malignant transformations. Thus, NK cell-derived cytokines are crucial for establishing an effective and coordinated immune response.

Related terms

Cytokines:

Small proteins that are important in cell signaling, influencing the behavior of immune cells, including the activation and proliferation of natural killer cells.

Lymphocytes: A subtype of white blood cells, including T cells, B cells, and NK cells, that are key components of the immune system involved in the adaptive and innate responses.

Immunotherapy: A treatment method that uses certain parts of the immune system to fight diseases like cancer, often involving the enhancement or manipulation of natural killer cells.