Natural killer cells

Definition

Natural killer cells are a type of lymphocyte in the immune system that play a critical role in the body's innate defense against tumors and virally infected cells. They are unique because they can recognize and eliminate abnormal cells without prior sensitization, making them a crucial component of the body's first line of defense in both innate and adaptive immunity.

5 Must Know Facts For Your Next Test

1. Natural killer cells are part of the innate immune system and can act quickly within hours of an infection.
2. They identify stressed or infected cells by recognizing certain surface molecules, allowing them to target and destroy these abnormal cells effectively.
3. Natural killer cells release cytotoxic granules that contain perforin and granzymes, which induce apoptosis (programmed cell death) in the target cells.
4. They also produce cytokines such as interferon-gamma, which helps to enhance the immune response and activate other immune cells.
5. Natural killer cells can adapt their response based on the local immune environment, demonstrating some level of functional plasticity.

Review Questions

• How do natural killer cells differ from other types of lymphocytes in terms of their mechanism of action?
  • Natural killer cells differ from other lymphocytes, such as T cells and B cells, primarily in their ability to recognize and destroy abnormal cells without prior sensitization. While T cells require specific antigen recognition for activation, natural killer cells can respond rapidly to stressed or infected cells through the recognition of certain surface markers. This ability allows them to provide immediate defense against infections and tumors, making them essential for the body's innate immune response.
• Discuss the role of natural killer cells in enhancing the adaptive immune response through cytokine production.
  • Natural killer cells play an important role in enhancing the adaptive immune response by producing cytokines, particularly interferon-gamma. This cytokine not only has direct antiviral effects but also activates macrophages and enhances the antigen presentation capabilities of other immune cells. By doing so, natural killer cells help bridge the gap between innate and adaptive immunity, ensuring a more robust and effective immune response against pathogens.
• Evaluate how the functional characteristics of natural killer cells contribute to their effectiveness in tumor surveillance and viral infections.
  • The functional characteristics of natural killer cells significantly contribute to their effectiveness in tumor surveillance and combating viral infections. Their ability to recognize and kill abnormal or infected cells without prior sensitization allows for a rapid immune response that is crucial during early stages of infection or tumor development. Additionally, their secretion of cytokines like interferon-gamma enhances the overall immune response, helping to activate other immune components. This combination of immediate cytotoxic action and supportive signaling makes natural killer cells a key player in maintaining cellular integrity and combating diseases.

Related terms

Innate Immunity: A form of immunity that is present at birth and provides immediate, non-specific defense against pathogens.

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

Cytotoxic T Cells: A type of T cell that specifically targets and kills infected or cancerous cells, similar to the function of natural killer cells but with a requirement for prior sensitization.