Cytotoxic T Lymphocytes

Definition

Cytotoxic T lymphocytes (CTLs) are a type of immune cell that plays a crucial role in the body's defense against infections and tumors by directly killing infected or cancerous cells. These specialized T cells recognize specific antigens presented by major histocompatibility complex (MHC) molecules on the surface of target cells, allowing them to target and destroy cells that exhibit abnormal or dangerous characteristics.

5 Must Know Facts For Your Next Test

1. Cytotoxic T lymphocytes are primarily involved in the immune response against viral infections and tumor cells, making them critical in the fight against cancer.
2. Upon activation, CTLs release perforin and granzymes, which create pores in target cell membranes and induce apoptosis, respectively.
3. The generation of CTLs is stimulated by exposure to antigens through antigen-presenting cells, which help in activating naïve T cells.
4. Memory cytotoxic T lymphocytes can persist long-term in the body after an infection, allowing for a faster and more effective response upon re-exposure to the same pathogen or tumor.
5. The effectiveness of cytotoxic T lymphocytes can be impaired in various cancers, as tumor cells may evade detection through changes in antigen presentation or secretion of immunosuppressive factors.

Review Questions

• How do cytotoxic T lymphocytes identify and target infected or cancerous cells?
  • Cytotoxic T lymphocytes identify infected or cancerous cells through their T cell receptors, which specifically recognize antigens presented by MHC molecules on the surface of these target cells. This recognition is essential for CTLs to activate and initiate a targeted attack. Once a CTL binds to an infected or malignant cell, it can release toxic substances to induce cell death, thereby helping to eliminate the threat from the body.
• What role do antigen-presenting cells play in the activation of cytotoxic T lymphocytes during an immune response?
  • Antigen-presenting cells (APCs), such as dendritic cells and macrophages, are crucial for activating cytotoxic T lymphocytes. They capture and process antigens from pathogens or tumors, presenting these fragments on their surface via MHC molecules. When CTLs encounter these APCs, they receive necessary co-stimulatory signals alongside antigen recognition, leading to their activation, proliferation, and differentiation into effector CTLs capable of targeting infected or malignant cells.
• Evaluate the impact of memory cytotoxic T lymphocytes on the long-term immune response to cancer and infectious diseases.
  • Memory cytotoxic T lymphocytes play a vital role in enhancing the long-term immune response by providing a more rapid and effective reaction upon re-exposure to previously encountered pathogens or tumors. After initial activation during an infection or tumor development, these memory CTLs persist in the body, enabling quicker recognition and destruction of cells exhibiting the same antigens. This adaptive memory can lead to improved outcomes in immunotherapy for cancer patients, as harnessing these memory responses may enhance the body's ability to fight recurrent or metastatic disease.

Related terms

T Cell Receptor: A molecule found on the surface of T cells that recognizes and binds to specific antigens presented by MHC molecules.

Apoptosis: A form of programmed cell death that cytotoxic T lymphocytes induce in their target cells to eliminate them effectively.

Antigen Presentation: The process by which protein fragments (antigens) are displayed on the surface of cells to be recognized by T cells, facilitating immune responses.