Cytotoxic T cells

Definition

Cytotoxic T cells are a type of immune cell that play a crucial role in the adaptive immune response by identifying and destroying infected or cancerous cells. They are primarily responsible for recognizing specific antigens presented by infected cells and executing a targeted attack, which is vital for controlling and eliminating pathogens from the body.

5 Must Know Facts For Your Next Test

1. Cytotoxic T cells are also known as CD8+ T cells, named for the CD8 glycoprotein found on their surface, which helps them recognize infected or abnormal cells.
2. They kill target cells through two main mechanisms: releasing cytotoxins like perforin and granzymes that induce apoptosis, and engaging death receptor pathways.
3. Cytotoxic T cells require activation from antigen-presenting cells, which present foreign antigens via MHC class I molecules for recognition.
4. Once activated, cytotoxic T cells undergo clonal expansion, rapidly increasing their numbers to effectively combat the infection or tumor.
5. Memory cytotoxic T cells can persist long-term after an infection is cleared, providing faster and more effective responses upon re-exposure to the same antigen.

Review Questions

• How do cytotoxic T cells recognize and target infected or cancerous cells?
  • Cytotoxic T cells recognize infected or cancerous cells through their CD8 glycoprotein, which interacts with MHC class I molecules presenting specific antigens on the surface of these target cells. When they bind to these antigens, they trigger activation signals that allow them to identify which cells to destroy. This targeted recognition is essential for the cytotoxic T cells to eliminate compromised cells without harming healthy ones.
• Discuss the role of antigen-presenting cells in the activation of cytotoxic T cells.
  • Antigen-presenting cells (APCs) play a critical role in activating cytotoxic T cells by processing and displaying foreign antigens on their surface via MHC class I molecules. When a cytotoxic T cell encounters an APC with a matching antigen, it binds to the antigen-MHC complex, which leads to its activation. This interaction is essential for initiating the immune response and ensuring that cytotoxic T cells can effectively target and kill infected or malignant cells.
• Evaluate the significance of memory cytotoxic T cells in long-term immunity against pathogens.
  • Memory cytotoxic T cells are crucial for long-term immunity because they persist in the body after an infection has been cleared, allowing for a quicker and more robust response if the same pathogen re-invades. Upon re-exposure, these memory cells can rapidly proliferate and differentiate into effector cytotoxic T cells, enhancing the efficiency of the immune response. This ability to remember past infections is fundamental to how vaccinations work, providing protection against future threats.

Related terms

Helper T cells: A subset of T lymphocytes that assist other immune cells by releasing cytokines, which help coordinate the immune response.

Antigen-presenting cells (APCs): Cells that process and present antigens on their surface to T cells, initiating the adaptive immune response.

Perforin:

A protein released by cytotoxic T cells that creates pores in the target cell membrane, leading to cell lysis and death.