Cytotoxic T cells

Definition

Cytotoxic T cells are a type of immune cell that play a crucial role in the body's defense against infections and cancer. They recognize and destroy infected or malignant cells by releasing cytotoxic substances, which induce apoptosis, or programmed cell death. These cells are essential for cell-mediated immunity, acting as the body's 'killer' cells to eliminate threats effectively.

5 Must Know Facts For Your Next Test

1. Cytotoxic T cells primarily express the CD8 glycoprotein on their surface, which distinguishes them from other T cell types and enhances their ability to recognize infected or cancerous cells.
2. These cells are activated when they recognize specific antigens presented by Major Histocompatibility Complex (MHC) class I molecules on the surface of infected or abnormal cells.
3. Once activated, cytotoxic T cells release perforin and granzymes, which form pores in target cell membranes and induce apoptosis.
4. Cytotoxic T cells can proliferate rapidly upon activation, producing a clone of effector cells that efficiently target and destroy infected or cancerous cells.
5. After an infection is cleared, some cytotoxic T cells become memory T cells, providing long-term immunity by responding more quickly upon re-exposure to the same pathogen.

Review Questions

• How do cytotoxic T cells differentiate from other types of T cells in terms of their functions and activation?
  • Cytotoxic T cells are specifically designed to kill infected or cancerous cells, while other T cell types like helper T cells primarily assist in orchestrating the immune response. Cytotoxic T cells express CD8 glycoproteins that help them recognize antigens presented by MHC class I molecules. Upon recognizing these specific antigens, they become activated and can directly kill target cells by inducing apoptosis. This functional specialization makes cytotoxic T cells essential for targeting intracellular pathogens and tumors.
• Describe the mechanism by which cytotoxic T cells induce apoptosis in target cells and the significance of this process in immune response.
  • Cytotoxic T cells induce apoptosis in target cells through a well-coordinated mechanism involving the release of perforin and granzymes. Perforin forms pores in the membrane of the target cell, allowing granzymes to enter and activate the apoptotic pathways within the cell. This process is significant because it allows for precise elimination of infected or malignant cells without causing widespread inflammation, maintaining tissue integrity while effectively clearing the threat.
• Evaluate the importance of memory cytotoxic T cells in long-term immunity and their role in future pathogen encounters.
  • Memory cytotoxic T cells play a vital role in long-term immunity by providing a faster and more robust response upon re-exposure to previously encountered pathogens. After an initial infection is cleared, some activated cytotoxic T cells differentiate into memory T cells, which persist in the body for extended periods. Upon subsequent encounters with the same pathogen, these memory T cells can quickly proliferate and mount a targeted attack, often neutralizing the threat before it can establish an infection. This mechanism underpins the effectiveness of vaccines and contributes to lasting immunity.

Related terms

Helper T cells: A subset of T cells that assist in activating other immune cells, including B cells and cytotoxic T cells, by releasing signaling molecules called cytokines.

Antigen presenting cells (APCs): Cells that process and present antigens to T cells, providing the necessary signals for T cell activation and differentiation.

Apoptosis: A form of programmed cell death that occurs in multicellular organisms, allowing for the elimination of damaged or unwanted cells without causing inflammation.