CD8+ T Cells

Definition

CD8+ T cells are a type of immune cell that play a crucial role in cell-mediated immunity by directly killing infected or cancerous cells. They recognize antigens presented by Major Histocompatibility Complex (MHC) class I molecules, which are found on almost all nucleated cells, allowing them to identify and destroy cells that display foreign or abnormal proteins. This targeted action is essential for controlling viral infections and eliminating tumors.

5 Must Know Facts For Your Next Test

1. CD8+ T cells are essential for the adaptive immune response, specifically targeting intracellular pathogens like viruses.
2. These cells undergo maturation in the thymus and are characterized by the expression of the CD8 glycoprotein on their surface.
3. Upon activation by recognizing a specific antigen presented by MHC class I, CD8+ T cells proliferate and differentiate into effector and memory T cells.
4. Effector CD8+ T cells can release cytotoxic molecules such as perforin and granzymes to induce apoptosis in infected or cancerous cells.
5. Memory CD8+ T cells persist long-term after an infection, allowing for a quicker and more effective response upon re-exposure to the same antigen.

Review Questions

• How do CD8+ T cells recognize and respond to infected or cancerous cells?
  • CD8+ T cells recognize infected or cancerous cells by binding to specific antigens presented on MHC class I molecules, which are displayed on nearly all nucleated cells. When a CD8+ T cell encounters a cell with a matching antigen, it becomes activated, proliferates, and differentiates into effector T cells. These effector CD8+ T cells then exert their function by directly killing the target cells using cytotoxic mechanisms.
• Discuss the roles of MHC class I molecules and antigen-presenting cells in the activation of CD8+ T cells.
  • MHC class I molecules are essential for presenting peptide antigens to CD8+ T cells, allowing these immune cells to monitor the health of other cells. Antigen-presenting cells (APCs) play a crucial role in this process by processing exogenous antigens and presenting them on MHC class I molecules to activate naïve CD8+ T cells. This interaction is critical for generating an effective cytotoxic response against intracellular pathogens.
• Evaluate the importance of memory CD8+ T cells in long-term immunity against viral infections.
  • Memory CD8+ T cells are vital for long-term immunity as they persist after an initial infection and enable a rapid and robust response upon re-exposure to the same pathogen. Their ability to quickly differentiate into effector cells allows for efficient clearance of viruses that invade the body again. This aspect of adaptive immunity highlights the significance of vaccination strategies that aim to enhance memory CD8+ T cell populations, providing protection against future infections.

Related terms

Cytotoxic T Lymphocytes: A subset of CD8+ T cells specifically responsible for killing infected or cancerous cells through the release of perforin and granzymes.

MHC Class I: A group of proteins found on the surface of almost all nucleated cells that present peptide fragments to CD8+ T cells, enabling immune surveillance.

Antigen-Presenting Cells (APCs): Cells such as dendritic cells and macrophages that process and present antigens on MHC molecules, playing a key role in activating CD8+ T cells.