Endogenous pathway

Definition

The endogenous pathway refers to the process by which intracellular proteins, particularly those derived from the cytosol, are processed and presented on Major Histocompatibility Complex (MHC) class I molecules to CD8+ T cells. This pathway is crucial for the immune system to recognize and eliminate infected or cancerous cells, as it allows T cells to detect peptides from proteins synthesized within the cell itself.

5 Must Know Facts For Your Next Test

1. The endogenous pathway is essential for monitoring cellular health, as it helps detect abnormal proteins from viral infections or mutations associated with cancer.
2. Peptides generated from intracellular proteins are transported into the endoplasmic reticulum, where they bind to MHC class I molecules before being presented on the cell surface.
3. This pathway plays a significant role in the activation of CD8+ T cells, which are crucial for adaptive immune responses against intracellular pathogens.
4. Defects in the endogenous pathway can lead to impaired immune surveillance, potentially resulting in increased susceptibility to infections and tumors.
5. The endogenous pathway is distinct from the exogenous pathway, which involves the presentation of extracellular antigens by MHC class II molecules to CD4+ T cells.

Review Questions

• How does the endogenous pathway contribute to the immune response against intracellular pathogens?
  • The endogenous pathway contributes to the immune response by processing and presenting peptides from proteins synthesized inside cells. When a cell is infected by a virus or becomes cancerous, it produces abnormal proteins. These proteins are degraded by the proteasome into smaller peptides that bind to MHC class I molecules, allowing them to be presented on the cell surface. This presentation enables CD8+ T cells to recognize and eliminate the affected cells, effectively controlling intracellular infections and tumor development.
• What role do proteasomes play in the endogenous pathway and how might dysfunctions affect immune function?
  • Proteasomes play a critical role in the endogenous pathway by degrading ubiquitinated proteins into peptides that are suitable for MHC class I loading. If proteasomes malfunction, there could be an accumulation of abnormal or damaged proteins within the cell. This would hinder the presentation of necessary antigens on MHC class I molecules, potentially leading to impaired CD8+ T cell activation. As a result, this dysfunction could allow persistent infections or malignant growths to evade immune detection.
• Evaluate the implications of understanding the endogenous pathway for developing targeted immunotherapies against cancer.
  • Understanding the endogenous pathway has significant implications for developing targeted immunotherapies against cancer. By enhancing this pathway, therapies can improve the presentation of tumor-specific antigens on MHC class I molecules, thereby increasing CD8+ T cell recognition and killing of cancer cells. Additionally, identifying ways to manipulate this pathway can lead to more effective vaccines and adoptive cell transfer strategies. Overall, targeting elements of the endogenous pathway could provide innovative approaches to harnessing the immune system for effective cancer treatment.

Related terms

MHC class I: A class of molecules found on the surface of all nucleated cells that present endogenous peptides to CD8+ T cells, facilitating immune recognition.

proteasome:

A protein complex in cells that degrades ubiquitinated proteins into smaller peptides, which are then transported into the endoplasmic reticulum for loading onto MHC class I molecules.

CD8+ T cells:

A subtype of T lymphocytes that are primarily responsible for killing infected or cancerous cells by recognizing antigens presented by MHC class I molecules.