Cytotoxic T Cell Response Notes

Cytotoxic T Cell Response to Viral Infection

Antigen Processing and Presentation

• Viral proteins are degraded into peptide fragments within the infected cell.
• These peptide fragments bind to Class I MHC molecules.
• The peptide-MHC complexes are then transported to the cell surface and displayed.

Cytotoxic T Cell (CTL) Interaction

• CTLs recognize virus-infected cells by interacting with two key components:
  • Viral antigen (peptide fragment).
  • Class I MHC molecule presenting the antigen.
• This interaction is crucial for target cell specificity.

Mechanism of Cytotoxicity

• Upon recognition, the CTL releases cytotoxins to induce apoptosis (programmed cell death) in the infected cell.
• Perforin is released, creating perforations or pores in the infected cell's membrane, leading to cell lysis.

Self-Protein Presentation and Tolerance

• Self-proteins are also degraded into fragments and presented via Class I MHC molecules.
• However, CTLs do not normally recognize these self-peptide/MHC complexes; this is a mechanism of self-tolerance.
• This prevents CTLs from attacking healthy, uninfected cells.

CTL Detachment and Continued Surveillance

• After inducing apoptosis or lysis of an infected cell, the CTL detaches.
• The CTL remains intact and active, moving on to find and eliminate other target cells displaying the same viral antigen.

Repeated Viral Infection

• When a virus infects a cell, the process of peptide fragment presentation via class I MHCs occurs.
• Cytotoxic T cells recognize both the antigen and the MHC, and the cytotoxic T cells kill the presented cell by using cytotoxins, which induce apoptosis, and perforin, which perforates the cell membrane.