Role of MHC Class I Molecules in Immune System | Basic Science Series

Role of MHC Class I Molecules in Immune System | Basic Science Series
Major Histocompatibility Complex (MHC), MHC class I molecules, Adaptive immune response, Cytotoxic T lymphocytes (CTLs), Antigen presentation, Peptide loading complex, Endoplasmic reticulum (ER), Antigen processing, Immunoregulation, Natural killer (NK) cells, Missing self recognition, Immune surveillance, Viral evasion mechanisms, Antigen-binding specificity, Proteasomes, Calreticulin, Intracellular pathogens, Antigenic peptides, Immune defense mechanisms, Immunotherapy, Antiviral therapies, Immune system function, Cell surface molecules, Immunogenetics, Immunodiagnostics.
1. Role of MHC Class I Molecules in Immune System
- Key role in adaptive immune response.
- Crucial for presenting intracellular antigens to CTLs.
- Enables recognition and elimination of infected or abnormal cells.
2. Structure of MHC Class I Molecules
- Glycoproteins on nucleated cell surfaces.
- Consist of polymorphic heavy chain and non-polymorphic β2m chain.
- Heavy chain has α1, α2, and α3 domains.
- Peptide-binding groove formed by α1 and α2 domains.
3. Peptide Loading Process
- Occurs in the endoplasmic reticulum (ER).
- Facilitated by a multi-subunit peptide-loading complex.
- Involves trimming and selection of suitable peptides.
- Tight-binding peptides retained, others released.
- Loaded complexes trafficked to cell surface for CTL inspection.
4. Factors Influencing Peptide Diversity
- MHC molecule's peptide-binding specificity.
- Abundance and turnover rate of intracellular proteins.
- Activity of proteasomes and proteolytic enzymes.
- Expression levels of accessory proteins like tapasin and chaperones.
5. Immunoregulatory Roles of MHC Class I Molecules
- Engage with inhibitory receptors on NK cells.
- Modulate NK cell activity, preventing killing of healthy cells.
- Ensure selective targeting of MHC class I-lacking cells by NK cells.
6. Role in Immune Surveillance Against Pathogens
- Target viruses and intracellular bacteria.
- Viruses evolve evasion mechanisms.
- Mechanisms include interference with antigen processing and downregulation of MHC class I expression.
These points outline the significance, structure, function, regulation, and immunoregulatory roles of MHC class I molecules in the immune system.
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[@omrnour6287]

Thank you for this great explanation but you have shown the protein part of MHC, where is the carbohydrate part within the molecule?
Thanks again 😊

[@BasicScienceSeries]

The carbohydrate part of the MHC molecule is integral to its structure and function, aiding in antigen presentation and immune recognition. Will discuss this soon, stay tuned Thanks! 😊

[@pmmp2801]

Wait but then how do these multiprotein complexes distinguish between endogenous and “strange” peptides in order to load them to MHC1? Increased transport rate or proteasome stimulated activity might be confused with some physiological acute stimuli, am I wrong? Great video btw! Keep on this, sending support from Spain!

[@BasicScienceSeries]

Absolutely! Cells have mechanisms to ensure accurate peptide loading onto MHC class I molecules, despite potential confusion from increased transport rates or proteasome activity. Thanks for your support from Spain! 😊🇪🇸