Exogenous Pathway of Antigen Presentation | MHC II Processing

Antigens from the extracellular space and sometimes also endogenous ones,[8] are enclosed into endocytic vesicles and presented on the cell surface by MHC-II molecules to the helper T cells expressing CD4 molecule. Only APCs do express the class II of MHC molecules on the surface in large quantity, such as dendritic cells, B cells or macrophages, so expression of MHC-II molecules is more cell-specific than MHC-I.

APCs usually internalise exogenous antigens by endocytosis, but also by pinocytosis, macroautophagy, endosomal microautophagy or chaperone-mediated autophagy. In the first case, after internalisation, the antigens are enclosed in vesicles called endosomes. There are three compartements involved in this antigen presentation pathway: early endosomes, late endosomes or endolysosomes and lysosomes, where antigens are hydrolized by lysosome-associated enzymes (acid-dependent hydrolases, glycosidases, proteases, lipases). This process is favored by gradual reduction of the pH. The main proteases in endosomes are cathepsins and the result is the degradation of the antigens into oligopeptides.

MHC-II molecules are transported from the ER to the MHC class II loading compartment together with the protein Invariant chain (Ii, CD74). A non classical MHC-II molecule (HLA-DO and HLA-DM) catalyses the exchange of part of the CD74 (CLIP peptide) with the peptide antigen.

[darianleduc]

I keep coming back to your videos to understand the immune system. Not sure why, but I get the most understanding out of your vids. Many thanks

[Habira]

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[adnankabir]

spending more than 3 hour's on just MHC-2 i couldn’t understand it.
After see 5 minutes video my all doubts are clear now.Thanks a lot❤

[srijalshukla]

Your hardwork is genuinely reflected in your videos ❤️... Amazing explanation...🤩🤩...!!!

[maham]

Amazing vedio keep it up sir thank you so much

[கவிநிலா]

Thank you so much for the wonderful presentation!

[TheRootofAfrica]

Thank you sir what a good explanation... You have helped many souls

[blazincate]

Very helpful explanation, thank you so much!

[bhuvankumar]

Thank you so much sir... your videos are really helpful for me ❤

[diamondhunter]

Thankyou so much sir i was so confised 😊

[rohinick]

Great attempt, really useful. Make more vedios

[dheerajshah]

Hello sir why all cells do not have mhc 2 ??

[bilalahmadmalik]

Its called exogenous pathway because antigen does not enter the ER . IS IT SO Sir??

[naziyasheikh]

Can you please share link of endogenous pathway

[daniyalyounas]

Can anyone tell me that how i get the related picture because i cant find it

[handam]

Usefulness but why mist of biologic video is indian ?? And thanks for exaplained 🌹🌹

[نورحسينبحرقيصان-ضل]

very good video, but you need to be slower to make your content more understandable, thank you.

[jgouqou]

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