MHC-I Processing | Antigen Processing and Presentation

Antigen processing or cytosolic' pathway is an immunological process that prepares antigens for presentation to special cells of the immune system called T lymphocytes. It is considered to be a stage of antigen presentation pathways. This process involves two distinct pathways for processing of antigens from an organism's own (self) proteins or intracellular pathogens (e.g. viruses), or from phagocytosed pathogens (e.g. bacteria); subsequent presentation of these antigens on class I or class II major histocompatibility complex (MHC) molecules is dependent on which pathway is used. Both MHC class I and II are required to bind antigen before they are stably expressed on a cell surface. MHC I antigen presentation typically (considering cross-presentation) involves the endogenous pathway of antigen processing, and MHC II antigen presentation involves the exogenous pathway of antigen processing. Cross-presentation involves parts of the exogenous and the endogenous pathways but ultimately involves the latter portion of the endogenous pathway (e.g. proteolysis of antigens for binding to MHC I molecules).
The endogenous pathway is used to present cellular peptide fragments on the cell surface on MHC class I molecules. If a virus had infected the cell, viral peptides would also be presented, allowing the immune system to recognize and kill the infected cell. Worn out proteins within the cell become ubiquitinated, marking them for proteasome degradation. Proteasomes break the protein up into peptides that include some around nine amino acids long (suitable for fitting within the peptide binding cleft of MHC class I molecules). Transporter associated with antigen processing (TAP), a protein that spans the membrane of the rough endoplasmic reticulum, transports the peptides into the lumen of the rough endoplasmic reticulum (ER). Also within the rough ER, a series of chaperone proteins, including calnexin, calreticulin, ERp57, and Binding immunoglobulin protein (BiP) facilitates the proper folding of class I MHC and its association with β2 microglobulin. The partially folded MHC class I molecule then interacts with TAP via tapasin (the complete complex also contains calreticulin and Erp57 and, in mice, calnexin). Once the peptide is transported into the ER lumen it binds to the cleft of the awaiting MHC class I molecule, stabilising the MHC and allowing it to be transported to the cell surface by the golgi apparatus.

[@learner1181]

Thanks,
Your videos are really amazing,
I am student of MSc Biochemistry, final year,
Your videos make tough concepts seem easy.

[@hussainbiology]

thanks for appreciation..Glad it helps ✌️

[@sheebazafer5476]

Wish you had uploaded this video last week... because Friday was my immunology exam and I was looking for this video in your video lists...

[@hussainbiology]

Bad luck.... but i hope this makes ur concept more concrete ..

[@sheebazafer5476]

No doubts...it does

[@ektamalik80]

Ur way of teaching is just awesome sir... U are one of the best teacher of immunology

[@hussainbiology]

thanks for appreciation..Glad it helps ✌️

[@ritammondal6909]

Literally unbelievable explanation , thank a lot Sir !!

[@hussainbiology]

thanks for appreciation
.Glad it helps

[@israaa7150]

thanx for explanation, ...I wish you explain correlation between autophagy and MHC molecule

[@hussainbiology]

Thanks for appreciation....
And do watch Autophagy lecture which is publishing on 11th March.
Then insha'Allah i will take ur suggestion into consideration

[@rajanpatyal5343]

Thankyou so much sir.you made this so easy. God bless you.

[@hussainbiology]

You are welcome ✌️

[@tarungupta2515]

Dear Hussain sir... This video is just awesome.. the way of presentation is up to the mark...keep it up🙂

[@hussainbiology]

thanks Tarun for appreciation

[@tarungupta2515]

Sir can u prepare animated video on phase contrast microscopy and atomic force microscopy?

[@bibisara4329]

Very informative sir .......
Thank u

[@hussainbiology]

So nice of you

[@meghabohra2601]

Great effort in making this vdo. Kudos!

[@hussainbiology]

It's my pleasure

[@nifatjan7458]

Sir ua vedios means a lot 4 us...thnx a million...

[@hussainbiology]

thanks for appreciation.... Glad to know that it helps

[@onlyhuman5544]

Sir this is the best video.

[@hussainbiology]

thanks for appreciation.. Glad it helps ✌️

[@sahalpa6322]

Thankyou sir
This made my concepts clear

[@hussainbiology]

Most welcome

[@rutujapatil4998]

Thank You❤️

[@poetxaastha]

Well explained 👍👍

[@shalinithakur2211]

Gr8 explanation sir 🙏🙏🙏🙏
U deserve millions of subscribers

[@dikshachoudhary8352]

Plz make a video on cross presentation and presentation of nonpeptide antigens

[@hussainbiology]

Surely

[@premaadhikari128]

Nice vedio sir

[@user-ty8ed9nh3v]

Sir, the calreticulin takes over the function of calnexin protein, which is the? What did u pronounce sir.

[@hussainbiology]

which is the Chaperonin...
apologies for my weird accent

[@Rishab1702]

Sir how enzyme differentiate between self and foreign protein molecule?

[@anjanasubran1348]

good presentation

[@celebglam224]

thank u so much sir, this really helped me a lot

[@SowmyaSwimInScience]

Nice way of detailed explanation👏

[@michaeleisenberg7867]

Dear Hussain, Very nice! Thank you.
How do the the T-Cells know the difference between self or friendly epitopes vs foreign epitopes presented by the MHC 1 molecules? Why do our cells present both self antigens and foreign antigens on the cell membrane?

[@tinadevassy2094]

I think coreceptors recognizes the forign and self antigens ...

[@shivrajnicholasmotilal9734]

T-cells are trained not to attack self-antigens via negative selection in the thymus before they are released

[@SowmyaSwimInScience]

The mode of antigen entry into cells and the site of antigen processing determine
whether antigenic peptides associate with class I MHC molecules in the rough endoplasmic reticulum or with class II molecules in endocytic compartments. (Kuby textbook of Immunology)

[@SowmyaSwimInScience]

For ex, abnormal endogenous proteins will be tagged with ubiquitin. These will go for MHC class I presentation.

[@ayezabhat5026]

Thanks sir plz keep uploading

[@hussainbiology]

You are Welcome...... Coming up MHC II ( Exogenous Pathway ) today

[@bhavanipydikondala552]

U r superb.....

[@misbahhussain1021]

Are mhc genes gets continuously synthesized or during pathogen attack only?????

[@misbahhussain1021]

Plz reply here sir
If APC's bears both mhc classes then can then present antigens by both of these pathways viz,endogenous and exogenous?

[@bijayachettri8689]

Woww your way of teaching and your daigrams are just amazing 😍 it really helped me sir ....do upload more videos so that I can clear all my doubts with your wonderful explanation ❤️❤️❤️❤️

[@hussainbiology]

Thanks Bijaya for appreciation..Glad it helps.....Keep sharing and supporting..

[@saimaqureshi1237]

Thnku so mch sir

[@shekinah6853]

thank you so much

[@fajarkr2854]

Tnku sir

[@biology_mcqs3037]

👍

[@syedaiman5846]

Thank u sir very much

[@hussainbiology]

You are welcome..Keep sharing and supporting ✌️

[@risharajkhowa5060]

😍😍😍😍😍

[@hussainbiology]

❤️

[@premaadhikari128]

Sir please refer a book for immunology.

[@hussainbiology]

Kuby

[@premaadhikari128]

@@hussainbiology jii thanks sir m reading that book.

[@saimas_craftastic_world]

Sir are u frm kashmir? 🌹

[@hussainbiology]

Yes , from Kashmir ✌️

[@AestheticMEDICO]

♾❤️

[@abulansari8072]

you speak too fast in each of your vedios making tough to understand

[@saimas_craftastic_world]

U can slower d vdeo in settings