T Cell Activation | Mechanism

A T cell is a type of lymphocyte, which develops in the thymus gland (hence the name) and plays a central role in the immune response. T cells can be distinguished from other lymphocytes by the presence of a T-cell receptor on the cell surface. These immune cells originate as precursor cells, derived from bone marrow,[1] and develop into several distinct types of T cells once they have migrated to the thymus gland. T cell differentiation continues even after they have left the thymus.
Activation of CD4+ T cells occurs through the simultaneous engagement of the T-cell receptor and a co-stimulatory molecule (like CD28, or ICOS) on the T cell by the major histocompatibility complex (MHCII) peptide and co-stimulatory molecules on the APC. Both are required for production of an effective immune response; in the absence of co-stimulation, T cell receptor signalling alone results in anergy. The signalling pathways downstream from co-stimulatory molecules usually engages the PI3K pathway generating PIP3 at the plasma membrane and recruiting PH domain containing signaling molecules like PDK1 that are essential for the activation of PKC-θ, and eventual IL-2 production. Optimal CD8+ T cell response relies on CD4+ signalling.[33] CD4+ cells are useful in the initial antigenic activation of naïve CD8 T cells, and sustaining memory CD8+ T cells in the aftermath of an acute infection. Therefore, activation of CD4+ T cells can be beneficial to the action of CD8+ T cells
The first signal is provided by binding of the T cell receptor to its cognate peptide presented on MHCII on an APC. MHCII is restricted to so-called professional antigen-presenting cells, like dendritic cells, B cells, and macrophages, to name a few. The peptides presented to CD8+ T cells by MHC class I molecules are 8-13 amino acids in length; the peptides presented to CD4+ cells by MHC class II molecules are longer, usually 12-25 amino acids in length,[37] as the ends of the binding cleft of the MHC class II molecule are open.
The second signal comes from co-stimulation, in which surface receptors on the APC are induced by a relatively small number of stimuli, usually products of pathogens, but sometimes breakdown products of cells, such as necrotic-bodies or heat shock proteins. The only co-stimulatory receptor expressed constitutively by naïve T cells is CD28, so co-stimulation for these cells comes from the CD80 and CD86 proteins, which together constitute the B7 protein, (B7.1 and B7.2, respectively) on the APC. Other receptors are expressed upon activation of the T cell, such as OX40 and ICOS, but these largely depend upon CD28 for their expression. The second signal licenses the T cell to respond to an antigen. Without it, the T cell becomes anergic, and it becomes more difficult for it to activate in future. This mechanism prevents inappropriate responses to self, as self-peptides will not usually be presented with suitable co-stimulation. Once a T cell has been appropriately activated (i.e. has received signal one and signal two) it alters its cell surface expression of a variety of proteins. Markers of T cell activation include CD69, CD71 and CD25 (also a marker for Treg cells), and HLA-DR (a marker of human T cell activation). CTLA-4 expression is also up-regulated on activated T cells, which in turn outcompetes CD28 for binding to the B7 proteins. This is a checkpoint mechanism to prevent over activation of the T cell

[@namhaimai2405]

SIr, my friends and I in Hanoi in Vietnam are extremely ready to watch your lecture videos as soon as possible we have time because you make something which is so so complicated easier to understand and after subscribing your lectures, we turn back to read the books (for example: kuby immunology, lodish, alberts, etc) and we feel everything becomes much clearer. Thank you from the bottom of all our heart. Wish all the best will come to you, Sir. Hope you and your family are doing well in this pandemic. Take great care, Sir. Keep up the great work!

[@hussainbiology]

thanks Nam for appreciation.. Really Glad to know that it helps.... Keep sharing and supporting
lots of love

[@namhaimai2405]

@@hussainbiology Thank you very very much for replying my comment so fast, Sir! The way that you use to deliver your lecture to people is such a superb thing, Sir. This Covid-19 is so terrible. Hope everything goes well with you, Dr. Hussain. You are my best teacher on the Internet (and maybe in my life). Thank you for inspiring me to help me follow my passion for Biology, Sir! You are beyond amazing!

[@hussainbiology]

@@namhaimai2405 thanks again Nam.... Yeah everything is going good now in this Pandemic and i hope u are also going great

[@hussainbiology]

what is ur name and what u study ??

[@namhaimai2405]

@@hussainbiology Dear Sir, thank you for your kind word

[@bigballstepper]

your my hero man! so many exams passed because of your video's! lovely channel!

[@hussainbiology]

that is so great buddy.,.. Glad to know that

[@learner1181]

Thanks,
You seem like feynman of biology,
Explaining such complex topics in easiest way possible,
Its amazing.

[@hussainbiology]

that's such a great compliment for me.... thanks for appreciation

[@priyankaswami6552]

What I can say now.. i commented on your so many videos.. i have no words to write here... I can simply says that these videos are very helpful for me and others..❤️

[@JV-cz6fz]

I disagree with the 3rd signal not being very important. It's VERY important. The cytokine milieu determines what TYPE of response is necessary. Cytokines tell you if the response must be Th1, Th2, T17, or Treg.

[@sniperking6321]

yes it is important for differentation. But not for activation my friend

[@anirudh_2OP]

Lot of love from INDIA sir🙏🙏🙏

[@hussainbiology]

✌️✌️✌️ thanks for appreciation..Glad it helps✌️

[@barashakalita7772]

Very helpful thanks

[@hussainbiology]

Glad it helped

[@THINKBIO123]

very good @ concept explanation in minimum time

[@hussainbiology]

thanks for appreciation

[@hasmita7916]

This is the best video for this topic. Thank you so much sir🙏

[@hussainbiology]

thanks for appreciation..Glad it helps ✌️

[@josy4767]

Very helpful and concise. Great illustrations, thank you

[@danialabdalvand4740]

Very good video but doesn't CD4 interact with the alpha section of the MHC2??

[@motlalepulantlaly3859]

Thank you so much for short understandable video ❤️🙏

[@hussainbiology]

thanks for appreciation..Glad it helps....✌️

[@domkizy8755]

Simply phenomonal. Thank you.

[@jcdjddtos]

Thank you so much! It's super clear

[@hussainbiology]

thanks for appreciation..Glad it helps ✌️

[@sajeelkhan4943]

Sir what if CD8 protien is present instead of CD4 protien which will interact with the beta chain of MHC , Will the remaining process be the same ??

[@nil7425]

Really increadible.
Thanks a lot sir ❤️

[@kelsseypierrelouis36]

also thank you for this one... i hope you are feeling better

[@hussainbiology]

thanks Kelssey for appreciation... Yeah i am feeling good...

[@aj-uo3uh]

Very good!

[@user-qi8md9ib7i]

Impressive , well done bro god blesses❤❤

[@hussainbiology]

Thank you 🙌

[@DuckyHellBird]

Great video! Thank you!

[@shwethakrishna3716]

Superb sir ji.

[@hussainbiology]

Thanks for appreciation...

[@mahaaddepalli]

You saved my life. thank you 🥲😍😍

[@hussainbiology]

thanks for appreciation..Glad it helps ✌️

[@chiaramariablando8235]

Perfect video! Thank you very much. I didn’t understand one thing.
Among all the cells that present the antigen are only denditic cells get to the lymph node ?
Does macrophage activate lymphocytes in the tissues?

[@michaeleisenberg7867]

Hello 👋 Shabir,
Another efficient and fascinating video. 👏🙌🙌👏💖💗💣💥 Well done!!
It's absolutely amazing that biologists can figure this stuff out. I can just imagine them looking with their electron microscope 🔬 and seeing your little color-coded animations moving about the cell. Tiny multicolored 🌈 dimers everywhere. Dimers. Dimers. Dimers. It's all about dimers. (I wish there was a dimer emoticon 😘.)
Stay Well,
Best Wishes,
Thank you!! 😍😊
Mike

[@hussainbiology]

Hello Doc.... It is So nice of you that u like my stuff... It is really a great feat for me.... thanks again....

[@hussainbiology]

Yeah... Dimers emoticon could have been a deal for us

[@onemanvoice1510]

Superb explanation Sir....Thank u for the nice lecture

[@hussainbiology]

Thanks for appreciation..Glad to know that it helps

[@phobos_miner4288]

Excellent video.

[@hussainbiology]

Accepted Sir ,,,,, i haven't cross checked it ( you are right ) I am pinning yr comment

[@phobos_miner4288]

@@hussainbiology I am not even sure now, my friend. I was confuse by Robbins as in one of the figures show CD4 binding to Alpha but latter on mention B2 domain while talk about MHC-2. I found a reference that mention that actually the binding site for CD4 are both alpha 2 and beta 2 region domains. Best

[@biotech2ndyear2ndterm68]

thank you , well explanation lecture

[@evamadaan4933]

As always superb content🙌🙌🙌🙌 which book are you preferring for this topics

[@hussainbiology]

thanks Eva for appreciation... Kuby , Lodish and sites like NCBI , Sciencedirect , Frontiers

[@merahimane5897]

what is the role of ZAP_70 exactly?

[@ritisharma12]

Sir can you please explain one step growth experiment?

[@merahimane5897]

What is the role of SLP_76?

[@yasmineedualex7071]

Mainly CAMP pathway and the mechanism of exchanging GDP with GTP
and the classification of GPCRS as it's a very confusing topic
thanks

[@merahimane5897]

what is the role of Lat?

[@merahimane5897]

what is the role of PLC

[@merahimane5897]

WHAT is the ROLE OF (VaV1)?

[@yasmineedualex7071]

please
upload a video on signaling pathways of G protein coupled receptors in details

[@hussainbiology]

Surely

[@yasmineedualex7071]

Thankyou so much sir
i am waiting 💟

[@measententia2154]

Superr👍👍👍

[@hussainbiology]

Thanks Nila for appreciation..Glad to know that it helps

[@a45sankhadiptoghosh64]

Can I write this type of detail explanation ( as your this or other videos) in class 11 or 12 standard or in my HS examination?🙂🙂

[@hussainbiology]

No u don't need that much in-depth explanation for HS....

[@a45sankhadiptoghosh64]

Then what are the duties of CD3 HETERODIMERS , please tell me , Sir

[@hussainbiology]

ITAMS of Zeta Epsilon and Gamma are said to have same functions till now...
Can Bind ZAP proteins
...

[@kelsseypierrelouis36]

please ooo please do BCR Activation and class switch.

[@hussainbiology]

Yes.. I will consider making videos on the said ones

[@biology_mcqs3037]

👍👏

[@merahimane5897]

What exactly is a role OF ITK

[@hussainbiology]

U can easily search for each molecule on NCBI site for their roles

[@merahimane5897]

@@hussainbiology I do not know using this site 😔

[@nishatfatima2091]

👌👌👌👌👌

[@oussamasahnoun1335]

cd4+ et cd8+ whate does the + mean

[@whitejasmine3886]

sir plz start medalian genetics
probability epitasis and all other genetics numericals ..plzzzzzzz req sir

[@hussainbiology]

Will consider making

[@TalentedLearners]

❤️❤️

[@taffetabyaiz7102]

👍

[@a45sankhadiptoghosh64]

At 2:10

[@hussainbiology]

The Co-Stimulatory Signal ( Interaction btwn B7 AND CD128 ) saves the cell from getting into Anergy State.
If Co-Stimulatory Signal is absent Cell gets into Anergy State ( dormant state - no Immune response )

[@HouraisanShijuunana]

Hussian Biology be like: sayantist

[@hussainbiology]

✌️✌️✌️

[@HouraisanShijuunana]

@@hussainbiology pog!

[@a45sankhadiptoghosh64]

Energy , not Anergy

[@hussainbiology]

ANERGY....
I REPEAT ANERGY...
it is absence of normal Immune response

[@biology_mcqs3037]

It's anergy not energy...... U can check the link below to clear your doubt.
T cell anergy is a tolerance mechanism in which the lymphocyte is intrinsically functionally inactivated following an antigen encounter, but remains alive for an extended period of time in a hyporesponsive state.
pubmed.ncbi.nlm.nih.gov/12471050/

[@jayeetanandi3022]

Yeah it's anergy

[@v23452]

I was lost after two sentences. Please, dear sir, accept it as a fact that you shouldn’t voice over your own videos - find yourself a voice artist, preferably a native speaker. I am neither of them, but if you send me your script, I will send you an mp3 with my rendition. Interested in the topic as I am, I can’t catch on what you’re saying - not great delivery...

[@SathvikaKasturiaratchi]

I understood everything perfectly, wym

[@prathameshahirrao8106]

You are the person who didn't have to do study.. And blame other for poor teaching... Hussain sir is a great teacher ❤❤

[@maydreams1911]

Maybe you should first read a book

[@afeefawani2295]

👍

[@gullnawabnawab9601]

👍

[@hussainbiology]

thanks