Antigen

An antigen (Ag) is a molecule or molecular structure, such as may be present at the outside of a pathogen, that can be bound to by an antigen-specific antibody (Ab) or B cell antigen receptor (BCR). The presence of antigens in the body normally triggers an immune response. The term "antigen" originally described a structural molecule that binds specifically to an antibody only in the form of native antigen,It was expanded later to refer to any molecule or a linear molecular fragment after processing the native antigen that can be recognized by T-cell receptor (TCR). BCR and TCR are both highly variable antigen receptors diversified by somatic V(D)J recombination. Both T cells and B cells are cellular components of adaptive immunity. The Ag abbreviation stands for an antibody generator.
Antigens are "targeted" by antibodies. Each antibody is specifically produced by the immune system to match an antigen after cells in the immune system come into contact with it; this allows a precise identification or matching of the antigen and the initiation of a tailored response. The antibody is said to "match" the antigen in the sense that it can bind to it due to an adaptation in a region of the antibody; because of this, many different antibodies are produced, each able to bind a different antigen while sharing the same basic structure. In most cases, an adapted antibody can only react to and bind one specific antigen; in some instances, however, antibodies may cross-react and bind more than one antigen.
Also, an antigen is a molecule that binds to Ag-specific receptors, but cannot necessarily induce an immune response in the body by itself.[3] Antigens are usually proteins, peptides (amino acid chains) and polysaccharides (chains of monosaccharides/simple sugars) but lipids and nucleic acids become antigens only when combined with proteins and polysaccharides.[4] In general, saccharides and lipids (as opposed to peptides) qualify as antigens but not as immunogens since they cannot elicit an immune response on their own. Furthermore, for a peptide to induce an immune response (activation of T-cells by antigen-presenting cells) it must be a large enough size, since peptides too small will also not elicit an immune response.
The antigen may originate from within the body ("self-antigen") or from the external environment ("non-self"). The immune system is supposed to identify and attack "non-self" invaders from the outside world or modified/harmful substances present in the body and usually does not react to self-antigens under normal homeostatic conditions due to negative selection of T cells in the thymus.
Vaccines are examples of antigens in an immunogenic form, which are intentionally administered to a recipient to induce the memory function of adaptive immune system toward the antigens of the pathogen invading that recipient.

[@Chris-pi2lm]

Found your TH-cam channel through an Instagram comment, this has got to be one of the most informative TH-cam channels for biology I’ve ever seen. Thank you and keep up the good work!

[@hussainbiology]

Thanks for appreciation.. Glad to know that it helps ✌️ What was in that comment though ??

[@Chris-pi2lm]

@@hussainbiology They just said if you are a bio major (I am) to check out your channel since you were really good at explaining :^)

[@hussainbiology]

@@Chris-pi2lm Great....✌️✌️ rise and shine..

[@dr.gabrielamase6666]

This is really educative. Keep it up

[@bluewave7120]

Clear & concise easy to understand explanation for us med students short on study time TY

[@hussainbiology]

thanks for appreciation..Glad it helps ✌️

[@hansaworld1]

This video explained this concept exactly the way needed to understand..thank you !!

[@hussainbiology]

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

[@stuffvlogs7521]

Pta nhi kya kya padhaya others TH-camr ❤ ne, bahut time baad apka tarika samjh aaya sir

[@hussainbiology]

thanks for appreciation..Glad it helps..

[@ishratbowa3502]

Very help full

[@tumharahelper7938]

Shayad chu ye kashur ❤❤👍👍👍👍

[@hussainbiology]

barabar... puz che

[@tumharahelper7938]

@@hussainbiology ❤❤❤❤❤❤❤❤❤❤👍👍👍👍👍❤❤❤❤👍👍

[@littlerushergaming2372]

Very Nice, Informative👍👍

[@hussainbiology]

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

[@rajipotnuru5368]

Thankyou so much sir... for sharing this most informative vedio which helps us to study in a simple way...🙏...it will be more useful for my exams.

[@neethuem8509]

Super presentation thanku so much sir, 🙏

[@hussainbiology]

You are most welcome 👍

[@uzmajan9762]

Thank u sir.... Seems to b very helpful in future.... And nice explanation. Keep making videos...

[@hussainbiology]

thanks for appreciation..Glad it helps

[@joeguidi296]

Great work! I appreciate your clear and thorough approach to these videos! Thank you.

[@hussainbiology]

thanks for appreciation..Glad to know that it helps

[@hafizabdullah3865]

Mashallah
Great Teacher .

[@michellehamilton4075]

Wow! This is so over my head.

[@hussainbiology]

thanks for appreciation..Glad it helps ✌️

[@varishaazmat1460]

It is very helpful for my exam 😇

[@hussainbiology]

Glad to know that ✌️✌️✌️

[@s.r0700]

Sir pls upload more videos on immunology series lectures..🙏🙏🙏

[@hussainbiology]

Surely i will

[@andianabando7411]

you teach very well, just be slower remember youtube is global so that international people will understand properly

[@hussainbiology]

Surely.... I will take these things into consideration......Thanks

[@onemanvoice1510]

Nice lecture Bhai...Keep it up

[@hussainbiology]

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

[@anythinggoes3955]

Please video on tumor antigens

[@mishkapathak]

Nice video thank u sir

[@zackaryclutter6192]

I liked video

[@aneesahmadchoudhry4487]

Wonderful work sir!!!!!!!!
May Allah bless you!!!!!!

[@hussainbiology]

thanks Anees for appreciation

[@nibeditaroynitu226]

Thank you, sir!

[@KrishnaKumar-ql1lv]

Thank you so much for your efforts

[@hussainbiology]

You are welcome ✌️

[@esharajput1301]

Please upload antigen antibody interaction video as soon as possible.....

[@hussainbiology]

Surely..i will

[@tahakadhim9095]

تكدر تشرح عربي

[@swatigayen7390]

thank you ..it was really helpful

[@hussainbiology]

You are welcome ✌️

[@gulshansen8484]

Please upload more videos on MHC-I and MHC II.
Love from India ♥️

[@stuffvlogs7521]

What is MHC 1,2 process what is the full form it?

[@stay..6062]

​@@stuffvlogs7521
MHC is major histocompatibility complex

[@amandhillon9840]

Which class topic is this sir

[@hussainbiology]

Advanded i guess

[@narenderpalsingh4401]

Good

[@just_abald_guy_who_love_to9324]

Nice channel

[@AnkeetKumar]

Awesome.

[@jenniferyoung8665]

30secs in and i'm already confused. it's not the lecturer...i'm just not wired to "get it". however, i do appreciate the video.

[@hussainbiology]

Apologies ...

[@0xGrowth]

Damn. 😂😂

[@GamingWimpGW360]

@@hussainbiologysir……..thanks you very much sir………..

[@krp_leop_pradhan1759]

Great video but you talk too fast little hard to catch up with your speed ,over all good

[@rasiyaferoze4718]

Sir ji going very fast....

[@hussainbiology]

Sorry for that... will be slower in upcoming videos

[@waninajma461]

Fabulous 👌 Are these lectures helpfull for CSIR NET

[@hussainbiology]

thanks for appreciation

[@AliMRAZA-sm2no]

Plz make videos in Urdu ya Indi language

[@shreyajadhav4242]

Why exogenous antigen doesn’t require take up ?

[@SY20039]

grey seed color in peas is dominant over white. In following experiment parents with known phenotype but unknown genotype produced following progeny-
gray. white
gray×white. 82. 78
gray×white 0. 50
gray×white. 74. 0
gray × white. 90 0
using G for gray and g for white give genotype of each parent.
plzz sir if possible answer the question in comment section. pllzzz.

[@zamannoyan3410]

عالی

[@kongsite78]

Really effective bro

[@PoojaSharma-he7cn]

Sir aapp acha prhate ho pr bahut tezz prhate ho

[@hussainbiology]

thanks for appreciation.. Mai dyaan rakhunga ✌️

[@AnkeetKumar]

Heptan Vs Adjuvant ,clear it to me. ?

[@biology_mcqs3037]

Hepten are small molecules that alone can not generate immune response. It generates immune response only when attached to large carrier molecules such as proteins. While as Adjuvants are substances which when mixed with antigen and injected help to boost immune response.

[@AnkeetKumar]

@@biology_mcqs3037 Thanks for the answer ,but are you Showkat sir (Botany teacher ) ? Plzz do reply .

[@biology_mcqs3037]

@@AnkeetKumar No brother I had done PG in biochemistry.

[@AnkeetKumar]

@@biology_mcqs3037 ok brother ,May God bless you. 🎉🎉. Thanks for the answer

[@hussainbiology]

Ankeet i hope u got the answer...... Showkat is great in explaining the stuff too

[@prettylilstaff8958]

Pls upload antibody video 🙏

[@hussainbiology]

Next video will be on Antibodies.....Stay Updated

[@lashazhvania6813]

I hear only noise, pls make your english more understandable. its impossible to get what you say

[@kunalkumarbhoi324]

Too fast please slow the video

[@varinderkaur9644]

where is superantigen video

[@hussainbiology]

th-cam.com/video/1f67oWbpoO8/w-d-xo.html

[@nishatfatima2091]

👍🙏🙏🙏👍

[@hussainbiology]

✌️✌️

[@seeratzehra8547]

🤗❤

[@hussainbiology]

✌️ Keep sharing and supporting

[@girlycamsit431]

Thanks it helped

[@okaforcaritas7723]

Where are u running to… u are too fast and it’s so annoying

[@hussainbiology]

sorry

[@cathg.956]

great!

[@am_ahtesham4149]

Tui chu koshur 🥹

[@hussainbiology]

awaaa

[@medicalbiochemistry_]

Good

[@hussainbiology]

✌️✌️