Antibody isotypes, idiotypes, and allotypes

Q. We’re doing immunology right now and I don’t get what the difference is between isotypes and idiotypes. Are they the same thing?

A. Good question! There’s another word that sounds similar too – allotypes. It’s pretty simple – here’s a quick summary.

Isotypes
Antibody isotypes are the same thing as antibody classes. There are 5 major isotypes: IgM, IgD, IgG, IgE, and IgA. The difference between these isotypes lies in the heavy chain (Mu, Delta, Gamma, Epsilon, or Alpha). You can have either kappa or lambda light chains with any of these isotypes. The most plentiful isotype in the body is IgA (if you’re just looking at the blood, the most common isotype is IgG); the least plentiful one is IgE. They all have different functions, which, come to think of it, is a good topic for another post.

Allotypes
Allotypes represent the genetically determined differences in antibodies between people. So you and I both have IgG, but unless we’re closely related, my IgGs are very slightly different than yours – maybe just by a couple amino acids in the constant region of the heavy or light chains. Allotypes are used for paternity testing.

Idiotypes
Idiotypes are antibodies that recognize different specific epitopes. The thing that determines the idiotype is way at the end of the variable region; it’s composed of a bunch of different idiotopes (or combining sites).

Of all of these concepts/words, the most important to focus on is isotypes. You should know a little bit (or a lot, depending on the depth of the material in your class) about each isotype.

More pathology!

36 Comments

zeenat on May 27, 2011 at 3:07 pm

nice concept
Kum kum on August 19, 2011 at 9:40 pm

Cleared my concept
N.K.David on September 7, 2011 at 12:20 pm

I am studying Immunology right now as part of microbiology as requirement for Vet. Medicine and I also write hubs. Isotypes are said to be similar within species. That is humans have same isotypes which are different from that of other species. Allotype has been implicated in Rheus factor cases like bleeding disease of new born.
dr duke on November 21, 2011 at 11:33 am

very best explanation,thanx a lot,its so confusing in levinson
God bless u..regards dr duke
subhraparna das on May 15, 2012 at 1:29 pm

thnks..i was puzzled
Rahul Ganguly on January 27, 2013 at 8:41 am

very good answer
javairya ansari on April 5, 2013 at 3:47 am

thaxx i got it.
namra on April 24, 2013 at 9:43 am

very simplified answers.thanks
Kalissa on May 15, 2013 at 8:57 am

Really great explanation, helped a lot in finally understanding the difference.
Abisola on May 21, 2013 at 4:43 pm

Beautiful piece…paints a better picture…goodwork!
gourav on July 27, 2013 at 1:40 am

beautiful explanation…
seo jung hwa on October 23, 2013 at 8:01 am

thank you very much! I have a immunology test tomorrow. you save me. 🙂
himadri sarkar on February 20, 2014 at 3:30 am

Thanks….
AMUJE EMMANUEL on October 8, 2015 at 6:53 am

Thanks alot. that was straight to the pont.
clarisse MUTIMUKEYE on October 24, 2015 at 10:08 am

thx alot for explanations. am really satisfied
Rurangirwa Alphoncla on November 4, 2015 at 9:11 am

Very helpful.
Haael on December 29, 2015 at 2:00 pm

Thanks this is very helpful
usha on March 25, 2016 at 10:58 am

thank you so much
it was very helpful..
Aisha on April 10, 2016 at 2:24 pm

Thanks alot it really helped me
vinh on April 22, 2016 at 4:04 am

thanks ! it’s very helpful
dan on April 26, 2016 at 6:23 pm

simply genius. thank you
yahya on May 27, 2016 at 12:41 am

well explained, Thanks for your help! i had some doubts of these, but know i understood!
Thank U so much.
Sanjukta on August 5, 2016 at 12:12 pm

Thank you for writing this post
rashid on September 29, 2016 at 2:17 am

Awesome
Dees on November 26, 2016 at 5:00 am

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Nesreen on February 28, 2017 at 11:27 am

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Rohit on May 18, 2017 at 5:23 am

This explanation is awesome and so easy. Thank you
Asmaa on August 13, 2017 at 1:43 pm

Thank you I understand this easily
ALEX MBUGUA on September 24, 2017 at 10:29 am

Thanks a lot. am grateful for the explanations
Miryam on December 8, 2017 at 12:48 pm

I’m an Italian Medical Biotecnologue student and I very thank you a lot for your post. It’s been useful and it helped me in studying Molecular Immunology.
So thank u really â™¡
Kristine on December 9, 2017 at 4:03 pm

Thanks, Miryam! So glad it was useful 🙂
Muhammad Ilyas on January 7, 2019 at 11:21 am

Much appreciation from Pakistan, well described.
Syafiqah Amin on September 20, 2020 at 3:36 am

Interesting concept!! Thank you
Mrunal Bonde on October 9, 2020 at 1:45 am

It’s very nice and helpful
Aaa on November 13, 2022 at 9:08 am

Wow