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.

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. In humans, the most plentiful 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 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 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.


26 Responses to Antibody isotypes, idiotypes, and allotypes

  1. zeenat says:

    nice concept

  2. Kum kum says:

    Cleared my concept

  3. N.K.David says:

    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.

  4. dr duke says:

    very best explanation,thanx a lot,its so confusing in levinson
    God bless u..regards dr duke

  5. subhraparna das says:

    thnks..i was puzzled

  6. Rahul Ganguly says:

    very good answer

  7. javairya ansari says:

    thaxx i got it.

  8. namra says:

    very simplified answers.thanks

  9. Kalissa says:

    Really great explanation, helped a lot in finally understanding the difference.

  10. Abisola says:

    Beautiful piece…paints a better picture…goodwork!

  11. gourav says:

    beautiful explanation…

  12. seo jung hwa says:

    thank you very much! I have a immunology test tomorrow. you save me. 🙂

  13. himadri sarkar says:


  14. AMUJE EMMANUEL says:

    Thanks alot. that was straight to the pont.

  15. clarisse MUTIMUKEYE says:

    thx alot for explanations. am really satisfied

  16. Rurangirwa Alphoncla says:

    Very helpful.

  17. Haael says:

    Thanks this is very helpful

  18. usha says:

    thank you so much
    it was very helpful..

  19. Aisha says:

    Thanks alot it really helped me

  20. vinh says:

    thanks ! it’s very helpful

  21. dan says:

    simply genius. thank you

  22. yahya says:

    well explained, Thanks for your help! i had some doubts of these, but know i understood!
    Thank U so much.

  23. Sanjukta says:

    Thank you for writing this post

  24. rashid says:


  25. Nesreen says:

    Thank you for sharing this post.
    great information and easy to understand.

  26. Rohit says:

    This explanation is awesome and so easy. Thank you

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