What I understand of these two terms is that:

Paratope is a portion of antibody that recognises and binds to specific antigen.

Idiotype is an antigenic determinant of antibody formed of CDRs that have specificity for a particular epitope. Some authors call the antibodies recognising a particular epitope an idiotype.

Well the CDRs, they actually form the paratope so is it right to say the CDR that acts as an paratope also forms the idiotypic determinant/ idiotype ?


2 Answers 2


I have read that the unique amino acid sequence of the VH and VL domains of a given antibody can function not only as an antigen-binding site but also as a set of antigenic determinants. the idiotypic determinants are generated by the confomation of the heavy- and light-chain variable region. Each individual antigenic determinant of the variable region is referred to as an idiotope. In some cases an idiotope may be the actual antigen-binding site (The paratope), and in some cases an idiotope may comprise variable region sequences OUTSIDE of the antigen-binding site. Therefore, each antibody will present multiple idiotopes, and the sum of the individual idiotopes is called the IDIOTYPE of the antibody.

I hope that had been helpful

  • $\begingroup$ Could you add your reference? $\endgroup$
    – Tyto alba
    Jun 8, 2017 at 8:31
  • 1
    $\begingroup$ Kuby Immunology, 4th Edition, Chapter: Immunoglobulins: Structure and Function (83-113) $\endgroup$
    – polonio210
    Jun 8, 2017 at 21:24

The following was a reply by an expert from assignmentexpert.com :

Paratope is only the part of Ab that binds to the epitope of an antigen. But this does not mean that every amino acid in the CDR should bind to epitope – it is possible that only 1-2 AAs per CDR bind directly to epitope. Therefore, paratope is the part of the idiotype that binds to the epitope.


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