Answer to Question #63146 in Molecular Biology for Sanjukta Ghosh

Question

How's idiotype different from paratype?

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 ?

Answer 1

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.