The paratope is the part of an antibody which recognizes an antigen, the antigen-binding site of an antibody. It is a small region (of 15–22 amino acids) of the antibody's Fv region and contains parts of the antibody's heavy and light chains.
The part of the antigen to which the paratope binds is called an epitope. This can be mimicked by a mimotope. The figure given on the right hand side depicts the antibody commonly found on a B leukocyte. The engraved inner portions of idiotype (encircled region no.5) is the paratope where the epitope of the antigen binds.