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[[File:Immunoglobulin basic unit.svg|thumb|
An antibody with a circled region depicting where the paratope is found.
1. Antigen-binding fragment
2. Antibody crystallizable region (Fc)
3. Heavy chains
4. Light chains
5. Variable region of the antibody. The paratope is the key-shaped section that makes direct contact with the antigen. (2025). 9781441998637, Springer. ISBN 9781441998637
6. Hinge regions
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In immunology, a paratope, also known as an antigen-binding site, is the part of an antibody which recognizes and binds to an antigen. (2025). 9781464189784 ISBN 9781464189784 It is a small region at the tip of the antibody's antigen-binding fragment and contains parts of the antibody's heavy and light chains. Each paratope is made up of six complementarity-determining regions - three from each of the light and heavy chains - that extend from a fold of anti-parallel . Each arm of the Y-shaped antibody has an identical paratope at the end.
Paratopes make up the parts of the B-cell receptor that bind to and make contact with the epitope of an antigen. All the B-cell receptors on any one individual B cell have identical paratopes. The uniqueness of a paratope allows it to bind to only one epitope with high affinity and as a result, each B cell can only respond to one epitope. The paratopes on B-cell receptors binding to their specific epitope is a critical step in the adaptive immune response.
In cows, an extra-long complementarity-determining region is considered to have an essential role in diversifying paratopes. Additionally, both chickens and rabbits use gene conversion to increase the number of paratopes that are possible.
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