Antigen 2026-10-13
In antibody binding, an antigen is material bearing a recognized epitope. An antigen need not be a protein; polysaccharides can also carry epitopes. One antigen may present several different epitopes, so recognizing one feature does not imply recognizing every part of the target. [ref]
The interaction of the antibody molecule with specific antigen. Immunobiology, 5th edition, §3-8: small recognized regions of protein and polysaccharide antigens
Paratope 2026-10-13
A paratope is the recognizing surface on an antibody; the epitope is the recognized feature on its antigen. Contacts depend on spatial arrangement and chemistry, including hydrogen bonds and Van der Waals forces. Thus a paratope is not simply a slot for a protein primary structure string. A folded protein can bring distant amino acid residues into one epitope. [ref]