The structure on the surface of an antigen that is recognized by and can bind to a specific antibody. Its shape is generally complementary to that of the antibody’s antigen-binding site. Examples are a group of sugar units of the polysaccharide component of a bacterial cell wall and a cluster of amino acids on the exposed surface of a protein molecule. Conformational (or discontinuous) epitopes are composed of parts of a molecule (especially a protein) that are juxtaposed by folding of the molecule into its natural conformation; continuous (or linear) epitopes consist of a single contiguous sequence of a molecule’s subunits (e.g. a short peptide from a protein chain).