Epitope

Epitope (from Greek epi "on, at" and topos "site") is a molecular structure that occurs in a molecule acting as an antigen and is specifically recognized by antibodies or the T-cell receptor via their antigen binding sites (antigenic determinant). Only small areas of a macromolecule trigger an immune reaction and only with them do the corresponding antibodies react. Large molecules therefore have a multitude of different epitopes, which can also be present in different molecular assemblies.

A distinction is made between continuous (also called linear or sequence epitopes ) and discontinuous epitopes (also called conformational epitopes) (see figure).

T cells typically recognize continuous peptide epitopes via their receptor, which are presented to them together with HLA antigens in a complex (antigen presentation).

Antibodies (IgG, IgM, IgE antibodies) are primarily directed against conformational epitopes on the three-dimensional surface of antigens. These consist of discontinuous sections of the protein chain, as well as of non-protein terminants such as carbohydrates or lipids.

1. Mishra A et al (2016) Mapping B-cell epitopes of major and minor peanut allergens and identifying residues contributing to IgE binding. J Sci Food Agric 96:539-547.
2. Robotham JM et al (2009) Linear IgE-epitope mapping and comparative structural homology modeling of hazelnut and English walnut 11S globulins. Mol immunol 46: 2975-2984.
3. Rosenfeld L et al (2012) Walnut allergy in peanut-allergic patients: significance of sequential epitopes of walnut homologous to linear epitopes of Ara h 1, 2 and 3 in relation to clinical reactivity. Int Arch Allergy Immunol 157:238-245.