The biological role played by a material entity when bound by a receptor of the adaptive immune system. Specific site on an antigen to which an antibody binds.
Any substance capable of eliciting an immune response only when attached to a large carrier such as a protein. Examples include dinitrophenols; oligosaccharides; peptides; and heavy metals.
A chemical compound, or part thereof, which causes the onset of an allergic reaction by interacting with any of the molecular pathways involved in an allergy.
An intermediate in the synthesis of phosphatidylcholine in tissues, it is frequently incorporated into the surface antigens of several pathogenic prokaryotes and eukaryotes.