Origin: Anc Greek
επί-/epi(=prefix meaning upon, on)
The surface portion of an antigen which is recognised by immune system (antibodies, B or T cells) and elicit an immune response. The part of an antibody that recognizes the epitope is called a paratope.
Jerne, N.K. (1974), "Towards a network theory of the immune System", Ann. Immunol. (
) 125C: 373–389 Paris