∞ generated and posted on 2016.01.12 ∞
Relatively complex molecules, mostly proteins but also some carbohydrates, that can be recognized by adaptive immune responses.
See also epitope/antigenic determinant, antibody, antigen-binding site, and also T-cell receptor.
Figure legend: A complex antigen, especially a protein, can be differentiated into a number of distinct epitopes (a.k.a., antigenic determinants). It is to these epitopes that the antigen-binding site of an antibody actually binds (antibody not shown in full).