Conformational epitope
![Recognition of conformational epitopes by B cells. Note how the segments widely separated in the primary structure have come in contact in the three-dimensional tertiary structure forming part of the same epitope[1]](/Images/godic/202501/06/Recognition_of_conformational_epitopes_by_B_cells3749.PNG")
A conformational epitope is a sequence of sub-units (usually amino acids) composing an antigen that come in direct contact with a receptor of the immune system.
An antigen is any substance that the immune system can recognize as foreign. Antigens are usually proteins that are too large to bind as a whole to any receptor so only specific segments, that form the antigen, bind with a specific receptor. Such segments are called epitopes. Likewise, it is only paratope of the receptor that comes in contact with the epitope.