Two wells are filled with related or partially identical antigens. The well on the left contains an ...

Two wells are filled with related or partially identical antigens. The well on the left contains an antigen with an additional epitope when compared with the antigen in the well on the right. The precipitin line on the left is formed by the reaction of an antibody to the shared epiotpe, and this line continues on the right, as in a line of identity. Also in the line on the left is the reaction of an antibody to the unique epitope and the antigen with the unique epitope. This reaction line continues beyond the line of identity because the antibody to the unique epitope is not stopped as it comes to the line formed by the antigen without this epitope and antibody to the shared epitope. For simplicity, the antigen has been drawn with 2 to 4 epitopes, but proteins usually have more than this number of epitopes.