How many epitopes does an antigen have?

Large molecules, or macromolecules, that the immune system recognizes as "foreign" include proteins and sugars, which are examples of antigens.

Antibodies identify particular patterns and/or chemical groups on an antigen; these are known as antigenic determinants or epitopes. The immune system produces antibodies against these foreign molecules, but never against the entire antigen.

Consequently, distinct antibodies can be produced to detect distinct epitopes on the same molecule. An antigen is defined as a molecule that contains at least one epitope; the number of epitopes varies depending on the antigen's size, for example.

The number of possible epitopes an antigen can have is estimated from the data that, for human proteins, epitopes are composed of 9 to 22 amino acids, not necessarily continuous but at least in close proximity when the protein is folded.

The number of epitopes an antigen has can vary widely depending on its size, structure, and complexity. Antigens typically have multiple epitopes, ranging from a few to hundreds.