"what is an antigen" "what macromolecules are the best antigens"

Antigens are molecular structures that trigger an immune response which later results in the production of antibodies. Macromolecules that are usually the best antigens have a lot of examples, however, they have four common characteristics: foreignness, size, complexity, and degradability. The more a macromolecule has these, the better it is as an antigen.