What is Antigen?
An antigen is a foreign substance or cell that is capable of activating the immune system. In response, antibodies will be produced. As a result, viruses and bacteria will be seen as foreign to the body, allowing the healing process to begin. There is antibody generating involved. Antigens are the proteins on the membranes or cells of the foreign body to which antibodies fit. An antigen will therefore prompt the immune system (in the form of B lymphocytes) to produce these antibodies.