Antigens
Antigens are substances that prompt the body’s immune system to produce antibodies, which are types of proteins designed to attack harmful substances. Antigens, therefore, tend to be foreign substances such as bacteria, fungi, viruses, dust, food proteins, pollen or chemicals, although they may also be created internally in the form of tissue cells or bacterial toxins. Cancer cells, for instance, are antigens. Moreover, neoantigens or tumour antigens are those that are found on the surface of tumour cells, which can sometimes be capable of destroying the tumour cells before they metastasise or spread across the body. Furthermore, antigens that create allergic reactions are caused allergens. Ultimately, anything that causes the immune system to produce antibodies is an antigen by definition.
Antigens can be classified as either exogenous antigens, endogenous antigens or autoantigens. Exogenous antigens are those that have entered the body externally, endogenous antigens are those that have been produced internally (within the cell), such as through normal cell metabolism or as a result of bacterial infection, and autoantigens are present in patients suffering from an autoimmune disease whereby normal proteins are abnormally attacked by the immune system.
The term ‘Antigen’ refers to the generation of antibodies to substances and originates from Ladislas Deutsch in 1899. Antigens are responded to by the immune system’s T and B cells, which serve different functions but may attack the same antigen at the same time. Antibodies are capable of remembering a specific kind of antigen and, should that antigen present itself in the body again, the antibodies will be able to recognise and attack it with greater effect. This is the practical framework upon which vaccinations are made possible.
