What is an antigen?
An antigen is a molecule that is foreign to the body and generates antibodies. An antigen is usually part of a bacterial cell, virus, or microorganism. In this article we will describe in more detail what an antigen is and what types of antigens are.
Types of antigens
So, an antigen is any substance foreign to an organism that causes a so-called immune response, that is, activation of antibodies in order to "expel a stranger." Most antigens are proteins and polysaccharides, although, in fact, any simple substance can cause the reproduction of antibodies. The antigens most known to man, allergens, are substances that cause allergic reactions.
Outside or inside
Antigens can enter the body from the environment, such antigens are called exogenous, and can also be formed during the metabolism process, these antigens are called endogenous.
Full or not?
Antigens are complete and defective. The first can cause the synthesis of antibodies and react with them. For each full-fledged antigen in the body there are strictly specific antibodies.
Defective antigens, or haptens, are substances that cannot stimulate the production of antibodies, but they enter into a specific reaction. Haptens are usually complex carbohydrates, lipids, polysaccharides and nucleic acids, as well as simple substances - iodine, bromine, dye, etc.