A antigen it is a substance that is introduced into the body and that the immune system interprets as a threat. These antigens can be viruses or bacteria. This introduction produces the creation of an immune response and facilitates the generation of other macromolecules called antibodies.
The term antigen comes from the Greek word “anti” which means opposite and “gene” which means to produce, create or generate.
For an organism to have a antigen response high (that is, the body responds positively by preventing the antigens from spreading through the body) it is necessary that the molecules involved (antibodies) have the following characteristics. These should be:
- Big
- Rigid
- complex
These antibodies (also called immunoglobins) identify and neutralize antigens. In this way, these antibodies form type B lymphocytes. Thus, the antibody binds to the antigen so that it is identified and then attacked by other lymphocytes.
Types of antigens
Antigens can be divided into 2 large groups:
- Exogenous. They are those who come from outside.
- endogenous. They are those that are inside the body. Among these are:
- Self-antigens. They are normal proteins that can be found in DNA or RNA. It happens that these antigens are not recognized by the immune system and it attacks it, interpreting that it is an aggressor agent. Under normal conditions this should not happen. For this reason it is indicated in patients with a specific autoimmune disease.
- tumor antigens. They are found on the surfaces of tumor cells.
- native antigens. They still have their original shape. The T lymphocytes (t cells) cannot join this. Therefore these cannot be attacked by the immune system.
Examples of exogenous antigens
- bacteria
- Pollen
- Dust
- rat feces
Examples of endogenous antigens
- Virus
- pathogenic fungi
- unicellular parasites
- multicellular parasites
Examples of super-antigens
Faced with the appearance of a common (or conventional) antigen, there is a type of macromolecules (called T cells) that detect the presence of unusual antigens (and potentially more harmful and dangerous than conventional antigens). These are called super-antigens.
- Staphylococcal enterotoxins. It occurs due to poisoning of certain foods.
- Staphylococcal toxic shock toxin. Also called “toxic shock syndrome.”
- Staphylococcal exfoliant toxins. It receives the name of “scalded skin syndrome”.
- Streptococcus pyrogenic exotoxins.