An antigen 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 ” geno ” which means to produce, create or generate.
For an organism to have a high antigenic response (that is, the body responds positively preventing the antigens from spreading through the body) it is necessary that the intervening molecules (antibodies) have the following characteristics. These should be:
These antibodies (which are also called immunoglobulins) identify and neutralize the 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
The antigens can be divided into 2 large groups:
Exogenous . They are those that come from outside.
Endogenous . They are those that are inside the organism. Within these are:
- Auto-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 present their original form. The T lymphocytes (T cells) can not join this. Therefore these can not be attacked by the immune system.
Examples of exogenous antigens
Foreign particles within the body such as:
- Rat stool
- Coat capsules
Examples of endogenous antigens
- 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 rare antigens (and potentially more harmful and dangerous than conventional antigens). These are called super-antigens .
- Staphylococcal enterotoxins. It occurs by poisoning certain foods.
- Staphylococcal toxic shock toxin. Also called “toxic shock syndrome”.
- Staphylococcal exfoliating toxins. It receives the name of “scalded skin syndrome”.
- Streptococcal pyrogenic exotoxins.