An antigen is a substance that enters the body and is interpreted by the immune system 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 antigen response (that is, for the body to respond 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:
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 can be identified and then attacked by other lymphocytes.
- It can help you: Parasitism
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 organism. 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 by interpreting that it is an aggressive 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 bind to this. Therefore these cannot be attacked by the immune system.
Examples of exogenous antigens
- Rat feces
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 due to food poisoning.
- Staphylococcal toxic shock toxin. Also called “toxic shock syndrome.”
- Exfoliating staph toxins. It is called “scalded skin syndrome.”
- Pyrogenic exotoxins of streptococci.