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Antigens are simply understood as substances that, when entering the human body, will be quickly recognized by the immune system and produce corresponding antibodies to specifically combine with that antigen. The antigen is usually a protein, a polysaccharide, but can be any type of molecule carrying small haptens attached to a carrier protein.
1. Antigen properties
1.1 Specificity This property indicates that an antigen is recognized only by the antibody it causes, not by antibodies produced by other antigens. The specificity of antigens is due to the foreignness and the determining group of antigens.
Strangeness: Immunologists have found that the body's immune response is stronger if the antigen is derived from different species than the species used for sensitization. That is, the more foreign the antigen is to the body, the stronger the ability to stimulate the creation of antibodies.
Antigen-determining group: This is the property that the surface structure of an antigen molecule is capable of combining with only one antibody molecule.
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1.2 Antibodies Antigen has the ability to stimulate the body's immune system to produce antibodies. Brand new antigens have this ability. The remaining antigens have a small molecular weight that is not able to stimulate the body to synthesize antibodies, but can only produce specificity for the binding of antibodies, which are called semi-antigens (hapten). . But when the hapten attaches to a protein molecule, it becomes a complete antigen, which can stimulate the immune system to produce very strong antibodies for the body.
2. Antigen classification
2.1 Classification according to the ability to produce antibodies Complete antigens and semi-antigens (incomplete antigens)
2.2 Classification according to genetic similarity Other antigens: Highly foreign, capable of generating antibodies are strong, but there are also groups of common determinants between species. Allogeneic antigens: Determines the differences between groups of individuals of the same type and produces antibodies in individuals that do not carry that antigen. Autoantigens are located on the cells of the self, causing antibodies against themselves, also known as the autoimmune process.
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2.3 Chemical classification Protein antigens can produce very strong antibodies. Nucleic acid antigens are semi-antigens that are not capable of producing antibodies. Pure lipid antigens are not capable of producing antibodies. 2.4 T-B-lymphocyte interaction classification Thymus-dependent antigens require thymic activity to produce antibodies. Anti-thymocytes are thymic-independent, capable of producing antibodies without the existence of a thymus. 2.5 Classification according to antigenic origin Plant antigens such as pollen, dust, cause allergic conditions. Bacterial antigens are very complex in the shell, walls, hairs, toxins... Viral antigens are on the surface or deep inside. 2.6 Types of cell antigens Are specific antigens for each cell line such as B lymphocytes, T lymphocytes of lymphocytes, or antigens on the surface of red blood cells and white blood cells.
3. Antigen tests
Some tests can identify antigens on the surface of various bacteria and pathogens. These tests can detect an infectious pathogen accurately and quickly, without the need to culture, look under the microscope as in the past.
For example, a stool sample test can immediately detect antigens on the surface of HP bacteria - bacteria that appear in the stomach and duodenum causing peptic ulcers. A stool antigen test indicates that you have HP bacteria in your intestines.
Different antigen tests will help diagnose a number of infections and different diseases quickly, accurately and save diagnostic time for doctors and patients.
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