AB0 system (English)

náhled|200px|Structure of antigens of each blood group of The AB0 system. ABO blood group system involves 4 blood groups – A, B, AB, 0 according to the presence of antigenes A, B a H (0), these are called agglutinogens.

Antigens
Antigens of the AB0 system are glycolipids, short oligosaccharides attached to an outer lipid molecule in the plasma membrane erytrocytes. Molecules A, B a H differ only in the last sugar residue. The last sugar residues are responsible for the molecules being recognized as three different antigens.
 * A: N-acetyl-galactosamine,
 * B: galactose,
 * H: -.

Interplay of several genes is required for the expression of AB0 system antigens: The expression of several enzymes is involved in the formation of individual antigens (fucosyltransferase, A transferase, B transferase). Their different combinations lead to the formation of 4 possible groups:A, B, AB or 0(H). When two recessive genes ( hh ) for fucosyltransferase are combined, the other two enzymes cannot be used and a so-called phenotype Bombay is formed. Erythrocytes do not express agglutinogens A nor do they express B, even though the enzymes for their formation are present in the genome of this individual. Typing of AB0 antigens is essential for blood transfusion, tissue and organ transplants, paternity testing (inaccurate and only tentative).
 * Main locus ABO: 9. chromosome;
 * H-locus: 19. chromosome.

Antibodies
náhled|200px|Chart of antigens and antibodies for each blood group of The AB0 system. The presence of IgM and IgG antibodies in the serum is characteristic. They are called agglutinogens. These antibodies are always designed to interact with antigens of the AB0 system, which are not present in the blood of their bearer .

Individuals with Bombay phenotype correspond to the group 0 with antibodies anti-A, anti-B, and even anti-H.

Distribution
Groups A a B make up to 11 subtypes, which differ in the number of antigenic structures on erythrocyte membrane. The most common are A1, A2. Individuals with Bombay phenotype occur very rarely.

Distribution of blood types in Europe is approximately: Representation in other parts of the world varies significantly.
 * A: 45 %
 * B: 16 %
 * AB: 6 %
 * 0: 33 %

Related articles

 * Krevní skupiny
 * Rh systém
 * Dědičnost krevních skupin
 * Imunopatologická reakce II. typu
 * Transfúze
 * Inkompatibilita AB0 při transfuzi