MEDICAL BIOLOGY, HUMAN ANATOMY, PHYSIOLOGY AND PATHOLOGY - Ya.I. Fedoniuk 2010

ANATOMY, PHYSIOLOGY, PATHOLOGY

CHAPTER 4. BLOOD SYSTEM

BLOOD GROUPS

ABO SYSTEM

Erythrocyte membranes carry Antigens. More than 400 antigens are known to exist. Among them, the ABO system antigens are of the utmost importance.

Antigenic Specificity is what determines Blood Groups. The ABO system distinguishes three antigens: A, B, and H, which are referred to as agglutinogens. The ABO system also contains Two Types of Antibodies, (alpha) and (beta), known as agglutinins.

Since ancient times, attempts have been made to transfuse blood from animals to humans or from human to human. However, this almost always resulted in the patient's death. The cause of fatality following such blood transfusions was the clumping of erythrocytes within the Blood Vessels (agglutination), followed by hemolysis and capillary blockage, which ultimately led to The Development of so-called transfusion Shock (hemo - blood, transfusion - transfusion).

What causes erythrocyte agglutination? Agglutination is driven by the agglutinogen-agglutinin reaction. Agglutination followed by hemolysis occurs exclusively when homologous agglutinins and agglutinogens—specifically A and B—meet. There is no corresponding agglutinin for agglutinogen H in blood serum. Homologous agglutinins and agglutinogens never coexist in the blood of the same individual.

Depending on the presence of specific agglutinogens and agglutinins in the ABO system (in honor of Landsteiner, the discoverer of agglutinogens, the modern nomenclature retains the "0-antigen" instead of "H"), human blood is divided into four groups: I (0) — erythrocytes contain the "0" agglutinogen, while the plasma contains agglutinins; II (A) — erythrocytes contain agglutinogen A, while the plasma contains agglutinin; III (B) — erythrocytes contain agglutinogen B, while the plasma contains agglutinin; IV (AB) — erythrocytes contain both agglutinogen A and B, while agglutinins are absent in the plasma.