Individuals with type A blood-without any prior exposure to incompatible blood-have preformed antibodies to the B antigen circulating in their blood plasma. This is not the case for the ABO blood group. Normally the body must be exposed to a foreign antigen before an antibody can be produced. ABO blood types are genetically determined. People with neither A nor B antigens are designated blood type O. People can also have both A and B antigens on their erythrocytes, in which case they are blood type AB. People whose erythrocytes have A antigens on their erythrocyte membrane surfaces are designated blood type A, and those whose erythrocytes have B antigens are blood type B. More than 50 antigens have been identified on erythrocyte membranes, but the most significant in terms of their potential harm to patients are classified in two groups: the ABO blood group and the Rh blood group.Īlthough the ABO blood group name consists of three letters, ABO blood typing designates the presence or absence of just two antigens, A and B. However, the load of hemoglobin released can easily overwhelm the kidney’s capacity to clear it, and the patient can quickly develop kidney failure.
This hemoglobin travels to the kidneys, which are responsible for filtration of the blood. As the erythrocyte clumps are degraded, in a process called hemolysis, their hemoglobin is released into the bloodstream.The clumps of erythrocytes block small blood vessels throughout the body, depriving tissues of oxygen and nutrients.Because the arms of the Y-shaped antibodies attach randomly to more than one nonself erythrocyte surface, they form clumps of erythrocytes.Proteins called antibodies (immunoglobulins), which are produced by certain B lymphocytes called plasma cells, attach to the antigens on the plasma membranes of the infused erythrocytes and cause them to adhere to one another. Following an infusion of incompatible blood, erythrocytes with foreign antigens appear in the bloodstream and trigger an immune response. In this chapter, we will use the more common terms antigens and antibodies.Īntigens are generally large proteins, but may include other classes of organic molecules, including carbohydrates, lipids, and nucleic acids. With RBCs in particular, you may see the antigens referred to as isoantigens or agglutinogens (surface antigens) and the antibodies referred to as isoantibodies or agglutinins.
(Seek more content for additional information on immunity.) Here, we will focus on the role of immunity in blood transfusion reactions. Antigens, Antibodies, and Transfusion ReactionsĪntigens are substances that the body does not recognize as belonging to the “self” and that therefore trigger a defensive response from the leukocytes of the immune system.
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