Chapter 18 - Section 18.3 - Blood Types - Before You Go On - Page 689: 13

Antibodies and antigens are key components of the immune system, and they play a crucial role in recognizing and responding to foreign substances in the body. Here's a breakdown of what they are and how they interact to cause a transfusion reaction: 1. **Antigens:** Antigens are molecules or molecular structures that are recognized by the immune system as foreign. They are usually found on the surface of pathogens (such as bacteria, viruses, and fungi) or on the surface of cells from other individuals, like those from a different blood type. Antigens can trigger an immune response when detected by the immune system, leading to the production of antibodies. 2. **Antibodies:** Antibodies, also known as immunoglobulins, are specialized proteins produced by certain immune cells called B cells. These antibodies are designed to recognize and bind to specific antigens. Each antibody is highly specific to a particular antigen, much like a lock and key mechanism. When an antibody binds to its corresponding antigen, it can mark the antigen for destruction by immune cells or neutralize its effects. **Transfusion Reaction:** A transfusion reaction occurs when there is an incompatible match between the antigens on the surface of the donor's blood cells and the antibodies present in the recipient's blood. This situation most commonly arises during blood transfusions when blood from a donor is infused into a recipient's bloodstream. The main concern is with the ABO blood group system and the Rh factor. 1. **ABO Blood Group System:** The ABO blood group system is determined by the presence or absence of specific antigens (A and B antigens) on the surface of red blood cells. Individuals can have blood type A (A antigens), blood type B (B antigens), blood type AB (both A and B antigens), or blood type O (neither A nor B antigens). People also produce naturally occurring antibodies against the ABO antigens they lack. For example, a person with blood type A has anti-B antibodies. 2. **Rh Factor:** The Rh factor, or RhD antigen, is another antigen present on the surface of red blood cells. Individuals are classified as Rh-positive (they have the Rh antigen) or Rh-negative (they lack the Rh antigen). Rh-negative individuals can produce anti-Rh antibodies if exposed to Rh-positive blood. **Transfusion Reaction Process:** If incompatible blood is transfused, a transfusion reaction can occur. For example, if a person with blood type A (who has anti-B antibodies) receives blood type B or AB, the anti-B antibodies in the recipient's bloodstream will recognize the B antigens on the donor's red blood cells as foreign. This recognition triggers an immune response, which can lead to the clumping (agglutination) and destruction of the donor's red blood cells. This process can cause various symptoms ranging from mild discomfort to life-threatening complications, including kidney failure and shock. To prevent transfusion reactions, blood typing and cross-matching are performed before transfusions to ensure compatibility between the donor's blood and the recipient's antibodies.

Antibodies and antigens are key components of the immune system, and they play a crucial role in recognizing and responding to foreign substances in the body. Here's a breakdown of what they are and how they interact to cause a transfusion reaction: 1. **Antigens:** Antigens are molecules or molecular structures that are recognized by the immune system as foreign. They are usually found on the surface of pathogens (such as bacteria, viruses, and fungi) or on the surface of cells from other individuals, like those from a different blood type. Antigens can trigger an immune response when detected by the immune system, leading to the production of antibodies. 2. **Antibodies:** Antibodies, also known as immunoglobulins, are specialized proteins produced by certain immune cells called B cells. These antibodies are designed to recognize and bind to specific antigens. Each antibody is highly specific to a particular antigen, much like a lock and key mechanism. When an antibody binds to its corresponding antigen, it can mark the antigen for destruction by immune cells or neutralize its effects. **Transfusion Reaction:** A transfusion reaction occurs when there is an incompatible match between the antigens on the surface of the donor's blood cells and the antibodies present in the recipient's blood. This situation most commonly arises during blood transfusions when blood from a donor is infused into a recipient's bloodstream. The main concern is with the ABO blood group system and the Rh factor. 1. **ABO Blood Group System:** The ABO blood group system is determined by the presence or absence of specific antigens (A and B antigens) on the surface of red blood cells. Individuals can have blood type A (A antigens), blood type B (B antigens), blood type AB (both A and B antigens), or blood type O (neither A nor B antigens). People also produce naturally occurring antibodies against the ABO antigens they lack. For example, a person with blood type A has anti-B antibodies. 2. **Rh Factor:** The Rh factor, or RhD antigen, is another antigen present on the surface of red blood cells. Individuals are classified as Rh-positive (they have the Rh antigen) or Rh-negative (they lack the Rh antigen). Rh-negative individuals can produce anti-Rh antibodies if exposed to Rh-positive blood. **Transfusion Reaction Process:** If incompatible blood is transfused, a transfusion reaction can occur. For example, if a person with blood type A (who has anti-B antibodies) receives blood type B or AB, the anti-B antibodies in the recipient's bloodstream will recognize the B antigens on the donor's red blood cells as foreign. This recognition triggers an immune response, which can lead to the clumping (agglutination) and destruction of the donor's red blood cells. This process can cause various symptoms ranging from mild discomfort to life-threatening complications, including kidney failure and shock. To prevent transfusion reactions, blood typing and cross-matching are performed before transfusions to ensure compatibility between the donor's blood and the recipient's antibodies.