Blood groups.pdf

Blood grouping & cross matching Enas Sabah MSc. Medical Physiology Antigenicity Causes Immune Reactions of Blood • When blood transfusions from one person to another were first attempted, immediate or delayed agglutination and hemolysis of the red blood cells often occurred, resulting in typical t...

Blood grouping & cross matching Enas Sabah MSc. Medical Physiology Antigenicity Causes Immune Reactions of Blood • When blood transfusions from one person to another were first attempted, immediate or delayed agglutination and hemolysis of the red blood cells often occurred, resulting in typical transfusion reactions that frequently led to death. O-A-B Blood Types • Two genes, one on each of two paired chromosomes, determine the O-A-B blood type. • These genes can be one of three types : type O, type A, or type B. • The type O gene is almost functionless, so it causes no significant type O agglutinogen on the cells. • Conversely, the type A and type B genes do cause strong agglutinogens on the cells. • The six possible combinations of genes, are OO, OA, OB, AA, BB, and AB. These combinations of genes are known as the genotypes, and each person is one of the six genotypes. A and B Antigens—Agglutinogens • Two antigens—type A and type B—occur on the surfaces of the red blood cells in a large proportion of human beings. It is these antigens (also called agglutinogens because they often cause blood cell agglutination) that cause most blood transfusion reactions. • Antigen is a molecule capable of stimulating an immune response. They may be proteins, polysaccharides or lipids. Each antigen has distinct surface features that are recognized by the immune system. • Antibody is a Y-shaped protein produced by immune system in response to exposure to antigens. • The tip of each Y-shaped arm contains antigen binding sites that bind to a specific portion of the antigen’s surface • This binding helps to eliminate antigens from the body Agglutinins • When type A agglutinogen is not present in a person’s red blood cells, antibodies known as anti-A agglutinins develop in the plasma. • Also, when type B agglutinogen is not present in the red blood cells, antibodies known as anti-B agglutinins develop in the plasma. • they are produced by bone marrow and lymph gland cells. Agglutination Process in Transfusion Reactions • Occur when the recipient’s serum contains antibodies directed against antigens found on donor’s RBCs, the red cells agglutinate as a result of the agglutinins’ attaching themselves to the red blood cells. • This causes the cells to clump, which is the process of “agglutination.” • Then these clumps plug small blood vessels throughout the circulatory system. • During hours to days, either physical distortion of the cells or attack by phagocytic WBCs destroys the membranes of the agglutinated cells, releasing hemoglobin into the plasma, which is called“hemolysis” of theRBCs. Acute Hemolysis Occurs in Some Transfusion Reactions • In this case, the antibodies cause lysis of the red blood cells by activating the complement system, which releases proteolytic enzymes that rupture the cell membranes. • Immediate intravascular hemolysis is less common than agglutination. Acute Kidney Shutdown After Transfusion Reactions • result from three causes: • 1. the antigen-antibody reaction releases toxic substances from the hemolyzing blood that cause powerful renal vasoconstriction. • 2. loss of circulating RBCs in the recipient, along with production of toxic substances, causes circulatory shock. The arterial blood pressure falls very low, and renal blood flow. • 3. hemoglobin precipitates and blocks many of the kidney tubules. Blood Typing •According to the ABO system the blood groups are as follow: Rh Blood Types • There are 6 common types of Rh antigens, each of which is called an Rh factor. • These types are designated C, D, E, c, d, & e. • The type D antigen is widely prevalent in the population and considerably more antigenic than the other Rh antigens. • Anyone who has this type of antigen is said to be Rh positive, whereas a person who does not have type D antigen is said to be Rh negative. • According to the Rh system groups are as follows: Erythroblastosis Fetalis (“Hemolytic Disease of the Newborn”) • It is a disease of the fetus and newborn child characterized by agglutination and phagocytosis of the fetus’s red blood cells. • An Rh-negative mother having her first Rh-positive child usually does not develop sufficient anti-Rh agglutinins to cause any harm. • After anti-Rh antibodies have formed in the mother, they diffuse slowly through the placental membrane into the fetus’s blood. There they cause agglutination of the fetus’s blood. Procedure 1. With pencil, divide the slide in to three compartments and label them as A, B and D respectively. 2. Add a drop from each type of anti-sera (anti A, anti B and anti D) 3. Put a drop of blood on each compartment of the slide. 4. Mix the blood and the anti-serum in each compartment well using the wooden sticks. Then rock the slide for few minutes. 5. Then check whether agglutination has occurred or not. • The result of the test will be as follows: Homework • Write 2-4 pages (hand writing) about: Antibody-Structure, Classes and Functions. • Please try to finish your homework before next week’s Lab. • Don’t take picture or upload, just bring it to the Lab.