BLOOD TYPING Learning Objectives: • I can define the blood to explain the composition of blood and to describe the function of blood cells. • I will be able to determine if a blood sample found at the scene of a crime matches the blood sample of a possible suspect • I can determine the blood type of blood cells. What is a Blood Type? • Before Nobel Prize awarded Karl Landsteiner discovered the ABO human blood groups in 1901, it was thought that all blood was the same. • This misunderstanding led to fatal blood transfusions. • Later, in 1940, Landsteiner was part of discovering another blood group, the Rh blood group system. • There are many blood group systems known today, but the ABO and the Rh blood groups are the most important ones used for blood transfusions. Blood typing Blood typing is a method to tell what type of blood you have. Blood typing is done so you can safely donate your blood or receive a blood transfusion. It is also done to see if you have a substance called Rh factor on the surface of your red blood cells What is Blood Made of? Blood consists of several types of cells floating around in a fluid called plasma. BLOOD • The red blood cells contain hemoglobin, a protein that binds oxygen. Red blood cells transport oxygen to, and remove carbon dioxide from, the body tissues. • The white blood cells fight infection. They flow through your bloodstream to fight viruses, bacteria, and other foreign invaders that threaten your health. • The platelets help the blood to clot, if you get a wound for example. • The plasma contains salts and various kinds of proteins. Human Blood Types • Landsteiner’s discovery was the existence of three blood types, classified on the basis of the presence of antigens he described as A, B, and O. • In 1902, another research group discovered the existence of a fourth type, called AB, with red blood cells which express both A and B antigens. • Antibodies(immunoglobulin) are proteins found in plasma. They're part of your body's natural defenses. They recognize foreign substances, such as germs, and alert your immune system, which destroys them. • Antigens are protein molecules found on the surface of red blood cells. • An enzyme is a type of protein found within a cell. ABO Blood Group System • Type A blood: A person with RBCs which express A antigen on their surfaces. • Type B blood: A person with RBCs which express B antigen on their surfaces. • Type AB blood: A person with RBCs which express both A and B antigen on their surfaces. • Type O blood: A person with RBCs that express neither A nor B antigen. ABO Blood Types Rh Factor • Each blood type is also grouped by its Rhesus factor, or Rh factor. Blood is either Rh positive (Rh+) or Rh negative (Rh-). About 85% of Americans have Rh+ blood. • Rhesus refers to another type of antigen, or protein, on the surface of red blood cells. The name Rhesus comes from Rhesus monkeys, in which the protein was discovered. ABO Blood Types • Our blood types are determined by heredity. People belong to either of eight different blood types: A Rh+, A Rh-, B Rh+, B Rh-, AB RH+, AB Rh-, 0 Rh+, or 0 Rh- . • The eight blood types have different combinations of certain molecules, antigens, on the surface of the red blood cells. The A and B antigens are sugars and the Rh antigens are proteins. The antigens expressed in the red blood cells determine an individual's blood type. Blood Type A Rh• Antigens (on the surface of the red blood cells): A indicates there are A antigens. (Rh- indicates there are no Rh antigens) • Antibodies (in the blood plasma): B antibodies. Rh antibodies. (If there are A antigens but no B nor Rh antigens, the antibodies in the blood plasma are B and Rh antibodies.) Blood Type A Rh+ • Antigens (on the surface of the red blood cells): A indicates there are A antigens. Rh+ indicates there are Rh antigens. • Antibodies (in the blood plasma): B antibodies. If there are A and Rh antigens but no B antigens, the antibodies in the blood plasma are B antibodies. How to determine your blood type • The blood type notation indicates what antigens there are on the surface of the red blood cells. So, to determine blood type, you need to find out which antigens are present. You can work that out by mixing the patient’s blood with three different reagents containing either of the three antibodies: A, B or Rh. Antibody A Antibody B Antibody Rh STEP 1 -Mix Mix the patient's blood with three different reagents including either of the three different antibodies, A, B or Rh antibodies! Step 2-Agglutination? The agglutination indicates that the blood has reacted with a certain antibody and is therefore not compatible with blood containing that kind of antibody. If the blood does not agglutinate, it indicates that the blood does not have the antigens binding the special antibody in the reagent. Step 3- Determine ABO No agglutination in test tube A, indicates that the patient's red blood cells do not have A antigens. Agglutination in the tube containing B antibodies indicates that the patients' red blood cells have got B antigens, thus belongs to blood group B. Step 4-Rh Group No agglutination indicates that the patient's red blood cells don't have Rh antigens, thus the blood is Rh-. Step 5-Determine Blood Type Now that you know which antigens are in the patient's blood, you can figure out the blood type! Since agglutination only occurred in the test tube containing B antibodies, the blood got B antigens but no A or Rh antigens. Thus the blood type is B Rh- . Blood Transfusions • In a blood transfusion, a patient must receive a blood type that is compatible with his or her own blood type—that is, the donated blood must be accepted by the patient's own blood. If the blood types are not compatible, red blood cells will clump together, making clots that can block blood vessels and cause death. • Type O– blood is considered the “universal donor” because it can be donated to people of any blood type. • Type AB+ blood is considered the “universal recipient” because people with this type can receive any blood type. Blood Transfusion Compatible blood For a blood transfusion to be successful, AB0 and Rh blood groups must be compatible between the donor blood and the patient blood. Therefore you need to know which blood types are “compatible”, that is which other blood types fit a patient with a certain blood type. For example, a person with blood type B Rh- has got A and Rh antibodies and cannot receive a blood transfusion with red blood cells which have A and Rh antigens like A Rh+ or AB Rh+.
