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Blood Typing Around 1900, Karl Landsteiner discovered that there are at least four different kinds of human blood, determined by the presence or absence of specific agglutinogens (antigens) on the surface of red blood cells (erythrocytes). These antigens have been designated as A and B. Antibodies against antigens A or B begin to build up in the blood plasma shortly after birth, the levels peak at about eight to ten years of age, and the antibodies remain, in declining amounts, throughout the rest of a person's of life. The stimulus for antibody production is not clear, however, it has been proposed that antibody production is initiated by minute amounts of A and B antigens that may enter the body through food, bacteria, or other means. Humans normally produce antibodies against those antigens that are not on their erythrocytes: A person with A antigens has anti-B antibodies: a person with B antigens has anti- A antibodies, a person with neither A nor B antigens has both anti-A and anti- antibodies, and a person with both A and B antigens has neither anti-A nor anti-B antibodies (Table 1). Blood type is based on the antigens, not the antibodies, a person possesses.
BLOOD TYPING Student Learning Objectives: Be able to identify A, B, AB or types. Be able to identify Rh+ or Rh- types. Explain the basis of blood typing and matching for blood transfusions. Explain the clinical significance and inheritance of the Rh factor Explain the process of hemagglutination. Blood Typing Around 1900, Karl Landsteiner discovered that there are at least four different kinds of human blood, determined by the presence or absence of specific agglutinogens (antigens) on the surface of red blood cells (erythrocytes). These antigens have been designated as A and B. Antibodies against antigens A or B begin to build up in the blood plasma shortly after birth, the levels peak at about eight to ten years of age, and the antibodies remain, in declining amounts, throughout the rest of a person's of life. The stimulus for antibody production is not clear; however, it has been proposed that antibody production is initiated by minute amounts of A and B antigens that may enter the body through food, bacteria, or other means. Humans normally produce antibodies against those antigens that are not on their erythrocytes: A person with A antigens has anti-B antibodies; a person with B antigens has anti- A antibodies, a person with neither Anor B antigens has both anti-A and anti-B antibodies; and a person with both A and B antigens has neither anti-A nor anti-B antibodies (Table 1). Blood type is based on the antigens, not the antibodies, a person possesses. The four blood groups are types A, B, AB, and O. Blood type 0, characterized by the absence of A and B agglutinogens, is the most common in the United States and is found in 45% of the population. Type A is next in frequency, and is found in 39% of the population. The frequencies at which types B and AB occur are 12% and 4% respectively,
Table 1. ABO System Blood Type Antigens on Erythrocytes (Agglutinogens A A B B AB A and B None 0 Process of Agglutination There is a simple test performed with antisera containing high levels of anti-A and anti-B agglutinins to determine blood type. Several drops of each kind of antiserum are added to separate samples of blood. If agglutination (clumping) occurs only in the suspension to which the anti-A serum was added, the blood type is A. If agglutination occurs only in the anti-B mixture, the blood type is B. Agglutination in both samples indicates that the blood type is AB. The absence of agglutination in any sample indicates that the blood type is O. Table 2. Agglutination Reaction of ABO Blood-Typing with Antisera Anti-A Serum Anti-B Serum Agglutination No Agglutination No Agglutination Agglutination Agglutination Agglutination No Agglutination No Agglutination
Importance of Blood Typing People can receive transfusions of only certain blood types, depending on the type of blood they have. If incompatible blood types are mixed, erythrocyte destruction, agglutination and other problems can occur. For instance, if a person with type B blood is transfused with blood type A, the recipient's anti- A antibodies will attack the incoming type A erythrocytes. The type A erythrocytes will be agglutinated, and hemoglobin will be released into the plasma. In addition, incoming anti-B antibodies of the type A blood may also attack the type B erythrocytes of the recipient, with similar results. This problem may not be serious, unless a large amount of blood is transfused. The ABO blood groups and other inherited antigen characteristics of red blood cells are often used in medico-legal situations involving identification of disputed paternity. A comparison of the blood groups of mother, child, and alleged father may exclude the man as a possible parent. Blood typing cannot prove that an individual is the father of a child; it merely indicates whether or not he possibly could be. For example, a child with a blood type of AB, whose mother is type A, could not have a man whose blood type is O as a father. We will discuss the genetics of blood typing in our "Meiosis - Genetics" lab. DID YOU KNOW? Donor blood contains only packed red blood cells. There is no plasma in donor blood, thus there are no antibodies present. Rh System: In the period between 1900 and 1940, a great deal of research was done to discover the presence of other antigens in human red blood cells. In 1940, Landsteiner and Wiener reported that rabbit sera containing antibodies for the red blood cells of the Rhesus monkey would agglutinate the red blood cells of 5% of Caucasians. These antigens, six in all, were designated as the Rh (Rhesus) factor, and they were given the letters C, D, D, E, and e by Fischer and Race. Of these six antigens, the D factor is found in 85% of Caucasians, 94% of African Americans, and 99% of Asians. An individual who possesses these antigens is designated Rht: an individual who lacks them is designated Rh- The anti-Rh antibodies of the system are not normally present in the plasma, but anti-Rh antibodies can be produced upon exposure and sensitization to Rh antigens. Sensitization can occur when Rh+ blood is transfused into an Rh- recipient, or when an Rh- mother carries a fetus who is Rh+. In the latter case, some of the fetal Rh antigens may enter the mother's circulation and sensitize ber so that she begins to produce anti-Rh antibodies against the fetal antigens. In most cases, sensitization to the Rh antigens takes place toward the end of pregnancy, but because it takes some time to build up the anti-Rh antibodies, the first Rh+child carried by a previously unsensitized mother is usually unaffected. However, if an Rh- mother, or a mother previously sensitized by a blood transfusion or a previous Rh+ pregnancy, carries an Rh+ fetus, maternal anti-Rh antibodies may enter the fetus circulation, causing the agglutination and hemolysis of fetal erythrocytes and resulting in a condition known as erythroblastosis fetalis (hemolytic disease of the newborn). To treat an infant in a severe case, the infant's Rh+ blood is removed and replaced with Rh- blood from an unsensitized donor to reduce the level of anti-Rh antibodies. A person with Rh- blood will make antibodies to donated Rh+ blood causing agglutination. They must therefore receive blood from Rh- donors. However, they can donate to Rh- or Rh people.
8. Blood type O is considered to be the universal donor type. However, if type O blood is transfused into a person with blood type B, which of the following is important to remember? a. Use the entire pint of type O blood for the transfusion b. Separate the type o blood into packed cells and plasma, and use only the packed cells for the transfusion c. Separate the type o blood into packed cells and plasma, and use only the plasma for the transfusion. 9. Explain Hemolytic disease of the newborn and the rationale for treatment.
10. An investigation at a crime scene discovers some body fluid on the victim's clothing. The investigator carefully takes a sample and sends it to the crime lab for analysis. On the basis of the analysis of antibodies, could the crime lab determine whether the sample is blood plasma or semen? Explain 11. Complete the following table. Rand Antigens on RBC surface (AgAntibodies irCan Receive BI Type A+ Anti B B+ B Rh 0+ 0-BB- B AB+ None AB Rh 0+ 0