L3.5: Blood Group and Transfusions

• BLOOD GROUP AND TRANSFUSIONS

  ● Large losses of blood have serious consequences

  ○ Loss of 15-30% causes pallor and weakness

  ○ Loss of over 30% causes severe shock, which can be fatal

  ● Blood transfusions are given for substantial blood loss to treat severe anemia or for thrombocytopenia

  ● The most vigorous transfusion reactions are caused by ABO and Rh blood group antigens
• BLOOD GROUP AND TRANSFUSIONS

  ● ANTIGENS

  ○ Genetically determined proteins present in the blood

  ○ Substances that the body recognizes as foreign and that the immune system may attack

  ○ Most antigens are foreign proteins

  ○ We tolerate our own self-antigens

  ○ There are over 30 common RBC antigens
• BLOOD GROUP AND TRANSFUSIONS

  ● ANTIBODIES

  ○ The “recognizers” that bind foreign antigens

  ○ Blood is typed by causing antibodies that will cause blood with certain proteins to clump (agglutination) and lyse
• BLOOD GROUP AND TRANSFUSIONS

  ● TRANSFUSION REACTIONS

  ○ Lysed RBCs release hemoglobin into the bloodstream

  ○ Freed hemoglobin may block kidney tubules, causing kidney failure and death

  ○ Fever, chills, nausea, and vomiting can also occur
• ABO BLOOD GROUP

  ● Based on the presence of 2 antigens: Type A and B

  ○ Type AB — presence of both A and B

  ○ Type A — presence of A

  ○ Type B — presence of B

  ○ Type O — absence of both A and B
• Rh BLOOD GROUP

  ● Named for 1 of the 8 antigens (agglutinogen D) identified in Rhesus monkeys

  ● If your blood type is negative, your blood cells lack Rh protein

  ● Most Americans are Rh+, carrying the Rh antigen

  ○ Anti-Rh antibodies are not automatically formed by the blood of Rh- individuals (unlike the antibodies of the ABO system)
• Rh BLOOD GROUP

  ● If an Rh- person receives Rh+

  ○ The immune system becomes sensitized and begins producing antibodies. Hemolysis does not occur because it takes time to produce antibodies

  ○ Then, transfusions involve antibodies attacking the donor’s Rh+ RBCs, and hemolysis occurs
• Rh BLOOD GROUP

  ● Rh-related problem during pregnancy

  ○ Danger occurs only when the mother is Rh- and the father is Rh+, and the child inherits the Rh+ factor

  ○ RhoGAM shot can prevent buildup of anti-Rh+ antibodies in mother’s blood
• Rh BLOOD GROUP

  ● The mismatch of an Rh- mother carrying an Rh+ baby can cause problems for the unborn child

  ○ The 1st pregnancy usually proceeds without problems; the immune system is sensitized after the 1st pregnancy

  ○ In the 2nd pregnancy, the mother’s immune system produces antibodies to attack the Rh+ blood (hemolytic disease of the newborn)
• BLOOD TYPING

  ● Blood samples are mixed with anti-A and anti-B serum

  ● Agglutination or the lack of agglutination leads to the identification of blood type

  ● Typing for ABO and Rh factors is done in the same manner ○ CROSS MATCHING — testing for agglutination of donor RBCs by the recipient’s serum and vice versa
• HOW TO KNOW YOUR BLOOD TYPE?

  • Agglutination with Anti-A serum - Type A
  • Agglutination with Anti-B serum - Type B
  • No Agglutination with both sera - Type O
  • Agglutination with Anti-D serum - Positive
  • No Agglutination with Anti-D serum - Negative
• 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