Blood Group

    • Blood Groups
      • More than 630 distinct antigens are expressed on the surface of RBCs; how- ever, only a few cause significant problems.
      • ABO antigens
        • The A and B codominant genes code for glycoproteins
        • A and B antigens, are added to an H precursor.(MCQ)
        • Patients homozygous for the O gene produce
          • neither the A nor the B antigen
          • produce only the H precursor.
          • Anti-A or anti-B antibodies are produced to the ABO antigen not expressed by the host.
        • When blood products are required emergently, type O RBCs and type AB plasma may be given with the least concern for transfusion reaction .(MCQ)
      • The Rh (Rhesus) antigens
        • large class of more than 50 related antigens, including D, C, c, E, and e.
        • Rh-positive individuals produce the D antigen
        • Rh-negative individuals
          • do not produce the antigen
          • do not produce antibodies to D unless exposed to it through pregnancy or another form of transfusion. (MCQ)
        • Rh antibodies may induce hemolytic reactions.



      • Erythroblastosis Fetalis (Hemolytic Disease of the Newborn)
        • It results from incompatibility between fetal and maternal blood groups, most commonly involving the Rh system (D antigen).
        • Sensitization of the mother is required.
        • Blood from Rh-positive fetus passes into the circulation of Rh-negative mother (>1 mL required). (MCQ)
        • Passage is usually transplacental during labor.
        • This leads to the formation of maternal anti-Rh IgM antibodies, which cannot cross the placenta.
        • The maternal immune response matures and IgG antibodies are formed, which can cross the placenta in subsequent pregnancies. (MCQ)
        • The resulting hemolysis varies in degree but may be detected in amniotic fluid samples.
        • Mild cases show increased fetal red blood cell production sufficient to maintain the fetal circulation.
        • Extramedullary hematopoiesis is seen in the liver and spleen
        • The child is born pale and variably anemic.
        • Hepatosplenomegaly may be present. .(MCQ)
        • Severe cases present with severe anemia and hypoxia leading to fetal organ failure.
        • Fluid moves into the extravascular spaces, resulting in massive, generalized edema (hydrops fetalis). .(MCQ)
        • Unconjugated hyperbilirubinemia (jaundice) develops.
        • Bilirubin also deposits in the brain, primarily in the basal ganglia (ker- nicterus). .(MCQ)
        • Treatment includes exchange transfusion and phototherapy, which oxidizes bilirubin into nontoxic, water-soluble molecules.
        • RhoGAM
        • Rh-negative mothers carrying Rh-positive fetuses are treated prenatally at 28 weeks and shortly after delivery  in <72 hours with anti-D Rhesus immune globulin (RhoGAM). .(MCQ)
        • RhoGAM prevents sensitization by binding to fetal red cells in the maternal circulation, rendering them non-antigenic. .

      Blood Grouping Experiment – Amrita University
      Blood Types
      Paul Andersen explains the importance of blood types in blood transfusions. He starts with a brief discussion of blood antigens and antibodies. He describes how the ABO differs from the Rh blood type. He shows you how to solve simple genetic problems using Punnett squares. He then talks about the percentage distribution of the different types and the problems that may result during pregnancy.
      Blood Types: ABO and Rh (with donuts and sprinkles!)
      All about blood types – ABO and Rh blood groups. Who donates to whom? How are blood types inherited? What are the medical issues involved with transfusions? DON’T memorize that donor / recipient table – watch this video instead!
      What are Blood Types?
      Quick Questions explains why, when it comes right down to it, there are really only eight kinds of people in the world.
      Human Blood Types