Blood Groups Lecture Notes PDF

Blood groups By Dr. Haitham Sewilam O-A-B blood group: The cell membrane of RBCs contain antigens called agglutinogen which has two types: *A agglutinogen *B agglutinogen The plasma contains γ – globulins (antibodies) called agglutinins belong to IgM which has two types: *...

Blood groups By Dr. Haitham Sewilam O-A-B blood group: The cell membrane of RBCs contain antigens called agglutinogen which has two types: *A agglutinogen *B agglutinogen The plasma contains γ – globulins (antibodies) called agglutinins belong to IgM which has two types: * anti A (alpha) * anti B (beta) * According to the presence or absence of the two agglutinogens (A& B) the human blood is classified into 4 groups: Only A agglutinogen & Anti – B antibodies → A blood group (41%) Only B agglutinogen & Anti – A antibodies → B blood group (9%) Both A & B agglutinogen & neither Anti – A nor Anti – B antibodies →A B blood group (3%) Neither A, B agglutinogen & have both Anti – A, B antibodies → O blood group (47%) Importance of ABO system: 1) Blood transfusion: * blood grouping & cross matching test should be done first before blood transfusion. * if the transfused blood is incompatible, the donor's RBCs will be destroyed by the recipient's antibodies. * Group O is the universal donor (no antigens on the RBCs). * Group AB is the universal recipient (no antibodies in plasma). 2) Disputed paternity: It is a good -ve test that excludes paternity rather than prove it. 3) Medico legal use: To prove or disprove the claim of the victim. Rh – factor: The person having type D-antigen on RBCs → Rh +ve (85% of white people) The person that don't have D-antigen on RBCs → Rh – ve (15% of white people) There's no anti-Rh antibodies (Anti – D) in normal plasma whether has antigen or not. Anti-D forms only when anigen-D transfer to person don't have this antigen. Rh +ve person never form anti-D. Importance of Rh-factor: 1- In blood transfusion: * When Rh -ve person, receives Rh + blood, he will develop agglutinins against Rh-factor, their maximum concentration reached 2 – 4 months * If this person receives Rh + ve blood again agglutination & hemolysis occur. 2- Hemolytic disease of the new born (erythroblastosis foetalis): * Rh-ve mother & Rh +ve father→ Rh +ve fetus * In first pregnancy → production of Anti-D antibody (Ig G) which can transfer through placenta not like IgM which can't, but this disease can occur in the 1st pregnancy, if the mother already had transferred Rh +ve blood one day before pregnancy, so already forms Anti-D antibody, so the 1st baby mostly not affected but not never. * In the 2nd pregnancy, the mothers anti- D agglutinins pass through the placenta to the fetus → agglutination & hemolysis of its RBCs. * If hemolysis is severe the fetus may die in the uterus, but if not severe the fetus is born with erythroblastosis fetalis (anaemia, jaundice, kernicterus). Treatment of erythroblastosis fetalis: Replacement of the neonates blood by Rh -ve blood→ 400 ml of RH -ve blood is infused in the same time fetal own blood is removed. This procedure is repeated many times during first few weeks, till anti-Rh agglutinins disappear from the circulation. Prevention of erythroblastosis fetalis: * By administration of anti- Rh antibodies (Rh immune – globulins) to the Rh-ve mother delivered Rh +ve infant within 72 hours after delivery or abortion. * Passive immunization → prevent active antibody production by the mother. * Repeated with every pregnancy Indications of blood transfusion: 1) To restore the whole blood as in hemorrhage. 2) To restore one element of the blood. * RBCs in severe anemia * WBCs in severe Leukopenia * Platelets in severe thrombocytopenia * Clotting factors in severe hemophilia. 3) Erythroblastosis foetalis. Precautions before blood transfusion: 1- The transfused blood should be compatible with recipients blood as regards ABO system & Rh system. 2- HB content of transfused shouldn't be less than 90%. 3- The transfused blood should be free from diseases 4- The transfused blood should be fresh not frozen (stored not more than 21 days). 5- Direct cross matching should be done before transfusion Dangers of blood transfusion: 1- Allergic reactions → leukocytes & platelets. 2- Transmission of diseases e.g. AIDS & viral hepatitis. 3- Dangers of massive transfusion: heart failure, Hypothermia. 4- Incompatibility of blood groups: a- Blockage of blood capillaries by clumped RBCs → backache, joint pain, anginal pain. b- Intravascular hemolysis: Circulatory shock, Jaundice, Acute renal failure.