Blood Groups PDF

BLOOD GROUPS Objectives To Know background of blood group Understand ABO system and its importance Identify RH factor and know its significance Perform blood grouping in the end of this section  BACKGROUND Hundreds of diffe...

BLOOD GROUPS Objectives To Know background of blood group Understand ABO system and its importance Identify RH factor and know its significance Perform blood grouping in the end of this section  BACKGROUND Hundreds of different antigens have been found on the surfaces of human red blood cells. Most of these antigens are weak and are mainly of importance in genetic studies. However, two particular groups of antigens are more likely than others to cause blood transfusion reactions. They are the O-A-B system of antigens and the Rh system.  ABO SYSTEM ABO system The cell membrane of RBC’s contains 2 related antigens – type A and type B (also called agglutinogens) in a large proportion of the population. According to the presence or absence of these 2 agglutinogens, the A and B agglutinogens, the human blood is normally classified into 4 major O-A- B blood groups:  41% 9% 3% 47% Blood group A Blood group B If you belong to the blood group A, you If you belong to the blood group B, you have A antigens on the surface of your have B antigens on the surface of your RBCs and B antibodies in your blood RBCs and A antibodies in your blood plasma. plasma. Blood group AB Blood group O If you belong to the blood group AB, you If you belong to the blood group O (null), you have both A and B antigens on the surface of have neither A or B antigens on the surface of your RBCs and no A or B antibodies at all in your RBCs but you have both A and B your blood plasma. antibodies in your blood plasma. The plasma contains -globulins called agglutinins which are antibodies to the red cell agglutinogens. These agglutinins belong mostly to the IgM and are also of 2 types: anti-A (or alpha) agglutinins and anti-B (or beta) agglutinins.  Importance of ABO system 1. Blood transfusion 2. Disputed parenthood 3. Medicolegal importance 4. Susceptibility to certain diseases THE RH(D) SYSTEM  The Rh factor is an agglutinogen, which was discovered in Rhesus monkeys. There are six common types of Rh antigens named C, D, E, c, d, and e. The type D-antigen is considerably the most antigenic than the others. Therefore, any one who has the type D-antigen is said to be Rh positive, whereas those who don’t have type D-antigen are said to be Rh negative Approximately 85% of all white races are RH positive and 15% are RH negative. In american blacks, the percentage of RH positive 95% whereas in african blacks it is about 100%. There are no anti –RH antibodies (anti-d) in normal plasma of both RH +ve blood or RH –ve blood. Rh +ve person never forms anti-d whether he receives RH +ve blood or RH –ve blood. Rh antibodies can be formed if RH +ve blood is transfused into RH –ve person. If that RH –ve person receives RH +ve blood again, agglutination and haemolysis of the infused red cells results. 1- Blood transfusion When an Rh –ve person is injected with Rh +ve red blood cells, he will produce agglutinins against Rh factor. The maximum concentration of agglutinins occurs 2-4 months later. If after sometime, this person is transfused with Rh +ve blood, agglutination occurs. 2- Hemolytic disease of the newborn (erythroblastosis foetalis) The erythroblastosis foetalis is manifested by: 1. Anemia. 2. Severe jaundice. 3. Many immature RBC’s (erythroblasts) in the foetal blood. 4. Kernicterus: it is a neurologic disease develops due to deposition of excess bilirubin in some brain centers (mainly motor areas) causing their damage.  Treatment by exchange blood transfusion. Prevention by single dose of anti Rh antibodies in the form of Rh immunoglobulins (RhoGam) within 72 hours after labour. Such passive immunization prevents active antibody formation by the mother. This has to be done with every pregnancy. DETERMINATION OF BLOOD GROUP  Mix one drop of blood with 1ml of isotonic saline in test tube. Put two separate drops of the diluted blood on a glass slide. Add one drop of anti-A serum (blue coloured) to one blood drop and one drop of anti B serum (yellow coloured) to the other blood drop. Mix the blood with anti-A and anti-B sera gently using the blunt end of two separate pins. After 2 min, examine for agglutination  Determination of Rh group: Put 2 drops of diluted blood on a glass slide. Add one drop of anti – D serum to the blood and mix gently with the blunt end of a pin. Examine for agglutination after 3min. agglutination occurs, the blood group is Rh +ve. If not, the blood group is Rh -ve. Thank you