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Fourth lecture

Fourth lecture. Blood groups. The surface f RBCs contain many antigens called agglutinogens. Two groups of antigens, the ABO & Rh antigens are important clinically. 1-ABO system: There are 4 main blood types, distinguished by their carbohydrate antigens:

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Fourth lecture

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  1. Fourth lecture

  2. Blood groups • The surface f RBCs contain many antigens called agglutinogens. • Two groups of antigens, the ABO & Rh antigens are important clinically. 1-ABO system: There are 4 main blood types, distinguished by their carbohydrate antigens: a- Type A has agglutinogen A on RBCs surface. b- Type B has agglutinogen B on RBCs surface. C- Type AB has both agglutinogens A & B. d- Type O has neither agglutinogen A nor B.

  3. Blood groups • Blood plasma contains antibodies against these agglutinogens called agglutinins. • There are 2 types of agglutinins: Anti A (α) which attacks A agglutinogens. Anti B (β) which attacks B agglutinogens. • The blood of any person does not contain one agglutinogen and its corresponding agglutinin.

  4. Blood groups • Universal donor: • Type O blood can be transfused to all blood groups, because it doesn’t contain any agglutinogen. • So, type O is therefore a universal donor. • Universal recipient: • Persons with type AB blood don’t contain anti A and anti B agglutinins in their plasma. • Persons of this type can receive blood from donors off all types. • So, type AB is therefore a universal recipient.

  5. Blood Types A B AB O B Antigen A & B Antigens Neither A nor B Antigens • Antibodies bind with antigens to cause clumping of blood cells (agglutination) so people with type A blood have circulating antibodies for type B = β. • People with blood type AB have neither αnor β antibodies. • People with blood type O circulate both α and β antibodies. A Antigen

  6. Agglutination Reaction

  7. Rhesus system • Rh system is so named because it was first discovered in the blood of the Rhesus monkey. • Rn system is important on blood transfusion like ABO system. • There are 6 common types of Rh antigens (agglutinogens) C, D, E, c, d, e. • The type D antigen is widely prevalent in the population.

  8. Rhesus system • A person which has the D antigen is said to be Rh positive. • Whereas, a person who does not have the D antigen is said to be Rh negative. • Normally, there is no anti Rh agglutinin in the plasma, but it can be formed in the following conditions:-

  9. A-Blood transfusion • If an Rh –ve person receives Rh +ve blood the body starts to make anti Rh agglutununs that will remain in the blood. • These agglutinins develop slowly and reach maximum after 2-4 months. • If a second transfusion of an Rh +ve is given later, the previously formed anti Rh agglutinins will react with the transfused Rh +ve RBCs & transfusion reaction occur.

  10. B-In pregnancy • If an Rh –ve mother becomes pregnant from an Rh +ve husband, the fetus will most probably be Rh positive like his father. • This stimulates the production of anti Rh agglutinin against the Rh +ve. • The anti Rh agglutinin rises slowly over a period of 2-4 months. • So the 1st baby passes unaffected.

  11. B-In pregnancy • With subsequent pregnancies with Rh +ve babies, the level of the anti Rh agglutinins rises progressively. • Anti Rh agglutinins can pass to the fetal blood causing agglutination of RBCs of the fetus. • At birth the newly born infant shows jaundice and severe anemia, a condition known as hemolytic disease of the newborn. • Administration of anti Rh gamma globulin to the Rh –ve mother immediately after delivery or abortion prevents the production of anti Rh agglutinin by the mother.

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