BLOOD GROUPS & Blood types

Objectives: 1. List the various types of blood groups. 2. Understand that the RBC surface antigens A or B, or their absence is responsible for determining the blood groups as A, B AB or O, and that these are genetically determined.. 3. Understand that the plasma contains antibodies of the same name 4. Explain why a person having a particular blood group (for example group A) can not have antibody of the same type in the plasma. 5. Compare the distribution of blood groups in the Omani population with some other populations 6. Describe the importance of the Rhesus blood group, and understand that humans are also classified as Rh+ve or Rh –ve, and that about 95% of Omanis are Rh +ve. 7. Define the term Rh incompatibility and understand that fetal RBC get hemolysed in this condition. 8. Define the term “Mismatched transfusion”. 9. Explain the terms blood grouping and cross matching 10. Define the term “transfusion hazards”.

antigens on RBC blood group antibody in plasma A Type A B B Type B A A & B Type AB nil O (nil) Type O AB

Genetic determination of blood groups Antigens are genetically determined Each gene carries 1.either NO antigen (O) 2.Antigen A 3.Antigen B Paired genes (one from each parent when they meet will have i. No antigen + antigen A : Genotype (OA): Blood group A ii. No antigen + antigen B Genotype (OB) Blood group B iii. No antigen + No antigen Genotype (OO) Blood group O iv. Antigen A + antigen B Genotype (AB) Blood group AB v. Antigen A + antigen A Genotype (AA) Blood group A vi. Antigen B + antigen B Genotype (BB) Blood group B

1.Antibodies: not present at birth. 2. Develop when small amts of antigens A & B enter body as food, in bacteria etc 3.Host develops antibodies to these. 4. Chemically these are Ig G and Ig M imunoglobulins

% distribution of Blood groups in Omani & other populations A B AB O Rh+ve OMANI White Americans Indian

Blood transfusion 1. Typing: blood groups of donor and recipient Type A cannot be given to B and vice versa Type O is “universal donor”: no antigen on RBC so no reaction Type AB : universal recipient: no antibodies blood

Type A group ( recipient) Antigen A & antibody B Type B group (donor) Antigen B & antibody A + antibody B of recipient will react with antigen B of donor (agglutination) and cause hemolyis of donor cells but Anti A of donor get too diluted to affect A type cells of Recipient. So recipient cells not affected significantly Clinical presentation of mismatched transfusion: 1.Donor RBCs affected 2.Immediate hemolysis : chills rigors, acute renal failure; shock 3.Delayed hemolysis: jaundice as macrophages digest the agglutinated RBCs

To avoid this mismatch: Blood grouping and typing is done 1. Drop of recipient blood and donor blood separately mixed with a drop of anti A and anti B 2. Observe for agglutination and confirm group type Then select donor type. Suppose A is selected as donor for recipient who is type A: Cross matching is to be done Donor RBCs + recipient’s serum to ensure that some other antibodies are not present in recipient blood

Blood Grouping and typing

Rh blood group (from Rhesus monkey) Those with antigen on RBC: Rh+ve 90-95% population is Rh +ve No anti Rh antibodies in plasma Those WITHOUT this antigen: Rh –ve. No antibodies in plasma (no spontaneous development of anti Rh) Rh -ve given Rh +ve blood: antibodies develop Next transfusion of Rh +ve to the same person: anti-bodies destroy RBCs

Hemolytic disease of the new born Mother Rh –ve + Father Rh +ve Fetus Rh +ve Some mixing of mother and fetal blood at delivery Mother develops anti-body to Rh antigen of fetus Next pregnanacy: antibody from mother passes palental barrier and affects RBC of fetus Hemolytic disease of the new born. Varied severity from mild hemolysis to death

Uncommon blood groups M, N, Duffy Bombay Blood Useful for genetic testing in Forensic Medicine Usually titre too low to cause any problems

Summary Types of blood groups Source of antigens and antibodies Blood groups of Omani population vis-à-vis others Blood grouping qnd crossmatching Effects of mismatched transfusions Rh blood group and hemolytic disease of the new born