LAB 16

• Agglutinogen


  A substance on the surface of red blood cells that can cause agglutination when mixed with the corresponding antibody
• Agglutinin


  An antibody that can cause agglutination of red blood cells when mixed with the corresponding antigen
• Blood types in the ABO system


  • Type A
  • Type B
  • Type O
  • Type AB
• Corresponding agglutinogens and agglutinins for ABO blood types

  • Type A: Agglutinogen A, Agglutinin anti-B
  • Type B: Agglutinogen B, Agglutinin anti-A
  • Type O: No agglutinogens, Agglutinins anti-A and anti-B
  • Type AB: Agglutinogens A and B, No agglutinins
• Blood typing procedure


  1. Prepare 10% RBC suspension

  2. Add 1 drop anti-A serum to left half of slide

  3. Add 2 drops cell suspension to each half

  4. Mix and tilt slide

  5. Examine for agglutination within 2 minutes
• Cross matching procedure


  1. Obtain 5cc each of Type A and Type B blood

  2. Centrifuge and separate serum

  3. Place Type A serum on slide

  4. Add 2 drops Type B RBCs

  5. Mix and examine for agglutination
• The primary purpose of the compatibility test is to prevent a transfusion reaction, whether it is hemolytic or less severe
• Another purpose of the compatibility test is to ensure that the patient benefits from the transfusion they are receiving
• The presence of hemolysis at any point in the procedure is evidence of an incompatibility and should never be dismissed as a negative reaction simply because the cells are not clumped
• Compatibility testing thus becomes the final criterion as to the suitability of a particular donor blood for a particular recipient
• Cell grouping


  • Testing unknown red cells with known anti sera
  • Agglutination = cells are group X, No agglutination = cells are not group X
• Serum testing


  • Using known serum against known red cells
  • Agglutination = incompatible, serum contains anti-X
  • No agglutination = compatible, serum does not contain anti-X
• Red cells are agglutinated if they possess a substance which reacts with a corresponding anti-substance present in the serum
• Antigen


  The substance on the surface of red blood cells that can cause agglutination when mixed with the corresponding antibody
• Antibody


  The substance in the serum that can cause agglutination of red blood cells when mixed with the corresponding antigen
• The antigens or agglutinogens determining the four blood groups of the ABO system reside on the surface of the red cells and are the result of the expression of three allelic genes: 0, A, and B, the latter two being dominant to 0
• The reciprocal antibodies or agglutinins are forming the globulin portion of the serum of plasma
• Agglutination


  • The combination of antigen and antibody
  • Stage 1: Actual combination which is instantaneous
  • Stage 2: Visible reaction taking place more slowly
• Agglutination


  Cells are destroyed or distorted, remain clumped
• Rouleaux formation


  Cell shape is preserved, cells are dispersed
• The test between a prospective recipient of a blood transfusion and his proposed donor is known as the CROSS MATCH or COMPATIBILITY TEST
• The cross match is performed to show any possible incompatibility between the recipient's serum and the donor's RBC (major cross match)
• The plasma of the donor is also tested against the red cells of the recipient (minor cross match)