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Rh Blood Group System


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Rh Blood Group System

  2. 3. Rhesus blood group system <ul><li>The Rh blood group system is one of the most polymorphic and immunogenic systems known in humans. </li></ul><ul><li>It is the most complex system, with over 45 antigens. </li></ul><ul><li>Discovered in 1940 after work on Rhesus monkeys. </li></ul><ul><li>RH gene located on short arm of chromosome 1. </li></ul>
  3. 4. Rhesus blood group system <ul><li>First demonstrated by testing human blood with rabit anti sera against red cells of Rhesus monkey & classifying Rh negative & Rh positive. </li></ul><ul><li>The genotype is determined by the inheritance of 3 pairs of closely linked allelic genes situated in tanderm on chromosome 9. </li></ul>
  4. 5. <ul><li>1939 Levine and Stetson defined D antigen (Rh factor) </li></ul><ul><li>1940 Landsteiner and Weiner discovered anti-Rh (named after Rh esus monkey) </li></ul><ul><li>Agglutinated 85% human RBCs </li></ul><ul><ul><li>15% RBCs did not agglutinate </li></ul></ul><ul><li>The antibody was similar to guinea pig and rabbit antibodies produced when stimulated with rhesus monkey RBCs </li></ul><ul><li>Although they were later shown to be different, the name remained </li></ul>
  5. 6. <ul><li>Land Steiner and Wiener reported on an antibody by guinea pigs and rabbits when they were transfused with rhesus monkey red cells. </li></ul><ul><li>This antibody which agglutinated 85% of human red cells was named Rh.+ </li></ul><ul><li>The name Rh was retained for the human produced antibody </li></ul><ul><li>Anti-rhesus formed by the animals was renamed anti-LW (Landsteiner and Wiener). </li></ul>
  6. 7. Rh Antigens <ul><li>Rh antigens are highly immunogenic , the D antigen is most potent </li></ul><ul><li>D  c  E  C  e </li></ul><ul><li>Highly Rarely </li></ul><ul><li>Immunogenic </li></ul><ul><li>Exposure to less than 1 ml of Rh positive red cells can stimulate Ab production in an Rh negative person. </li></ul>
  7. 8. Rh Genetics <ul><li>2 closely linked genes control the expression of ALL Rh antigens (codominant alleles) </li></ul><ul><ul><li>RHD gene - determines the expression of the D antigen </li></ul></ul><ul><ul><li>RHCE gene - determines the expression of the C, c, E, and e antigens </li></ul></ul>
  8. 9. RHD gene RHCE gene Chromosome 1 Proteins
  9. 10. Rh Nomenclature <ul><li>There are several different systems of nomenclature that theorize the inheritance of the Rh system </li></ul><ul><ul><li>Fisher-Race </li></ul></ul><ul><ul><li>Wiener </li></ul></ul><ul><ul><li>Rosenfield </li></ul></ul>
  10. 11. Fisher-Race Nomenclature <ul><li>CDE terminology </li></ul><ul><li>Most commonly used (i.e. WHO) </li></ul><ul><li>Developed by Ronald Fisher and Robert Race of England </li></ul><ul><li>They theorized that the Rh antigens are controlled by a complex of 3 sets of genes with closely linked loci (i.e. Dce gene complex codes for D, c, e antigens) </li></ul>
  11. 12. Fisher-Race D d C c E e 3 closely linked genes “ d” antigen not produced Produces D antigen Produces C/c antigen Produces E/e antigen
  12. 13. Fisher-Race <ul><li>There are 8 gene complexes at the Rh locus </li></ul><ul><li>Fisher-Race uses DCE as the order </li></ul><ul><li>Others alphabetize the genes as CDE </li></ul>dce DCE dcE Dce dCE DcE dCe DCe
  13. 14. Wiener Nomenclature <ul><li>Rh-Hr terminology </li></ul><ul><li>Rarely used, but good for describing phenotype </li></ul><ul><li>A single gene at the Rh locus leads to the expression of the Rh antigens </li></ul><ul><li>Each parent contributes 1 Rh gene </li></ul><ul><li>8 alleles exist at each gene locus </li></ul><ul><li>Each gene controls production of an agglutinogen composed of three factors (antigens) </li></ul>
  14. 15. Wiener Theory Single gene at Rh locus rh’ hr’ Rh 0 rh” hr” Rh 0 D rh’ C rh” E hr’ c hr” e 5 Major Rh Factors/Antigens: (longhand version) Produces D antigen on RBC Produces C antigen on RBC
  15. 16. Rosenfield Nomenclature <ul><li>Antigens are designated by number </li></ul><ul><ul><li>Rh1:D </li></ul></ul><ul><ul><li>Rh2:C </li></ul></ul><ul><ul><li>Rh3:E </li></ul></ul><ul><ul><li>Rh4:c </li></ul></ul><ul><ul><li>Rh5:e </li></ul></ul><ul><ul><li>Example </li></ul></ul><ul><ul><ul><li>D+, C+, E-, c+, e+ is written as Rh:1,2,-3,4,5 </li></ul></ul></ul>
  16. 17. Genotype vs. Phenotype <ul><li>The phenotype is the result of the reaction between the red cells and antisera </li></ul><ul><li>The genotype is the genetic makeup and can be predicted using the phenotype and by considering the race of an individual. </li></ul>
  17. 18. Positive R 2 R 2 cDE/cDE R Positive R 2 r cDE/cde Positive R 1 r CDe/cde Positive R 1 R 2 CDe/cDE Positive R 1 R 1 CDe/CDe Negative rr cde/cde Rh(D) status Symbol Genotype
  18. 19. CcDe R 1 r Cce rr’ CDE R Z R Z cEe rr’’ CdE R 2 R 2 cDe R 0 R 0 cDEe R 2 r ce rr CDe R 1 R 1 CcDEe R 1 R 2 CDE Rh Phenotype
  19. 20. Why is an Rh incompatibility so dangerous when ABO incompatibility is not during pregnancy? <ul><li>Most anti-A or anti-B antibodies are of the IgM class (large molecules) and these do not cross the placenta. </li></ul><ul><li>In fact, an Rh− / type O mother carrying an Rh+ / type A, B, or AB foetus is resistant to sensitisation to the Rh antigen. </li></ul><ul><li>Her anti-A and anti-B antibodies destroy any foetal cells that enter her blood before they can elicit anti-Rh antibodies in her. </li></ul>
  20. 21. <ul><li>This phenomenon has led to an effective preventive measure to avoid Rh sensitisation. </li></ul><ul><li>Shortly after each birth of an Rh + baby, the mother is given an injection of anti-Rh antibodies (or Rhogam). </li></ul><ul><li>These passively acquired antibodies destroy any foetal cells that got into her circulation before they can elicit an active immune response in her. </li></ul>Rh incompatibility during pregnancy (cont.)
  21. 22. D TESTING: <ul><li>Protocol </li></ul><ul><ul><li>Add Anti-D to “D” tube; Rh control to “C” tube </li></ul></ul><ul><ul><li>Spin, read and record </li></ul></ul><ul><ul><ul><li>If “D” is positive, cells are Rh positive </li></ul></ul></ul><ul><ul><ul><li>If “D” is negative, continue testing </li></ul></ul></ul><ul><ul><li>Add 22% albumin and incubate for 20” at 37 o C </li></ul></ul><ul><ul><li>Spin, read, and record </li></ul></ul><ul><ul><li>Wash 3 X in saline </li></ul></ul><ul><ul><li>Add AHG, spin, read, and record </li></ul></ul><ul><ul><li>If “D” is positive after heat/albumin or AHG  cells are weak D positive; if negative, cells are Rh negative; “C” should always be negative </li></ul></ul><ul><ul><li>Add check cells to neg. tubes; spin, read & record </li></ul></ul>
  22. 23. Importance of the Rh system <ul><li>After the A and B antigens, the D antigen is the most important red cell antigen in blood banking </li></ul><ul><li>The D antibody can cause transfusion reactions and hemolytic disease of the newborn (HDN)/Erythroblastosis fetalis </li></ul>
  23. 24. <ul><li>A person with Rh- blood can develop Rh antibodies in the blood plasma if he or she receives blood from a person with Rh+ blood, whose Rh antigens can trigger the production of Rh antibodies. </li></ul><ul><li>A person with Rh+ blood can receive blood from a person with Rh- blood without any problems. </li></ul>                                                                            
  24. 25. THANK YOU