3 Rh Blood Group System

• Rh blood group is the second most important human blood group system

  • Antigens are very immunogenic
  • D antigen is the most immunogenic
• Rh blood group is currently composed of 61 different antigens
• Antibodies are immune in nature; it causes significant HDFN and HTR

  • Pregnancy and blood transfusion are ways to be exposed in D antigen
• Rh typing is the test to detect for the presence of D antigen
• In 1939, transfusion practices continued to result to morbidity and mortality despite ABO cross matching
• Levine and Stetson described a Hemolytic Transfusion Reaction in an obstetric patient after being transfused with her husband’s blood after delivering a stillborn infant

  • Postulated that the fetus and the husband has a common factor that the patient lack
• Landsteiner and Wiener reported antibodies from guinea pigs and rabbits after transfusion with Rhesus Monkey RBCs; antibodies were named Rh
• Basis of Fisher-Race is postulated genetic mechanism
• Basis of Wiener & Rosenfield is the presence or absence of a given antigen
• In fisher-race or DCE terminology, antigens were produced by three closely linked alleles

  • D/C (or c) / E (or e) – one set of allelic genes
  • Each gene and corresponding antigens were given the same letter designation
  • Individuals inherit a set of Rh gene from each parent
  • Co-dominantly expressed
• C and E has antithetical meaning within a gene, where there is a two possible product but only one haplotype is produced
• Wiener or Rh-Hr terminology postulated that Rh gene produces an agglutinogen that contain a series of blood factors.
• A) Dce

  B) Rhorh'hr''

  C) Rhohr'rh''

  D) DCE

  
• A) hr'hr''

  B) dCe

  C) hr'rh''

  D) dCE

  
• Rosenfield or Alphanumeric terminology is proposed by Rosenfield and his associates, a system that assigns a number to each Rh antigen

  • Demonstrates the presence or absence of the antigen on RBCs
  • Minus sign designates the absence of the antigen
• Two closely linked genes at chromosome 1 control the expression of Rh antigens:

  • RHD – codes for D
  • RHCE – codes for C/c and E/e
• D status determination is required for donor recipient compatibility testing

  • Rh-positive indicates presence of D or weak D
  • Any Rh-negative result by slide or tube method must be confirmed by weak D testing
• Phases of D testing (Du testing):

  • 37°C incubation
  • Indirect Anti Human Globulin testing
• • Rh-positive RBCs demonstrate strong reaction (+3-+4) with anti-D antisera
  • Individuals with Du Phenotype are considered Rh-positive
• In genetic weak D, there is an inheritance of Rh genes that code for a weakened expression of D antigen → antigen is complete but few in numbers
• C trans effect is a position effect on gene interaction effect

  • D gene in trans position to allele carrying C gene (Example: DCE/Ce)
  • Antigen is normal and complete but steric arrangements of C in relation to D appears to interfere with the expressed of D
• Partial D or D mosaic is when one or more epitopes within the entire antigen is missing or altered

  • Alloantibody against the missing epitope may be produced upon exposure to the complete D antigen
• LW antigen is phenotypically similar to Rh

  • Anti-LW reacts strongly with most D-positive RBCs, weakly with D-negative RBCs and no reactions with Rh null RBCs
• All antibodies that react at 37°C and AHG phase, they are clinically significant meaning they can cause HDFN and HTR
• Rh antibodies are produced after exposure to Rh-positive RBCs through transfusion or pregnancy
• IgG1 and IgG3 anti-D are the most clinically significant Rh antibody; rapidly cleared
• • IgG1 – best placental crosser
  • IgG3 – best complement activator
• Rh antigen do not bind to complement proteins
• RBCs sensitized with anti-D are destroyed through extravascular hemolysis
• Circulating anti-D appears within 20 days post-primary exposure and 2-7 days post-secondary exposure
• Rh-associated hemolytic transfusion reaction results in extravascular hemolysis of IgG-coated RBCs
• Rh-associated hemolytic disease of the newborn are often severe since Rh antigen are well developed in fetal RBC and anti D are primarily IgG
• Rh immune globulin are purified preparation of IgG anti D; it is given during pregnancy and following delivery of a D-positive fetus
• Rh antibodies are the most frequent cause of HDFN/erythroblastosis fetalis
• Saline based anti-D sera is the first typing reagent for D antigen.

  • Low-protein based
  • Can be used to test TBCs coated with IgG
  • Cannot be used for Du testing
• High Protein based anti-D sera is a human plasma containing high titer anti D

  • Potentiators are added to optimize reaction in slide and tube method
  • False+ reaction is likely
  • Reduce incubation and be used for Du testing
• Clinically modified anti-D sera replaces the need for saline (IgM) and anti D reagents

  • S-S bonds are disrupted to span distance between RBCs
  • Few False+ due to low protein medium
• Monoclonal Antibodies anti-D sera are derived from single clones to hybridoma cells

  • Usually a mixture of monoclonal clones to ensure reaction with D+ RBCs
  • Some are mixtures of IgM and IgG to allow maximum visualization of reaction
• A) suspension

  
• A) warm saline