Rh blood groups

  1. Fisher Race nomenclature
    • follows order of loci genes DCE
    • DCE genes are inherited and linked
    • each gene produces Ag
    • absence of D = d
    • little c and little e means gene are present present
  2. weiner nomenclature
    • 1 RHo gene codes for agglutinogen which encodes for Rh antigens
    • Rh',rh"
  3. weiner and fisher race conversion
    • R = D
    • 1 = C
    • 2 = E

    • r = d
    • ' = C
    • " = E
    • Rz = DCE
    • ry = dCE
  4. ISBT (international society of blood transfusion)
    • 6 digit number for each Ag specificity
    • first 3 indicate 004 = Rh
    • last 3 indicate Ag specifity = 004001 = D
  5. follow the ISBT numerical code
    Image Upload 1
  6. genotype frequencies
    • Ro = Dce = blacks
    • R1 = DCe = whites
    • R2 = DcE = 14% white, 9% black
    • r = dce =38% white, 25% black
  7. why Molecular testing for phenotyping and genotyping is becoming more popular
    • cannot use anti sera on recently transfused individuals
    • anti sera not available for some antigens
    • fetal genotyping for D can be done on fetal DNA present in maternal plasma
  8. Rh antigens
    • nonglycosylated proteins
    • transmembrane proteins with loops exposed to surface of RBC
    • transport CO2 or ammonia
    • across plasma membrane
    • integral part of RBC membrane
    • Rh null people have mild hemolytic anemia
  9. typing for phenotype and genotype
    • only anti D required for routine testing
    • other typing sera used for typing RBCs to resolve antibody problems or family studies use statistical probability to determine most probable genotype
  10. Rh phenotyping used for
    • parental testing
    • predicting hemolytic disease of newborn
    • confirmation of Rh Ab specificity
    • finding compatible blood for Rh Abs specificity.
  11. protocol for Rh phenotyping
    • mix unknown RBCs with Rh antiserum (forward typing)
    • take tubes through phases ( IS, 37C, AHG, CCC)
    • use published frequencies
  12. location of RHCE and RHD and RHAG
    Image Upload 2
  13. function of Rh and RhAG
    • Rh and RhAG form a complex
    • maintain cell stability
    • regulate cell volume
    • transports ammonia
  14. genetics of Rh
    • Rh locus on chromosome 1
    • 2 closely linked Rh genes RHD and RHCE carry Rh antigens
    • alleles are autosomal codominant
    • linked together as a haplotype (DCe/dce, R1r)
  15. Image Upload 3
    Rh haplotype locus
  16. Rh associated glycoprotein (RhAG
    • ABH antigens on 1st loop, no Rh antigens
    • on chromosome 6
    • serves as a helper for expression of Rh antigens
  17. Weak expression of D protocol
    • if RBC not immediately agglutinated by anti D must be tested for weak D
    • 1. incubate cells with anti D at 37 C, will sensitize if present
    • 2 wash x3 add AHG
    • AHG will bind to anti D coating cells if present
    • if negative, individual is D negative
    • if positive individual is D positive
  18. 3 mechanisms for weak D
    • genetic - inheriting D genes resulting in lowered densities of D Ags on RBC membranes
    • C-trans position -D gene is in trans arrangement big D is trans to C (Dce/dCe)
    • D mosaic/partial D - parts of D Ag is missing, may result in production of anti D
  19. are people with weak D considered Rh+ or Rh-
    • Rh+ and will receive Rh+
    • except mosaic which will receive Rh-
  20. weak D gene will result in ___ densities of D antigens on RBC membranes
  21. Weak D in the lab
    • Dw mothers do NOT receive RhoGAM
    • D negative do not receive Dw
    • Dw may receive D neg
  22. enhanced D antigen
    cDe/cDe (C has limiting effect on expression)
  23. Allelic deletions of D
    • very rare
    • may be Ee or Cc
    • must be homzygous for deletion to be detected
    • no reaction when RBCs are tested with anti serum
    • requires transfusion of other D deletion red cells, bc these individuals may produce antibodies with specificities
    • written as D - - or -D-
  24. Rh null
    • will have NO Rh antigens on RBCs
    • genotype written as ---/---
    • can only give an Rh null to an Rh null
  25. what effects of RBC will an Rh null have
    • stomatocytosis
    • hemolytic anemia
    • why? lack of antigens will disrupt structural integrity
  26. two types of Rh null phenotypes
    • regulator type - Rh gene inherited, but not expressed due to mutation in RHAG gene
    • amorph type - RHD gene is absent or no exxpression of RHCE gene, when RHAG is normal
  27. what is Rhmod
    weakened expression of all Rh Ag
  28. compound antigens occur when and would react only with
    • when two Rh genes are on the same chromosome, cis position
    • f positive cells will only react with other f positive cells in cis position, not trans
  29. types of compound antigens
    • f antigens - c and e are in cis (dce/dce)
    • rh1 or Ce antigen - when C and e are in cis (dCe/dce)
  30. G antigen
    • encoded by the same gene for C or D
    • present in cells with C or D
    • anti G mimics anti C and anti D
  31. weak C (Cw)
    • C & Cw usually seen together
    • 2% whites, very rare in blacks
    • anti Cw may be naturally occuring and shows dosage
  32. D testing ( anti D reagents )
    • saline based: for low protein, long incubation times, cannot perform weak D testing
    • protein based: faster, incs false positives, requires control. can be used for weak D
    • chemically modified anti D: in low protein, few false positives, saline control performed. can be for weak D testing
    • blends of mAbs: using hybridized myeloma cells. Specific for Ab cells can be used for weak D. standard technique used now
  33. protocol for D testing
    • have two tubes with Anti D (labeled D) and Rh control (labeled C)
    • centrifuge and read
    • if D pos: Rh positive
    • if D neg: continue testing for weak D
    • add adjuvant and incubate
    • centrifuge
    • was 3 to 4 times with saline
    • add AHG
    • centrigue
    • if D pos in any phase and control is neg, RBCs are Rh+
    • if D and control are neg = RBC are neg
    • if control is positive = indeterminate
  34. why must you wash anti D with saline 3 to 4 times?
    to get rid of fibrin or protein, or else they would neutralize the coombs reagent giving a false negative
  35. Rh antibodies
    • IgG
    • react warm or with AHG
    • does not bind to complement, RBC destruction by Rh Abs isĀ extravascular
  36. what is the order of immunogenicity for Rh antibodies
    D > c > E > C > e
Card Set
Rh blood groups
rh blood groups