Rh BLOOD GROUP SYSTEM

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Rh BLOOD GROUP SYSTEM

• AHLS 311

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HISTORY

• Ab in serum of mother of stillborn child
  responsible for the death of fetus? (1939, Levine
  and Stetson)
• Rb-derived Ab to Rhesus monkey RBCs reacts with
  85 of human subjects same Ab as reported by
  Levine? (1940, Landsteiner and Weiner)
• Erythroblastosis fetalis (HDN) linked with
  Anti-Rh (1941, Levine et al)

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NOMENCLATURE 4 VERSIONS

• Fisher Race
• Suggested 3 sets of closely linked alleles (D and
  d, C and c, E and e)
• Each gene (except d, which is an amorph) causes
  production of an Ag
• Inherited from parents in linked fashion as
  haplotypes
• See Tables 6-1 and 6-2

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NOMENCLATURE

• Weiner
• Multiple alleles at 1 complex locus
• 1 locus encodes for production of an agglutinogen
  which has 3 factors (antigens or epitopes)
• Abs can recognize single or multiple factors
• See Table 6-3

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WEINERS THEORY
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WEINER FISHER-RACE TERMINOLOGY
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WEINER FISHER-RACE TERMINOLOGY
D R
1 ( C)
Z (both C E )
2 ( E )
0 (neither C or E )
D C
D c E
D c e
D C E
d r
( C)
y (both C E )
( E )
(neither C or E )
d C e
d cE
d c e
d C E
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NOMENCLATURE

• Rosenfield
• No genetic assumptions made
• Numerical system
• If listed alone, the Ag is present (Rh1 D Ag)
• If listed with a -, the Ag is not present
  (Rh1, -2, 3 DcE)
• If not listed, the Ag status was not determined
• Adapts well to computer entry

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COMMON Rh TYPES BY 3 NOMENCLATURES
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NOMENCLATURE

• Internatl. Soc. of Blood Transfusion
• 6 digit number for each Ag specificity
• First 3 indicate the blood group, eg., 004 Rh
• Last 3 indicates the Ag specificity, eg., 004001
  D Ag of Rh system
• For recording of phenotypes, the system adopts
  the Rosenfield approach

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Rh PHENOTYPING

• Uses
• Parentage testing
• Predicting hemolytic disease of the newborn (HDN)
  
• Confirmation of Rh Ab specificity
• Locating compatible blood for recipients with Rh
  Abs
• Protocol
• Mix unknown RBCs with Rh antisera
• Take tubes through phases (IS, heat/potentiator,
  AHG, CCC) record data
• Use published frequencies and subject information
  to determine genotype

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GENOTYPE FREQUENCIES

• Dce (R1) 0.42
• dce (r) 0.37
• DcE (R2) 0.14
• Dce (R0) 0.04
• dCe (r) 0.02
• dce (r) 0.01
• DCE (Rz) lt0.01
• dCE(ry) lt0.01
• The probability of 2 frequencies appearing
  together the product of those 2 frequencies.
  For example, DCe/dce occurs with a frequency of
  0.42 X 0.37 or 0.155.

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Rh ANTIGENS

• Nonglycosylated proteins (A,B,H are CHOs)
• Transmembrane molecules
• D and CE are epitopes of proteins with 417 Aas
  that traverse the membrane 12 X
• DNA sequences of D and CE differ by only 44 base
  pairs CE, Ce, cd and cE are even more similar to
  D
• Integral part of RBC membrane (Rhnull people have
  mild hemolytic anemia)
• Density of Rh Ags on RBCs varies by phenotype
  (see Table 6-7)

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MODEL OF Rh PROTEIN
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D ANTIGEN VARIATIONS

• Weak D
• Some cells require addition of AHG (IDAT) to
  demonstrate agglutination with Anti-D
• 3 mechanisms causing weak D expression
• Genetic - inheritance of D genes which result in
  lowered densities of D Ags on RBC membranes
• C trans - position effect the D gene is in trans
  to the C gene, eg., Dce/dCe (C and D Ag
  arrangement causes steric hindrance weakening D
  expression)
• D mosaic - 1 or more parts of the D Ag is
  missing may result in production of Anti-D
• People with weak D are considered Rh and receive
  Rh blood (except mosaics)

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D ANTIGEN VARIATIONS

• Enhanced D
• When c and D are in double doses, eg., cDe/cDe,
  (C has limiting effect on expression of D)
• D-- or D .. represent partial locus deletions
  usually seen in consanguinous situations

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D TESTING

• Anti-D reagents
• Saline-based - Low protein (fewer false
  positives) long incubation times cannot convert
  to weak D testing
• Protein-based - Faster, increased frequency of
  false positives requires use of Rh control tube,
  converts to weak D testing
• Chemically modified - Relaxed form of Anti-D in
  low protein medium few false positives saline
  control performed converts to weak D testing
• Blends of mAbs
  
  
  
  
  

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D TESTING

• Protocol
• Add Anti-D to D tube Rh control to C tube
• Spin, read and record
• If D is positive, cells are Rh positive
• If D is negative, continue testing
• Add 22 albumin and incubate for 20 at 37oC
• Spin, read, and record
• Wash 3 X in saline
• Add AHG, spin, read, and record
• 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
• Add check cells to neg. tubes spin, read
  record

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WEAK D Ag IN THE LAB

• Differences from normal D expression
• Quantitative (inherited weak D or position
  effects)
• Qualitative (mosaic D could produce Anti-D)
• If cells are weak D, consider the person to be Rh
  
• Dw not given to D negative recipients
• D positives usually OK for Dw recipients
• Dw mothers do not receive RhoGAM
• Donors and expectant mothers should be tested for
  weak D transfusion recipiencts /- for weak D
  testing (Dw people may receive D negative blood)

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OTHER ALLELES AND ANTIGENS

• Weak C (Cw)
• Not allelic to C and c (C and Cw usually seen
  together)
• 2 of whites very rare in blacks
• Anti-Cw may be naturally occurring and shows
  dosage
• f (ce)
• When c e are in cis, eg., dce/DCe
• Combination Ag
• Anti-f may be helpful in phenotyping

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OTHER ALLELES AND ANTIGENS

• Ce
• When C and e in cis
• Compound Ag
• Ab helpful in phenotyping
• G
• Always found with C-positive RBCs usually with
  D-positive cells
• Anti G appears to bind to D, C, and G
• Many others

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ALLELIC DELETIONS

• No Cc and/or Ee epitopes
• DC-, Dc-, D-E, D--
• Enhanced or exalted D Ag expression
• Rhnull (no Rh Ag expression at all)
• ---/--- (double bar rr)
• Or, because of independently inherited suppressor
  genes
• If exposed to any Rh Ags, make Abs to those and
  to Rh 29 (pan or total Rh)
• Causes a mild hemolytic anemia
• Rhmod - weakened expression of all Rh Ags

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Rh ANTIBODIES

• Immune IgG Abs (IgG1 and IgG3 most important)
• React optimally at 37oC or with AHG
• Order of immunogenicity
• D gt c gt E gt C gt e
• Do not bind complement (RBC destruction by Rh Abs
  is extravascular)
  
  

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Rh Abs CLINICAL SIGNIFICANCE

• Severe HDN
• Severe transfusion reactions