Transcript Rh BLOOD GROUP SYSTEM

Notas de internet
 Para
Rh/D
Rh BLOOD GROUP SYSTEM
HISTORY
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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)
NOMENCLATURE:
4 VERSIONS
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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
NOMENCLATURE
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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
WEINER’S THEORY
WEINER & FISHER-RACE
TERMINOLOGY
WEINER & FISHER-RACE
TERMINOLOGY
D=R
1 ( C)
2(E)
DC
DcE
0 (neither C or E )
Dce
Z (both C & E )
DCE
d= r
‘( C)
‘’ ( E )
(neither C or E )
dCe
d cE
dce
y (both C & E )
dCE
NOMENCLATURE
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Rosenfield
 No genetic assumptions made
 Numerical system
 If listed alone, the Ag is present (Rh:1 = D Ag)
 If listed with a “-”, the Ag is not present (Rh:1, 2, 3 = DcE)
 If not listed, the Ag status was not determined
 Adapts well to computer entry
COMMON Rh TYPES BY
3 NOMENCLATURES
NOMENCLATURE
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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
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
Rh GENOTYPING
PHENOTYPING
DATA
POSSIBLE
GENOTYPES
Reactions with
Anti-:
D
C
E
c
e
+
+
-
-
+
-
-
-
+
+
+
+
-
+
+
+
+
+
+
+
1st
2ND
CHOICE CHOICE
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GENOTYPE
FREQUENCIES
Dce (R1)
dce (r)
DcE (R2)
Dce (R0)
dCe (r’)
dce (r”)
DCE (Rz)
dCE(ry)
0.42
0.37
0.14
0.04
0.02
0.01
<0.01
<0.01
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.
Rh ANTIGENS
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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)
MODEL OF Rh PROTEIN
D ANTIGEN VARIATIONS
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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)
D ANTIGEN VARIATIONS
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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
D TESTING
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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
D TESTING
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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
WEAK D Ag IN THE LAB
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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)
OTHER ALLELES AND
ANTIGENS
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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
OTHER ALLELES AND
ANTIGENS
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Ce
 When
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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
ALLELIC DELETIONS
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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
Rh ANTIBODIES
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Immune IgG Abs (IgG1 and IgG3 most important)
React optimally at 37oC or with AHG
Order of immunogenicity:
D>c>E>C>e
Do not bind complement (RBC destruction by Rh
Abs is extravascular)
Rh Abs:
CLINICAL SIGNIFICANCE
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Severe HDN
Severe transfusion reactions