Transcript Other Blood Group Systems

Unit 9 Other Blood Group
Systems
Part 1
Terry Kotrla, MS, MT(ASCP)BB
Introduction
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ISBT recognizes 30 blood group systems with over 600
antigens.
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Some VERY rare only found in certain ethnic groups.
Some associated with diseases or resistance to infection.
Most important are ABO and D
“High incidence”, “public” or “high frequency” antigens
are those present on almost every person’s red blood
cells
“Low incidence”, “private” or “low frequency” antigens
are present on very, very few individuals red blood cells
Introduction
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Each known antigen initially identified
through the detection of its specific
antibody in the serum.
Knowledge of serologic behavior and
characteristics of blood group antibodies is
CRITICAL for identification
Introduction
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Essential when evaluating antibody screen
and panel studies.
Considerations given to:
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Phase of reactivity
Antibody class involved
Ability to cause HDFN and HTR
Introduction
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Clinically insignificant
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Reactive in-vitro at IS
IgM class
In-vivo- NO hemolysis/decreased RBC survival
Clinically significant
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Reactive in-vitro at 37C and/or AHG
IgG
In-vivo implicated in HDFN and/or HTR.
Introduction
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For each blood group system you MUST know:
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Antigen development, if important.
Antibody class usually involved.
Phase of reactivity in in-vitro tests.
Clinical significance.
Whether donor units must be antigen negative.
Any unique characteristics of the blood group
antigens and/or antibodies.
Introduction
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Most textbooks will divide discussion of
the blood groups into two distinct groups:
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Cold reacting, considered nuisance, IgM
Warm reacting, considered significant, IgG
If you know the phase of reactivity you
will know the antibody class involved AND
the clinical significance.
I/i Blood Group (ISBT 027)
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Related to ABO and Lewis by its
biochemical structure
Two antigens: I and i
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Fetal RBCs rich in i antigen and lack I antigen.
First 2 years I develops, lose i
Anti-I reacts most strongly with adult cells,
negative or weakly with cord RBCs
Strength of I antigen varies on adult cells
Rare instances I never develops.
I/i Blood Group
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Anti-I is associated with cold agglutinin
hemagglutinin disease
Decreased expression of I and increased
expression of i antigens is observed in:
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oncogenesis,
thalassemias,
sickle cell anemias,
associated with congenital cataracts in Asian
populations.
I Antibodies
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Cause of non-specific agglutination in tests performed at
RT
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Positive reactions with all cells tested: reverse, antibody screen
and crossmatches regardless of ABO blood group
May cause ABO discrepancy
Can be detected in serum of most normal adults if serum
is tested at 4C
Associated with atypical pneumonia caused by M.
pneumoniae , cold agglutinin titers used to monitor the
disease.
May cause hemolytic anemia when present in high titers
Anti-i
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Anti-i associated with certain diseases
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Infectious mononucleosis
Epstein-Barr virus
Cytomegalovirus
This antibody is rarely encountered
Clinical Significance of Anti-I
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Usually benign
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Clinically significant examples seen in Cold Agglutinin
Syndrome (CAS)
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Cannot cause HDFN – TWO REASONS
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Antibodies are of high titer (1000>)
High thermal amplitude
Cause hemolytic anemia
Transfuse blood through blood warmer
Antibody class is IgM
Antigen not well developed on fetal RBCs
Does not cause HTR
Serological Confirmation of Anti-I
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Test serum agains 3 adult group O RBCs
and 3 group O cord RBCs and an autocontrol
Adult cells and auto-control = positive
Cord RBCs = negative/very weak positive
Reactivity enhanced using enzyme treated
cells
Serological Confirmation of Anti-I
O Cord O Cord O Cord O Adult
0/+w 0/+w 0/+w
4+
0
0
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4+
4+
O Adult
4+
0
O Adult
4+
4+
Row 1 of reactions confirms anti-I
Row 2 of reactions indicates some “other”
alloantibody.
AC
4+
0
Prewarmed Technique
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Prewarmed technique will eliminate reactivity of most examples
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Original reactions at AHG
Prewarmed 1 – no other alloantibody present.
Prewarmed 2 – alloantibody present which must be identified.
AHG
Original
Screen 1 Screen 2
Screen 3
3+
3+
3+
Prewarmed 1
0
0
0
Prewarmed 2
2+
0
0
Cold Autoabsorption of Anti-I
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Very strong examples of anti-I may react at AHG and
require cold autoabsorption or rabbit erythrocyte stroma
test (REST) to rule out presence of other antibodies.
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Collect EDTA blood samples, place at 37C
Harvest EDTA cells, wash with 37C saline
Place clotted blood sample at 4C, separate serum
Add 1 mL serum to 1mL rbcs, incubate at 4C for 1 hour
Harvest serum and test against screen cells, if negative,
continue screen, if positive repeat absorption with new aliquot of
RBCs.
Lewis System (ISBT 007)
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Identified in 1946 and named after
antibody maker, Mrs. Lewis.
Major antigens Lea and Leb , other
antigens include Lec, Led and Lex
Lewis Antigenic Development
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Antigens ARE NOT intrinsic to RBCs but are
absorbed from the plasma and inserted
into RBC membrane.
Genetic control reside in single gene “Le”
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Amorph le, if homozygous will not have Lewis
antigens
Lea formed first, then modified to form Leb which is
adsorbed preferentially over Lea
Lewis phenotype of RBC can be changed by
incubating with plasma containing Lea or Leb
glycoplipid.
Lewis System
Lewis Phenotypes and Their Frequencies
White
Black
Le (a+b-)
22%
23%
Le (a-b+)
72%
55%
Le (a-b-)
6%
22%
Le (a+b+)
Rare
rare
Lewis System
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Lewis antigens in infants
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Antigens absent or extremely weak at birth
Expression of Leb is gradual
Birth Le (a-b-)
 2 months Le(a+b-)
 12 to 18 months Le(a+b+)
 2 to 3 years Le (a-b+)
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Lewis antigens cannot be used for
paternity testing on infants.
Lewis Antigens and Pregnancy
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Antigen strength may decline dramatically
during pregnancy.
Transiently Le (a-b-) may produce Lewis
antibodies during pregnancy.
Antigens return after delivery and
antibodies disappear.
Interaction of Le, Se and H Genes
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The le, h and se genes are amorphs and
produce no detectable products.
lele will not have Lewis antigens, but if Se
present will have A, B and H in secretions
Genotype se/se and have one Lewis gene
will have Lea in their secretions but no A,
B or H.
Lewis System
Lewis Phenotype
ABH Secretor
Lewis Secretor
Le (a+b-)
All ABH NON-Secretors
All Lea Secretors
Le (a-b+)
All ABH secretors
All secretors of Lea and
Leb
Le (a-b-)
80% ABH secretors
20% ABH NON secretors
NONE
Lewis Antibodies
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Naturally occurring, NOT clinically significant
Almost always IgM
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React most often at RT
Agglutination relatively fragile, easily dispersed
May cause ABO discrepancy if reverse cells have
Lewis antigen.
Occur almost exclusively in Le (a-b-) and
production of anti-Lea AND –Leb not unusual
Anti-Lea frequently encountered, anti-Leb rarely
encountered.
Lewis Antibodies
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Although most react at RT reactivity may be seen at
37C, but is weaker and may be weakly reactive at
AHG
Can bind complement and cause IN-VITRO
hemolysis, most often with enzyme treated cells
Antibodies NOT implicated in HDFN – TWO
REASONS
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Antibodies are IgM and
Antigens are poorly developed at birth
Lewis Antibodies
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Can be neutralized in-vitro by addition of
Lewis Substance
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Le antigens are present in secretions
Add to serum with Lewis antibodies and the
antibodies will be bound to the soluble Lewis
antigens
Useful when multiple antibodies are present
and one is a Lewis, eliminates the reactivity of
the antibody
Lewis Neutralization
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Row 2 antibody reacting with S1 and S3 which are Lewis
positive.
Row 2 indicates antibody was neutralized by Lewis
substance, no other antibodies present.
Row 3 indicates additional antibody present.
Original
Le Substance – only Le Ab
Le Substance-Le and additional Ab
S1 S2 S3
2+ 0 2+
0
0 0
1+ 0 0
Lewis Antibodies - Transfusion Practice
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Transfused RBCs will acquire the Lewis
phenotype of the recipient within a few days
Lewis antibodies in patient will be neutralized by
Lewis substance in donor plasma
Lewis antibodies rarely cause in-vivo hemolysis
It is not necessary to phenotype donors for
Lewis antigens prior to transfusion, give
crossmatch compatible
P Blood Group (ISBT 003)
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Discovered 1927 when Landsteiner immunized rabbits
with human RBCs
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Initially named “P” but as complexity of P blood group was
discovered renamed “P1”
RBCs lacking P1 are P2
Other P phenotypes exist but are rare(<1%): P, P1k and P2k
Whites
Blacks
P1
79%
94%
P2
21%
6%
P1
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Strength of the P1 antigen varies among different
RBC samples and antigen strength reported to diminish
when RBCs are stored.
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Characteristics creates difficulties, both in testing RBCs for the
antigen and in the identification of the antibody.
Anti-P1 blood typing reagents usually sufficiently potent to detect
weak forms of the antigen.
An antibody that is weakly reactive at RT testing can
often be shown to have anti-P1 specificity by lowering
the incubation temperature or using enzyme treated
RBCs.
Anti-P1
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The sera of P2 persons commonly contain anti-P1.
The antibody reacts optimally at 4 C but may
occasionally be detected at 37 C.
Rarely may cause in-vitro hemolysis.
As it is nearly always IgM, it does not cross the
placenta and has not bee reported to cause HDFN
(antigen poorly expressed on fetal cells).
Anti-P1 little clinical significance unless reactive at 37 C.
Anti-P1 has rarely been reported to cause hemolysis in
vivo.
Neutralization of P1 Antibodies
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Hydatid cyst fluid or P1 substance derived
from pigeon eggs inhibits the activity of
anti-P1.
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Neutralization or inhibition is a useful aid to the
identification of anti-P1, especially if the antibody is
present in a serum with multiple antibodies.
The anti-P1 is neutralized (becomes non-reactive)
revealing other specificities (if present).
Neutralization of P1 Antibodies
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Row 1 – original testing
Row 2 – antibody successfully neutralized, no
underlying antibody.
Row 3 – presence of additional antibody
S1 (P1 pos) S2 (P1 neg) S3 (P1 pos)
Original
2+
0
1+
Neutralized
0
0
0
Neutralized
1+
0
0
Transfusion Practice P
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Clinically insignificant RT agglutinin.
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Not necessary to provide antigen negative
blood.
Must be crossmatch compatible.
If reactive at 37C or AHG select
crossmatch compatible blood.
References
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AABB Technical Manual, 2008.
Wikipedia, http://tinyurl.com/4jysjyc