Transcript Other Blood Group Systems

Other Blood Group Systems
Terry Kotrla, MS, MT(ASCP)BB
Introduction
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Over 500 blood group antigens
“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
I Blood Group
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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 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 Blood Group
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Antibodies: anti-I anti-I
Anti-I
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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
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
I Blood Group
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Anti-i associated with certain diseases
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Infectious mononucleosis
Epstein-Barr virus
Cytomegalovirus
Antibody is rarely encountered
I Blood Group
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Clinical Significance
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Usually benign
Clinically significant examples seen in Cold Agglutinin
Syndrome (CAS)
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Antibodies are of high titer (1000>)
High thermal amplitude
Cause hemolytic anemia
Transfuse blood through blood warmer
Cannot cause HDFN
Does not cause HTR
I Blood Group
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Serological Confirmation
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Test serum agains 3 adult O RBCs and 3 cord
RBCs and an auto-control
Adult cells and auto-control = positive
Cord RBCs = negative/very weak positive
Prewarmed technique will eliminate reactivity
of most examples
Reactivity enhanced using enzyme treated
cells
I Blood Group
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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
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Major antigens Lea and Leb , other
antigens include Lec, Led and Lex
Antigens ARE NOT intrinsic to RBCs but
are absorbed from the plasma and
inserted into RBC membrane.
Lewis System
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Antigenic Development
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Genetic control reside in single gene “Le”
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 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 System
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Lewis antigens and pregnancy
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Antigen strength may decline dramatically
Transiently Le (a-b-) may produce Lewis
antibodies during pregnancy
Antigens return after delivery and antibodies
disappear
Lewis System
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Interaction of Le, Se and H Genes
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lele will not have Lewis antigens, but if Se
present will have A, B and H in secrections
Genotype se/se and have one Lewis antigen
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 System
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Lewis Antibodies
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Almost always IgM, react strongly at RT, 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 System
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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
Because antibodies are IgM and antigens are poorly
developed at birth antibodies NOT implicated in
HDFN.
Lewis System
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Lewis antibodies
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Can be neutralized in-vitro by additions of
Lewis Substance
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 1
is a Lewis, eliminates the activity of the antibody
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Lewis System
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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
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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%