ABO Blood group system (and H) Flashcards
(131 cards)
1
Q
Who first described the ABO system?
A
-Karl Landsteiner
-collected samples from himself and 5 other associates
-separated cells and serum and mixed each cell sample with each serum
-he was the first individual to inadvertently perform forward and reverse grouping
-he discovered the A, B, and O blood groups
-this is the only blood group system in which individuals have antibodies in their serum to antigens absent from their RBCs
2
Q
What happens if you fail to determine an accurate ABO group?
A
-mortality and morbidity
-transfusion of incompatible blood may result in an immediate lysis of donor RBCs producing a severe if not fatal reaction
3
Q
What is the leading cause of death in hemolytic transfusion reactions today?
A
-transfusion of the wrong ABO group
4
Q
What is the ABO group frequencies of B +
A
8.5%
5
Q
What is the ABO group frequencies of B-
A
1.5%
6
Q
What is the ABO group frequencies of A-
A
6.3%
7
Q
What is the ABO group frequencies of O-
A
6.6%
8
Q
What is the ABO group frequencies of AB+?
A
3.4%
9
Q
What is the ABO group frequencies of AB-
A
.6%
-most rare
10
Q
What is the ABO group frequencies of A+
A
35.7%
11
Q
What is the ABO group frequencies of O+?
A
37.4%
-most common
12
Q
ABO frequencies for white people
A
O - 45
A - 40
B - 11
AB - 4
*most common is O and A
13
Q
ABO frequencies for black people
A
O - 50
A - 26
B - 20
AB - 4
*most common is O
14
Q
ABO frequencies for Hispanic people
A
O - 56
A - 31
B - 10
AB - 3
* most common is O
15
Q
ABO frequencies for Asian people
A
O - 40
A - 28
B - 25
AB - 7
*Most common is O
16
Q
Forward grouping
A
-use known commercial antisera (anti-A, anti-B)
-use the patient’s red cells
-detect antigens on the patient’s red cells
AKA: Front type
17
Q
Reverse grouping
A
-use known reagent RBCs (A1 cells and B cells)
-use the patient’s serum
-detects ABO antibodies in the patient’s serum
AKA: Back type
18
Q
ABO grouping
A
-most frequently performed test in the blood bank
-front and back typing is done on all patients
-inverse reciprocal relationship between front and back type (serve as a check for each other)
19
Q
Group A: antigens, antibodies
A
Antibodies in plasma: Anti-B
Antigens in red blood cells: A antigen
20
Q
Group B: antigens, antibodies
A
Antibodies in plasma: Anti-A
Antigens in red blood cells: B antigen
21
Q
Group AB: antigens, antibodies
A
Antibodies in plasma: None
Antigens in red blood cells: A and B antigens
22
Q
Group O: antigens, antibodies
A
Antibodies in plasma: Anti-A, Anti-B
Antigens in red blood cells: None
-O phenotype is an autosomal recessive trait because 2 non-functional genes are inherited
23
Q
Naturally occurring antibodies
A
-it has been postulated that bacteria/pollen are chemically similar to A and B antigens
-bacterial/pollen is widespread, and we are constantly exposed
–exposure serves as a source of stimulants of Anti-A and Anti-B
-antibody production in most other blood groups requires the introduction of foreign RBCs (via transfusion or pregnancy)
24
Q
What does naturally occurring mean
A
-produced without any exposure to RBCs
25
ABO antibodies
-naturally occurring
-individuals normally produce antibodies directed against the A/B antigens absent from their RBCs
-predominantly IgM
-activate complement
-react at RT and colder
-produce strong direct agglutination reactions during ABO testing
-production begins at 3-6 months old, peaks at 5-10 years, and diminishes when elderly
26
Can you detect antibodies in babies just birthed?
-Even though the production of antibodies is initiated at birth, the titers are too low to detect until around 4 months
-this is why front types are only performed on babies
27
What happens to elderly people and their antibodies?
-elderly people might have lower levels of Anti-A and Anti-B and therefore their back type (reverse grouping) may be weak or missing, resulting in ABO discrepancy
28
What class is Anti-A and Anti-B predominantly?
-IgM but may have IgG component
29
What antibodies do group O individuals have?
-they produce Anti-A, Anti-B, and Anti-A, B
-Anti-A.B is not a mix of Anti-A and Anti-B
-it has a separate cross-reacting antibody
-it is IgG in nature
**This can be a problem for a group O mom having an A or B baby, which can cause hemolytic newborn disease. Often the cord samples for babies of type O mom are tested for possible ABO HDFN
30
When is the Anti-A, B reagent used?
-routinely used in ABO confirmation of blood donors, it is more economical to use one reagent instead of two when verifying group O RBCs
31
Reagent Anti-A
-Monoclonal
-highly specific
-IgM
-clear blue reagent
-expect 3-4+ rxn
32
Reagent Anti-B
-monoclonal
-highly specific
-IgM
-clear yellow reagent (contains acriflavine dye)
-expect 3-4+ rxn
33
Reagent Anti-A.B
-more effective at detecting weak A/B antigens
-not as necessary since monoclonal Anti-A and Anti-B antisera were developed
-This reagent is more sensitive and can detect weaker expressions
-not routinely used for patient ABO grouping
-used for ABO confirmation of donor blood
-more economical, cheaper to use one reagent
34
Bernstein- Inheritance of ABO blood groups
-1924
-inherit one ABO gene from each parent
-these two genes determine which ABO antigens are on the RBC membrane
-Inheritance follows Mendelian genetics
-codominant expression
35
Which chromosome is the A, B, and O gene located on?
9
36
Is the O gene an amorph?
-Yes, no antigens are produced
37
Autosomal codominant inheritance
-blood group genes are not carried on sex genes, hence autosomal and not sex-linked. Whenever the gene is inherited the antigen is expressed on the RBCs, thus its codominant
38
Phenotype
-saying someone is group O or A
39
Genotype
- AA/OO/AO etc is referring to genotype
40
Can you determine genotype serologically?
-no you cannot, family studies or molecular assays are necessary to determine the exact genotype
-you can for O because it is an autosomal recessive and results from inheriting 2 O genes (OO)
-you can for AB because codominant, so A came from one parent and B from another
41
What are the 3 different genes that form the ABH antigen?
-ABO
-Hh
-Se
42
What is the precursor material A, B, and H antigens are made from?
-paragloboside or glycan
43
A, B, and H antigens
-ABH genes do NOT code for antigens, they produce (code for) glycosyltransferases (enzymes)
-these enzymes add sugars to precursor substances
44
Which antigen is found in the greatest concentration of a group O individual
H antigen
45
How come the H antigen may not be detected in group A1 individuals?
- The A1 gene is so good at converting H antigens into A
-the more A, the less H antigen available
-the H antigen on A1 and A1B RBCs are so well hidden that occasionally anti-H is found in the serum
46
What is anti-H?
-a naturally occurring IgM cold agglutinin that reacts best below room temp
-IgM can react at temperatures up at 37 C but will react better at cold
47
What is the precursor on which A and B antigens are made of?
H antigen
48
Are Hh and Se genes a part of the ABO system?
NO
-but their inheritance does influence A and B antigen expression (Chromosome 19)
49
Hh genes form ABO antigens where?
RBCs
50
Se gene form ABO antigens where?
Secretions
-you need to inherit this to form ABO antigens in secretions
51
Type 1 and Type 2
-type 1 and 2 refer to linkages found between the terminal sugars of D-galactose and N-acetylglucosamine
52
Type 1
-precursor substance in secretions
B1 --> 3 Linkage
-number 1 carbon of D-galactose --> number 3 carbon of N-acetylglucosamine
53
Type 2
-precursor substance on RBCs
-B1 --> 4 linkage
-the terminal galactose on the precursor substance is attached to the N-acetylglucosamine in a beta 1 --> 4 linkage
54
ABH antigen expression
-ABH antigen develops early in fetal life
-Newborn RBCs have 25-50% number of antigenic sites found on adult RBCs (newborns have weaker front-type reactions)
-A and B antigen expression is fully developed by 2-4 years of age
-ABH antigen phenotypic expression can vary with race, genetic interaction, disease states
55
H gene
-Group O individuals inherit at least one H gene (genotype = HH or Hh) and 2 O genes
-H gene produces enzyme a-2-L-fucosyltransferase
-Transfer sugars (L-fucose) to an oligosaccharide chain on terminal galactose of type 2 chain
-produce the H antigen
-O gene does NOT make catalytically active transferase
-H substance is unmodified in group O
56
Immunodominant sugars
-the sugars that occupy terminal positions on this precursor chain confer blood group specificity
ex: L-fucose confers H specificity, blood group O has the highest concentration of H antigens
-need L-fucose (H substance) for other sugars to attach in response to A and B genes
57
Bombay phenotype (Oh)
-lacks normal expression of ABH antigens, so do not react with anti-A, anti-B, or anti-H
-FUT1 (H gene) is silenced
-genotype is hh (extremely rare), is an autosomal recessive trait, and 99.99% of the population have H gene
-Does not produce a-2-L-fucosyltransferase
-L-fucose is NOT added to type 2 chains and H substance is not expressed on RBCs
-individuals may inherit ABO genes, but not express them because no H antigen to build upon
-ABH substance also absent from saliva, FUT2 (Se gene) is also silenced
58
What will a Bombay phenotype show as?
-As group O, but true O RBCs react with anti-H lectin and Bombay does not (because no H antigen)
59
Who can a Bombay patient receive blood from?
-A Bombay person can only receive blood from another Bombay because anti-H can be potent and react at 37 C
-normal group O RBCs have many H antigens and Bombays anti-H would cause immediate lysis
60
The A gene codes for what enzyme?
a-3-N-acetylgalactosaminyltransferase
61
What does a-3-N-acetylgalactosaminyltransferase do?
transfer N-acetyl-D-galactosamine (GalNAc) sugar to the H substance
62
What is GalNAc sugar responsible for?
-A specificity
63
A gene
-has more transferase than B gene, thus producing more antigen sites
-810,000 to 1,170,000 A antigen sites on adult A1 RBC
64
The B gene codes for what enzyme?
a-3-D-galactosyltransferase
65
What is the job of a-3-D-galactosyltransferase?
-transfers D-galactose (Gal) sugar to the H substance
66
What sugar is responsible for B specificity?
D-galactose
67
When both A and B genes are inherited, which one competes more efficiently?
-the B enzyme seems to compete more efficiently for the H substance than the A enzyme
-so on an AB person's RBC there are approximately 600,000 A antigens and 720,000 B antigens
68
What are the three immunodominant sugars?
Fucose - Group H
N-acetyl-D-galactosamine - Group A
Galactose - Group B
*** As more A or B antigen is made, less H antigen remains
69
H antigen amount
O >A2>B>A2B>A1>A1B
70
ABH soluble antigens
-found in all body secretions
-presence depends on ABO genes inherited AND inheritance of secretor genes (Sese)
-solubles are only on glycoproteins
71
Secretors
SeSe or Sese
-80% of the US population are secretors
72
Non-secretors
sese
73
What does the Se gene code for?
a-2-L-fucosyltransferase
74
What does a-2-L-fucosyltransferase do?
-modifies type 1 precursor substance in secretions to form H substance
-that H substance can then be modified to express A or B substance if the corresponding ABO gene is present
75
Where can RBC antigens be found on?
-glycolipids, glycoproteins, and glycosphingolipids
76
secretor studies
-80% of the population has the Se gene
-these people secrete water-soluble blood group substances in their saliva and body fluids
Group A = secrete A substance and some H
Group B = secrete B substance and some H
Group O = secretes H only
Group AB = secretes A and B substances and a little H
77
Agglutination inhibition
-is used to determine the secretor status
-the presence of agglutination = negative test
-no agglutination = positive test
* for valid tests the control needs to agglutinate
*2 steps to this process
1. antibody neutralization
2. agglutination inhibition
78
Antibody neutralization
-saliva is mixed with commercial antisera and incubated
-if the patient is a secretor, soluble blood group antigens in the saliva will react with the antibodies in the commercial antisera
79
Agglutination inhibition
-commercial RBCs of appropriate blood groups are added to the test mixture
-if the patient is a secretor, there is no free antibody left for the commercial RBCs to react with
-thus if a patient is a secretor there will be NO agglutination
80
ABO subgroups
-subgroups show weaker variable serologic reactivity with polyclonal anti-A, anti-B, and anti-A, B reagents
-due to decreased # of antigen sites
-not as often seen now due to the use of monoclonal reagents
81
A subgroups
-more common than B subgroups
-99% of group A people are A1 or A2
82
What is the percentage of A1?
80%
83
What is the percentage of A2 or other A subgroups?
20%
84
What are the immunodominant sugars on the A1 and A2?
-N-acetyl-D-galactosamine
85
A1 gene
-higher concentrations of a-3-N-acetylgalactosaminyltransferase than A2
-A1 enzyme is 5-10 times more active than A2
-A1 is more effective at converting H antigen to A antigen
-A1 cells have 1,000,000 A antigens
86
A2 gene
-A2 individuals have increased levels of H antigen, second only to group O
-A2 cells have 250,000 A antigens
87
Weaker A subgroups
-subgroups weaker than A2 are rare, usually found through ABO discrepancies
-Subdivide individuals into A3, Ax, Aend, Am, Ay, Ael, etc
* secretor studies
*adsorption-elution tests
*molecular testing
-have less antigen, varying degrees of agglutination with anti- A, B variability in detectability of H antigen (anti-H)
-A3 RBC characteristically demonstrates a mixed-field pattern of agglutinations with anti-A
-if a weak A subgroup is suspected make sure the patient doesn't have a disease that makes altered ABH antigens
88
Potential problems: Weaker A subgroups
-if an Ax donor is mistyped as O type and transfused to O recipient, the recipient's anti-A, B will agglutination/ lyse Ax RBCs --> rapid intravascular hemolysis
89
A3 RBCs
-looks mixed field with anti-A and anti-A, B
-antigen sites: 35,000
-Anti -A1 may be present in the serum of A3 people and A substance is detected in saliva if secretor
90
Ax RBCs
-not agglutinated by anti-A, but do agglutinate with anti-A, B
-Antigen sites: 4,000
-almost always produced anti-A1, but only H substance in saliva if secretor
-anti-A can be adsorbed and eluted from Ax cells without difficulty
91
Anti-A1
- 1-8% of A2 individuals make anti-A1 in their serum
- 22-35% of A2B individuals make anti-A1
- reagent anti-A agglutinates both A1 and A2 RBCs
-usually first detected in the BackType, anti-A1 will react with the A1 cells used in the reverse typing
-naturally occurring IgM cold reacting antibody and is unlikely to cause transfusion reaction b/c it only usually reacts below body temp
-Both A1 and A2 strongly react with Anti-A in routine testing, but A1 can be distinguished through A1 lectin
92
Anti-A1 lectin
name: dolichos biflorus
- use this to differentiate A1 and A2
-Anti A1 lectin will agglutinate A1 but NOT A2 cells
93
Lectins
-lectin are seed extracts that agglutinate human cells with some degree of specificity
94
Dolichos biflorus
-agglutinates A1 cells
95
Bandeiraea simplicifolia
agglutinates B cells
96
Ulex europaeus
-agglutinates O cells (is anti-H lectin)
-since the A2 phenotype reflects the inefficient conversion of H antigen to A antigen, A2 shows increased reactivity with anti-H lectin
97
Adsorption/eluate studies for identification of A subgroups
-commercial anti-A is adsorbed onto red cells believed to be A subgroup
-eluate is prepared from the RBCs and then tested for anti-A
-if anti-A is recovered, presenced of A antigens is confirmed
98
Subgroups of A
Aint, A3, Ax, Am, Aend, Ael, etc.
99
B subgroup
-very rare
-like A subgroups, result from alternate alleles at the B gene locus
-usually have variations in reaction strength with anti-B and anti-A, B
-Includes B3, Bx, Bm, and Bel
-can do adsorption/eluate studies with anti-B
-presence/absence of ABO isoagglutinin in serum
-may initial front type as group O
100
B3
-mixed field with anti-B and A,B (like A3), and B substances in secretions
* the most frequent B subgroup
101
Bx
weak agglutination with anti-B and anti-A, B, readily adsorb and eluate anti-B
-secretors have lots of H substance and some B substance that is hard to detect
102
Bm
-doesn't agglutinate anti-A or anti-A, B
103
How can disease states alter RBC antigens?
-can weaken reactions
-can acquire pseudoantigens (these would be seen during forward grouping)
-can cause forward grouping issues
104
Weaker front-type reactions
-depressed antigen strength
-can look like mixed field
-can be due to leukemia, chromosome 9 translocations, thalassemia (stress hematopoiesis), Hodgkin's disease
-antigen strength increases when in remission
-antigen strength increases when in remission
105
Weaker- Back type reactions
-isoagglutinin (anti-A, anti-B, anti-A, B) may be weak/absent
-chronic lymphocytic leukemia (CLL)
*leukemia with hypogammaglobulinemia
-malignant lymphomas (non-Hodgkin's)
*decreases in gamma globulin fraction
-agammaglobulinemia
106
Acquired B phenomenon
-due to increased permeability of the intestinal wall (due to obstruction, colon/rectal cancer)
-allows passage of bacterial polysaccharides from E.coli serotype O86 into the patient's circulation
-the patient's group A RBCs adsorb the B-like polysaccharide and react with some anti-B reagents
-their forward grouping may appear as AB but with a weaker reaction with the anti-B antisera
-their reverse type would like group A
107
What does bacterial deacetylase do?
-works on the A antigen by converting N-acetylgalactosamine (the terminal sugar for A antigen) to N-galactosamine (very similar to the terminal sugar for the B antigen- D galactose)
108
When should you suspect acquired B phenomenon?
Acquired B is a transient serologic discrepancy seen in group A individuals. Acquired B should be suspected when a historical group A patient now has weak B expression in the front type (anti-B = 2+ or less)
109
How would you resolve a patient with acquired B?
-retype using a different monoclonal anti-B or acidified human anti-B, acidified human anti-B will not react with the acquired B antigen
110
What two mechanisms have been postulated for acquired B?
1. In vivo: bacterial enzyme de-acetylase modifies the terminal a-N-acetyl-D-galactosamine into a D-galactosamine which looks like a D-galactose (B-antigen) and can react with anti-B
2. In vitro: blood group B activity can be conferred onto A/O RBCs adsorbing B-active bacterial polysaccharides
111
Undetectable ABO antigens
-can occur with carcinoma of the stomach or pancreas
-patient's RBCs are unchanged, serum contains increased concentrations of blood-group specific soluble substances (BGSS)
*may neutralize antisera used in forward grouping
112
ABO discrepancies
-forward and reverse grouping disagree
-must be resolved prior to transfusion
-can be due to problems with patient RBCs (forward group) or patient serum (reverse group)
-can be due to technical errors, labeling, missing reagents, contamination, etc.
-4 groups of discrepancies
*should always add serum and antiserum first then red cells, should always record results to prevent transcription error
113
Group 1 discrepancies
-unexpected reactions in BACK TYPE due to weak/missing antibodies
-most common discrepancy group
114
Who is affected by group 1 discrepancies?
1. newborns/elderly (have lower antibodies levels)
2. immunosuppression (ex: agammaglobulinemia)
3. BMTs
4. Dilution
5. Subgroups (ABO)
*patients with malignant lymphomas/CLL
*patients who have been diluted by FFP transfusions
115
How to resolve Group 1 discrepancies?
-get patient history
-increase serum to cell ratio
-increase the incubation time
-decrease temperature
* incubate at 4C with auto control and group O control cells (additional cells needed because decreased temp increases chance of detecting cold agglutinin reactivity)
116
Group 2 discrepancies
-least frequent discrepancy
-unexpected reactions in FRONT TYPE due to weak/antigens
-blood group specific soluble (BGSS) substances
-chimerism
117
How to resolve Group 2 discrepancies?
-increase incubation time by up to 30 minutes
-can decrease the temperature to 4C and run with auto control and group O cells
*If acquired B:
secretor studies: if the patient is a secretor, only A substance will be present
-can also treat cells with acetic anhydride-acquired B cells lose reactivity
118
Who is affected by group 2 discrepancies?
*subgroups of A/B
*leukemias
*acquired B phenomenon
119
BGSS Substances
-can occur due to carcinoma of the stomach/pancreas
*excess amounts of BGSS substances are present in plasma
*neutralize reagent anti-A or anti-B
*leaves no unbound antibody to react with patient cells
*cause a false negative or weak reaction in front type
-resolve by washing patient cells several times with saline
120
chimerism
-presence of 2 cell populations in 1 person
-true chimerism is very rare and occurs in twins
-blood exchange occurs in utero
*2 cell population emerge
*both recognize as self, so the body doesn't make anti-A or anti-B
-if no history of twins, could be due to dispermy (2 sperm + 1 egg) and maybe mosaic
121
Artificial chimerism
-is more frequent than true chimerism and can be due to non-ABO matched blood transfusions, BMTs, exchange transfusions, FMH
122
Group 3 discrepancies
-caused by protein or plasma abnormalities (in vitro problems like rouleaux)
123
Who causes group 3 discrepancies?
-waldenstrom's macroglobulinemia
-multiple myeloma
-some advanced Hodgkins lymphomas
-increased levels of fibrinogen
-plasma expanders (dextran)
-wharton's jelly (cord blood only)
124
Rouleaux
-RBCs stacked like coins
125
How to resolve group 3 discrepancies?
-resolve rouleaux with saline replacement
*remove patient serum and replace with equal volume saline
*true agglutination remains
-Resolve Wharton's jelly by washing cord cells up to 6 times with saline
126
Group 4 discrepancies
-cold reactive autoantibodies
*RBCs so heavily coated that they spontaneously agglutinate
-mixed field
*more than one ABO group type RBCs circulating (ex: non-ABO identical RBC transfusion, BMT, stem cell transplant, ABO subgroup (A3))
-unexpected ABO isoagglutination or non-ABO alloantibody
-acriflavine antibody
127
How to resolve group 4 discrepancies? due to cold autoantibodies
-if due to cold autoantibody-incubate patient RBCs at 37C and wash with 37C saline 3 times (get valid front type)
-can also treat RBCs with DTT to break up IgM agglutination
-can pre-warm
-can perform auto adsorption (get valid back type)
128
How to resolve group 4 discrepancies? due to unexpected ABO isoagglutinin
-may be due to anti-A1
-identify anti-A1 using 3 examples of A1 cells, A2 cells, B cells, O cells, and auto control
-pattern determines the specificity
-test patient RBCs with dolichos biflorus (Anti-A1 lectin-agglutinates A1 cells)
129
How to resolve group 4 discrepancies? due to unexpected alloantibodies
ex: anti-M
-perform antibody identification process
-find reagent A1 and B cells negative for antigen to correct reverse typing
130
acriflavine antibody
-forms a complex that attaches to patients' RBCs and causes agglutination in the forward type
-resolve by washing the patient's cells with saline 3 times
131
What is acriflavine?
-is the yellow dye in some anti-B antisera reagents, when someone has an antibody to this dye, it forms an acriflavine-anti acriflavine complex that attaches to patient RBCs and causes agglutination in the front type
