ABO Flashcards
Exam 1
An individual with type A blood will have which ABO antibodies present?
Anti-B
An individual with type B blood will have which ABO antibodies present?
Anti-A
An individual with type O blood will have which ABO antibodies present?
Anti-A, Anti-B, and Anti-A,B
An individual with type AB blood will have which ABO antibodies present?
None
Describe the process of performing a forward grouping
Add 1 drop of reagent (anti-A, B, or D), add 1 drop of a 3-5% patient RBC suspension, centrifuge for 30 seconds, and read
Describe the process of performing a reverse grouping
Add 1 drop of A1 or B cells, add 2 drops of patient plasma, centrifuge for 30 seconds, and read
The forward grouping is detecting patient _________________.
Antigens
The reverse grouping is detecting patient _________________.
Antibodies
What are the frequencies of the different blood types?
O: 45% A: 40% B: 11% AB: 4%
Are ABO antibodies natural or immune antibodies?
Natural
Are ABO antibodies usually IgM or IgG?
IgM
At which temperature do ABO antibodies react best?
Room temperature or colder (4C- 24C)
Can ABO antibodies cause hemolytic transfusion reactions and hemolytic disease of the fetus and newborn?
Yes
Describe the strength of ABO antibodies throughout life.
Birth: initiate antibody production- undetectable. 3-6 months: titers are strong enough to be detected. 5-10 years: antibodies are at their peak strength. Increasing age: antibody titers decline. Elderly: antibodies may entirely disappear
If an individual is type A, what possible genotypes could they have inherited?
AO or AA
Which gene in the ABO blood group system is an amorph and which gene in the Hh blood group system is an amorph?
ABO: O, Hh: h
The ABO and H genes produce what kinds of enzymes and what do these enzymes do?
Produce glycosyltransferases which add sugars to a precursor substance
Describe the difference between type 1 precursors and type 2 precursors.
Type 1: beta 1-3 linkage, found as soluble antigens in body secretions. Type 2: beta 1-4 linkage, found on red cells.
For an individual to be group O, what genes must they have inherited?
At least 1 H gene and 2 O genes
Which enzyme does the H gene produce?
a-2-L-fucosyltransferase
What is an immunodominant sugar?
The sugar at the terminal position of the antigen determining the blood group
What is the immunodominant sugar for group O?
L-fucose
Which antigen must be present on the precursor chain before A or B can attach?
H antigen
For an individual to be group A, what genes must they inherit?
At least one A gene and one H gene
Which enzyme does the A gene produce?
a-3-N-acetylgalactosaminyltransferase
What is the immunodominant sugar for group A?
N-acetyl-D-galactosamine (GalNAc)
For an individual to be group B, what genes must they inherit?
At least one B gene and one H gene
Which enzyme does the B gene produce?
a-3-d-galactosyltransferase
What is the immunodominant sugar for group B?
D-galactose
For an individual to be group AB, what genes must they inherit?
One A gene, one B gene, and at least one H gene
Which ABO enzyme produces the highest concentration of transferase and therefore converts the most H substance?
A enzyme- a-3-N-acetylgalactosaminyltransferase
Which blood types have the least amount of H substance?
A1B and A1
Which blood types have the most amount of H substance?
O
Which blood type is most likely to make an autoanti-H and why?
A1 and A1B because they have the least amount of H substance unconverted and their body is more likely to recognize the H antigen as foreign
Which blood type is the universal donor and universal recipient for red cell transfusion?
Universal Donor: O, Universal Recipient: AB
Which blood type is the universal donor and universal recipient for plasma transfusion?
Universal donor: AB, Universal recipient: O
What enzyme does the secretor gene produce and what does this enzyme do?
a-2-L-fucosyltransferase, modifies the type 1 precursor substance by adding the H substance to the chain.
If a person is a secretor, what antigens can be found in their secretions?
A, B, and H
What percentage of the population is a nonsecretor?
20%
What percentage of the type A population is A1?
80%
What are the differences between type A1 and type A2?
A1: 1,170,000 sites converted to A, more antigen sites, higher amounts of transferase enzyme, more branching. A2: 290,000 sites converted, a single-base substitution alters the active site of the transferase causing a decreased amount of transferase enzyme, a decrease in the amount of sites converted to A antigen, and decreased branching, can also form anti-A1.
What is the Anti-A1 lectin made from?
Seed extract of Dolichos biflorus plant
What is the Anti-H lectin made from?
Ulex europaeus
How will an A1 individual react with Anti-A1?
Positive reaction- agglutination
How will an A2 individual react with Anti-A1?
Negative reaction- no agglutination
What are common characteristics of a weak subgroup of A that can help identify them?
Decreased # of A antigen sites, varying agglutination with anti-A,B, increased detectability with H antigen, presence or absence of anti-A1.
How is the antibody anti-A,B different from the other ABO antibodies?
It is usually IgG and not IgM therefore it can also cross the placenta
What will happen if an individual inherits hh instead of Hh or HH?
They have inherited the Bombay phenotype (null phenotype), no a-2-L-fucosyltransferase will be created, no L-fucose attaches, therefore no H substance is present on the red cell. Without the H substance, A and B antigens are unable to attach as well.
If an individual inherits hh and AA, what will their blood type appear to be?
They have inherited the Bombay phenotype and will type as O, even though there is nothing wrong with their ABO genes
What antibodies does a Bombay individual create?
Anti-A, anti-B, anti-A,B, anti-H
If an individual has inherited the Bombay phenotype, what reactions would you expect when testing their plasma with screening cells?
Their plasma should react with all screening cells because they have anti-H in their plasma. Because screening cells are type O, they are covered in H antigen with which the anti-H will react.
If an individual with the Bombay phenotype needs a transfusion, what type of red cells should be given?
Must be RBCs from another Bombay individual (negative for H antigen)
How does para-Bombay type differ from the Bombay phenotype?
Parabombay can have ABH antigens in secretions and sometimes small amounts on the RBCs
Why is the ABO system the most important to match of all the blood group systems?
Only blood group system where individuals already have antibodies in their serum to antigens absent from their red cells. Produces severe if not fatal lysis of donor RBCs.
What exposure serves as the source of stimulation for anti-A and anti-B?
Exposure to bacteria, pollen, and other substances chemically similar to A and B antigens
Group B is found twice as frequently as Caucasians in what populations?
African American and Asian populations
What ABO testing is performed on neonates? Why?
Only forward ABO grouping is performed since neonates have not formed ABO antibodies that are serologically detectable yet.
Which ABO antibodies are predominantly IgM?
Anti-A and Anti-B and Anti-H
Which ABO antibodies are primarily IgG?
Anti-A,B
Which blood group(s) can form anti-A,B?
O
Which gene (A or B) elicits higher concentrations of transferase?
A - leads to conversion of nearly all H antigen on RBCs
In an AB patient, is more H converted to A antigen or B antigen? Why?
More is converted to B as the B enzyme seems to compete more efficiently for the A substance than the A enzyme
On what 5 types of cells are ABH antigens found?
RBCs, endothelial cells, platelets, lymphocytes, epithelial cells
How does the single base substitution for the A2 allele change the A enzyme and antigen?
Alters the active site of the enzyme leading to a less efficient enzyme that only converts the unbranched straight chains of H1 and H2 well.
What are the characteristics of an anti-A1 antibody?
Naturally occurring IgM cold-reacting antibody unlikely to cause transfusion reactions
What are the characteristics of an anti-H antibody made by type A1 or A1B individuals?
Naturally occurring IgM cold agglutinin reacting most strongly with group O cells
What is the structural difference between H1, H2, H3, and H4 antigens?
H1 and H2 are unbranched straight chains that are converted well by A1 and A2 individuals. H3 and H4 are complex branched chains that are only converted well by A1 individuals.
Will a Bombay patient’s RBCs react with anti-H lectin?
No, there is no H antigen present on their RBCs
What are the characteristics of an anti-H antibody formed by Bombay individuals?
IgM that reacts strongly at 37C binding complement and causing RBC lysis
What 2 genetic mutations cause the Para-Bombay phenotype?
- Mutated FUT1 that produces small amounts of H, A, and B antigens on RBCs
- Silenced FUT1 gene with active FUT2 (Se) gene that produces H, A, and B antigens in secretions that can be absorbed onto RBCs in small amounts
