ABO, H, Lewis, and P Flashcards
The enzyme responsible for conferring H activity on the red cell membrane is:
a. Galactosyl transferase
b. N-acetylgalactosaminyl transferase
c. L-fucosyltransferase
d. N-acetylfucosaminyl transferase
L-fucosyltransferase
L-fucosyltransferase helps add/bestow an L-fucose molecule to the terminal galactose of the precursor chain.
Know the organic compounds which become carbohydrate based blood groups and the transferases which confer (bestow) activity.
The H antigen can be developed using a type 1 or type 2 precursor. Either mechanism confers activity of H via L-fucosyltransferase.
Individuals who are non-secretor, group A, Le(a+b-) would have which substance in their saliva?
a. A, H, Lea, Leb
b. A, H, Lea
c. A, Lea, Leb
d. Lea only
Correct: Lea only
short answer;
If a person is a nonsecretor (sese), then they will NOT have ABH substances in their secretions.
Additionally, a person who inherits the Le gene, will only produce Leb substance ONLY IF they possess the secretor gene (Sese or SeSe)
Long answer;
The secretor gene and Lewis gene use the same precursor chain, having a preference for the type 1 chain (this means that technically type 1 and/or type 2 chains can be used but the precursor prefers type 1).
For simplicity sakes when discussing Lewis, let’s just talk type 1 chains.
To confirm the specificity of a serum containing Anti-P, an inhibition/neutralization study was performed and the following results were obtained:
Inhibition Test: NEG
Inhibition Control: NEG
What conclusions can be made from these results?
a. Anti-P is confirmed
b. Anti-P is ruled out
c. The Anti-P was inhibited
d. The test is not valid
Correct: This test is NOT valid
The inhibition/neutralized control should be always be positive!
Here is a piece from the tech manual describing why
The absence of agglutination in the dilution control tube means that the dilution in the neutralization step was too great for the antibody present, and the results of the test are invalid.
The steps in a neutralization procedure include the following:
Action (neutralization for Sda)
- Mix equal volumes of thawed urine and test plasma.
Example: tube name- neutralized plasma contents- 10 drops urine + 10 drops test plasma - Prepare a dilution control tube containing equal volumes of Saline and test plasma.
Example:
tube name- dilution control
contains- 10 drops saline + 10 drops test plasma
- Incubate all tubes at room temperature for 30 minutes.
- Mix 1 drop of each test red cell sample with 4 drops from each of the tubes: neutralized plasma and saline+plasma. Test each one using standard procedures.
If the dilution control is negative, you’ve demonstrated that you have DILUTED the antibody of interest (which makes your testing invalid). You would also expect your neutralized plasma to be negative but you cannot positively confirm whether this is due to diluting the antibody or neutralization.
The dilution control must always be positive for your test to be valid to indicate you have not DILUTED your antibody of interest.
A pregnant woman’s serum contains hemolytic Anti-Lea. Her husband’s RBC type is Le(a+). What is the chance that the fetus will develop immune-mediated HDN?
a. 100%
b. 75%
c. 25%
d. 0%
correct: 0%
Lewis antigens are not expressed on infant’s RBCs at birth, so there is no risk of HDN
Some ordering physicians request Lewis titers on pregnant mothers. An astute serologist will understand that this testing is unnecessary.
A 10 year old child is admitted to the hospital for an investigation of unexplained hemolysis. The mother reported that the child recently had a mumps infection. The child had been playing in the snow, and after he came in from the cold the mother reported he had red urine. The next best test to perform to determine the antibody specificity is:
a. Antibody ID panel
b. Ham’s test
c. Donath Landsteiner Test
d. Elution
correct: Donath Landsteiner test
This is a classical pattern of Paroxysmal Cold Hemoglobinuira (PCH). An auto-anti-P antibody develops after a viral infection, and this antibody is biphasic. The antibody binds complement to the RBCs in a cooler temperature, and then causes hemolysis when the temperature rises. These examples are typically seen in children and young adults. A donath landsteiner test is performed to prove the biphasic antibody is present.
Red blood cells from a patient with HEMPAS typically exhibit which characteristic?
a. increased amounts of i antigen
b. decreased amounts of i antigen
c. increased amounts of H antigen
d. increased amounts of sialic acid
correct: increased amounts of i antigen
HEMPAS (Hereditary Erythroblastic Multinuclearity with a Positive Acidified Serum test) is a congenital anemia in which the rbc membranes are abnormal. These cells typically have increased amounts of i antigen, decreased amounts of H antigen, and decreased sialic acid.
A mother who is Lu(a-b+) and a father who is Lu(a+b-) have three children. Their lutheran phenotypes are: Child 1 Lu(a+b+), Child 2 Lu(a+b+), Child 3 Lu(a-b-).
The result of child 3 can best be described by which situation?
a. Inheritance of In(Lu)
b. lulu genotype
c. non-paternity
d. crossing over
correct: lulu genotype
The mother is probably Lub lu and the father is probably Lua lu In this situation, the child 3 could have inherited two copies of the lu gene, which is an amorph. A lulu genotype, results in a Lutheran phenotype of Lu(a-b-)If either of the parents had the In(Lu) gene, then they would be Lu(a-b-) as this is a dominant gene which inhibits the formation of Lutheran antigens)Non-paternity is a possiblity, but not the best description here, since the child could in fact have inherited two copies of the recessive lu gene, which is an amorphCrossing over is a rare genetic event, and is not the most likely explanation
Which of the following antigens are NOT developed on cord cells?
a. I and Sda
b. M and N
c. D and c
d. K1 and Lea
Correct: I and Sda
The other antigens are well developed on cord cells.
Recall from previous questions newborns express “i” which develop into “I” with age.
Additionally, Sda is a carbohydrate antigen (as is i/I) synthesized by an enzyme. Sda has a characteristic mixed field appearance with free red cells when viewed microscopically. Sda is inhibited by urine from Sda+ individuals (some friends of mine in the IRL had to void their urine!) and by guinea pig urine. Anti-Sda is not generally considered clinically significant.
Sda is noted for its “refractile” appearance under the microscope mixed with tightly bound red cells.
Characteristics of PCH include:
a. The antibody is usually IgM
b. The antibody has P specificity
c. The antibody is nonreactive with enzyme treated cells
d. All of the above are true
Correct: antibody has P specificity.
PCH is caused by a biphasic, IgG antibody, which does react with enzyme treated cells.
Diagnostic methods of PCH
Diagnosis is based on evidence of anemia linked to hemolysis, the presence of hemoglobin in urine, a positive result from the Donath-Landsteiner (DL) test and evidence of anti-P specificity of the IgG autoantibodies.
Management and treatment
Most cases of PCH are self-limited so treatment is usually symptomatic, including keeping the patient warm and red blood cell transfusion if necessary. Patients with few clinical symptoms and slight anemia may not require drug therapy. Corticosteroids and splenectomy are usually ineffective and should not be considered. In cases of life-threatening PCH, plasmapheresis can temporarily dampen the hemolysis. Some patients may respond to rituximab, although responses are usually short-lived. If syphilis is present, treatment with antibiotics generally eliminates the concurrent hemolysis.
Paroxysmal Cold Hemoglobinuria (PCH) is caused by an IgG biphasic hemolysin that most commonly has P blood group specificity. The antibody (autoanti-P) optimally binds red cells at 4C. However, complement is activated and red cells are lysed at 37C. The Donath-Landsteiner test consist of incubating a patient’s serum with P positive red cells at 4C alone, at 37C alone and at 4C followed by 37C. The DL test is positive when the degree of hemolysis is greater in 4C followed by 37C tube. PCH is an autoimmue hemolytic anemia that is associated with viral infections typically in young children. (resource: Transfusion Medicine Self Assessment Review 3rd edition Blackall et al)
Which of the statement(s) is(are) TRUE for the I/i system?
a. I and i are alleles
b. little i antigen is comprised of many branched chains
c. HDN due to potent anti-I has been described
d. Patients with M. pneumoniae infection often develop strong cold agglutinins with I specificity
Correct: Patients with M. pneumoniae infection often develop strong cold agglutinins with I specificity
The production of autoanti-I may be stimulated by microorganisms carrying I like antigen on their surface. Patients with Mycoplasma pneumoniae often develop strong cold agglutinins with I specificity as a crossreactive response to mycoplasma antigen and can experience a transient episode of acute abrupt hemolysis just as the infection begins to resolve. I an i are not really alleles. At birth, infant red cells are rich in i, and I is almost undetectable. Over the next 18 months the infant’s red cells will convert from i to I antigen. Remember that the i antigen is a straight chain form, and the I antigen, is a branched form of the chain. HDN due to potent anti-I has not been described, since fetal cells have only i antigen, and not the I antigen.
There are two disease associations with development of anti-i and anti-I.
anti-i development associated with infectious mononucleosis
anti-I development associated with M. pneumonia (ie “walking pneumonia”)
I remember because mononucleosis has circle letters as the letter “i” has the circle at the top and “I” looks like a leg so I remember this as walking pneumonia. (kind of silly but maybe you’ll remember this way too!)
Which gene is needed to produce Lea substance in the saliva of an individual
a. Le
b. Se
c. H
d. Lea
Correct: Le
There is no Lea gene. Only the Le gene, which can be modified by the presence of the Secretor gene Se.
Your institution is developing the Percutaneous Umbilical Blood Sampling (PUBS) technique. Physicians need to distinguish RBCs of fetal and maternal origin. Which method below is the best approach for discerning cellular origin?
a. Perform an ABO, RH, and DAT on the sample drawn.
b. Perform P phenotype on the sample
c. Perform a freeze-thaw elution on PUBS sample
d. Perform I phenotype on sample
Correct : Perform I phenotype on sample
Neonates have i antigen on their red cells and almost undetectable amounts of I antigen.
Which of the antibody specificities below is a benign autoantibody, found in many normal healthy people?
a. anti-I
b. anti-H
c. anti-P1
d. anti-i
Correct: anti-I
It is quite common for patients to have an auto-anti-I which reacts only at 4 C.
The antibody will not be detected often though since we routinely do not screen at 4 C for antibodies, and also use anti-IgG as the primary antiglobulin reagent (not anti-C3 or anti0IgG/C3)
A patient has the genotype hh, AB. What blood group will he appear to be on the forward ABO typing?
a. O
b. B
c. A
d. AB
Correct: O
This individual LACKS the ability to produce
A bleeding patient is in need of group O blood. From which US ethnic group would one find the most group O donors?
a. European-American
b. African-American
c. Asian-American
d. Native American
e. Melanesian-American
Correct: D Native American
African-American: 49%
Asian-American: 41%
European-American: 44%
Native American: 79%
A mixed-field agglutination reaction may be observed in which of the following situations?
a. Between anti-B and some weak subgroups of B
b. After recent transfusion of group O RBCs to a non-group O individual
c. Between anti-Sda and Sda-positive red cells in the antiglobulin phase of testing
d. All of the above
e. None of the above
D. All of the above
Bombay phenotype (Oh) individuals:
a. Have red cells that do not agglutinate with either anti-A or anti-B but do agglutinate with Ulex europaeus lectin
b. Have naturally occurring anti-A, anti-B, and anti-H
c. Can be transfused safely with blood from donors of any blood group (A, B, AB, O)
d. Have naturally occuring anti-A and anti-B but they are not reactive at 37 C
e. Inherit SeSe at the Se locus
Correct: B
Which of the following red cell types is most frequently used to demonstrate the specificity of anti-I?
a. Adult cells
b. Oh Bombay cells
c. Cord cells
d. Le(a+b+) cells
e. i adult cells
Correct: C
The Leb antigen serves as a receptor for which microorganism?
a. Candida albicans
b. Escherichia coli
c. Streptococcus suis
d. Helibacter pylori
e. Yersinia enterolitica
Correct: D
Which of the following antigens or phenotypes occurs more frequently in people of African ethnicity than in those of European ethnicity?
a. A
b. I-negative adult
c. Le (a-b-)
d. p
e. P2
Correct: C
Which of the following antibodies is characteristically associated with in-vitro hemolysis?
a. Anti-C
b. Anti-D
c. Anti-Fya
d. Anti-K
e. Anti-Lea
Correct: e
An antibody associated with a positive Donath-Landsteiner test result is most likely to have specificity for which blood group antigen?
a. E
b. M
c. I
d. P
e. Lua
Correct: D
Which of the following statement(s) is (are) TRUE for the I/i system?
a. I and i are alleles
b. HDN due to potent anti-I have been described
c. i antigen is comprised of many branched chains
d. Patients with M. pneumoniae infection often develop strong cold agglutinins with I specificity
Correct: D
A Le (a-b-) individual with an anti-Lea in his serum is transfused with Le (a+) red blood cells. Which statement below best describes the most likely result of this transfusion?
a. The patient will not have a transfusion reatction, and the DAT will be negative
b. The patient will have a moderately severe delayed transfusion reaction
c. The patient will have a mild transfusion reaction, having only a positive DAT
d. The patient will have a severe intravascular hemolytic transfusion reaction
Correct: a
There are two reasons why the patient is not likely to have a transfusion reaction.
1. The anti-Lea antibodies are typically IgM cold reacting antibodies, which do not react at warmer temperatures.
2. Lewis antigens are not intrinsic to the RBC membrane, but rather are Type 1 carbohydrate chains which are absorbed from the plasma. This adsorption is reversible, and as such the donor cells typically acquire the Lewis phenotype of of the transfusion recipient within a few days of transfusion.
