P Blood Group Flashcards
Exam 1
What are the 3 antigens of the P system?
P1, P, Pk
What are the 5 phenotypes of the P system?
P1, P2, p, P1k, P2k
The P genes code to make what type of proteins? What is the function of these proteins?
Glycosyltransferases, their function is to add sugars to a precursor substance
Which antigens does the P1 phenotype have?
P1, P, Pk
When storing cells with the P1 antigen for a longer period of time, what happens to the antigen?
It deteriorates
At what point in life is the P1 antigen fully developed?
7 years
Which phenotypes will produce an anti-P1?
P2 and P2k. These lack the P1 antigen. Even though p also lacks the antigen, it makes an antibody in a combined form of anti-PP1Pk
Is anti-P1 an immune or naturally occurring antibody?
Naturally occurring
Is anti-P1 typically an IgM or IgG antibody?
IgM
At what temperature does anti-P1 react best?
Room temperature or colder
Why is anti-P1 not a cause of HDFN?
It is IgM and can’t cross the placenta and the P1 antigen is poorly developed on fetal RBCs
Approximately what percentage of the population is positive for the P1 phenotype?
80%
What substances can be used to neutralize P1 antibody?
Hydatid Cyst fluid from Echinococcus granulosus and Avian P1 substance (in dropping of pigeons and turtle doves)
The P2 phenotype lacks which antigen(s)?
P1, it contains the P and Pk antigens
Approximately what percentage of the population has the P2 phenotype?
20%
If an individual inherits the P1k phenotype, what antigens do they form?
P1 and Pk (lack the P antigen)
If an individual inherits the P2k phenotype, what antigens do they form?
Pk (lack P1 and P antigens)
What antibody could a P1k individual form?
Anti-P
If an individual inherits the p phenotype, what antigens do they form?
None
What antibody can an individual with the p phenotype form?
Anti-PP1Pk
Can an anti-PP1Pk cause transfusion reactions and HDFN?
Yes
Which P system antibody is usually seen as an autoantibody?
Autoanti-P
Which antibody is the cause of Paroxysmal Cold Hemoglobinuria?
Autoanti-P
In what demographic is Paroxysmal Cold Hemoglobinuria usually seen?
Secondary to viral infections in young children
Describe the process by which the autoantibody destroys red cells in Paroxysmal Cold Hemoglobinuria?
The antibody is biphasic- the antibody binds in the cold (when blood is in your extremities) and lyses when the body temp rises (in your core)
What is the recommended treatment for Paroxysmal Cold Hemoglobinuria?
Stay away from the cold
Describe how the Donath-Landsteiner test is performed.
Patient serum (with potential autoanti-P) is added to P+ cells in 2 different tubes. The first tube is incubated at 37C for 60 min. The second tube is incubated at 4C for 30 minutes and 37C for another 30 minutes. If the autoanti-P is present the tube that was incubated in the cold first and then the warm should have hemolyzed the red cells causing the serum to be red. The tube kept at warm temperatures should remain clear and yellow.
What is the typical DAT reaction of a patient with Paroxysmal Cold Hemoglobinuria?
Polyspecific reagent is positive, anti-IgG reagent is negative, and anti-C3d is positive
Individuals with which P system phenotypes will lack the Luke antigen?
Pk phenotypes and p phenotype
Do the majority of people have the Luke antigen or lack the Luke antigen?
The majority are Luke antigen positive
