MNS Blood Group Flashcards
Exam 1
What is the most common MNS phenotype?
M+N+S-s+
Which antigens are on glycophorin A?
M and N
Which antigens are on glycophorin B?
S and s
The MNS system show’s dosage. What does this mean?
Stronger reactions will occur with a double dose (homozygous) of the antigen and weaker reactions with a single dose.
What happens to the M and N antigens on RBCs when they are treated with enzymes?
They are destroyed
What happens to the S and s antigens on RBCs when they are treated with enzymes?
They react variably, but are usually destroyed.
Approximately what percentage of individuals are negative for the M antigen?
26%
Approximately what percentage of individuals are negative for the N antigen?
27%
Are anti-M and anti-N immune or naturally occurring antibodies?
Naturally occurring
Are anti-M and anti-N most commonly IgG or IgM antibodies?
They are both. 50-80% are IgG, the rest are IgM
At which temperature do anti-M and anti-N react best?
Colder temperatures
Do anti-M and anti-N bind complement?
No
Does anti-M or anti-N commonly cause transfusion reactions or HDFN?
No
When it is said that anti-M can be pH dependent, what does this mean?
Anti-M reacts best at a pH of 6.5, this means it can be detected in plasma in EDTA tubes due to the acidic anticoagulants, but it may not be detected in serum because it is unacidified.
What does it mean for the anti-M antibody to be glucose dependent?
The antibody may only react with RBCs that have been exposed to a glucose solution (such as reagent RBCs or donor RBCs with preservative).
Why is anti-N less commonly seen than anti-M?
Glycophorin B has an ‘N’-like antigen. Because of this the body thinks that the N antigen is not foreign even though they lack the real N antigen.
Which phenotype will make the most potent anti-N?
M+N-S-s- or those who lack glycophorin B
What happens to renal patients dialyzed on equipment that was sterilized with formaldehyde?
The formaldehyde alters the M and N antigens so the body thinks these are foreign. They may make an antibody (anti-Nf) which is clinically insignificant in response.
Approximately what percentage of individuals are negative for the S antigen?
65%
Approximately what percentage of individuals are negative for the s antigen?
10%
Are anti-S and anti-s immune or naturally occurring antibodies?
Immune
Are anti-S and anti-s usually IgM or IgG antibodies?
IgG
At what temperature do anti-S and anti-s react best?
37C (body temperature)
Are anti-S and anti-s capable of causing transfusion reactions and HDFN?
Yes
Are anti-S and anti-s capable of binding complement?
They may bind complement
If an individual lacks the U antigen, what is the rest of their MNS phenotype look like?
M and N are unchanged, they will however be S-s- because they lack U and glycophorin B
In what population is the S-s-U- phenotype more common?
African population
Are the antibody characteristics of anti-U more similar to anti-S or anti-M?
Anti-S
If a patient has formed an anti-U and is transfused U positive units, will this cause a transfusion reaction?
Yes, can cause fatal transfusion reactions
The Ena negative phenotype results from what mutation?
GYPA mutation that prevents the GPA protein from forming
What antigens does an individual with the Ena negative phenotype lack?
M and N
The Mk phenotype results from what mutation?
A deletion of the GPA protein and GPB protein
What antigens does an individual with the Mk phenotype lack?
M-N-S-s-U-Ena- or all of the MNS blood group antigens
Which MNS blood group antibodies are commonly found as autoantibodies?
Anti-U and anti-Ena these are associated with warm autoimmune hemolytic anemia
