MNS Blood Group

Question 1

What is the most common MNS phenotype?

Answer 1

M+N+S-s+

Question 2

Which antigens are on glycophorin A?

Answer 2

M and N

Question 3

Which antigens are on glycophorin B?

Answer 3

S and s

Question 4

The MNS system show’s dosage. What does this mean?

Answer 4

Stronger reactions will occur with a double dose (homozygous) of the antigen and weaker reactions with a single dose.

Question 5

What happens to the M and N antigens on RBCs when they are treated with enzymes?

Answer 5

They are destroyed

Question 6

What happens to the S and s antigens on RBCs when they are treated with enzymes?

Answer 6

They react variably, but are usually destroyed.

Question 7

Approximately what percentage of individuals are negative for the M antigen?

Answer 7

26%

Question 8

Approximately what percentage of individuals are negative for the N antigen?

Answer 8

27%

Question 9

Are anti-M and anti-N immune or naturally occurring antibodies?

Answer 9

Naturally occurring

Question 10

Are anti-M and anti-N most commonly IgG or IgM antibodies?

Answer 10

They are both. 50-80% are IgG, the rest are IgM

Question 11

At which temperature do anti-M and anti-N react best?

Answer 11

Colder temperatures

Question 12

Do anti-M and anti-N bind complement?

Answer 12

No

Question 13

Does anti-M or anti-N commonly cause transfusion reactions or HDFN?

Answer 13

No

Question 14

When it is said that anti-M can be pH dependent, what does this mean?

Answer 14

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.

Question 15

What does it mean for the anti-M antibody to be glucose dependent?

Answer 15

The antibody may only react with RBCs that have been exposed to a glucose solution (such as reagent RBCs or donor RBCs with preservative).

Question 16

Why is anti-N less commonly seen than anti-M?

Answer 16

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.

Question 17

Which phenotype will make the most potent anti-N?

Answer 17

M+N-S-s- or those who lack glycophorin B

Question 18

What happens to renal patients dialyzed on equipment that was sterilized with formaldehyde?

Answer 18

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.

Question 19

Approximately what percentage of individuals are negative for the S antigen?

Answer 19

65%

Question 20

Approximately what percentage of individuals are negative for the s antigen?

Answer 20

10%

Question 21

Are anti-S and anti-s immune or naturally occurring antibodies?

Answer 21

Immune

Question 22

Are anti-S and anti-s usually IgM or IgG antibodies?

Answer 22

IgG

Question 23

At what temperature do anti-S and anti-s react best?

Answer 23

37C (body temperature)

Question 24

Are anti-S and anti-s capable of causing transfusion reactions and HDFN?

Answer 24

Yes

Question 25

Are anti-S and anti-s capable of binding complement?

Answer 25

They may bind complement

Question 26

If an individual lacks the U antigen, what is the rest of their MNS phenotype look like?

Answer 26

M and N are unchanged, they will however be S-s- because they lack U and glycophorin B

Question 27

In what population is the S-s-U- phenotype more common?

Answer 27

African population

Question 28

Are the antibody characteristics of anti-U more similar to anti-S or anti-M?

Answer 28

Anti-S

Question 29

If a patient has formed an anti-U and is transfused U positive units, will this cause a transfusion reaction?

Answer 29

Yes, can cause fatal transfusion reactions

Question 30

The Ena negative phenotype results from what mutation?

Answer 30

GYPA mutation that prevents the GPA protein from forming

Question 31

What antigens does an individual with the Ena negative phenotype lack?

Answer 31

M and N

Question 32

The Mk phenotype results from what mutation?

Answer 32

A deletion of the GPA protein and GPB protein

Question 33

What antigens does an individual with the Mk phenotype lack?

Answer 33

M-N-S-s-U-Ena- or all of the MNS blood group antigens

Question 34

Which MNS blood group antibodies are commonly found as autoantibodies?

Answer 34

Anti-U and anti-Ena these are associated with warm autoimmune hemolytic anemia