Rh Blood Group

Question 1

What are the 5 main Rh antigens?

Answer 1

D, C, c, E, e

Question 2

What is the frequency of the D antigen in the population?

Answer 2

85%

Question 3

What is the frequency of the C antigen in the population?

Answer 3

70%

Question 4

What is the frequency of the c antigen in the population?

Answer 4

80%

Question 5

What is the frequency of the E antigen in the population?

Answer 5

30%

Question 6

What is the frequency of the e antigen in the population?

Answer 6

98%

Question 7

Name two genes are involved in Rh genetics and what does each code for?

Answer 7

RHD- codes for the D antigen, RHCE- Codes for Cc and Ee antigens

Question 8

Describe the mechanism by which most people of European ethnicity inherit the Rh negative phenotype.

Answer 8

The RHD gene is deleted

Question 9

Describe the mechanism by which most people of African descent inherit the Rh negative phenotype.

Answer 9

They inherit an RHD pseudogene due to a missense mutation. This mutation prevents them from producing the protein.

Question 10

Describe the mechanism by which most people of Asian descent inherit the Rh negative phenotype.

Answer 10

They inherit the Del mutation. This mutation causes the individual to create a lower number of D antigen sites which causes them to type as D negative.

Question 11

What is the significance of the Rh-associated Glycoprotein (RhAG)?

Answer 11

It is a coexpressor and must be present for the Rh antigens to be present.

Question 12

What function to the Rh antigens provide for the red cell?

Answer 12

Maintain RBC membrane integrity

Question 13

How do you test for the D antigen on red cells?

Answer 13

Add one drop of 3-5% patient RBCs to 1 drop of anti-D reagent then centrifuge for 30 seconds. An indirect antiglobulin test can be performed to detect a weak D.

Question 14

What are the 4 mechanisms which will allow a weak D antigen to occur?

Answer 14

C in trans to D, Weak D, Partial D, Del

Question 15

What is meant when it is said that C is inherited trans to D?

Answer 15

The allele carrying RHD is on the opposite haplotype from the allele carrying C. This interferes with the expression of the D antigen causing a weakened expression.

Question 16

Describe the difference between weak D and partial D.

Answer 16

Weak D is a weakened expression of the complete D epitope which causes a fewer number of D antigens (internal change). Partial D is when one or more of the D epitopes is changed or missing (external change).

Question 17

Which weak D phenotype can make anti-D? Why?

Answer 17

Partial D phenotype. They can make an antibody to the part of the D epitope that they are missing.

Question 18

If a patient has a weak D, should they be transfused Rh negative or Rh positive blood?

Answer 18

Rh positive

Question 19

If a patient has a partial D, should they be transfused Rh negative or Rh positive blood?

Answer 19

Rh negative

Question 20

List three situations where a weak D test may be performed and why it would need to be performed in that situation.

Answer 20

All Rh negative donor units to ensure those labeled as Rh negative are truly Rh negative, Rh negative OB patients to determine if they need Rhogam, Rh negative newborns to determine if they may be Rh positive. If they are, the Rh negative mother will need Rhogam.

Question 21

Which Rh antigen is the most immunogenic?

Answer 21

D antigen

Question 22

Which Rh antigen is the least immunogenic?

Answer 22

Little e

Question 23

Is Rh reactivity increased or decreased by enzymes?

Answer 23

Increased

Question 24

What immunoglobulin class are Rh antibodies?

Answer 24

IgG

Question 25

Do Rh antibodies cause HDFN and TRXNs?

Answer 25

Yes

Question 26

Do the Rh antigens bind complement?

Answer 26

No

Question 27

How is HDFN from anti-D prevent in Rh negative mothers?

Answer 27

The mother is given Rhogam which binds to Rh positive fetal cells, preventing the mother from forming anti-D.

Question 28

What does it mean when an individual inherits the Rh null phenotype?

Answer 28

They are lacking all of the Rh antigens.

Question 29

What is the mechanism by which the regular type Rh null phenotype is formed?

Answer 29

There is a mutation in the RHAG gene preventing the RHAG protein from being expressed. Because there is no RHAG protein, the RHD and RHCE proteins cannot bind, even though those genes are normal.

Question 30

What is the mechanism by which the amorphic type Rh null phenotype is formed?

Answer 30

There is a mutation in both RHCE genes inherited preventing formation of the RHCE proteins. The individual must also inherit the usual RHD deletion. The RHAG gene in this case is normal.

Question 31

What symptoms will a patient have that inherits the Rh null phenotype?

Answer 31

Mild compensated hemolytic anemia, reticulocytosis, stomatocytosis, increased HgF, decreased serum haptoglobin, sometimes elevated bilirubin

Question 32

What is the mechanism by which the Rhmod phenotype is formed?

Answer 32

There is a mutation in the RHAG gene that causes a weakened expression of RHAG, RHD, and RHCE.

Question 33

What symptoms will a patient have that inherits the Rhmod phenotype?

Answer 33

Same as Rh null, but less severe

Question 34

What is the frequency of the Cw antigen?

Answer 34

Occurs in <1% of the population, 2% of Caucasians

Question 35

How does a person express the f antigen?

Answer 35

It is only expressed when c and e are present on the same haplotype (cis position). It is expressed on the Rhce protein.

Question 36

If a person with an anti-f needs a transfusion, what type of red cells should they be given?

Answer 36

Little c or little e negative red cells. They only need to be negative for one since both must be present for them to have the f antigen.

Question 37

When does a person express the G antigen?

Answer 37

On most D+ and all C+ red cells

Question 38

If a person with an anti-G needs a transfusion, what type of red cells should they be given?

Answer 38

D and C negative

Question 39

Why is it important to distinguish anti-D and C from anti-G during pregnancy?

Answer 39

If the patient already has an anti-D, then Rhogam will not benefit them. If a person however has an anti-G, then Rhogam should be administered to prevent them from forming an anti-D.

Question 40

What is the frequency of V and VS in Caucasians vs. African Americans?

Answer 40

In Caucasians it is a low frequency antigen, however 30-32% of African Americans are positive for the antigen.

Question 41

What are the characteristics of the Deletion Phenotype?

Answer 41

There is no Cc or Ee reactivity and an unusually strong D expression. These people have the ability to make anti-Rh17 or anti-Hr0.

Question 42

How can you tell the difference between anti-LW and anti-D?

Answer 42

Anti-LW will react weakly or not at all with Rh negative red cells while anti-D will definitely be negative with Rh negative red cells. Anti-LW will have equal reactivity between Rh negative and Rh positive cord cells while anti-D will be positive with Rh positive cord cells and negative with Rh negative cord cells.