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Blood Bank CCF > Rh Blood Group > Flashcards

Rh Blood Group Flashcards

Exam 2

1
Q

What are the 5 main Rh antigens?

A

D, C, c, E, e

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2
Q

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

A

85%

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3
Q

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

A

70%

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4
Q

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

A

80%

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5
Q

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

A

30%

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6
Q

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

A

98%

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7
Q

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

A

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

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8
Q

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

A

The RHD gene is deleted

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9
Q

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

A

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

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10
Q

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

A

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.

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11
Q

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

A

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

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12
Q

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

A

Maintain RBC membrane integrity

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13
Q

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

A

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.

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14
Q

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

A

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

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15
Q

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

A

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.

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16
Q

Describe the difference between weak D and partial D.

A

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).

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17
Q

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

A

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

18
Q

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

A

Rh positive

19
Q

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

A

Rh negative

20
Q

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

A

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.

21
Q

Which Rh antigen is the most immunogenic?

A

D antigen

22
Q

Which Rh antigen is the least immunogenic?

A

Little e

23
Q

Is Rh reactivity increased or decreased by enzymes?

A

Increased

24
Q

What immunoglobulin class are Rh antibodies?

A

IgG

25
Q

Do Rh antibodies cause HDFN and TRXNs?

A

Yes

26
Q

Do the Rh antigens bind complement?

A

No

27
Q

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

A

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

28
Q

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

A

They are lacking all of the Rh antigens.

29
Q

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

A

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.

30
Q

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

A

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.

31
Q

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

A

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

32
Q

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

A

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

33
Q

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

A

Same as Rh null, but less severe

34
Q

What is the frequency of the Cw antigen?

A

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

35
Q

How does a person express the f antigen?

A

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

36
Q

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

A

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.

37
Q

When does a person express the G antigen?

A

On most D+ and all C+ red cells

38
Q

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

A

D and C negative

39
Q

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

A

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.

40
Q

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

A

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

41
Q

What are the characteristics of the Deletion Phenotype?

A

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.

42
Q

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

A

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.

Blood Bank CCF (26 decks)

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