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2.2 Transfusion Science > The Rh Blood Group System > Flashcards

The Rh Blood Group System Flashcards

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1
Q

What is the Rh blood group system also called

A

Rhesus System

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2
Q

How was the Rh blood group discovered
(4)

A

Injected Rhesus monkey cells into a guinea pig

Took blood from these guinea pigs and mixed it’s plasma with human blood

85% of human donors reacted with the guinea pigs blood (rhesus antibody discovered)

A lady had a baby, second pregnancy kept resulting in miscarriages, Rhesus antibody was seen in this women

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2
Q

How was the Rh blood group discovered
(4)

A

Injected Rhesus monkey cells into a guinea pig

Took blood from these guinea pigs and mixed it’s plasma with human blood

85% of human donors reacted with the guinea pigs blood (rhesus antibody discovered)

A lady had a baby, second pregnancy kept resulting in miscarriages, Rhesus antibody was seen in this women

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3
Q

Who discovered the Rhesus antibody

A

Landsteiner and Wiener

(Experiment with monkeys and guinea pigs)

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4
Q

Who discovered the Rh antibody in humans?

A

Levine and Stetson

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5
Q

Describe the Levine and Stetson experiment
(5)

A

Group O lady with one previous kid had a miscarriage and required a transfusion

Transfused with husband’s group O blood

Immune system reaction occurred

She had an anti-D antibody

She was RhD negative and had made anti-D after first pregnancy

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6
Q

How is rhesus antigen and Rh antigen different?

A

In monkeys -> anti LW

In humans -> anti Rh

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7
Q

What does RhD negative mean?

A

Dont have the Rh antigen on rbcs

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8
Q

What does RhD positive mean

A

Have the Rh antigen on rbcs

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9
Q

What type of blood do you give if a patient produces anti-D?

A

You have to give D-Negative blood

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10
Q

Why won’t we give D positive to women?

A

In case a women later want’s to get pregnant

This ensures her first pregnancy will go smoothly -> no immediate immune reaction

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11
Q

What are the two ways expression of anti-D can be induced

A

Pregnancy

After transfusion

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12
Q

Comment on C and E sets of alleles
(4)

A

C, E, c, e

The products of two sets of alleles

Co-dominant genes

Antibodies to these occur as immune events and are typically IgG -> potent -> clinical significance

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13
Q

What are the Rh proteins??

A

A family of non-glycosylated membrane proteins

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14
Q

What are the Rh protein genes?

A

RHD and RHCE

Located on chromosome 1

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15
Q

What does RHD express

A

The D antigen

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16
Q

What does RHCE express

A

The C, c, E and e antigens

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17
Q

What is the Fisher-Race theory

A

Rh antigens are controlled by 3 closely linked loci (D/d, C/c, E/e)

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18
Q

What is the Wiener theory

A

Rh antigens are controlled by alleles at one gene locus (you have one of 6 alleles at at locus)

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19
Q

What happens in almost all D negs?

A

The RHD gene is deleted (dd results)

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20
Q

How does the RHD protein differ from that of RHCE?

A

By 36 amino acids

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21
Q

By how much does C differ from c

A

Differs by 4 amino acids

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22
Q

By how much does E differ from e

A

Differs by 1 amino acid

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23
Q

By how much does D differ from d

A

Differs by 36 amino acids

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24
Q

What is special about the amino acid proline

A

It causes a change in direction in the chain of amino acid

This is why C is so different from c

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25
Q

What is the CDE haplotype referred to as?

A

Rz

26
Q

What is the cde haplotype referred to as?

A

r

27
Q

Do we use a R or r with a big D?

A

R

28
Q

Do we use a R or r with a small D

A

r

29
Q

What do we use when we have a big C?

A

C+D = 1

C+ d = ‘

30
Q

What do we use when we have a big E?

A

E + D = 2

E + d = ‘’

31
Q

What is the haplotype for dCe

A

r’

32
Q

What is the haplotype for dcE

A

r’’

33
Q

What is the haplotype for dCE

A

Ry

34
Q

What is the haplotype for Dce

A

Ro

35
Q

What is the haplotype for Dce

A

R1

36
Q

What is the haplotype for DcE

A

R2

37
Q

What are the most common haplotypes in caucasians

A

R1
r
R2
R0

38
Q

What are the most common haplotypes in black populations

A

R0
r
R1
R2

39
Q

What blood group antigen is the most immunogenic?

A

The D antigen

40
Q

Why should you give RhD negative blood to RhD negative patients

A

Most RhD negative will produce anti-D antibodies

41
Q

What is ISBT Terminology

A

International Society of Blood Transfusion

Assigns six-digit numbers to each blood group specificity

42
Q

What does the number 004 refer to?

A

Rh system

43
Q

What is the Rosenfield nomenclature

A

RH1 = D

Rh2 = C

Rh3 = E

Rh4 = c

Rh5 = e

44
Q

What does the ISBT number 002 refer to?

A

It refers to Rh2 or the C antigen

45
Q

What does Rh: 1,2,-3,4,5 mean?

A

R1r
DCe/dce

46
Q

When might a transfusion reaction occur

A

Rh antibody levels may be undetectable in a patient for years but they might produce a rapid response upon reexposure to the antigen via transsfusion

47
Q

What is HDFN

A

Haemolytic disease of the foetus and newborn

48
Q

How does HDFN occur
(3)

A

Mother is RHd negative
Baby is Rhd positive

Mother is exposed to antigen and produces antibodies during first pregnancy

Mother produces antibodies against babies rbcs which pass over through the placenta

49
Q

How do weak antigens occur
(3)

A

Mutation in the amino acid chain of the antigen

Antigen can no longer sit correctly into the rbc membrane

Charged amino acids cannot sit inside the inner lipid of the cell membrane (this doesn’t like charges)

50
Q

Why is it important to identify weak D positives

A

We don’t have much D negative blood so we want to be picking up this D positive so we don’t waste blood

51
Q

How do we classify weak antigens

A

RBCs that only test positive by the indirect antiglobulin test (IAT)

52
Q

What can we use to detect weak antigens other than the indirect antiglobulin test?

A

Monoclonal reagents

53
Q

Why is weak D antigen seen more in black population

A

Due to inheritance of a weaker form of the D antigen

Often the cDe haplotype

54
Q

What is meant by the position effect of weak D antigens?
(4)

A

A D antigen that appears weak due to a C antigen inherited trans to D

Rhce and RhCE as well as RhD and Rhd

RhCE will be copied more than RhD

Leads to a weaker expression of D

55
Q

What does it mean if alleles are in trans to one another

A

They are on opposite chromosomes

56
Q

What does it mean if alleles are in cis to one another

A

They are on the same chromosome

57
Q

What does it mean to be partial D?
(3)

A

Individuals are D positive but are missing parts of the D antigen

Individuals may produce antigens towards the missing parts of the D antigen when exposed to it

Patients should be given D negative blood

58
Q

What is important to note about partial D blood in hospitals vs donations?

A

Partial D should be labelled D positive when donated

Partial D should be given D negative blood in hospital

59
Q

How many partial D phenotypes are there?

A

There is 30+ epitopes on antigen D so there is different mutations whereby these epitopes are missing

60
Q

Give an example of a partial D

A

D6 (partial D)

61
Q

What happens with RhD incompatibility

A

Possibly fatal

Often serious morbidity

Leading cause of HDN

62
Q

What is Rh null
(3)

A

The absencce or severe reduction of Rh polypeptide expression

An autosomal recessive disorder resulting in haemolytic anaemia and sphcrostomatocytosis

Patients produce Rh29 which is linked with autoantibody haemolytic states

2.2 Transfusion Science (22 decks)

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