The Rh Blood Group System Flashcards
What is the Rh blood group system also called
Rhesus System
How was the Rh blood group discovered
(4)
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
How was the Rh blood group discovered
(4)
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
Who discovered the Rhesus antibody
Landsteiner and Wiener
(Experiment with monkeys and guinea pigs)
Who discovered the Rh antibody in humans?
Levine and Stetson
Describe the Levine and Stetson experiment
(5)
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
How is rhesus antigen and Rh antigen different?
In monkeys -> anti LW
In humans -> anti Rh
What does RhD negative mean?
Dont have the Rh antigen on rbcs
What does RhD positive mean
Have the Rh antigen on rbcs
What type of blood do you give if a patient produces anti-D?
You have to give D-Negative blood
Why won’t we give D positive to women?
In case a women later want’s to get pregnant
This ensures her first pregnancy will go smoothly -> no immediate immune reaction
What are the two ways expression of anti-D can be induced
Pregnancy
After transfusion
Comment on C and E sets of alleles
(4)
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
What are the Rh proteins??
A family of non-glycosylated membrane proteins
What are the Rh protein genes?
RHD and RHCE
Located on chromosome 1
What does RHD express
The D antigen
What does RHCE express
The C, c, E and e antigens
What is the Fisher-Race theory
Rh antigens are controlled by 3 closely linked loci (D/d, C/c, E/e)
What is the Wiener theory
Rh antigens are controlled by alleles at one gene locus (you have one of 6 alleles at at locus)
What happens in almost all D negs?
The RHD gene is deleted (dd results)
How does the RHD protein differ from that of RHCE?
By 36 amino acids
By how much does C differ from c
Differs by 4 amino acids
By how much does E differ from e
Differs by 1 amino acid
By how much does D differ from d
Differs by 36 amino acids
What is special about the amino acid proline
It causes a change in direction in the chain of amino acid
This is why C is so different from c
What is the CDE haplotype referred to as?
Rz
What is the cde haplotype referred to as?
r
Do we use a R or r with a big D?
R
Do we use a R or r with a small D
r
What do we use when we have a big C?
C+D = 1
C+ d = ‘
What do we use when we have a big E?
E + D = 2
E + d = ‘’
What is the haplotype for dCe
r’
What is the haplotype for dcE
r’’
What is the haplotype for dCE
Ry
What is the haplotype for Dce
Ro
What is the haplotype for Dce
R1
What is the haplotype for DcE
R2
What are the most common haplotypes in caucasians
R1
r
R2
R0
What are the most common haplotypes in black populations
R0
r
R1
R2
What blood group antigen is the most immunogenic?
The D antigen
Why should you give RhD negative blood to RhD negative patients
Most RhD negative will produce anti-D antibodies
What is ISBT Terminology
International Society of Blood Transfusion
Assigns six-digit numbers to each blood group specificity
What does the number 004 refer to?
Rh system
What is the Rosenfield nomenclature
RH1 = D
Rh2 = C
Rh3 = E
Rh4 = c
Rh5 = e
What does the ISBT number 002 refer to?
It refers to Rh2 or the C antigen
What does Rh: 1,2,-3,4,5 mean?
R1r
DCe/dce
When might a transfusion reaction occur
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
What is HDFN
Haemolytic disease of the foetus and newborn
How does HDFN occur
(3)
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
How do weak antigens occur
(3)
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)
Why is it important to identify weak D positives
We don’t have much D negative blood so we want to be picking up this D positive so we don’t waste blood
How do we classify weak antigens
RBCs that only test positive by the indirect antiglobulin test (IAT)
What can we use to detect weak antigens other than the indirect antiglobulin test?
Monoclonal reagents
Why is weak D antigen seen more in black population
Due to inheritance of a weaker form of the D antigen
Often the cDe haplotype
What is meant by the position effect of weak D antigens?
(4)
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
What does it mean if alleles are in trans to one another
They are on opposite chromosomes
What does it mean if alleles are in cis to one another
They are on the same chromosome
What does it mean to be partial D?
(3)
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
What is important to note about partial D blood in hospitals vs donations?
Partial D should be labelled D positive when donated
Partial D should be given D negative blood in hospital
How many partial D phenotypes are there?
There is 30+ epitopes on antigen D so there is different mutations whereby these epitopes are missing
Give an example of a partial D
D6 (partial D)
What happens with RhD incompatibility
Possibly fatal
Often serious morbidity
Leading cause of HDN
What is Rh null
(3)
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
