Major Blood Group Systems Dependent on AHG Flashcards
What three blood group systems were discovered because of the IAT antiglobulin test
Kell
Duffy
Kidd
These are known as the ‘Big 3’
They are the most clinically significant after ABO and Rh
When was the IAT discovered?
1946
Why are Duffy, Kidd and Kell clinically significant?
They can all interact with complement
Duffy can also cause HDFN
Disovery of the Kell Blood group system
(5)
First defining antigen of the Kell Blood Group was discovered in 1946 (same year as IAT) by an antibody in the serum of a Mrs Kelleher
It was discovered by Lancer; Coombs, Mourant and Race
It was found that she had an antibody which reacted with her husbands, her daughters and newborns red blood cells
Her antibody also reacted with 9% of a random population -> antibody against antigen called K (K1)
In 1949 (3 yrs later) the allelic partner/corresponding antigen k (K2) was discovered
Origin of the Kell Blood group system
(5)
First defining antigen of the Kell Blood Group was discovered in 1946 (same year as IAT) by an antibody in the serum of a Mrs Kelleher
It was discovered by Lancer; Coombs, Mourant and Race
It was found that she had an antibody which reacted with her husbands, her daughters and newborns red blood cells
Her antibody also reacted with 9% of a random population -> antibody against antigen called K (K1)
In 1949 (3 yrs later) the allelic partner/corresponding antigen k (K2) was discovered
When was the K antigen discovered, when was k discovered?
K was discovered in 1946 in a Mrs Kellaher by Lancet; Coombs, Mourant and Race
k was disocvered in 1949
What are the four most common Kell antigens?
K (K1)
k (K2)
Kpa
Jsa
What is an anti-k antibody known as and why?
This is known as Cellano as it was found in a Ms. Cellano
Why is a Cellano difficult to work up and why?
An anti-k will usually cause a pan reactive panel
This is because 99.8% of the population are either Kk or kk
-> only 0.2% of people are KK => panreactive panel as we rarely get K- cells as part of our screen
It just means it can be more difficult to rule out other antibodies, might have to elute of anti-k etc etc
What chromosome is Kell located on?
Chromosome 7
Why did Ms Kellaher’s anti-K react with 9% of red cells?
This is because:
- 8.8% of people are Kk and 0.2% of people are KK
=> 9% of people have a K which her antibody would react against
What is the percentage of each Kell phenotype?
91% are kk (K/Kell negative)
8.8% are Kk
0.2% are KK
How immunogenic is K antigen?
1 in 10 produce an antibody if exposed to K antigen
-> since 90% of people are K- this can be seen
There are many reports of anti-K in transfused patients and multiparous women
Hence why women get K- blood in ireland
How many antigens are there in the Kell system, why so many?
There are 27 antigens total
Due to multiple allelic system giving rise to antithetical antigens
There is actualy so many possible combinations that not all possible genotypes have been found yet e.g. Kpa and Jsa have occured on separate chromosomes in patient but never on the one gene
What Kell antigens are found in nearly 100% of people?
k, Kpb and Jsb are found in nearly everyone
What are the 11 Kell antigens you need to be concerned with?
K and k
Kpa, Kpb and Kpc (Kpa most common in caucasions)
Jsa and Jsb (Jsa in Blacks)
K11 and K17
K14 and K24
What Kell phenotype will any Kpa+ be?
They will all be k+
i.e. Kpa+ only occurs in k+
Why might it be that weve never recorded a Kpa and Jsa on the same chromosome?
This is because Kpa is predominantly found in whites (2.3% of caucasians)
While Jsa is found in predominantly blacks (20%)
Other than Kpa and Jsa what is another Kell group antigen combination that has never been recorded, white might this be?
K and Kpa
Might be due to the realtively low frequency of both antigens
Only (9% of people have a K and only 2.3% of people have a Jsa)
What is the Kell null state?
Ko
This is due to a lack of K gene or Kx gene (covalently bonded on rbc surface)
They produce an anti-Ku
Describe the Kell glycoprotein, how does it express the antigens, what protein
A 93kD transmembrane, single-pass protein which carries the Kell antigens
It is an endothelin-3-converting enzyme
The Kell antigens are expressed in Low Desnity on the cell
What is the function of Kell glycoprotein?
(3)
It is an endothelin-3-converting enzyme
It cleaves an inactive precursor called big-endothelin-3 to create active endothelin-3
This is a potent constrictor of blood vessels
What kind of antigen is both Kell and Kx?
They are both glycoproteins (different though)
Kell is a single pass while Kx is a multipass (passes membrane 10 times)
What treatments can affect Kell antigen expression?
Daratumumab and ZAP
-> No K expression after dara treatment - hence ehy typing is required before starting treatment
What treatments can affect Kell antigen expression?
Daratumumab and ZAP
-> No K expression after dara treatment - hence ehy typing is required before starting treatment
What method is in place to negate daratumumab interference?
Send sample to IBTS for DTT treatment -> negates DARA interference
What chromosome is Kx antigen encoded on?
X chromosome - hence why its called Kx
What chromosome is Kx antigen encoded on?
X chromosome - hence why its called Kx
What can affect the Kell glycoprotein, how does this affect it?
Thiol degradation of double disulphide bonds (s-s-disulphide bonds)
These are needed for structural integrity
But this fact can be used in serologica investigations e.g. where there is an anti-K and an anti-Fya
-> it means we can remove Kell antigens if we need to investigate other antibodies
What are three methods of thiol degradation that can be used on Kell antigens?
DTT
ZZAP
AET
What are three methods of thiol degradation that can be used on Kell antigens?
DTT
ZZAP
AET
When might thiol degradation of Kell be needed?
If we have an anti-k -> we rarely will have an anti-K well rarely have a K- cell to use in panel -> often pan reactive
To rule out any other antibodies we can treat the red cells with a thiol degradation method - we can then rerun the panel to check for other antibodies
What is the molecular basis of the K and k antigens?
k and K are the two major codominant alleles
They result from a SNP (698C ->T)
The corresponding k and K antigens differ by a single amino acid change (thr193Met)
What is Kmod?
Kmod is a weakened expression of the Kell antigens
It is similar to weak D caused by point mutations
How is Kel affected by enzymes
Kell is not mean to be affected by enzymes
It is not destroyed by enzymes
In practice you might see that K is actually weakened by enzymes but this is more to do with the actual reagents used and not the actual enzyme activity
How immunogenic is K, why is this significant?
1 in 10 chance of making an anti-K if K+ blood given to K-
It is IgG, it reacts at 37 degrees, it is not complement binding
Because of this all K- women of childbearing age are given K- blood
it can cause a severe haemolytic transfusion reaction
It can occur naurally
Anti-K and anti-Ku are capable of causing a severe reaction
Comment on the immunigenicity of the different Kell antibodies
Anti-K and Ku are caoable of causing a severe reaction (severe haemolytic transfusion reaction)
Anti-k, anti-Kpa, anti-Kpb and anti Jsa and anti-Jsb cause milder reactions
Why is it thought that anti-K is so immunogenic?
The K antigens develop early on in erythropoiesis
This means anti-K can destroy rbc before they even get a chance to form haemoglobin
Because of this bilirubin is not considered a good measurement of a transfuion reaction involving anti-K, haemoglobin should be measured directly e.g. Dopler ultrasound or cordocentesis in HDFN etc
For the same reason, anti-K titre is considered not reliable measurement of the actual in vivo situation
How can anti-K caused HDFN result in foetal death?
Causes anti-K foetal anaemia due to suppression of erythropoesis not foetal RBC destruction
Talk about the Kx gene
(4)
Kx gene locus on X Chr Xp21
It gives rise to the Kx antigen
It is found on the glycoprotein to which the kell antigen attache covalently
Kx is not affected by DTT or AET unlike K
Even Ko cells will still have Kx expression (different gene)
Talk about deletions in the Kx gene
Deletions in this gene give rise to a number of disorder
Depending on the size of the deletion, the severity differs
Talk about deletions in the Kx gene
Deletions in this gene give rise to a number of disorder
Depending on the size of the deletion, the severity differs
List the conditions associated with Xp21 gene deletions, ie. Kx deletions
(4)
Retinitis pigmentosa
Duchenne’s muscular dystroph
X-linked Chronic Granulomatous Disease (CGD)
Mc Leod Syndrome - Lack of Kx
These are x-linked conditions, only affecting men
What is Mc Leod Syndrome?
(6)
A very rare x-linked condition affecting only 60 males
It is a complete lack of Kx
It results in weakly expressed Kell antigens
It causes reduced rbc survival, acanthocytes and decreased rbc permeability to eater
Patients suffer from a compensated anaemia
These patients often have an anti-Kx
What are the symptoms of Mc Leod syndrome?
Muscular wasting
Seizures
Cardiomyopathy
Psychiatric disorders
What are the symptoms of Mc Leod syndrome?
Muscular wasting
Seizures
Cardiomyopathy
Psychiatric disorders
What is the history of the Duffy Blood Group System, what are the antigens?
It was discovered in 1950 in a multi-transfused Haemophiliac Mr Duffy who had an anti-Fya
In 1955 is was discovered that many black populations lacked the Duffy antigens enitrely i.e. were Fy(a-b-)
Fya, Fyb, Fy3, Fy4, Fy5, Fy6, Fyx antigens
Fya is much more common than Fyb
The Duffy gene was the first blood group to have its gene located
Talk about anti Duffy antibodies
These antibodies are IgG
They are rarely found on their own -> they tend to occur in the multi-transfused or mothers of multiple children etc
How difficult is it to get blood for someone with an anti-Fya?
1 in 3 units is Fya negative -> easy to find
How difficult is it to get blood for someone with an anti Jka?
1 in 4 units are Jka negative
Relatively easy to get blood for
What is Fyx?
Fyx is a weakened version of the Duffy blood group system
The Fyx allele encodes the Fyb antigen where B is only weakly expressed and is not always detected by anti-Fyb
Fy(b+x)
What is the frequency of each duffy phenotype?
49% Fy(a+b+)
33% Fy (a-b+)
17% Fy (a+b-)
Fy(a-b-) is rare in Caucasians but seen in 68% of Blacks
Comment on the action of enzymes on Duffy antigens
Fya and Fyb are destroyed by enzymes
Fy3, 4 and 5 are not destroyed and may be enhanced
What kind of antibodies are Fya and Fyb?
(5)
They are IgG antibodies
They are complement binding
They are involved in HDN and Haemolytic Transfusion Reactions (HTR)
They are associated with Delayed HTR in SCDPs
Antigen deterioration can cause problems in panels
What blood groups might a serum sample be required for the investigation of antibodies?
Anti Duffy and anti Kidd
What is considered the gold standard for Duffy antibody investigation?
(3)
Serum sample prefferred as EDTA anti-coagulant will bind calcium and complement which reduces the strength of the Duffy reaction
Serum samples will have double the strength of the reaction due to both complement and antibody binding
You will also have to get a fresh set of reagent red cells for a panel as Duffy antigen expression deteriorates with time and causes weaker reactions
Write a note on the genetics of the Duffy blood group system
Duffy locus is on chromosome 1 -> its syntenic to the Rh locus - it was the first gene assigned to a specific locus
It encodes a glycosylated protein with 7 trans-membrane domains of 339 AA with 63 being extracellular (potentially antigenic)
DARC appears to be a receptor for IL-8 and other chemokines
FYA and FYB differ by a single nucleotide at positiion 125 (G->A)
Fya and Fyb antigens differ by a single amino acid at residue 42 (glycine -> aspartic acid)
Write a note on the genetics of the Duffy blood group system
Duffy locus is on chromosome 1 -> its syntenic to the Rh locus - it was the first gene assigned to a specific locus
It encodes a glycosylated protein with 7 trans-membrane domains of 339 AA with 63 being extracellular (potentially antigenic)
DARC appears to be a receptor for IL-8 and other chemokines
FYA and FYB differ by a single nucleotide at positiion 125 (G->A)
Fya and Fyb antigens differ by a single amino acid at residue 42 (glycine -> aspartic acid)
What chromosome is the Duffy locus encoded on?
Chromosome 1
What does the Duffy gene encode?
It encodes a glycosylated protein with 7 trans-membrane domains of 339 AA with 63 being extracellular (potentially antigenic)
What is DARC?
Duffy-Antigen Receptor Chemokine (DARC)
What is the function of DARC?
Its a receptor for IL-8 and other chemokines
It is also the entry point for malaria (Fy6)
What exactly are the Duffy antigens Fy3-Fy6?
They represent variations in the Fya and Fyb epitopes
How is Fya different from FyB?
(2)
FyA differs from FyB by a single nucleotide at position 125 (G->A)
FyA differs from FyB antigens by a single amino acid at residue 42 (glycine -> aspartic acid)
What strain of plasmodium does Fya-b- confer resistance against?
Plasmodium Knowlesi and Plasmodium vivax
What is the site of plasmodium invasion into cells?
Fy6
(which is absent on Fy(a-b-) cells)
Talk about antigen expression in the Fy(a-b-) individuals
(3)
This phenotype is caused by mutation in the erythroid promoter region of the FYB gene
This results in the lack of Fy expresson on the RBCS only
Fyb proteins are normal and expressed in other non-erythroid tissues
What antibodies are produced by an Fy(a-b-) individual, why is this significant?
These individuals would produce an anti-Fya but not an anti-Fyb as this phenotype still produces FyB on non erythroid tissues
-> this means we can give then Fya-b+ blood
-> this is great because we very rarely have Fya-b- blood available
What is the history on the Jk (Kidd) blood group system?
This system was discovered in 1951 in a John Kidd born to a Mrs Kidd (anti-Jka)
John was the 6th child of Mrs Kidd
John was a case of HDFN
Mrs Kidd also have an anti-K
In 1953 the predicted anti-Jkb was found in a transfusion reaction patient who also had an Fya
In 1959 the third (and final) antigen of this system Jk3 was discovered
What are the three antigens of the Kidd system?
Jka
Jkb
Jk3
When was Jka, Jkb and Jk3 found?
Jka in 1951
Jkb in 1953
Jk3 in 1959
What is Jk3?
Jk3 is found in Jka-b- people
What is the frequence of Jkab phenotypes in Caucasians?
50% Jka+b+
27% Jka+b-
23% Jka-b+
What is the frequence of Jkab phenotypes in Blacks?
51% Jka+b-
41% Jka+b+
8% Jka-b+
Genetics of the Kidd Blood group
(3)
Kidd locus is HUT11 gene on Chromosome 18
Jka and Jkb are antigen products of two alleles inherited in a co-dominant fashion
It is a urea transporter
Who is Jka-b- seen in?
Its very very rare
Only seen in Polynesiand - 1% and Finish
What is Jk(a-b-), how does it occur?
Homozygous inheritence of a silent Jk allele at the JK locus
- two damaged alleles together = no expression
OR (amorph type) inheritence of a dominant inhibitor gene In(Jk) unlinked to the JK locus
What is the inhibitor Jk gene In(Jk)?
an inhibitor gene which results in lack of expression of Jk a and b
A similar inhibitor is seen in the Lutheran system
This gene doesnt affect the actual gene as with RhD or Kidd null types but instead affects the assembly of the protein into the red cell membrane i.e. the actual gene protein is completely fine it just cant be expressed correctly
What is the antibody produced by Rhnull individuals?
Its anti-Rh 29
What is significant about anti-Jk antibodies?
Jk antibodies can cause severe reactions
Jk antibodies also tend to disappear -> have been seen to dissappear in as little as two weeks
This can be scary as it means you will not see the antibody when doing a screen or panel
If you dont have patient history of antibody you will not pick it up
Hence why they are commonly seen in transfusion reactions
Hence need for Medlis
What is significant about anti-Jk antibodies?k
Jk antibodies can cause severe reactions
Jk antibodies also tend to disappear -> have been seen to dissappear in as little as two weeks
This can be scary as it means you will not see the antibody when doing a screen or panel
If you dont have patient history of antibody you will not pick it up
Hence why they are commonly seen in transfusion reactions
Hence need for Medlis
Where are Jk antigens expressed?
Mostly rbcs and the vasa recta of the kidney
Where are Jk antigens expressed?
Mostly rbcs and the vasa recta of the kidney
What exactly does the Kidd gene produce, what is its function?
Gene produces an integral membrane protein (389 aa) which spans the membrane 10 times
The Kidd antigen is a urea transporter
How does Jka differ from Jkb?
There is only a single nucleotide difference
838G->A transition from Jka to Jkb
This results in an aspartic acid->asparagine at aa 280
What affects does Jknull have on patient?
No pathological effects
Write a little about anti Kidd antibodies
They are responsibly for 30% of DHTRs
Antigen deterioration as well as antibody dosage possibly contribute to missing anti-Jk antibodies
They are partially IgG/IgM
They can activate complement causing significant haemolysis
Occassionally causes AIHA
HDN is rare but Kidd antigen are found on foetal cells as early as week 11
Serum sample gold standard for antibody investigation
What percentage of DHTR are caused by Kidd antibodies, why is this?
30% of DHTRs
Anti-Kidd antibodies are effervessent antibodies i.e. they disappear from blood after 2 weeks they are undetectable
What was lecturers interaction with Kidd antibodies?
Fabian only seen 1 fatality
- Associated with Jk
- Woma had a GIT bleed - needed 6 units of blood
- She was anaemic - low haemoglobin - lots of blood needed to bring it up
- Following day her haemoglobin fell quickly 10,8,6, etc etc
She died at 54 -> she was also a Ms. Kidd (what are the chances)
Can Kidd cause HDFN?
Yes, but rarely
Kidd antigens are expressed on faetal cells from 11 weeks
What are the two things Kidd antibodies are known for
Causing delayed transfusion reactoins
For being found with other antiodies
What are the two things Kidd antibodies are known for
Causing delayed transfusion reactoins
For being found with other antiodies
What was the IBTS experience with anti-JK3
Woman had a miscarraige, she was panreactive but DAT and auto negative
There was no evidence of rouleaux
Panel was done in tubes and was not resolved
Sample was sent to IBTS for full typing where she was typed as Jka-b-
Patient was a suspected anti-Jk3 but there was not enough sample to continue as patient had left hospital
Patient came back the following year with another miscarriage when we got another sample
Using imported blood we were able to identify the presence of anti-Jk3 i.e. she had an anti-Jka, jkb and jk3
The following year the patient returned but pregnant
Adsorption techniques used to exclude any other antibodies
Jka-b- units were imported on a monthly basis from UK and Finland until baby was delivered via C section -> happy healthy baby
Baby was Dat positive though as he was Jka-b+, eluate contained an antiJk3
