Kell Blood Group Flashcards
Exam 2
Compared to the Rh antigens how immunogenic are the Kell antigens?
Less immunogenic than Rh but overall the 2nd most immunogenic blood group system
Why is anti-K able to cause extremely severe HDFN?
Antigens are very well expressed on fetal cells and they are also expressed well on erythroid precursor cells. Because of this not only are mature cells being destroyed.
What protein is necessary to be present in order for the Kell antigen to be expressed?
XK protein
What two genes are involved in the Kell antigen formation?
KEL gene on chromosome 7 codes for the Kell antigen itself. XK gene on the X chromosome codes for the Kx antigen that is necessary for the Kell antigen to be able to bind to the red cell. These are two independent genes.
What are the low frequency Kell antigens?
Kp(a), Js(a)
What are the high frequency Kell antigens?
Little k, Kp(b), Js(b)
What is the frequency of the big K antigen?
9% positive for K antigen
How does the K antigen react to enzyme treatment?
It is resistant to enzymes
What immunoglobulin class is anti-K?
IgG
At what temperature does anti-K react best?
37C body temperature
Does anti-K cause HDFN and transfusion reactions?
Yes
Does anti-K bind complement?
Some- about 20%
When the Kp(a) antigen is expressed what will happen to the other Kell antigens?
The other antigens’ expression will be suppressed
Which low frequency Kell antigen is found in about 20% of African Americans?
Js(a)
What does DTT do and how does it affect the Kell antigens?
It dissociates IgM antibodies leaving only IgG antibodies. However it also breaks down the antigens of the Kell system.
If someone inherits the K0 phenotype what Kell antigens do they express?
None, they do not form Kell antigens. They do form the Kx antigen.
If an individual has the K0 phenotype what antibody are they able to form?
Anti-Ku (K5)
If someone inherits the McLeod phenotype what antigens are they lacking?
Kx and Km antigens
What happens to the Kell antigens when an individual lacks the Kx antigen?
The Kell antigen has issues binding. They still have some Kell antigen just a very small amount.
What are the symptoms of McLeod Syndrome?
Acanthocytic RBCs, reduced in vivo RBC survival, chronic hemolytic anemia, muscle and nerve disorders, muscular dystrophy at 40-50 years, cardiomegaly
With what disease is the McLeod phenotype associated?
Chronic Granulomatous Disease
Since the Kx antigen is inherited on the X chromosome what happens if a female inherits one functioning XK gene and one non-functioning XK gene?
Only 1 X chromosome is active in every cell. They will exhibit two cell populations because a different one shuts down in every cell. Some will be normal, some will have the McLeod phenotype.
What four instances can cause a weaker expression of the Kell antigens?
McLeod phenotype, Kp(a) gene expression, Gerbich negative phenotype, autoimmune hemolytic anemia directed against Kell.
How might an individual express an acquired K antigen?
If the individual is infected with Streptococcus faecium, the bacteria can convert K- cell to K+. There cells will return to normal after the infection resolves.
