Kell Flashcards
What Chromosome is KEL located on?
Chromosome 7
When can Kell antigens be detected during gestation?
7-10 weeks gestation
What cells are Kell found on?
Only RBC’s
What is the frequency of K?
9% of whites are positive
3% of Blacks are positive
What is the frequency of k?
High Freq
0.2% Whites are negative
<0.1% Blacks are negative
What is the frequency of Jsa?
Jsa + seen in blacks
20% are positive
What is the frequency of Jsb?
High freq
1% of blacks are negative (Jsa/Jsa)
Anti-Jsb seen in black population
What is the frequency of Kpa?
2% are postive
What is the frequency of Kpb?
<0.1% are Kpb negative
Characteristics of anti-K
K antigen is second to D for antigenicity
A K- person receives K+ there is a 10% chance they will make anti-K
May activate complement, cause TRN RXN, and HDFN
Usually IgG1 reacts at 37C with AHG
Can show dosage
Can be naturally occurring and sometimes reacts at RT
How does anti-K cause HDFN?
Kell antigens are present on early RBC precursor cells before hgb is present. Macropages in the fetal liver phagocytsis cells. Reduced retics and low bilirubin.
Antibody titers don’t predict severity of disease
What gene affects Kell expression?
Kell antigen expression depends on XK gene that produces Kx protein
Kx antigen spans the membrane 10X
What chromosome is the XK gene located on?
X chromosome
What is Kpc?
3 allelle antithetical to Kpa and Kpb
Low frequency
Found in Japan
What is the amino acid that defines K?
Methionine
Same as S
What is the amino acid that defines k?
Threonine
Same as s
What are the low frequency antigens in the Kell system?
UIa, K23, and KYO
What antigens does DTT destroy?
KEL, JMH, LW, Lutheran, Dombrock, Cromer, Knops
Does not destroy Kx antigen
What is the effect of enzymes on Kell antigens?
Kell antigens are resistant
What are the Kell haplotypes?
k, Kpb, Jsb are inherited together
Only one mutation can occur per haplotype
Can Type as K+ and Kpa+ if inherited one from each parent. Does not occur on same haplotype
Closely linked so crossing over doesn’t occur
How is Kx expression effected by Kell antigen expression?
Kx is weak when Kel antigens are present
Anti-Kx reacts strongly with KoKo cells with no Kell antigens
The less Kell antigen the stronger Kx antigen
What potentiator enhances Kell antibody?
PEG can enhance reactivity
Some anti-K will react poorly with LISS or in Automated systems
What is the structure of Kel antigen?
its a type II membrane glycoprotien that spans the membrane once
It is connected to Kx with a single disulfide bond
the glycoprotein is highly folded by disulfide linkages = DTT destroys
Why are Kell autoantibodies formed?
There may be a transient depression of Kell antigens due to disease
Autoantibodies can be benign or hemolytic
Will react with all except Ko cells
What is Ku?
KEL5
U stands for universal antigen
Present when Kell glycoprotein is present; absent in Ko cells
What is Km?
KEL20
Thought to be a product of the interaction of Kx and Kell. Both must be present for expression
What is the Ko phenotype?
Kell is silenced = no Kell antigens
No Ku or Km
Can make anti-Ku and other Kell antibodies
Kx will be strongly expressed
Ko heterozygotes will have normal K antigen
Occurs 1 in 25,000 whites
What is the Mcleod Phenotype?
Very rare. No XK gene.
No Kx or Km
Kell antigens are very weak. May need absorb/elute.
W/ CGD = Make anti-Kx or Km
W/O CGD = Only make anti-Km (Ko cells compatible)
What abnormalities are caused by Mcleod syndrome?
Acathocytosis, Retic’s, compensated hemolytic anemia
Muscular and neurological abnormalities
Muscle wasting, reduction in deep tendon reflexes
Increased CPK enzymes
Can have Mcleod phenotype w/o syndrome
What disease is associated with Mcleod Phenotype?
Some individuals will also have chronic granulomatous disease (CGD)
Causes recurrent bacterial infections early in life that result in death
Granulocytes phagocytize but unable to kill
What causes weak Kell antigen expression?
- When Kpa is present Kell antigens are weakend due to a reduced amount of Kell glycoprotein
- Kmod phenotype have reduced Kell expression but increased Kx
- Leach phenotype = Gerbich negative cells have a weak Kell antigens
What antibody is made by Kmod individuals?
Some make Ku like antibody
What donors should you screen for Kpb negative and Jsb negative blood?
Kpb negative is more common in whites
Jsb negative is more common in blacks
What antibody will react strongly with DTT treated cells?
Anti-Kx. DTT destroys the Kell antigen so Kx is enhanced
What chemicals will destroy Kell antigens?
DTT, AET, ZZAP, and EGA destroys kell antigens
What cells will anti-Kx react with?
Weakly with normal cells (blocked by Kell antigens)
Strongly with DTT treated cells
Strongly with Ko and Kmod cells
Negative with Mcleod (No Kx)
What cells will anti-Km react with?
Km expressed with Kell and Kx are present
Positive with normal cells
Negative with Ko and Mcleod cells
Strongly positive with Kmod cells
What cells will anti-Ku react with?
Positive with normal cells
Weakly with McLeod and Kmod cells
Negative with Ko cells
