Kell antigen system

  • UniProt: Q0KH87
  • OMIM: 314850
  • UniProt: P51811

The Kell system (also Kell Cellano System) is currently one of 30 blood group systems. Currently 34 antigens are summarized in this system, the antithetical antigens K ( KEL1, Kell ) and k ( KEL2, Cellano ) are the most important.

The Kell system, due to its clinical relevance in addition to the AB0 system and the Rhesus system is the third most important blood group system dar. In blood donors in Germany and Austria is regularly tested for the Kell antigen KEL1.

Kell and Cellano antigens

The two major antigens of the Kell system are the antithetical antigens K ( KEL1, also called Kell ) and k ( KEL2, also called Cellano ). About 92 % of people are ( Kell ) K- negative ( kk). In particular, K -negative girls and women of childbearing age should receive only K- negative blood. 7.8% K- positive heterozygous (KK) and the blood can be obtained positive and negative K- antigen. Only 0.2 % of people are homozygous K- positive ( KK). ( Cellano ) k- negative blood is therefore rare, patients with an anti -k can not be supplied more easily.

In the blood group determination is tested on the K- antigen, the genotype K- negative ( kk ) is then reported as " Kell negative ," the two K -positive genotypes ( Kk, and KK) are grouped under the name " Kell positive."

The antigens are clinically relevant, as people without the corresponding antigen can be immunized by contact ( transfusion or pregnancy), which can cause the resulting antibodies to haemolytic transfusion reactions or hemolytic disease of the newborn. The antigens Kell and Cellano were as previously usual named after the name of the patients in which the antibodies were first described.

The antigens of the Kell system, have been described based on a total of 34 mutations in the KEL gene on chromosome 7, this gene encodes an enzyme which is incorporated into the cell membrane of erythrocytes. The different variants usually differ only by point mutations. The Blutgruppenphänotyp in the absence of the Kell protein is described as Knull.

McLeod syndrome and XK gene

The glycoprotein of the Kell gene is closely related to the organism to the membrane protein of the XK gene. which are connected via a disulfide bridge. Limitations of the membrane protein lead to a reduction of the Kell protein on the red blood cells.

The rare - McLeod syndrome ( Kxnull phenotype ) is based on a mutation of the XK gene on the X chromosome, leading to a lack of expression of this gene, and thus the absence of the XK protein. The syndrome manifests itself in with acanthocytosis, anemia and neuromuscular diseases (eg, Huntington's ). The absence of the XK protein leads to a significantly attenuated expression of Kell antigens ( see above).

In contrast, the absence of the Kell protein ( Knull ) does not result in the absence of protein and a XK- McLeod syndrome. An involvement of the membrane protein XK of transport channels in the cell membrane is not clear, but it also occurs in other cell types in appearance. For XK protein is also a Kx antibody is formed, so it is described as an independent blood group.

Importance in pregnancy

The antibody screening in pregnant women includes not only the finding of rhesus antibodies and the detection of anti-Kell antibodies. The effect of Kell incompatibility between mother ( Kell - negative with antibodies after sensitization) and child ( Kell - positive) is similar to Rhesus incompatibility, however, is less common in appearance, and can result in severe cases, hemolytic disease of the newborn. Since there are no preventive therapy on the type of anti-D prophylaxis, a close monitoring of pregnancy ( titer ) is required.

Human Genome Organisation Zygosity#Heterozygous Zygosity#Homozygous Immunization Neuroacanthocytosis Chorea
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