Kell-Cellano system
| K1 antigen (Kell blood group, metallo-endopeptidase) | ||
|---|---|---|
| Properties of human protein | ||
| Mass / length primary structure | 732 amino acids | |
| Identifier | ||
| Gene names | KEL , ECE3, CD238 | |
| External IDs | ||
| Occurrence | ||
| Parent taxon | Chordates | |
| K2 antigen (Kell blood group antigen Cellano) | ||
|---|---|---|
| Mass / length primary structure | 730 amino acids | |
| Identifier | ||
| Gene name (s) | KEL | |
| External IDs | ||
| XK (X-Linked Kell bloodgroup precursor) | ||
|---|---|---|
| Identifier | ||
| Gene name (s) | XK, X1k, XKR1 | |
| External IDs | ||
The Kell system (also Kell-Cellano system ) is one of the 35 blood group systems that the International Society of Blood Transfusion leads. There are 34 antigens in this system, the antithetical antigens K (KEL1, Kell) and k (KEL2, Cellano) being the most important. Further antigens in the Kell-Cellano system are Penney (K3, Kp a ), Rautenberg (K4, Kp b ), Sutter (K5, Js a ) and Matthews (K6, Js b ).
Due to its clinical relevance, the Kell system is the third most important blood group system alongside the AB0 system and the Rhesus system . Blood donors in Germany and Austria are regularly tested for the Kell antigen KEL1.
Kell and Cellano antigens
The two most important 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 only receive K-negative blood. 7.8% are heterozygous K-positive (Kk) and can receive blood with positive and negative K-antigen. Only 0.2% of people are homozygous K-positive (KK). (Cellano-) k-negative blood (i.e. (Kell-) K-positive blood) is therefore rare, patients with an anti-k cannot always be treated without problems. The Kell-Cellano system, i.e. the antigens Kell and Cellano, was named after two pregnant women (Kellacher and Cellano) in whom these blood group characteristics or antibodies were first described in 1945 and 1957.
The Kell antigen is a 732 amino acid type II membrane glycoprotein located on the erythrocyte membranes . As zinc-dependent endopeptidases ( metalloproteins ), it is responsible for the enzymatic cleavage of endothelin 3 .
When determining the blood group, the K-antigen is tested, the genotype for K-negative (kk) is then shown as "Kell negative" , the two K-positive genotypes (Kk and KK) are summarized under the name "Kell positive" .
The antigens are clinically relevant because people without the corresponding antigen can be immunized through contact ( transfusion or pregnancy ) , whereby the antibodies produced can lead to haemolytic transfusion reactions or haemolyticus neonatorum disease.
The total of 34 antigens of the Kell system described so far are based on mutations in the KEL gene on chromosome 7 . This gene codes for an enzyme that is incorporated into the cell membrane of erythrocytes . The different variants usually only differ through point mutations . The blood group phenotype in the absence of the Kell protein is described as K zero .
| Blood group characteristic |
frequency | ||
|---|---|---|---|
| Germany | Austria | worldwide | |
| Kell negative (kk) | 91% | 91% | 92% |
| Kell positive (KK or Kk) | 9% | 9% | 8th % |
McLeod syndrome and XK gene
The glycoprotein of the Kell gene is closely related to the membrane protein of the XK gene in the organism . connected by a disulfide bridge. Membrane protein limitations lead to a decrease in Kell proteins on red blood cells.
The rare McLeod syndrome (Kx zero - phenotype ) is based on a mutation of the XK gene on the X chromosome , which to a lack of expression carries the gene and thus lack the XK protein. The syndrome manifests itself, among other things, with acanthocytosis , anemia and neuromuscular diseases ( e.g. chorea ). The lack of the XK protein also leads to a significantly reduced expression of the Kell antigens (see above).
In contrast, the absence of the Kell protein (K zero ) does not lead to a lack of the XK protein and McLeod syndrome. The involvement of the membrane protein XK in transport channels in the cell membrane has not been clarified, but it is also evident in other cell types. A Kx antibody is also formed for the XK protein, which is why it is described as a separate blood group.
Importance in pregnancy
The Kell antigen follows the Rhesus antigen in terms of its immunogenic potency and can lead to fatal transfusion incidents. The antibody search test for pregnant women includes not only the determination of Rhesus antibodies but also the detection of Kell antibodies. The effect of a Kell incompatibility between mother (Kell-negative with antibodies after sensitization) and child (Kell-positive) is similar to the Rhesus incompatibility , but occurs less frequently and in severe cases can lead to neonatorial haemolytic disease . Since there is no preventive therapy in the manner of anti-D prophylaxis, careful monitoring of the pregnancy (titer determination) is necessary.
The Kell antibodies are mostly IgG antibodies.
Individual evidence
- ^ Table of blood group antigens within systems. (No longer available online.) August 2008, archived from the original on August 18, 2011 ; Retrieved January 2, 2010 . Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice.
- ^ RRA Coombs, AE Mourant, RR Race: A new test for the detection of weak and incomplete Rh agglutinins. In: Br J Exp Pathol. 26, 1945, p. 255.
- ↑ blood group - historical background. In: Encyclopædia Britannica . Retrieved December 31, 2008 .
- ↑ Axel M. Gressner, Torsten Arndt: Lexicon of Medical Laboratory Diagnostics . Springer-Verlag, Berlin / Heidelberg / New York 2013, ISBN 978-3-642-12921-6 , p. 771.
- ^ S. Lee, X. Wu, M. Reid, T. Zelinski, C. Redman: Molecular basis of the Kell (K1) phenotype. In: Blood. 85 (4), 1995, pp. 912-916. PMID 7849312
- ↑ B. Chown, M. Lewis, K. Kaita: A new Kell blood-group phenotype. In: Nature. 180 (4588), 1957, p. 711. PMID 13477267 .
- ^ FH Allen Jr, SM Krabbe, PA Corcoran: A new phenotype (McLeod) in the Kell blood-group system. In: Vox Sang. 6. 1961, pp. 555-560. PMID 13860532 .
- ↑ Relevance of a positive antibody screening test (AKS) in pregnancy. ( Memento from March 7, 2015 in the web archive archive.today ) In: Labor , December 28, 2006: "About 99% of pregnant women have no relevant antibodies against erythrocytes detectable." / "Frequency of positive AKS: Anti-D 13% , Anti-E 11%, Anti-M 11%, Anti-c 6%, Anti-Le a 6%, Anti-C 6%, Anti-Jk a 4%, Anti-S 4%, Anti-Le b 4 %, Anti-C w 4%, Anti-P 1 4%, Anti-K 3% ”.
