Medicine:Kidd antigen system
The Kidd antigen system (also known as Jk antigen) are proteins found in the Kidd's blood group, which act as antigens, i.e., they have the ability to produce antibodies under certain circumstances. The Jk antigen is found on a protein responsible for urea transport in the red blood cells and the kidney.[1] They are important in transfusion medicine. People with two Jk(a) antigens, for instance, may form antibodies against donated blood containing two Jk(b) antigens (and thus no Jk(a) antigens). This can lead to hemolytic anemia, in which the body destroys the transfused blood, leading to low red blood cell counts. Another disease associated with the Jk antigen is hemolytic disease of the newborn, in which a pregnant woman's body creates antibodies against the blood of her fetus, leading to destruction of the fetal blood cells. Hemolytic disease of the newborn associated with Jk antibodies is typically mild, though fatal cases have been reported.[2]
The gene encoding this protein is found on chromosome 18.[3] Three Jk alleles are Jk (a), Jk (b)and Jk3. Jk (a) was discovered by Allen et al. in 1951 and is named after a patient (Mrs Kidd delivered a baby with a haemolytic disease of the newborn associated with an antibody directed against a new antigen Jk (a). Whereas Jk (b) was discovered by Plant et al. in 1953, individuals who lack the Jk antigen (Jk null) are unable to maximally concentrate their urine.[4]
Genetics and biochemistry
Kidd comprises three antigens on a glycoprotein with 10 transmembrane spanning domains, cytoplasmic N- and C-termini and one extracellular N-glycosylation site.[5]
Clinical diagnostic
Clinical testing in patient care for Kidd antigens follows published minimum quality and operational requirements,[6] similar to red cell genotyping for any of the other recognized blood group systems. Molecular analysis can identify gene variants (alleles) that may affect Kidd antigens expression on the red cell membrane.
Kidd antigens
Jka (JK1) and Jkb (JK2)
Jka and Jkb are the products of alleles with Asp280 and Asn280 in the fourth external loop of the Kidd glycoprotein. Jka and Jkb have similar prevalences in White and Asian populations but Jka is more common in Black populations than Jkb.[5]
Jk(a-b-) and Jk3
Jk(a-b-) represents the null phenotype and usually results from homozygosity for a silent gene at the JK locus.[5] The null phenotype is rare in most populations but does have increased prevalence in Polynesians (one in 400) and Niueans (1.4%).[5]
A rare null phenotype in Japanese individuals results from heterozygosity for an inhibitor gene. In(Jk) in analogy with the In(Lu) dominant inhibitor of Lutheran and other antigens.[5]
Very weak expression of Jka and/or Jkb can be detected on In(Jk) red blood cells in adsorption/elution tests.[5]
Kidd antibodies and clinical significance
Antibody subtypes and complement fixation
Anti-Jka and -Jkb are not common. They are usually warm-reacting IgG1 and IgG3 but may also include IgG2, IgG4 or IgM. Approximately 50% of anti-Jka and -Jkb antibodies are capable of binding complement.[7]
Dosage
Laboratory detection
Clinical significance
Kidd antibodies are dangerous as they are capable of causing severe acute hemolytic transfusion reactions. They are unique in that they are capable of dropping to low or even undetectable levels after several months following an exposure.[5] Thus, on pre-transfusion testing, an anti-Jka or -Jkb may go undetected. Following transfusion, a subsequent robust antibody response in the patient can occur (anamnestic response), resulting in hemolysis of the transfused red blood cells. Kidd antibodies are often capable of binding complement and causing intravascular hemolysis. More often, however, Kidd antibodies cause acute extravascular hemolysis.[8] They are a notorious cause of delayed hemolytic transfusion reactions, and may occur up to a week after transfusion in some instances. Kidd antibodies only rarely cause hemolytic disease of the fetus and newborn.[5]
Kidd glycoprotein as urea transporter
Kidd antigens are located on a red blood cell urea transporter (human urea transporter 11- HUT11 or UT-B1).[9] As red blood cells approach the renal medulla (where there is a high concentration of urea), the urea transporter allows for rapid uptake of urea and prevents cell shrinkage in the hypertonic environment of the medulla.[5] As the red cell leaves the medulla, the urea is transported back out of the cell, preventing cellular swelling and preventing the urea from being carried away from the kidney.[5] HUT11 was detected on endothelial cells of the vasa recta (vascular supply of the renal medulla) but it is not present in renal tubules.[5]
The Jk(a-b-) phenotype has no clinical defect, although two individuals with this phenotype have been reported to have mild urine-concentrating defects.[4]
Kidd antibodies in transplant patients
Kidd antibodies are capable of behaving as histocompatibility antigens in renal transplants and may be responsible for allograft rejection in some cases.[10]
References
- Online Mendelian Inheritance in Man (OMIM) 111000 – OMIM page on the Kidd antigen system protein
- ↑ Olives B, Mattei MG, Huet M, Neau P, Martial S, Cartron JP, Bailly P (Jun 1995). "Kidd blood group and urea transport function of human erythrocytes are carried by the same protein". Journal of Biological Chemistry 270 (26): 15607–10. doi:10.1074/jbc.270.26.15607. PMID 7797558.
- ↑ Kim WD, Lee YH (Feb 2006). "A fatal case of severe hemolytic disease of newborn associated with anti-Jk(b)". Journal of Korean Medical Science 21 (1): 151–4. PMID 16479082.
- ↑ Geitvik GA, Hoyheim B, Gedde-Dahl T, Grzeschik KH, Lothe R, Tomter H, Olaisen B (Nov 1987). "The Kidd (JK) blood group locus assigned to chromosome 18 by close linkage to a DNA-RFLP". Human Genetics 77 (3): 205–9. doi:10.1007/BF00284470. PMID 2890568.
- ↑ 4.0 4.1 Sands JM, Gargus JJ, Frohlich O, Gunn RB, Kokko JP (Jun 1992). "Urinary concentrating ability in patients with Jk(a-b-) blood type who lack carrier-mediated urea transport". Journal of the American Society of Nephrology 2 (12): 1689–96. PMID 1498276.
- ↑ 5.00 5.01 5.02 5.03 5.04 5.05 5.06 5.07 5.08 5.09 5.10 Roback et al. AABB Technical Manual, 16th Ed. Bethesda, AABB Press, 2008.
- ↑ "Association for the Advancement of Blood & Biotherapies (AABB). (2025). Standards for molecular testing for red cell, platelet, and neutrophil antigens, 7th ed. (ISBN: 978-1-56395-516-7)". https://www.aabb.org/aabb-store/product/standards-for-molecular-testing-for-red-cell-platelet-and-neutrophil-antigens-7th-edition-print-18521318.
- ↑ Klein HG, Anstee DJ. Mollison's Blood Transfusion in Clinical Medicine. 11th Ed. Oxford: Blackwell Publishing, 2005.
- ↑ Cite error: Invalid
<ref>tag; no text was provided for refs namedMais - ↑ Sands JM. Molecular Mechanisms of Urea Transport. Journal of Membrane Biology. 2003; 191: 149-63.
- ↑ Hold S, Donaldson H, Hazelhurst G, et al. Acute Transplant Rejection Induced By Blood Transfusion Reaction to the Kidd Blood Group System. Nephrology Dialysis Transplantation. 2004; 19: 2403-6.
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