Kidd antigen system
Editor-In-Chief: C. Michael Gibson, M.S., M.D. 
The Kidd antigen system (also known as Jk antigen) is present on the membranes of red blood cells and the kidney and helps determine a person's blood type. The Jk antigen is found on a protein responsible for urea transport in the red blood cells and the kidney. The gene encoding this protein is found on chromosome 18. Two common Jk alleles are Jk(a) and Jk(b). Individuals who lack the Jk antigen (Jk null) are unable to maximally concentrate their urine.
The Jk antigen is 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. HDN associated with Jk antibodies is typically mild, though fatal cases have been reported.
- 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. Kidd blood group and urea transport function of human erythrocytes are carried by the same protein. J Biol Chem. 1995 Jun 30;270(26):15607-10. PMID 7797558
- ↑ Geitvik GA, Hoyheim B, Gedde-Dahl T, Grzeschik KH, Lothe R, Tomter H, Olaisen B. The Kidd (JK) blood group locus assigned to chromosome 18 by close linkage to a DNA-RFLP. Hum Genet. 1987 Nov;77(3):205-9. PMID 2890568
- ↑ Sands JM, Gargus JJ, Frohlich O, Gunn RB, Kokko JP. Urinary concentrating ability in patients with Jk(a-b-) blood type who lack carrier-mediated urea transport. J Am Soc Nephrol. 1992 Jun;2(12):1689-96. PMID 1498276
- ↑ Kim WD, Lee YH. A fatal case of severe hemolytic disease of newborn associated with anti-Jk(b). J Korean Med Sci. 2006 Feb;21(1):151-4. PMID 16479082
- Kidd at BGMUT Blood Group Antigen Gene Mutation Database at NCBI, NIH