Blood Group System - Kidd

Shortly after the development of the antiglobulin test for the detection of red cell antibodies, the first example of a Kidd antibody was reported in 1951. A patient, Mrs. Kidd, was described who produced an antibody that caused hemolytic disease in her newborn son. After determining that the new antigen was independent of the other then-known blood groups, it was given the name Jka. Soon afterwards, the allele was found by Plaut and designated Jkb. In 1959, the first example of the null phenotype, i.e., Jk(a-b-), was founnd in a woman who had produced an antibody that appeared to be anti-Jka plus anti-Jkb. Since the specificities were inseparable, the antibody was renamed anti-Jk3 which recognizes an antigen found whenever Jka or Jkb is present. To date, no low frequency antigens have been associated with the Kidd blood group.

The first example of the Jk(a-b-) phenotype was found in a woman who experienced a delayed transfusion reaction. She was a Filipino of some Chinese and Spanish ancestry. Another family of Filipino-Chinese ancestry was reported that contained three Jk(a-b-) members. Since these first reports, many such individuals of Asian or Polynesian extraction have been identified. One study found a total of 66 (0.9%) Jk(a-b-) donors among 7425 tested; all were of Polynesian backgrounds. Other populations reporting this phenotype include tribes from Mato Grasso, Brasil, Hindus from India and Japanese blood donors. The Jk(a-b-) phenotype is strikingly absent from Caucasians although rare cases have been found in a French, an Australian and a Finnish family. The molecular basis for Jknull has been shown to be splice-site and misense mutations, as well as a partial gene deletion. The Jka/Jkb polymorphism is a A8386 base pair change at amino acid 280, changing Asp to Asn.

Interestingly, the Jk(a-b-) red cells were shown to be resistant to lysis in high concentrations of urea as opposed to normal cells that completely lyze in ~1 minute. This observation led to biochemical studies which identified the Kidd antigens on the urea transport protein which is found not only in red blood cells but also in the kidney. One study of individuals with the Jk(a-b-) phenotype has reported that they have a decreased ability to concentrate urine but this does not appear to cause a health problem.