Temporary suppression of Kidd system antigen expression accompanied by transient production of anti-Jk3.

This report describes an 85-year-old woman of Russian Jewish extraction whose red cell Kidd system phenotype changed during the 2 years in which her blood was studied. Certainly once, and perhaps twice, the patient's phenotype changed from Jk(a+b-) to Jk(a-b-). On both occasions, it reverted to Jk(a+b-).