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-). During the first episode of loss of Jka, she formed anti-Jk3. Although this antibody was weak, it was capable of in vivo destruction of Jk(a+b-) and Jk(a-b+) red cells. A lack of details about the patient's clinical condition precludes speculation as to the cause of suppression of Jka expression. The phenomenon appeared to affect only the Kidd blood group system. This case should alert others that antigen loss can occur in the Kidd system as it has been shown to occur in, at least, the Rh, Kell, and Ge systems.