XK (also known as Kell blood group precursor) is a protein found on human red blood cells and other tissues which is responsible for the Kx antigen which helps determine a person's blood type. The Kx antigen plays a role in matching blood for blood transfusions. Absence of XK protein leads to McLeod syndrome, a multi-system disorder characterized by hemolytic anemia, myopathy, acanthocytosis, and chorea.
Malandrini A, Fabrizi GM, Truschi F, Di Pietro G, Moschini F, Bartalucci P, Berti G, Salvadori C, Bucalossi A, Guazzi G. Atypical McLeod syndrome manifested as X-linked chorea-acanthocytosis, neuromyopathy and dilated cardiomyopathy: report of a family. J Neurol Sci. 1994 Jun;124(1):89-94. PMID 7931427
XK is located on the X chromosome and absence of the XK protein is an X-linked disease.Ho MF, Monaco AP, Blonden LA, van Ommen GJ, Affara NA, Ferguson-Smith MA, Lehrach H. Fine mapping of the McLeod locus (XK) to a 150-380-kb region in Xp21. Am J Hum Genet. 1992 Feb;50(2):317-30. PMID 1734714 XK is a membrane transport protein of unknown action.Jung HH, Russo D, Redman C, Brandner S. Kell and XK immunohistochemistry in McLeod myopathy. Muscle Nerve. 2001 Oct;24(10):1346-51. PMID 11562915
