The Kell blood group, Kx antigen, and chronic granulomatous disease.

The Kell blood group has 18 associated red cell antigens. One, named KX, is the product of an X-linked gene and appears to be a precursor in the Kell biosynthetic pathway. Lack of KX on red cells, caused by inheritance of a variant allele at the X-linked locus, results in gross changes in Kell antigenicity, an effect called the McLeod phenotype. Such cells also show striking morphologic changes. Normal phagocytic leukocytes lack Kell antigens but have strong KX. The leukocytes of boys with X-linked chronic granulomatous disease lack KX antigen and have defective bactericidal function. The fundamental defect in chronic granulomatous disease appears to be failure to inherit the X-linked gene that determines KX synthesis. The enzymatic and functional disorders of the leukocytes, and the structural changes in the red cells, are consequences that follow.