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Leukocytes of nine unrelated boys with X-linked chronic granulomatous disease lack Kx antigen. In three of these cases, the red cells also lack Kx and have the McLeod phenotype and abnormal morphology. X-linked chronic granulomatous disease CGD can thus be separated into two types. Type I cases have an antigenic deficiency that is restricted to the phagocytic leukocytes while in type II, the deficiency involves both leukocytes and red cells. Red cells of type II CGD patients have enhanced i antigen activity suggesting that they are under hemopoietic stress. Normal Kx synthesis is directed by an X-linked gene named X1k. Three variants, X2k, X3k, and X4k order the different permutations of leukocyte and red cell Kx antigen production that have been recognized.

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.

KX, an antigen related to the Kell blood group system, is present in trace amounts on normal red cells and is strongly active on the neutrophils of all of 50 persons thus far tested. Normal circulating monocytes are now shown to also bear KX determinants. Absence of neutrophil KX has been associated with all of three previously tested patients with chronic granulomatous disease. In this study two male siblings with CGD also have been shown to have KX negative leukocytes, and white blood cells from their heterozygous mother were found to have a reduced competency to absorb anti-KX. Five CGD boys are known to lack KX; the probability of this occurring by chance is greater 10(-6).

Fifteen antigenic determinants are known to be related to the Kell blood group. Some boys with X-linked chronic granulomatous disease have the very rare McLeod or Ko phenotype on their red cells. Serological studies of the McLeod type suggest that the weak Kell antigens that are present differ qualitatively and quantitatively from those on red cells of common Kell type. A new antigen, Kx, has been characterized and shown to be present on red cells and neutrophil leucocytes. Lack of red-cell Kx is associated with the McLeod phenotype, lack of leucocyte Kx is associated with chronic granulomatous disease.

The McLeod phenotype is an X-linked, recessive disorder in which the red blood cells demonstrate acanthocytic morphology and weakened antigenicity in the Kell blood group system. The phenotype is associated with a reduction of in vivo red cell survival, but the permanent hemolytic state is usually compensated by erythropoietic hyperplasia. The McLeod phenotype is accompanied by either a subclinical myopathy and elevated creatine kinase (CK) or X-linked chronic granulomatous disease (CGD). Seven males with the McLeod red-blood-cell phenotype and associated myopathy but not CGD, one male with the McLeod phenotype associated with CGD, and two males known to possess large deletions of the Duchenne muscular dystrophy (DMD) locus were studied. DNA isolated from each patient was screened for the presence or absence of various cloned sequences located in the Xp21 region of the human X chromosome. Two of the seven males who have only the McLeod phenotype and are cousins exhibit deletions for four Xp21 cloned fragments but are not deleted for any portion of either the CGD or the DMD loci. Comparison of the cloned segments absent from these two McLeod cousins with those absent from the two DMD boys and the CGD/McLeod patient leads to the submapping of various cloned DNA segments within the Xp21 region. The results place the locus for the McLeod phenotype within a 500-kb interval distal from the CGD locus toward the DMD locus.

A 3-year-old black male child with X-linked chronic granulomatous disease and red cells of the rare McLeod phenotype is presented. The red cells showed acanthocytosis and did not react with anti-KL. Similarly the leukocytes were nonreactive with anti-Kx. The Xk and Xg linkage could not be investigated since all members of his family were Xg (a+).

The relationship between neutrophil function and the neutrophil antigen, Kx, as well as the linkage of the gene, Xk, with Xg was examined in a kindred with X-linked chronic granulomatous disease. Four of the eight male siblings had chronic granulomatous disease by clinical history and tests of neutrophil function, and all four had Kx-negative neutrophils. The remaining four were in good health and had normal nitroblue tetrazolium reduction tests. However, one of these latter four had Kx-negative neutrophils that functioned normally. These data suggest that closely linked but distinct genes on the X chromosome code for chronic granulomatous disease and Kx. In addition, close linkage was demonstrated between Xk and Xg, a gene coding for an erythrocyte surface antigen.