Cytochrome b deficiency in an autosomal form of chronic granulomatous disease. A third form of chronic granulomatous disease recognized by monocyte hybridization.

Three patients (two sisters and a brother) in one family are described with chronic granulomatous disease. The granulocytes of these patients did not respond with a metabolic burst to various stimuli and failed to kill catalase-positive microorganisms. The magnitude of the cytochrome b signal in the optical spectrum of the patients' granulocytes was less than 4% of the normal value, whereas the amount of noncovalently bound flavin in these cells was normal. The mode of inheritance of the genetic defect in this family is autosomal because the granulocytes of both parents (first cousins) and a nonaffected sister of the patients expressed 70-80% of the normal cytochrome b signal, showed low-normal or subnormal oxidative reactions during stimulation, and did not display mosaicism in the stimulated nitroblue-tetrazolium slide test. Somatic cell hybridization was performed between the monocytes from the affected boy in this family with monocytes from either a cytochrome b-negative male patient with X-linked chronic granulomatous disease or a cytochrome b-positive male patient with the classic autosomal form of this disease. In both combinations, monocyte hybrids were observed with nitroblue tetrazolium reductase activity after stimulation with phorbol myristate acetate. This complementation of the oxidase activity required protein synthesis. Our results prove that the defect in this family is genetically distinct from that in the other two forms of chronic granulomatous disease. Moreover, our results also indicate that the expression of cytochrome b in human phagocytes is coded by at least two loci, one on the X chromosome and one on an autosome.