Fig. (4)Patient phenotypes and direct sequencing of the CYBB gene A. Flow cytometry with DHR-123 demonstrated that reactive oxygen species were produced at low levels in neutrophils obtained from the patient. The effects of a null mutation (del425_426CT, 142S>fsX) are shown as a negative control.B. Flow cytometry with anti-cytochrome b₅₅₈ monoclonal antibodies showed markedly decreased surface expression of cytochrome b₅₅₈ on the patient’s neutrophils.C. Direct sequencing of the CYBB gene indicated that the patient had a homozygous single G>C nucleotide substitution at position +5 in the consensus 5’-donor splice site of intron 5.