Chemiluminescence assay for superoxide production by PMA activated neutrophils derived from sham treated and transduced CD34⁺ cells at 17 days of culture. The vertical axis represents the average light unit integral over 40 minutes as a measure of superoxide production. Bar A is the average of six cultures of sham treated normal CD34⁺ cells. Bars B through F represent the average value of four experiments each with p67^phox deficient CGD CD34⁺ cell cultures for each bar seen. Bar B is sham treated patient cells; bars C through F are patient cells transduced with MFGS-p67^phox derived from clones 2, 5, 20, 37, respectively. Error bars represent standard error of the mean.