Superoxide dismutase-inhibitable superoxide production was measured in nonadherent BM cells (which contain ≈50% to 60% mature neutrophils) using a continuous cytochrome c reduction assay, as described in Materials and Methods. Data are the mean ± SD. Greater than 95% of wild-type nonadherent BM neutrophils were NBT⁺, whereas the percentage of NBT⁺ neutrophils in X-CGD mice after transplantation with MSCV-m91Neo–transduced BM ranged from 62% to 82% (mean, 68% ± 7%). Two of the transplanted X-CGD mice had been challenged with A fumigatus 10 weeks after transplantation; the remaining three were studied 6 weeks after transplantation and were not challenged with A fumigatus.