Fig. 5. Role of TNF and ROS in hematopoietic suppression. (A) The ROS scavenger NAC or deletion of Tnfr1 gene rescued progenitor growth. WT, Fancc^–/– mice or their littermates lacking Tnfr1 were injected with PBS or TNF (0.1 mg/kg per day) for 2 consecutive days. Mice were injected with NAC (1 mg/mouse per day) 30 minutes before and after TNF injection. Twenty-four hours later, BM cells were isolated and subjected to clonogenic assay. Data shown represent the mean ± s.d. of the total number of colonies from three independent experiments; ^*P<0.05. (B) Anti-oxidant NAC or deletion of the Tnfr1 gene restored HSC self-renewal ability. 2x10⁶ BM mononuclear cells isolated from the mice described in A were transplanted together with 1x10⁶ competitor cells from B6.BoyJ mice (CD45.1⁺) into lethally irradiated recipient mice; long-term engraftment was evaluated 16 weeks after transplantation. Data represent the mean ± s.d. of three independent experiments with three recipients per group for each experiment. ^*P<0.05.