Kit down-regulation in SLAM marker-labeled HSCs. (A) Representative FACS plots for lin⁻Sca1⁺CD48⁻CD150⁺ staining 4 weeks post final injection indicates severe reduction of Kit expression in SLAM marker-enriched HSCs from fl/fl:cre⁺ BM. (B) Median fluorescence intensity (MFI) for Kit staining of lin⁻Sca1⁺CD48⁻CD150⁺ cells (n = 4). (C) FACS histogram plots illustrating Kit staining of lin⁻Sca1⁺CD48⁻CD150⁺ cells at different time points after first poly-I:C injection, indicating immediate Kit down-regulation after acute Shp2 deletion. (D) Immunoblotting of BM cells after first poly-I:C injection showed gradually increased deletion from day 7 to 16. Tubulin was used as loading control. ***P < .001, **P < .01,*P < .05, error bars are SD; see also supplemental Figure 4.