SCL-deleted marrow contains increased lineage-negative cells. (A) Southern blot of tissues from a MxSCL^-/loxP mouse tail DNA prior to poly(I:C) or hematopoietic tissues 6 or 60 days after poly(I:C). B indicates bone marrow; S, spleen; and T, and thymus. The probe detects loxP-targeted (loxP), deleted loxP (Δ), and null (-) SCL alleles. (B) Representative contour plots of bone marrow cells from SCL-heterozygous (MxSCL^+/loxP) and SCL-deleted (MxSCL^-/loxP) mice 3 months after administration of poly(I: C). Lineage markers include Mac-1, B220, TER119, and CD3. The percentage of Lin^neg cells in the gate is shown. Gated cells were analyzed for the expression of c-kit and Sca-1. (C) Fold increase of unfractionated whole bone marrow (WBM), Lin^neg, Lin^neg c-kit⁺ Sca-1^- (LK), and Lin^neg c-kit⁺Sca-1⁺ (LKS) cells in SCL-deleted mice (n = 9) compared with SCL-heterozygous mice (n = 10). Results are expressed as the mean and SEM. Comparison of cell numbers was performed by a 2-sided paired Student t test. ^*P < .05; ^**P < .005. (D) Representative histogram plot of c-kit expression on Lin^neg bone marrow cells from SCL-heterozygous and SCL-deleted mice. The peak fluorescence of Lin^neg c-kit⁺ cells is shown.