Decreased proliferation of hematopoietic stem/progenitor cells in IFN-γRKO hosts. (A) Proportion of apoptotic elements among donor-derived Lin⁺ and LSK BM cells on day 15 after transplantation. Three mice per group from 1 representative experiment of 2. (B) BM cellularity in recipients injected with anti-FasL MFL4 antibody (FasL neutralization +) or a control antibody (FasL neutralization⁻; ≥ 6 mice per group). (C) Representative Hoechst staining pattern of donor Lin⁺ and LSK cells in wt versus IFN-γRKO hosts on day 15 after transplantation. The Hoechst staining pattern of unmanipulated donor type (C3H.SW) cells is shown as a control. Percentages represent the proportion of cycling cells (phases S, G₂-M). (D,E) Proportion of cycling Lin⁺, LSK, LSKF⁻, and LSKF⁺ cells on day 15 after transplantation (3 mice per group, from 1 representative experiment out of 2). (F) Levels of Ccnd1 and Myc transcripts in donor-derived LSKF⁻ cells sorted from the BM of wt and IFN-γRKO hosts on day 15. Levels are expressed relative to the amount of transcripts in BM LSKF⁻ cells from untreated C3H.SW mice (arbitrary level of 1), using HPRT as an endogenous control. Histograms represent the mean and SD for 3 mice per group from experimental triplicates. * and ** correspond to P values < .05 and < .01, respectively.