Impaired ability of T-bet^−/− LN cells in the destruction of host hematopoietic stem and progenitor cells. BM cells from TBI-only (n = 11), B6 LN (n = 13), and T-bet^−/− LN (n = 16) mice were stained and analyzed for the presence of hematopoietic stem and progenitor cells by use of the Lin⁻Kit⁺Sca1⁺CD34⁻ (KSLCD34⁻) marker combination shown as representative dot plots (A) as well as means with SEs (B). Infusion of B6 LN cells reduced (P < .05) BM hematopoietic cells. As a surprise but consistent observation, infusion of T-bet^−/− LN cells markedly increased (P < .01) the hematopoietic stem and progenitor cells in recipient BM.