LMPP and CLP populations contain thymic settling progenitors. (A) Schematic for experimental design of short-term homing assay. BM cells (CD45.2) were intravenously injected into congenically marked recipients (CD45.1). Twenty-two hours later, thymi were harvested from recipient mice, and donor cells were sorted and plated on OP9-DL4 cultures in the presence of IL-7 and Flt3 ligand. Cocultures were analyzed 2 to 3 weeks later. (B) Short-term homing assay of WT LMPPs or CCR7/CCR9 double knockout LMPPs intravenously injected into WT recipients (n = 2; P < .05 using Fisher’s exact test). (C) Short-term homing assay of HSCs, MPPs, LMPPs, and CLPs sorted from WT mice. Each population was intravenously injected into WT recipients. Cocultures were analyzed 2 to 3 weeks later (n = 3; P < .05 using Fisher’s exact test).