Impaired short-term homing in vivo despite identical selectin ligand expression. (A) Experimental design for short-term homing experiment. Mutant 15-day FTL cells were isolated, genotyped, and labeled with either CFSE or CSA-SE. These were mixed in a 1:1 ratio with wt cells labeled with the opposite fluorescent tracker prior to intravenous injection into irradiated recipients. Relative frequency of CFSE- and CSA-SE–labeled cells in BM and SPL was determined 16 hours later by FACS. In control experiments, the fluorescent labels were reversed to rule out dye toxicity. (B) Percent homing efficiency of wt or mutant FTL cells to SPL (right panel) or BM (left panel). The wt cells were assigned a frequency of 100%. Results from CFSE and CSA-SE homing were pooled together and standard deviation calculated for the number of mice analyzed (n = 4 per genotype). (C-D) The percentage and mean RFI of E-, P-, and L-selectin binding to wt, cd34^-/-, podxl^-/-, or podxl^-/-cd34^-/- FTL cells. Shown are results from 2 independent experiments. (B-D) □ indicates wt; ▦, cd34^-/; ▨, podxl^-/-; and ▪, podxl^-/-cd34^-/-.