Toxin treatment of HPC derived from mobilized blood does not affect the number of CFU observed. Mobilized HPC from a lymphoma patient were enriched using a negative selection approach described in Materials and Methods. Increasing numbers of enriched HPC (25 to 200 cells per culture) in Methylcult were treated or not with 5 μg/mL SLT-1 for 60 minutes, washed, and finally dispensed in microtiter wells to measure colony formation. At day 20, the number of colonies were counted for replicate wells at each cell concentration. Values represent the average number of colonies (±SE) calculated from counting colonies present in 8 to 12 replicate wells. HPC from this patient were also shown to be negative for binding FITC-SLT-B (not shown).