The stem cells that are collected through the apheresis procedure are treated in the laboratory with the Hum195/Gelonin conjugate. This procedure is known as purging and it is being studied to learn if the treatment of the stem cells with the HuM195/Gelonin conjugate can eliminate leukemia cells without damaging the normal stem cells. Since the best dose of HuM195/Gelonin conjugate for purging is not known, the cells of the participants in this study will receive 1 of 3 different doses of HuM195/Gelonin. The dose of HuM195/Gelonin that the cells will receive will be decided randomly according to the experience of the participants treated earlier in the study.