Development of chimerism after conditioning with 5-FU and KL. Recipients prepared with two weekly doses of saline, 5-FU, 5-FU + KL, 5-FU + KL (low dose), or 5-FU + KL (low dose) + G-CSF were transplanted with 3 × 10⁷ BM cells divided over 3 consecutive days (24, 48, and 72 hours after the last 5-FU injection). The level of chimerism was determined at various times after BMT by Gpi-phenotyping of PB erythrocytes.