Effect of priming chemotherapy on the number and clonal origin of CD34⁺HLA-DR⁻ cells in marrow and blood. Marrow was obtained before and BM and PB were obtained after priming chemotherapy. CD34⁺HLA-DR⁻ cells were selected using sequential Ficoll-Hypaque separation, column enrichment, and FACS selection. To calculate the number of CD34⁺HLA-DR⁻ cells that would be available for transplantation the following calculations were made: For marrow, the number of CD34⁺HLA-DR⁻ cells present per 10⁶ BM cells was multiplied by the calculated number of cells present in a hypothetical marrow harvest of 2.5 L. For PBPC collections, the number of CD34⁺HLA-DR⁻cells in each PB collection was determined by multiplying the number of CD34⁺HLA-DR⁻ cells present in 10⁶ PB cells and the total number of cells per collection. When more than one collection was obtained, the number of CD34⁺HLA-DR⁻ cells in each collection was combined to calculate the total number of CD34⁺HLA-DR⁻ cells available for transplantation. The number of CD34⁺HLA-DR⁻cells available was then divided by the weight of the patient to determine CD34⁺HLA-DR⁻ cells/kg. (○), BCR-ABL negative; (•), BCR-ABL positive; (□), no PCR.