Mean numbers of clonogenic human progenitors ± SEM contained in the marrow of chimeric transplantation recipients.

From the BM of 17 mice receiving G₀CD34⁺ cells and 15 mice transplanted with G₁CD34⁺ cells, 2 × 10³ CD45⁺CD34⁺ cells were assayed in methylcellulose as described in “Materials and methods.” Total number of colonies (■) represent the arithmetic sum of BFU-E– (▨); CFU-GM– (▤); CFU-GEMM– (▪) derived colonies. Only from 3 NOD/SCID recipients of G₁CD34⁺ cells was it necessary to assay more than 10⁵ total BM cells. In each case, the total number of detected hematopoietic colonies was within 2 SDs of the mean, demonstrating that these samples behaved similarly to those in which fewer than 10⁵ cells were used.