Comparison of the fluorescence profiles of lin− CFSE⁺ BM cells after maintenance in culture or in vivo (in the marrow) for 3 and 4 days.

Lin⁻ BM cells were labeled overnight, and then CFSE⁺ cells were analyzed after being maintained in vitro or for another 2 or 3 days with FL, SF, and IL-11 (left panels) or for 2 or 3 days in vivo (after 1 day in culture) prior to being recovered from the BM of mice injected with cells taken immediately after they were labeled (right panel). The open peak indicates the fluorescence profile of cells maintained in vitro with colcemid to block cell division and analyzed at the same time. In the top right graph, the recipient was injected with 1.8 × 10⁵lin⁻ CFSE⁺ cells, and in the bottom right graph the recipient was injected with 1.5 × 10⁶ lin⁻CFSE⁺ cells. The 2 right-hand graphs show the results obtained from 1 of 2 mice sacrificed at each time point. The results show the same slight shift to the left in the profiles obtained for the transplanted cells as seen in Figure 3.