Comparison of the fluorescence profiles of CFSE⁺ BM cells after maintenance in culture or in vivo in different tissues.

LD BM cells were labeled overnight, and then CFSE⁺ cells were analyzed after 3 further days of culture (labeled BM cells cultured with FL, SF, and H-IL-6 growth factors, top left panel) or after 3 days after transplantation of 3 × 10⁶–labeled LD BM cells. Results are shown for cells harvested from the BM (top right panel), spleen (bottom left panel), and blood (bottom right panel) of the injected mice. The distribution of cells among different subpopulations with different proliferative histories is similar for the cells expanding in vitro and in vivo, although there is a slight but obvious shift to the left of the cells obtained from the mice (up to 8 cell divisions in the spleen) compared with the cells maintained in culture for the same period prior to analysis (just a few cells entering the seventh progeny generation). The open peak indicates the fluorescence profile of the same cells maintained in vitro with colcemid to fix the position of the undivided cells.