Assessment of the effects of TGF-β1 on colony formation by CD34⁺ cells. Purified CD34⁺ cells (obtained by immunomagnetic isolation, see the Materials and Methods) were sorted individually into 96-well plates using a FACSVantage and cultured in serum-free medium in the presence of GM-CSF, TNFα, and SCF or in medium additionally supplemented with FL or FL plus TGF-β1 for 10 days (see the Materials and Methods). Bars show percentage cloning efficiency for Lag⁺ dendritic cell colonies and small (20 to 50 cells/colony) or large (<50 cells/colony) colonies (CFC).