The functional maturation of TGF-β1–induced monocytes/macrophages into mature DC-like cells. Murine Lin⁻c-kit⁺ HPCs were first cultured in the presence of GM-CSF + SCF for 12 days with the addition of TGF-β1 (A and C). These cultured cells were then washed twice and recultured in the presence of GM-CSF + TNF for an additional 3 to 5 days (B and D). A three-color immunofluorescence analysis was performed to show the capacity of FITC-DX and FITC-Latex uptake by gating on CD11b^−/dullCD11c⁺ cells as described in Materials and Methods. Solid and dotted lines indicate the FITC intensity of cells as a control and the test of FITC-DX or FITC-latex uptake, respectively. (E) TGF-β1–induced monocytes/macrophages (□) matured into DC-like cells (◊) with the capacity to potently stimulate allogenic MLR. The results are representative of three experiments.