TGF-β1 polarized the differentiation of murine Lin⁻c-kit⁺ HPCs into DCs through the monocyte/macrophage differentiation pathway. 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, B, and C). The cultured cells were then washed twice and recultured in the presence of GM-CSF + TNF for an additional 3 to 5 days (D, E, and F). (A and D) Observation by phase-contrast inverted microscope; (B and E) Giemsa-Wright staining; (C and F) NSE staining. Original magnifications: for (A) and (D) × 200; for (B), (C), (E), and (F) × 400.