The role of stromal cells in the induction of DCs from FL-derived Lin⁻c-kit⁺ HPCs.

13 dpc FL-derived HPCs were cultured in the presence of cytokines, GM-CSF + SCF + Flt3L, with or without stromal cell line OP9 or PA6 cells in a transwell culture system. M-CSF was added into these cultures as indicated. After 12 to 14 days of culture, the nonadherent cells were replanted in a new 6-well plate, restimulated with GM-CSF + mTNFα for an additional 3 to 5 days and then collected for immunofluorescence analysis. Ia⁺CD86⁺ cells were examined by staining with PE-labeled Ia MoAb and biotinylated CD86 MoAb, and revealed by FITC-streptavidin. Results are expressed as the mean ± SD of 3 independent experiments. *P < .05 significance compared with cultures lacking stromal cells or M-CSF addition, or between different stromal cells. Gray bars represent cultures without M-CSF; colored bars, with M-CSF.