Figure 1.

Exposure of bone marrow cells to bacteria inhibits dendritic cell (DC) differentiation. Bone marrow cells were cultured with non-pathogenic bacteria at a 1 : 1 bacterium : progenitor cell ratio in the presence of granulocyte–macrophage colony-stimulating factor for 7 days and the phenotype of cells was determined by multi-colour flow cytometry for the expression of classical bone marrow-derived DC markers (a). Costimulatory molecule expression was also examined by flow cytometry (b). Values in the upper right indicate percentages of cells falling in the indicated gate. Mean values ± SEM are expressed. n = 7 independent experiments. *P ≤ 0·05, **P≤ 0·01, ***P ≤ 0·001 compared to control cultures.