MSC inhibit monocyte progression to immature DCs. A representative experiment. Expression of CD14, CD1a, CD80, CD86, and CD83 on monocytes (at day 0) and after induction of DC differentiation to immature DCs (day 5) or full maturation (day 7). Phenotypic analysis of monocytes was performed on PBMCs by gating on the leukocyte subset according to the forward scatter and side scatter scatter, whereas iDC surface phenotype was analyzed in CD14⁺ cells cultured for 5 days with GM-CSF and IL-4 either in the absence or in the presence of MSCs. Mature DC phenotype was analyzed after LPS-induced maturation of cells cultured alone or with MSCs either starting at day 0 or at day 5. Numbers indicate percentages of positive cells for CD14 and CD1a expression, whereas they represent mean fluorescence intensity for the surface density of CD80, CD86, and CD83 markers.