Figure 4.
The inhibitory effect of hMSCs is partially mediated by IL-10 but not by TGF-β. (A) CD4+ T cells, monocytes, and hMSCs were cultured alone (▪) or in combination (▦), in the presence or absence of SEB, as indicated. The levels of TGF-β in the conditioned media were assayed by ELISA after 72 hours. The data represent the mean of triplicate samples and standard deviations. (B) PBMCs were stimulated with SEB in the absence or presence of hMSCs (5 × 104 cells of each cell type). Neutralizing anti–TGF-β1-2 Abs (1 μg/mL) were added and IFN-γ secretion was measured in the conditioned media after 72 hours. The data are presented as percentage of inhibition of IFN-γ secretion in the presence of hMSCs compared with cells stimulated in the absence of hMSCs. The data in panels A and B are from 1 experiment; similar results were obtained in 2 other experiments. (C) Coculturing hMSCs with monocytes induces IL-10 secretion. PBMCs were either left untreated or were stimulated with SEB (1 ng/mL) in the absence (▪) or presence (▦) of hMSCs (left panel). Either monocytes or monocytes and CD4+ T cells that were either untreated or stimulated with SEB (1 ng/mL) were cultured alone (▪) or in the presence (▦) of hMSCs (5 × 104 cells per well; right panel). After 72 hours, the level of IL-10 in the various conditioned media was determined by ELISA. No IL-10 was detected in conditioned media of hMSCs cultured alone (right panel). The data represent the mean values of triplicate samples and standard deviations. (D) Purified CD4+ T cells were stimulated with SEB in the presence of monocytes and in the absence or presence of hMSCs (5 × 104 cells of each cell type were plated). Neutralizing anti–IL-10 receptor Abs (1 μg/mL) were added and either proliferation (right panel) or IFN-γ (left panel) and TNF-α (middle panel) secretion was measured in the conditioned media after 72 hours. Similar results were obtained when whole PBMCs were used (data not shown). The data are presented as percentage of inhibition of proliferation and cytokine secretion in the presence of hMSCs compared with cells stimulated in the absence of hMSCs. The results shown in panels C and D are representative of 3 separate experiments.