hMSC-conditioned APCs exhibit a particular pattern of activation markers. Purified CD4⁺ T cells were stimulated with SEB (1 ng/mL) in the presence of either monocytes (A,C) or DCs (B,D) in the absence (-) or presence (+) of hMSCs (5 × 10⁴ cells of each cell type were plated). After 72 hours, conditioned media were collected and the levels of the indicated cytokines in the media were determined using the appropriate ELISA kit (A,B). The data represent the mean values of triplicate samples and standard deviations. A representative of 4 separate experiments is shown. The cells were collected and the levels of CD86 and HLA-DR surface expression either on CD14⁺ cells (C) or CD11c⁺ cells (D) were determined by immunofluorescence and flow cytometry. Data are presented as mean fluorescent intensity of CD86 and HLA-DR staining. One of 3 experiments is shown. ^*P < .001, based on t test.