Human MSCs and TSG-6 reduced amplification of the pro-inflammatory signals by mesothelial cells. (A) Human mesothelial (Mesoth) cells were incubated with zymosan and cultured alone or in cocultures with mouse macrophages (Mφ). Stimulation of the human mesothelial cells was assayed with human-specific RT-PCR assay for hIL-6. (B) As in panel A except TSG-6 was added to some of the cultures and stimulation of the human mesothelial cells was assayed with human-specific real-time RT-PCR assays for hIL-6, hIL-8, and hCCL2. (C) Systemic effects of the inflammatory cascade as indicated by plasma levels of mIL-6 assayed 8 hours after zymosan with or without subsequent infusion of hMSCs or TSG-6. Values are mean ± SD (n = 6 for HBSS, n = 3 for hMSCs and n = 4 for TSG-6; *P < .05; **P < .005; ***P < .005).