Endothelial stromal cell–derived IL-10 is involved in the differentiation of CD11b^hiIa^lo DCs from HSCs. (A) HSCs were cocultured with ESSCs either directly or separated from ESSCs by permeable membrane of transwell insert in an indirect way. After 10 days of culture, CD11b^hiIa^lo DCs in both culture systems were collected and added into CD4/mDC coculture to compare their inhibitory function. On day 5, the relative cell number of viable peptide-specific CD4 T cells was assayed by FACS. (B) At the beginning of the culture, indicated antibodies (5 μg/mL) were added into the transwell culture system. After 10 days, cells in the upper insert were collected to test their inhibitory functions. *P < .01. (C) HSCs were cocultured with wt-ESSCs or IL-10–KO-ESSCs or IL-10–KO-ESSCs plus exogenous IL-10 (5 ng/mL). After 10 days of culture, nonadherent cells from the coculture system were collected to compare their inhibitory function. On day 5, the relative cell number of viable peptide-specific CD4 T cells was assayed by FACS. *P < .01. (D) The nonadherent cell number from wt-ESSCs or IL-10–KO-ESSC coculture system were tested by FACS. *P < .01.