Fig. 4

hfcMSCs exhibit immunomodulatory effects on CD4⁺ lymphocytes through regulated PD-1 expression and interaction. a Histograms showing CellTrace™ CFSE dilution in a representative sample of CD4+ T cells following 3 days of incubation in the presence or absence of hfcMSCs and/or blocking αPD-1 antibody. b The effect of hfcMSCs on CD4+ T cell division, shown as proliferation index, after co-culture with hfcMSCs in the presence or absence of blocking αPD-1 antibody. c The presence of hfcMSCs decreased the median fluorescence intensity (MFI) cell surface expression of PD-1 on isolated, activated CD4+CD25+ T cells. The same effect was observed when the cell types were separated by a transwell filter, indicating a predominant role for soluble mediators. d Effects of hfcMSCs on CD4+ T cell activation, depending on cell/cell contact or soluble mediators, shown as IL-2RA (CD25) expression after 3 days of direct co-culture or separation of the two cell types with transwell filters, in the presence or absence of blocking αPD-1 antibody. e The combined bar graph/scatter dot plot depicts T cell proliferation as incorporation of ³H-thymidine after direct co-culture with hfcMSCs, followed by restimulation with IL-2. The experiments were performed on cells from four different hfcMSC donors (n = 4). Data from a–d were derived from two T cell donors (n = 8). Graph data are presented as mean ± SEM. *P < 0.05, **P < 0.01, ***P < 0.001, ****P < 0.0001