The consequence of this altered accessory repertoire on R-DC is that cocultured T cells acquire a deep anergic state 12, 13. Here we demonstrate that R-DC induce suppressor function in cocultured T cells. The inhibitory effect was found to be caused by the culture supernatant (SN) of CD4+ and CD8+ peripheral blood T cells, activated with R-DC, but not with naïve T cells from cord blood (CB). We found that R-DC-induced Treg produced and released IL-35, which Selleckchem Palbociclib is responsible for the inhibitory effect of the Treg SN. Most importantly,

blocking of B7-H1 and sialoadhesin on R-DC with specific mAb against both receptors prevented the induction of IL-35. Thus, inhibitory signals delivered from R-DC

to T cells via B7-H1 and sialoadhesin were essential to the induction of human IL-35-producing Treg, defining a novel route of T-cell instruction. We have recently demonstrated that HRV is able to subvert the T-cell stimulatory function of human DC. Cocultured T cells acquire a deep anergic state 12. This study was aimed to investigate whether T cells stimulated with R-DC gain a regulatory function. The results presented in Fig. 1A demonstrate that addition of T cells prestimulated with R-DC strongly inhibited T-cell proliferation, induced by untreated DC. Such an effect AZD6244 did not occur when T cells were primed with untreated DC. Prior fixation of R-DC-induced Treg reverted the inhibitory function (Fig. 1B). Addition of the inhibitor WIN 52035-2 at the time of transfer, which specifically blocks HRV binding to its cellular receptor ICAM-1 14, did not remove the suppressive effect, which indicates that viral transfer is not involved in the inhibitory response (Fig. 1C). Depletion of R-DC from the coculture with T cells did not alter the results: the purified prestimulated T cells still Thiamet G showed

eminent inhibitory effects when added to an MLR (data not shown). We conclude that T cells prestimulated with R-DC are responsible for the inhibitory effect observed. FOXP3 is a forkhead family transcription factor important in the development of Treg; therefore we evaluated its levels in R-DC-induced Treg. Analysis of FOXP3 expression in CD25- T cells revealed that induction of FOXP3 does not differ between DC and R-DC stimulated T-cells, indicating that the suppressive capacity of R-DC stimulated T cells is not directly correlated with an increased induction of FOXP3. Also FOXP3 levels drop again after 48 and 96 h in T cells, stimulated with R-DC or DC (Fig. 1D). Activation-induced transient FOXP3 expression in human T cells has been frequently observed before 10, 15–17 and is not necessarily correlated with regulatory activity 7, 10, 18. In order to analyze whether the inhibitory effect was mediated through (a) soluble factor(s), we added the SN of the R-DC-induced Treg to T-cell/DC cocultures.