Human rhinoviruses induce IL-35-producing Treg via induction of B7-H1 (CD274) and sialoadhesin (CD169) on DC.

IL-35 is a heterodimer of EBV-induced gene 3 and of the p35 subunit of IL-12, and recently identified as an inhibitory cytokine produced by natural Treg in mice, but not in humans. Here we demonstrate that DC activated by human rhinoviruses (R-DC) induce IL-35 production and release, as well as a suppressor function in CD4(+) and CD8(+) T cells derived from human peripheral blood but not in naïve T cells from cord blood. The induction of IL-35-producing T cells by R-DC was FOXP3-independent, but blocking of B7-H1 (CD274) and sialoadhesin (CD169) on R-DC with mAb against both receptors prevented the induction of IL-35. Thus, the combinatorial signal delivered by R-DC to T cells via B7-H1 and sialoadhesin is crucial for the induction of human IL-35(+) Treg. These results demonstrate a novel pathway and its components for the induction of immune-inhibitory T cells.