Interleukin-10-secreting Peyer's patch cells are responsible for active suppression in low-dose oral tolerance

We demonstrate the induction of antigen-specific interleukin-10 (IL-10)-secreting cells in murine Peyer's patches (PPs) after low-dose β-lactoglobulin (BLG) feeding. In addition, we show that PP cells can inhibit the T-cell proliferative response in vitro as well as T-cell-mediated inflammation in vivo. The active suppression mediated by these regulatory cells was seen only within a narrow range of antigen dosage (feeding), with the most prominent effect at 5 × 1 mg BLG. On either side of this range, T-helper 1-like cytokine responses were observed when PP cells were stimulated with antigen in vitro. This result correlated with reduced production of regulatory cytokines as well as reduced activity of bystander suppression. We found that changes in IL-10 production correlated inversely with changes in interferon-γ production. Inhibitory effects mediated by CD4⁺ PP cells were partially neutralized by antibodies to IL-10 and transforming growth factor-β. Interestingly, the generation of such regulatory cells after low-dose BLG feeding exhibited organ dependence. Among spleen, lymph node and PP cells derived from orally tolerized mice, PP cells were the most effective in promoting bystander suppression in the presence of BLG, indicating the significance of PPs as an inductive site for antigen-specific regulatory cells upon induction of low-dose oral tolerance. Moreover, PP cells from mice fed 5 × 1 mg BLG were shown to suppress a BLG-specific delayed-type hypersensitivity response induced in footpads, suggesting that IL-10-secreting PP cells regulate systemic inflammation.