IL-22BP dictates characteristics of Peyer's patch follicle-associated epithelium for antigen uptake

Interleukin-22 (IL-22) acts protectively and harmfully on intestinal tissue depending on the situation; therefore, IL-22 signaling needs to be tightly regulated. IL-22 binding protein (IL-22BP) binds IL-22 to inhibit IL-22 signaling. It is expressed in intestinal and lymphoid tissues, although its precise distribution and roles have remained unclear. In this study, we show that IL-22BP is highly expressed by CD11b⁺CD8α^- dendritic cells in the subepithelial dome region of Peyer's patches (PPs). We found that IL-22BP blocks IL-22 signaling in the follicle-associated epithelium (FAE) covering PPs, indicating that IL-22BP plays a role in regulating the characteristics of the FAE. As expected, FAE of IL-22BP-deficient (Il22ra2^/-) mice exhibited altered properties such as the enhanced expression of mucus and antimicrobial proteins as well as prominent fucosylation, which are normally suppressed in FAE. Additionally, Il22ra2^/- mice exhibited the decreased uptake of bacterial antigens into PPs without affecting M cell function. Our present study thus demonstrates that IL-22BP promotes bacterial uptake into PPs by influencing FAE gene expression and function.