The Stromal Intervention: Regulation of Immunity and Inflammation at the Epithelial-Mesenchymal Barrier

The immune system safeguards organ integrity by employing a balancing act of inflammatory and immunosuppressive mechanisms designed to neutralize foreign invaders and resolve injury. Maintaining or restoring a state of immune homeostasis is particularly challenging at barrier sites where constant exposure to immunogenic environmental agents may induce destructive inflammation. Recent studies underscore the role of epithelial and mesenchymal barrier cells in regulating immune cell function and local homeostatic and inflammatory responses. Here, we highlight immunoregulatory circuits engaging epithelial and mesenchymal cells in the intestine, airways, and skin and discuss how immune communications with hematopoietic cells and the microbiota orchestrate local immune homeostasis and inflammation.