focuses on the molecular and cellular fundamentals of homeostatic and defense responses of tissue barriers, covering the damaging impacts and exposure to pathogens and engineered nanomaterials. Sections emphasize the role of mesenchymal stoma, vascular, epithelial, telocyte, myofibroblast, lymphoid and reticuloendothelial cells, along with reactions that bridge the effects of ambient factors, medical treatments, drag delivery systems with alterations in barrier integrity, tissue/organ functions, and metabolic status. Other sections cover the role of progenitor cells of different origins in the remodeling and regeneration of tissue stroma, vasculature of blood-tissue barriers, and more.