44 Figure 1 | Immune homeostasis and alterations in healthy and inflamed intestinal mucosa. Schematic illustration of the intestinal mucosa showing a gradient of disrupted intestinal barrier integrity with concomitant inflammation and microbial dysbiosis. Under physiological conditions, when the gut microbiota live in homeostasis (eubiosis), intestinal epithelial cells sense the luminal contents for potential antigens and secrete mucins, AMPs and regulatory cytokines (e.g. TSLP, IL-25, IL-33, TGF-β) upon stimulation, favoring a tolerogenic immunological environment. Antigen-presenting cells (APCs) such as DCs and macrophages stimulate the development of regulatory T-lymphocytes (T-regs) via secretion of anti-inflammatory cytokines such as TGF-β and IL-10. These cytokines, in turn, promote the activity of secretory IgA-producing plasma cells. In addition, induced T-regs further contribute to a homeostatic mucosal environment by maintaining a state of immunological tolerance. Chapter 2
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