Kraehenbuhl J P, Pringault E, Neutra M R
Swiss Institute for Experimental Cancer Research and Institute of Biochemistry, University of Lausanne.
Aliment Pharmacol Ther. 1997 Dec;11 Suppl 3:3-8; discussion 8-9. doi: 10.1111/j.1365-2036.1997.tb00803.x.
The mucosal epithelia of the digestive tract acts as a selective barrier, permeable to ions, small molecules and macromolecules. These epithelial cells aid the digestion of food and absorption of nutrients. They contribute to the protection against pathogens and undergo continuous cell renewal which facilitates the elimination of damaged cells. Both innate and adaptive defence mechanisms protect the gastrointestinal-mucosal surfaces against pathogens. Interaction of microorganisms with epithelial cells triggers a host response by activating specific transcription factors which control the expression of chemokines and cytokines. This host response is characterized by the recruitment of macrophages and neutrophils at the site of infection. Disruption of epithelial signalling pathways that recruit migratory immune cells results in a chronic inflammatory response. The adaptive defence mechanism relies on the collaboration of epithelial cells (resident sampling system) with antigen-presenting and lymphoid cells (migratory sampling system); in order to obtain samples of foreign antigen, these samples must be transported across the barriers without affecting the integrity of the barrier. These sampling systems are regulated by both environmental and host factors. Fates of the antigen may differ depending on the way in which they cross the epithelial barrier, i.e. via interaction with motile dendritic cells or epithelial M cells in the follicle-associated epithelium.
消化道的黏膜上皮作为一种选择性屏障，对离子、小分子和大分子具有通透性。这些上皮细胞有助于食物消化和营养吸收。它们有助于抵御病原体，并经历持续的细胞更新，这有利于清除受损细胞。固有防御机制和适应性防御机制都能保护胃肠道黏膜表面免受病原体侵害。微生物与上皮细胞的相互作用通过激活特定转录因子触发宿主反应，这些转录因子控制趋化因子和细胞因子的表达。这种宿主反应的特征是在感染部位募集巨噬细胞和中性粒细胞。招募迁移性免疫细胞的上皮信号通路的破坏会导致慢性炎症反应。适应性防御机制依赖于上皮细胞（常驻采样系统）与抗原呈递细胞和淋巴细胞（迁移采样系统）的协作；为了获取外来抗原样本，这些样本必须在不影响屏障完整性的情况下穿过屏障。这些采样系统受环境和宿主因素的调节。抗原的命运可能因它们穿过上皮屏障的方式而异，即通过与运动性树突状细胞或滤泡相关上皮中的上皮M细胞相互作用。
