Bacterial colonization and the development of intestinal defences.

摘要: In humans, intestinal defences develop during gestation and, at full term, have the capacity to respond in an appropriate manner infectious agents and foreign antigens. Before active protective response can occur, however, gut must first be exposed colonizing bacteria. Colonization with diverse microbes is necessary for development of important defenses such as synthesis secretion polymeric immunoglobulin A generation a balanced T helper (Th) cell response. Insights into normal immune physiological been made by studying germ-free animal defenses. These studies provided insights physiology responses. Two immunological functions are protect surface against harmful stimuli inhibition systemic commensal bacteria food proteins (eg, oral tolerance) prevent chronic inflammation. Neither function exists state, but rapidly develops after conventionalization (colonization) animal. present review, importance bacterial colonization on appearance mucosal clinical consequences inadequate disease will discussed. For example, excessive Th2 activity lead atopy, whereas Th1 predominance found conditions Helicobacter pylori gastritis Crohn's disease. With eradication diseases developed countries past three decades, incidence atopic autoimmune has increased. This epidemiological observation explained 'hygiene hypothesis', which suggests that reduction microbial burden public health measures contributed imbalance intestine. family pattern recognition receptors (Toll-like receptors) lymphoid epithelial cells mediates innate responses molecular patterns thereby, orchestrates acquired immunity. As role communication within (bacterial-epithelial cross-talk) clarified, physicians should able modulate responses, use probiotics.