MICROBIAL FACTORS IN CHRONIC INTESTINAL INFLAMMATION

This review summarizes recent investigations of microbial influences i n ulcerative colitis, Crohn's disease, and experimental intestinal inf lammation in rodents, Current data do not suggest that a specific pers istent infection causes Crohn's disease but indicate that resident (no rmal) luminal bacteria induce chronic intestinal and systemic inflamma tion in genetically susceptible hosts. Anaerobic bacteria and bacteria l products appear to be dominant stimulants in Crohn's disease and exp erimental colitis, whereas functionally abnormal aerobes may be involv ed in ulcerative colitis. Viable bacteria secondarily invade ulcerated mucosa, and enhanced uptake of bacterial cell wall polymers, chemotac tic molecules, and antigens across the inflamed mucosa activate lamina propria inflammatory cells to perpetuate local inflammation. Systemic distribution of bacterial constituents leads to extraintestinal manif estations, The delicate balance between luminal microbial constituents and protective mucosal forces can be disturbed by genetically determi ned immunoregulatory abnormalities and environmental triggers, leading to chronic, relapsing intestinal inflammation.