Interactions between commensal bacteria and mucosal immunocompetent cells

The intestinal mucosa, colonised by commensal microorganisms, constitutes t he interface with the external environment, through which most pathogens in itiate infectious processes. :Intestinal mechanisms of defense need to disc riminate accurately between comensal microflora, and exogenous pathogens. W e studied the capacity of mucosal immunocompetent cells to react to bacteri al signals generated by non-pathogenic microorganisms in vitro. A character istic response to different components of the microflora has been detected. Two different patterns of innate response were shown, discriminating betwe en Gram-negative and Gram-positive bacteria. Furthermore, differences in th e cellular activation of non-pathogenic Lactobacillus species were observed . We demonstrate the importance of non-pathogenic microorganisms in modulat ion of host gut mucosal defences and maintenance of homeostasis and integri ty. The understanding of these modulatory functions will provide a unique o pportunity to prevent or treat intestinal disorders associated with food al lergy, intestinal infections, inflammatory bowel disease and autoimmunity. (C) 1999 Elsevier Science Ltd. All rights reserved.