Interactions between commensal bacteria and mucosal immunocompetent cells

The intestinal mucosa, colonised by commensal microorganisms, constitutes the interface with the external environment, through which most pathogens initiate infectious processes. Intestinal mechanisms of defense need to discriminate accurately between comensal microflora, and exogenous pathogens. We studied the capacity of mucosal immunocompetent cells to react to bacterial signals generated by non-pathogenic microorganisms in vitro. A characteristic response to different components of the microflora has been detected. Two different patterns of innate response were shown, discriminating between Gram-negative and Gram-positive bacteria. Furthermore, differences in the cellular activation of non-pathogenic Lactobacillus species were observed. We demonstrate the importance of non-pathogenic microorganisms in modulation of host gut mucosal defences and maintenance of homeostasis and integrity. The understanding of these modulatory functions will provide a unique opportunity to prevent or treat intestinal disorders associated with food allergy, intestinal infections, inflammatory bowel disease and autoimmunity.