Innate and specific gut-associated immunity and microbial interference.

Certain bacterial species isolated from the gastrointestinal microbial communities release low-molecular-weight peptides into milk products using bacteria-derived proteases that degrade milk casein, and thereby generate peptides, triggering immune responses. The intestinal microbial communities contributes to the processing of food antigens in the gut. The present study was designed to investigate the immunomodulatory effects of microbial interference to determine whether casein degraded by probiotic bacteria-derived enzymes could modulate the cytokine production and peripheral blood mononuclear cells in atopic infants with cow or other synthetic milk allergy. Without hydrolyzation, casein reduced the production of interleukin-4, which indicates that probiotics modify the structure of potentially harmful antigens and thereby alter the mode of their immunogenicity. Intraluminal bacterial antigens have been reported to elicit specific responses in the gut-associated lymphoid tissue (GALT) through the binding capacity of intraluminal bacterial antigens to epithelial cells, which allows antigen entry via enterocytes and aids in evading the tolerance function in Peyer's patches. Such tonic immune responses in the GALT may allow control of the metabolic activity and balance of the gut microbial communities.