Probiotic bacteria down-regulate the milk-induced inflammatory response inmilk-hypersensitive subjects but have an immunostimulatory effect in healthy subjects

Background Probiotic bacteria can influence immune responses both specifica lly by stimulating antibody production and nonspecifically by enhancing pha gocytosis of pathogens and modifying cytokine production. Objective The authors hypothesized that probiotic bacteria can alleviate hy persensitivity by influencing phagocytes. The modulation of phagocytes may be different in healthy subjects compared with hypersensitive subjects. Sub jects and methods In a double-blind, cross-over study, challenges with milk in milk-hypersensitive and healthy adults with or without an intestinal ba cterial strain, Lactobacillus GG (ATCC 53103) were performed. The challenge -induced immunoinflammatory response was recorded by measuring the expressi on of phagocytosis receptors prior to and after the challenge using flow cy tometry. Results In milk-hypersensitive subjects, milk challenge increased significa ntly the expression of CR1, Fc gamma RI and Fc alpha R in neutrophils and C R1, CR3 and Fc alpha R in monocytes. Milk with Lactobacillus GG prevented t he increase of the receptor expression. In healthy subjects, milk challenge did not influence receptor expression while milk with Lactobacillus CG inc reased significantly the expression of CR1, CR3, Fc gamma RIII and Fc alpha R in neutrophils. Conclusion Probiotic bacteria appear to modulate the nonspecific immune res ponse differently in healthy and hypersensitive subjects. This is seen as a n immunostimulatory effect in healthy subjects, and as a down-regulation of immunoinflammatory response in milk-hypersensitive subjects.