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

BACKGROUND: Probiotic bacteria can influence immune responses both specifically by stimulating antibody production and nonspecifically by enhancing phagocytosis of pathogens and modifying cytokine production. OBJECTIVE: The authors hypothesized that probiotic bacteria can alleviate hypersensitivity by influencing phagocytes. The modulation of phagocytes may be different in healthy subjects compared with hypersensitive subjects. SUBJECTS AND METHODS: In a double-blind, cross-over study, challenges with milk in milk-hypersensitive and healthy adults with or without an intestinal bacterial strain, Lactobacillus GG (ATCC 53103) were performed. The challenge-induced immunoinflammatory response was recorded by measuring the expression of phagocytosis receptors prior to and after the challenge using flow cytometry. RESULTS: In milk-hypersensitive subjects, milk challenge increased significantly the expression of CR1, FcgammaRI and FcalphaR in neutrophils and CR1, CR3 and FcalphaR in monocytes. Milk with Lactobacillus GG prevented the increase of the receptor expression. In healthy subjects, milk challenge did not influence receptor expression while milk with Lactobacillus GG increased significantly the expression of CR1, CR3, FcgammaRIII and FcalphaR in neutrophils. CONCLUSION: Probiotic bacteria appear to modulate the nonspecific immune response differently in healthy and hypersensitive subjects. This is seen as an immunostimulatory effect in healthy subjects, and as a down-regulation of immunoinflammatory response in milk-hypersensitive subjects.