Mice Treated with an Antibiotic Cocktail Containing Metronidazole Show Attenuated Allergy Responses through the Induction of Regulatory T Cells in the Intestinal Mucosa

This study sought to determine whether antibiotic treatments affect the pathogenesis of allergic diseases. We demonstrated that mice treated with a mixture of four antibiotic agents （ampicillin, neomycine, metronidazole, and vancomycin） showed significantly decreased antigen-specific IgE production compared to control mice, whereas mice treated with the same cocktail without metronidazole showed no change in IgE production compared to controls. Regulatory T cell suppression induced by particular antibody combinations is a possible mechanism of this effect, with an increased frequency of regulatory T cells also observed in the mesenteric lymph nodes （MLN） of mice treated with the mixture of four antibiotics, but not in the second cocktail without metronidazole. Our antibiotic treatments also dramatically decreased the diversity of mouse intestinal microbiota compared to control mice, based on 16SrRNA analysis of the cecum fecal composition. In conclusion, mice treated with antibiotic mixtures containing metronidazole, but not those treated without metronidazole, showed attenuated allergy responses and increased induction of regulatory T cells in the mucosa.