A-E. coli, although certain epidemiological ones have been operated [19,20,37,38]. Hence in our study, we utilized administration of nonpathogenic E. coli ATCC 25922 before the OVA sensitization and challenged phase, 
and assessed whether E. coli ATCC 25922 was able to either suppress the induction of allergic airway inflammation or regulate the immune responses. Our study, for the first time, showed that E. coli infection suppressed the hallmark features of the allergic responses. E. coli infection before AAD phase, significantly attenuated allergic symptoms of nasal rubbing and sneezing, decreased the pathology of eosinophil Eliglustat price infiltration and goblet cell metaplasia in the nasal mucosa and lung, inhibited serum OVA-specific IgE levels, and suppressed levels of Th2 cytokines in NALF and BALF. These data confirmed the hygiene hypothesis that the lack of bacterial infections, including the gut microflora, would favour theEscherichia coli on Allergic Airway InflammationFigure 5. Goblet cell metaplasia assessed on alcian blue-periodic acid Stiff (AB-PAS) stained tissue sections of the nasal mucosa and lung. Original magnification was 6400 for nose and 6200 for lung (A). Goblet cells were counted as the blue cells stained positive by AB-PAS. Percentages of goblet cell metaplasia were calculated from the total numbers of cells counted around the nasal mucosa (B) and the lung (C). Goblet cell metaplasia was relatively minor in mice infected with E. coli. Data is expressed as mean percent 6 SEM, n = 10. *p,0.05, **p,0.01 as conducted. doi:10.1371/journal.pone.0059174.gdevelopment of allergic disease. More importantly for the rigidity of the experiment, the above findings were profoundly confirmed by the three AN-3199 manufacturer patterns of intragastric administration of E. coli, thus illustrating their stable capability to regulate the immune responses during allergic airway inflammation. To our knowledge, in the low intestine, E. coli and other variety of gut microflora colonized to an extraordinary density and evolved to degrade kinds of plant polysaccharides and other related dietary substances [39]. Not only has it enhanced the host digestive efficiency and ensured a steady nutrient supply for microbes, but also probably driven the evolution of the immune system, thus protecting the host from the pathogens and regulating the induction of immunological tolerance [13,19]. For this reason, it was plausible that E. coli infection possessed a formidable potential immunomodulatory function to allergic disease. In the analysis of fecal stool flora in our study, we detected that E. coli neonatally infected mice had a statistically noteworthy increase in the total number of normal intestinal flora especially in the quantities of enterobacteria, compared to that of the uninfected neonatal mice, by identifying patterns of Gramstained fecal flora and using molecular detection methods. These changes might be associated with infectious disease in a healthybody, but potentially beneficial in the context of an allergic surrounding. Furthermore, we didn’t find the appearance of any enteric pathogens in the fecal microbiota of E. coli infected mice, such as Staphylococcus aureus, Pseudomonas aeruginosa, Klebsiella pneumoniae, Proteus mirabilis and so forth (data not shown). As far as we know, it was the first time for the present study to investigate the potential role of E. coli in the modulation of allergic responses in a mouse model. So what is the underlying mechanism? Data.A-E. coli, although certain epidemiological ones have been operated [19,20,37,38]. Hence in our study, we utilized administration of nonpathogenic E. coli ATCC 25922 before the OVA sensitization and challenged phase, and assessed whether E. coli ATCC 25922 was able to either suppress the induction of allergic airway inflammation or regulate the immune responses. Our study, for the first time, showed that E. coli infection suppressed the hallmark features of the allergic responses. E. coli infection before AAD phase, significantly attenuated allergic symptoms of nasal rubbing and sneezing, decreased the pathology of eosinophil infiltration and goblet cell metaplasia in the nasal mucosa and lung, inhibited serum OVA-specific IgE levels, and suppressed levels of Th2 cytokines in NALF and BALF. These data confirmed the hygiene hypothesis that the lack of bacterial infections, including the gut microflora, would favour theEscherichia coli on Allergic Airway InflammationFigure 5. Goblet cell metaplasia assessed on alcian blue-periodic acid Stiff (AB-PAS) stained tissue sections of the nasal mucosa and lung. Original magnification was 6400 for nose and 6200 for lung (A). Goblet cells were counted as the blue cells stained positive by AB-PAS. Percentages of goblet cell metaplasia were calculated from the total numbers of cells counted around the nasal mucosa (B) and 
the lung (C). Goblet cell metaplasia was relatively minor in mice infected with E. coli. Data is expressed as mean percent 6 SEM, n = 10. *p,0.05, **p,0.01 as conducted. doi:10.1371/journal.pone.0059174.gdevelopment of allergic disease. More importantly for the rigidity of the experiment, the above findings were profoundly confirmed by the three patterns of intragastric administration of E. coli, thus illustrating their stable capability to regulate the immune responses during allergic airway inflammation. To our knowledge, in the low intestine, E. coli and other variety of gut microflora colonized to an extraordinary density and evolved to degrade kinds of plant polysaccharides and other related dietary substances [39]. Not only has it enhanced the host digestive efficiency and ensured a steady nutrient supply for microbes, but also probably driven the evolution of the immune system, thus protecting the host from the pathogens and regulating the induction of immunological tolerance [13,19]. For this reason, it was plausible that E. coli infection possessed a formidable potential immunomodulatory function to allergic disease. In the analysis of fecal stool flora in our study, we detected that E. coli neonatally infected mice had a statistically noteworthy increase in the total number of normal intestinal flora especially in the quantities of enterobacteria, compared to that of the uninfected neonatal mice, by identifying patterns of Gramstained fecal flora and using molecular detection methods. These changes might be associated with infectious disease in a healthybody, but potentially beneficial in the context of an allergic surrounding. Furthermore, we didn’t find the appearance of any enteric pathogens in the fecal microbiota of E. coli infected mice, such as Staphylococcus aureus, Pseudomonas aeruginosa, Klebsiella pneumoniae, Proteus mirabilis and so forth (data not shown). As far as we know, it was the first time for the present study to investigate the potential role of E. coli in the modulation of allergic responses in a mouse model. So what is the underlying mechanism? Data.