Figure 1.
The experimental protocol and different groups.
Mice were infected with E. coli or PBS, and then sensitized & challenged with OVA or PBS, as described previously in Materials and methods. Mice were divided into five different groups in this work.
Figure 2.
The changes of allergic symptoms.
The control group showed no or less allergic symptoms, whereas AAD model group had remarkable frequency of nasal rubbing and sneezing. Nevertheless, the frequency was noticeably decreased by E. coli infection. Data is shown by box and whisker plots, with whisker ends indicating minimal and maximal values and horizontal bars representing medians, n = 10. *p<0.05, **p<0.01 as conducted.
Figure 3.
Absolute numbers of inflammation cells in 1.2 ml of NALF and BALF at 24 h after final challenge.
Original magnification was ×400 (A, B). Total inflammation cells and eosinophils in NALF (C) and BALF (D) were significantly inhibited by E. coli infection in AAD mice model. Each bar represents the mean cell number ± standard error of the mean (SEM), n = 10. *p<0.05, **p<0.01 as conducted.
Figure 4.
Eosinophil inflammation assessed on hematoxylin and eosin (HE) stained tissue sections of the nasal mucosa and lung.
Original magnification was ×400 for nose and ×200 for lung (A). Numbers of eosinophils in the nasal mucosa (B) and inflammation scores of the lung (C) were counted to verify the inflammation changes among groups. Eosinophil infiltration was significantly higher in AAD model group than in the control group. Interestingly, E. coli infection before AAD phase drastically suppressed the eosinophil inflammation. In addition, numbers of eosinophils in the (108infN+OVA) group were lower than the (106infN+OVA) and (108infA+OVA) group. Data is expressed as mean ±SEM, n = 10. *p<0.05, **p<0.01 as conducted.
Figure 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 ×400 for nose and ×200 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 ± SEM, n = 10. *p<0.05, **p<0.01 as conducted.
Figure 6.
The changes of serum OVA-specific IgE levels.
OVA-specific IgE levels were apparently higher in AAD model group than that in the control group. However, the levels in E. coli infected mice were significantly inhibited, especially in the (108infN+OVA) group. Bars indicate the mean secretion ng/ml ± SEM, n = 8∼10. *p<0.05, **p<0.01 as conducted.
Figure 7.
The changes of cytokines IL-4, IL-10, IFN-γ and IL-2 in NALF (A) and BALF (B).
As shown above, administration of E. coli exhibited significant inhibition of levels of Th2 cytokines IL-4. Interestingly, the effect was accompanied by high levels of Th1 cytokines IFN-γ and IL-2, as well as the increased production of IL-10 secreted abundantly by Tregs. Additionally, the effects were more significant in neonatal mice infected with 108CFU E. coli. Data is represented as the mean secretion pg/ml ± SEM, n = 8∼10. *p<0.05, **p<0.01 as conducted.
Figure 8.
Tregs accumulated in PTLN of E. coli infected mice, especially in the (108infN+OVA) group.
Representative scatter plots denoted the fraction of CD4+ cells that were CD4+ CD25+ FoxP3+ Tregs (A). Ratios of Tregs were calculated per mouse (B). Percentages of Tregs in AAD model group were increased, compared to the control group. Interestingly, mice infected with E. coli present a more significant up-regulation in numbers of Tregs. Additionally, numbers of Tregs in the (106infN+OVA) and (108infA+OVA) group were lower than that in the (108infN+OVA) group. Data is expressed as mean ± SEM, n = 8. *p<0.05, **p<0.01 as conducted.