Effects of early allergen exposure on airway inflammation responses and airway hyper-reactivity in an asthma mouse model / 中华微生物学和免疫学杂志

ABSTRACT

Objective:To investigate the effects of early allergen exposure on airway inflammation responses and airway hyper-reactivity in a mouse model of asthma and the possible mechanism.Methods:Neonate BALB/c mice were randomly divided into three groups of normal control group, asthma group and early exposure group with eight in each group. The mice in the early exposure group were subcutaneously injected with 0.1 ml of ovalbumin (OVA) once a day for 10 consecutive days on the third day after birth and the other two groups were treated with 0.1 ml of PBS. Six weeks after birth, the mice in the asthma group and the early exposure group were sensitized with 0.2 ml of OVA allergen once a day for five consecutive days and then challenged with OVA 7 d after sensitization. The normal group was sensitized and challenged with PBS. Pathological changes in 1ung tissues were detected by HE or PAS staining. Flow cytometry was performed to quantify T cell subsets in bronchoalveolar lavage fluid (BALF). Th2-related cytokines (IL-4, IL-5 and IL-13) in BALF and the levels of OVA-specific IgE and IgG in serum were measured by ELISA. The percentages of CD4 + IFN-γ + T(Th1), CD4 + IL-4 + T(Th2) and CD4 + CD25 + Foxp3 + Treg cells in lung tissues were detected by flow cytometry. The airway resistance was detected using a small animal lung function testing system. Results:The pathological changes in lung tissues were less severe in the early exposure group than in the asthma group. However, PAS staining results showed no significant difference in cell metaplasia was found between the two groups. Compared with the asthma group, early exposure to OVA allergen significantly reduced the percentage of Th2 cells [(16.2±2.4)% vs (19.4±3.4)%, P<0.05] and increased the proportion of Treg cells [(3.7±0.4)% vs (2.1±1.4)%, P<0.05]. Moreover, the levels of IL-4 [(65.3±17.1) pg/ml vs (144.4±23.1) pg/ml] and IL-5 [(103.3±21.1) pg/ml vs (198.3±23.1) pg/ml] in BALF were significantly down-regulated in the early exposure group. A reduced production of OVA-specific IgE but not IgG in serum and an inhibited airway hyper-reactivity following OVA challenge were observed in the early exposure group. Conclusions:Early exposure to OVA allergen could offer a protective effect against OVA re-exposure-induced pathological changes, inflammatory responses and airway hyper-reactivity in grown-up mice.