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Title: [Continuous inhalation of allergen induces immunotolerance in a mouse asthma model].
Author: Shi JH, Liu GL, Xu WB, Xu F, Chen H, Yang XF, Lin YG.
Journal: Zhonghua Jie He He Hu Xi Za Zhi; 2006 Nov; 29(11):735-9. PubMed ID: 17327052.
Abstract:
OBJECTIVE: To investigate the mechanism of immunotolerance caused by allergen immunotherapy in allergen-induced asthmatic airway inflammation. METHODS: Sixty ovalbumin (OVA)-sensitized BALB/c mice were randomly divided into two groups, 50 in the experimental group and 10 in the control group. The mice in the experimental group were treated with 3 injections of ovalbumin intraperitoneally (1 mg for each separated for two weeks) and challenged by ovalbumin inhalation 1 h/day for 10 successive days. Then the mice were divided further into group A, group B, group C, group D and E with 10 mice in each group. The mice in group A were sacrificed after 10 day challenge. The mice in group B and D were continuously exposed to inhaled OVA for 4 and 8 weeks (1 h/day, 5 days a week), respectively, then to inhaled OVA 1 h/day for 10 successive days. The inhalation was interrupted for 4 weeks in group C after initial challenge and restarted for another 10 days (1 h/day) afterwards. The mice in group E were exposed continuously to inhaled OVA for 4 weeks (1 h/day, 5 days a week) after initial challenge, which was interrupted for 4 weeks, and restarted for 10 days (1 h/day). Bronchoalveolar lavage (BAL) was performed, and total cells, eosinophils, lymphocytes were assessed; CD4+, CD8+, CD4+ IL-10+ cells were determined using flow cytometry, and IL-4, IFN-gamma and IL-10 in the BAL fluid were measured by ELISA. Serum ovalbumin-specific IgE, IL-4, IFN-gamma and IL-10 were also determined. Pathologic manifestation of the lung was analyzed. RESULTS: The percentage of EOS, B lymphocytes, CD4+ IL-10+ cells in BAL were 0.010 +/- 0.000, 2.1 +/- 1.9 and 4.9 +/- 1.5, respectively in the control group; 0.480 +/- 0.110, 5.1 +/- 2.6 and 5.1 +/- 2.3, respectively, in group A; 0.120 +/- 0.020, 8.9 +/- 3.6, and 10.4 +/- 3.6, respective, in group B; 0.560 +/- 0.050, 4.7 +/- 1.7 and 6.3 +/- 3.1, respectively, in group C; 0.070 +/- 0.030, 10.1 +/- 2.9 and 12.7 +/- 4.5, respectively, in group D; 0.680 +/- 0.030, 5.6 +/- 3.2 and 6.1 +/- 3.4, respectively, in group E. The difference was significant among different groups (F = 36.46, 31.89, 167.89 respectively; all P < 0.01). The percentage of CD4+ IL-10+ cells in BAL was increased in group B and group D, which were significantly higher than those in group A (q = 5.8, 6.4, P < 0.05). The levels of IL-4 and IL-10 in BAL fluid were (21 +/- 3) pg/ml and (44 +/- 12) pg/ml, respectively, in the control group; (128 +/- 23) pg/ml and (68 +/- 18) pg/ml, respectively, in group A; (54 +/- 12) pg/ml and (127 +/- 27) pg/ml, respectively, in group B; (133 +/- 21) pg/ml and (78 +/- 17) pg/ml, respectively, in group C; (8 +/- 18) pg/ml and (135 +/- 34) pg/ml, respectively, in group D; (143 +/- 26) pg/ml and (76 +/- 15) pg/ml, respectively, in group E. The difference was statistically significant among different groups (F = 37.20, 143.78 respectively; all P < 0.01). The levels of IL-10 in BAL fluid were increased in group B and group D, which were significantly higher than that in group A (q = 7.8, 9.6, all P < 0.05). CONCLUSION: The results show that continuous allergen inhalation suppresses allergen-induced airway inflammation and produces immunotolerance, in which IL-10 may play an important role.

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