[Continuous inhalation of allergen induces immunotolerance in a mouse asthma model].
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).


CONCLUSIONS
The results show that continuous allergen inhalation suppresses allergen-induced airway inflammation and produces immunotolerance, in which IL-10 may play an important role.
Shi
Ju-hong
JH
Department of Respiratory Medicine, PUMC Hospital, Chinese Academy of Medical Science & Peking Union Medical College, Beijing 100730, China.
Liu
Guo-liang
GL
Xu
Wen-bing
WB
Xu
Fei
F
Chen
Hao
H
Yang
Xian-feng
XF
Lin
Yao-guang
YG
D000485:Allergens / Q000009:adverse effects*; D000818:Animals; D001249:Asthma / Q000209:etiology* / Q000276:immunology*; D004195:Disease Models, Animal; D007108:Immune Tolerance; D007073:Immunoglobulin E / Q000097:blood; D007249:Inflammation; D007371:Interferon-gamma / Q000097:blood; D016753:Interleukin-10 / Q000097:blood; D015847:Interleukin-4 / Q000097:blood; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D010047:Ovalbumin / Q000009:adverse effects; D050378:T-Lymphocytes, Regulatory / Q000276:immunology
D000485:Allergens; D016753:Interleukin-10; D015847:Interleukin-4; D007073:Immunoglobulin E; D007371:Interferon-gamma; D010047:Ovalbumin