Effects of Bacillus Calmette-Guerin on T_H1/T_H2 balance in a mouse model of asthma
Objective To investigate the effects of BCG on T_H1/T_H2 balance in a mouse model of asthma. Methods C57BL/6 mice ( n =8, for each group) were sensitized and challenged by ovabumin (OVA) as positive group, and mice were treated by saline as negative group. Mice were injected with BCG intradermally 2 weeks before the first OVA challenge. Then IL-5 and IFN-γ in the perfusion fluid of pulmonary alveoli as well as the peripheral blood were analysed by ELISA, and the peripheral blood T_H1/T_H2 lymphocytes ratio by using three-color flow cytometry method. Results Compared with negative group mice, positive group mice has higher IL-5 level and lower IFN-γ level both in BALF and in peripheral blood. And after BCG infection IL-5 level decreased but IFN-γ level increased both in BALF and in peripheral blood compared with the positive group mice. Blood T_H2/T_H1 cells ratio was higher in the positive group compared with negative group [(1.57±0.56)vs(0.37± 0.05 )], ( P 0.01). After infection with BCG the T_H2/T_H1 ratio decreased(0.59±0.11), also the blood Tc2/Tc1 ratio decreased compared with the positive group[(0.62±0.07)vs(1.15±0.18)], ( P 0.05). Conclusion The T_H2 immune response is stronger than T_H1 immune response in the mouse model of asthma. Infection with BCG could correct the imbalance of T_H1/T_H2 both on cytokine level and single-cell level.