Objective: To study the impact of neonatal bacillus Calmette-Guerin(BCG) vaccination on lung Th17 cells and IL-17 in murine asthma model.
Methods: Neonatal BALB/c mice were divided into three groups: control, OVA and BCG/OVA groups. BCG was administerd in the BCG/OVA group on postnatal day 2 or 3. Except the control group, the mice in the other two groups were sensitized and undergone OVA challenge. Inflammatory cell numbers and morphological identification of leucocytes in bronchoalveolar lavage fluid (BALF) were measured by light microscopy. Cytokine IFN-gamma and IL-17 levels in BALF were measured using ELISA. The percentage of lung Th17 cells were assayed by flow cytometry.
Results: There was significantly larger number of total cells, lymphocytes, eosinophils and neutrophils in BALF in the OVA and BCG/OVA groups compared with the control group. The number or percentage of those cells in the BCG/OVA group was lower than that in the OVA group. The level of IL-17 in BALF was significantly higher in the OVA and the BCG/OVA groups compared with the control group, while the level of IFN-gamma was lower. The OVA group had higher level of IL-17 than the BCG/OVA group. The mice in the OVA and the BCG/OVA groups had a higher percentage of Th17 cells in lungs compared with the control group, but there were no significant differences in the percentage of Th17 cells between the OVA and the BCG/OVA groups.
Conclusions: Th17 cells and IL-17 play roles in the pathogenesis of asthma. BCG vaccination can reduce the level of IL-17 in BALF and the reduced IL-17 may be mainly from other IL-17-producing cells in the lungs, not Th17 cells.