The Effect Of Bacillus Calmette-guerin Vaccination And PPD On The Lung Pathology And CD4～+CD25～+ Regulatory T Cells In A Murine Model Of Asthma

Objective: This study examined the effect of BCG vaccination and PPD on CD₄⁺CD₂₅⁺ regulatory T cells in asthmatic mice and its preventive effect on airway inflammation.Methods: 36 BALB/C mice were divided into 4 groups(group A, B, C and D) randomizedly. There were 10 mice in group A, B and C respectively,and there were 6 mice in group D. On the first day, the mice of group A and B were vaccinated intradermally with BCG. On the 25th day, the mice of group A were injected with BCG again, the mice of group B were injected intradermally with PPD instead. the mice of group C and D were injected with the same volume of saline solution. Then,the mice of group A, B, and C were sensitived and challenged with ovalbumin(OVA) to establish asthmatic models. Half of mice of each group were killed at day 60 and day 65 respectively. The percentage of CD₄⁺CD₂₅⁺Treg and other T-lymphocyte subsets in peripheral blood was detected with flow cytometry,and the lung tissues of mice were stained with HE and PAS(periodic acid-schiff reaction) methods.Results :(1) The percentage of CD₃⁺,CD₄⁺,CD₈⁺T cells and the ratio of CD₄⁺/CD₈⁺ in group A, B and C were significantly lower than those in group D(P<0.05).The percentage of CD₃⁺ T in group A and B was significantly higher than that in group C(P<0.05). but there was no significant difference between group A and B(P>0.05); There were no significant difference of the percentage of CD₄⁺, CD₈⁺T cells and the ratio of CD₄⁺/CD₈⁺ among group A, B and C(P>0.05).(2) The percentage of CD₄⁺CD₂₅⁺Treg in CD₄⁺ T cells in groupA, B and C was significantly lower than those in group D(P<0.05). The percentage of CD₄⁺CD₂₅⁺Treg in group A and B was significantly higher than that in group C(P<0.05). but there was no significant difference between group A and B(P>0.05). (3) More eosinophils were found in the lung tissue in group C, but fewer were found in group A and B when compared with those in group C, and no eosinophil was found in group D. There were mucus hypersecretion in the epithelial cells in group C ,and mucus secretion was lower in group A and B when compared with that in group C, but no mucus secretion in group D. The level of the airway inflammation in group B was less than that in group A.Conclusion: (1) Disorder of T lymphocyte subtype plays an important role in asthma pathogenesis. (2) The reduction of CD₄⁺CD₂₅⁺Treg maybe was an etiological factor of asthma.(3) Either BCG alone or with PPD could prevent the airway inflammation and increase CD₄⁺CD₂₅⁺Treg in a mouse model of asthma.The preventive effect of BCG+PPD on the airway inflammation was better than that of BCG+BCG.