Abstract: Objective To investigate the role of regulatory T cell(Treg) in allergic alveolitis and the effect of Treg on the activation of dendritic cells (DC) during the development of allergic alveolitis.Methods Intraperitoneal injection of anti-CD25mAb was used to develop Treg depletion model and introtrachea administration of 1-3-β-glucan was used to set up allergic alveolitis model in mice.The activation of DC in hiliar lymph node and spleen was checked with flow cytometry.Hematoxylin and eosin staining was used to compare the inflammation and granuloma among different groups.Results Compared with the glucan group,the Treg's percentage in hiliar lymph node in glucan+anti-CD25 group(6.76±0.91%) reduced obviously(P < 0.05).Histological observation showed that the lung inflammation degree in glucan+anti-CD25 mice was significantly higher than that of glucan group.According to the examination of flow cytometry,the percentage of CD80+MHCII+DC in glucan group was increased in the early stage after glucan administration.Meanwhile,the percentage of CD80+MHCII+DC in glucan+anti-CD25 group in both hiliar lymph node and spleen(37.3±5.8%) was increased compared with that in glucan group (24.3±1.9%).Conclusion Treg participates in regulating the development of allergic alveolitis through suppressing the activation of DC.