Tehran University of Medical Sciences Iranian Journal of Allergy, Asthma and Immunology 1735-1502 16 5 2017 10 28 386 395 EN Meng Gao Department of Pediatrics, Binzhou Medical University Hospital, Binzhou, China Liang-Xiao Liu Department of Pediatrics, Binzhou Medical University Hospital, Binzhou, China AND Department of Pediatrics, College of Clinical Medicine, Binzhou Medical University, Binzhou, China Fu-Ling Wu Department of Pediatrics, Binzhou Medical University Hospital, Binzhou, China Xuejing Zhang Department of Pediatrics, Binzhou Medical University Hospital, Binzhou, China AND Department of Pediatrics, College of Clinical Medicine, Binzhou Medical University, Binzhou, China Ying-Ying Li Department of Pediatrics, Binzhou Medical University Hospital, Binzhou, China Tao Shi Department of Pediatrics, Binzhou Medical University Hospital, Binzhou, China De-Zhi Li Department of Pediatrics, Binzhou Medical University Hospital, Binzhou, China Ting-Ting Han Department of Pediatrics, Binzhou Medical University Hospital, Binzhou, China 2016 06 08 2017 06 28 Respiratory syncytial virus (RSV) is the leading cause of bronchiolitis and hospitalization that lead to high morbidity and mortality among young infants. T helper 17 (Th17) cells and regulatory T cells (Tregs) play essential roles in the pathogenesis of autoimmune, cancer, and inflammatory diseases. However, whether changes in T-cell subsets are related to the systemic immune responses in RSV-caused bronchiolitis merit further investigation. Three-week-old Sprague Dawley (SD) rats were randomly divided into the normal control (NC) and RSV bronchiolitis (RSV-B) groups. An RSV-B model was successfully established using nasal drip containing RSV. Furthermore, pathological changes in the lung tissues were observed using hematoxylin and eosin staining. Flow cytometry determined the levels of Th17 and Treg subsets. The related cytokines were measured using enzyme-linked immunosorbent assay (ELISA). The expression levels of related transcription factors, such as RORγt and FOXP3, were examined using real-time quantitative PCR and western blot analysis. The RSV-B group exhibited pulmonary interstitial hyperemia and edema, inflammatory cell infiltration, wide alveolar septa, and bronchial collapse and deformation. The percentage of Th17 cells in RSV-B group was about 2.3 fold higher than that of NC group, and the concentration of IL-17, IL-23 and RORγt was higher than in NC group. In contrast, the percentage of Treg cells in the RSV-B group was approximately 0.7 fold lower than that in the NC group, and the levels of IL-10, TGF-β, and FOXP3 in the RSV-B group were lower than those in the NC group. The above results were statistically significant. The changes of Th17/Treg, and their associated cytokines, specific transcription factors, are present in RSV bronchiolitis model rats, which may play an important role in the pathogenesis of RSV bronchiolitis.  https://ijaai.tums.ac.ir/index.php/ijaai/article/view/952 https://ijaai.tums.ac.ir/index.php/ijaai/article/download/952/775