Study design and subjects
From July 2017 to March 2018, wheezing Chinese children aged 3 months to 6 years hospitalized or in clinic in the Division of Pulmonary Pediatrics at Shanghai Xinhua hospital and Shanghai children’s Medical center affiliated to Shanghai Jiao Tong University School of Medicine were enrolled in this study (wheezing was confirmed by doctors at the time of admission or from documentation in medical records). Exclusion criteria were: 1) bronchopulmonary dysplasia, tracheobronchial foreign bodies or congenital heart disease; 2) acute and chronic infectious diseases; 3) immunomodulatory treatment before or during the study; and 4) the researchers considered the patient inappropriate for inclusion. The study was examined and approved by the Ethics Committee of Shanghai Xinhua hospital Affiliated to Shanghai Jiao Tong University School of Medicine and the guardians of all included children provided signed informed consent. The history of allergic diseases (AR and AD diagnosed by specialists) and family allergic history were collected through questionnaires filled out by the parents. Additionally, respiratory symptoms and history of anti-allergy drug use were provided by the family members and recorded for the study. At inclusion, 2 ml peripheral blood was taken without anticoagulant from all the patients for allergen-specific IgE testing, and 1 ml blood using heparin as anticoagulant was collected to determine the proportion of circulating CD4+CCR6+CRTh2+memory-type Th2 cells flow-cytometrically.