Abstract: Objective To explore the clinical characteristics and the expression of interferon-γ（IF-γ，Th1 cytokine），interleukin-4 and interleukin-33（IL-4，IL-33，Th2 cytokine） of infants and young children with the first wheezing caused by Mycoplasma pneumoniae（MP） and respiratory syncytial virus（RSV）. Methods Totally 82 cases and 68 cases with respectively confirmed MP and RSV infection causing first-time wheezing in infants and young children were collected from January 2019 to December 2020，and they were regarded as MP and RSV infection group，and 30 healthy infants and young children were selected as healthy control group. The clinical characteristics of the MP group and the RSV group were compared，and the IFN-γ，IL-4 and IL-33 contents of the peripheral blood of the three groups were detected . The ratios of IFN-γ/IL-4 and IFN-γ/IL-33 were calculated and compared. Results Compared with the RSV infection group，MP infection group had an older age，shorter wheezing course，fewer proportion of fever,higher level of WBC count,lower proportion of lymphocyte，higher total IgE level，lower CRP level，with a statistical difference between the two groups（P＜0.05）.Compared with the health control group，IFN-γ levels decreased，IL-4 and IL-33 levels increased，and IFN-γ/IL-4 and IFN-γ/IL-33 ratios decreased in MP and RSV infection groups，and the differences were statistically significant（P＜0.05）.Compared with the MP infection group，the RSV infection group had lower IFN-γ levels，higher IL-4 and IL-33 levels，and lower ratio of IFN-γ/IL-4 and IFN-γ/IL-33, with a statistical difference between the two groups（P＜0.05）. Conclusion Cytokines IFN-γ，IL-4，IL-33 and Th1/Th2 imbalance with Th2 advantaged response may be involved in the first wheezing caused by MP and RSV infection in infants and young children.

Key words:

Mycoplasma pneumonia, Respiratory syncytial virus, Infants and young children with the first wheezing, Cytokines