Fan R, et al. - In a pediatric population with a diagnosis of acute respiratory tract infection, the link between serum regulatory cytokines concentrations and respiratory syncytial virus (RSV) disease was assessed. Serum regulatory cytokine interleukin (IL)-10 and IL-35 concentrations were found to be increased among children with RSV infection. Findings also showed a contribution of elevated expression of IL-10 and IL-35 to protect hypoxia and attenuate the severity of disease.