Abstract. the pathogenesis of viral bronchiolitis is poorly understood. the aim of this study was to analyze interleukin (il)-15, il-18 and interferon (iFn)-γ concentrations and the activity of nK cells and cd4 + and cd8 + lymphocytes in 23 children not older than 30 months of age with acute viral bronchiolitis using blood samples drawn within the first 24 h of their hospital admission, in comparison to a healthy group. in children with bronchiolitis, the mean concentrations of il-15, il-18 and iFn-γ were 9.39±11.55, 884.03±645.44 and 17.92±27.14 pg/ml, respectively, and were significantly higher than those in the control group [2.34±0.61 pg/ml (p<0.05), 248.69±98.73 pg/ml (p<0.001) and 2.75±1.72 pg/ml (p<0.005), respectively]. in the bronchiolitis group, mean z-scores were -1.15±1.9 for cd4 + cells and -0.9±1.23 for cd8 + cells; these scores were significantly lower than those of the general polish population (p<0.001 and <0.01, respectively). however, the mean z-score of the ratio of cd4 + /cd8 + and the nK cell count in children with bronchiolitis did not differ significantly from those of the controls. in conclusion, cytokines such as il-15, il-18 and iFn-γ play a role in the pathogenesis of bronchiolitis in children.
IntroductionBronchiolitis in children is a serious self-limiting disease (mortality rate <1%) of respiratory tract infections. however, in high-risk groups such as children with bronchopulmonary dysplasia, congenital heart disease or cystic fibrosis, mortality increases to 5-10%. the leading cause of bronchiolitis are viral infections, with the most common agent being respiratory syncytial virus infection (rSV) (60-80% of cases) (1-4). during rSV infection, the cytokine cascade is activated, leading to the activation of th1 and th2 lymphocytes. thus, an increase in the concentrations of cytokines such as interleukin (il)-2, -6, -10, -12, -13 and a decrease in interferon (iFn)-γ and il-4 concentrations are observed (5-12). during non-rSV viral infections, the th1 type response of the immunologic system with an increase in the iFn-γ concentration is commonly observed (5,8,13,14).il-15 and il-18 are relatively newly discovered cytokines that are produced principally by macrophages during immune response. il-15 has multiple biological properties, including the induction of the production of other cytokines and the inhibition of T-cell apoptosis (15,16). IL-18 is a pro-inflammatory cytokine with pleiotropic properties and plays a crucial role in the maintenance of th1-cell response. this cytokine activates nK cells, leads to eosinophilia and increases histamine concentrations (17)(18)(19)(20). there are various reports indicating that, during viral infection, il-15, il-18 and iFn-γ concentrations are elevated (21). a secondary increase in nK cell activity has also been reported (22). however, the role of il-15 and il-18 in viral bronchiolitis in children remains unknown. the aim of this study was to analyze il-15, il-18 and iFn-γ concentrations and the activity of nK cells as well as cd4 + and cd8 +...