Cytokine and chemokine responses in pediatric patients with severe pneumonia associated with pandemic A/H1N1/2009 influenza virus.

Severe pneumonia and leukocytosis are characteristic, frequently observed, clinical findings in pediatric patients with pandemic A/H1N1/2009 influenza virus infection. The aim of this study was to elucidate the role of cytokines and chemokines in complicating pneumonia and leukocytosis in patients with pandemic A/H1N1/2009 influenza virus infection. Forty-seven patients with pandemic A/H1N1/2009 influenza virus infection were enrolled in this study. Expression of interleukin (IL)-10 (P = 0.027) and IL-5 (P = 0.014) was significantly greater in patients with pneumonia than in those without pneumonia. Additionally, serum concentrations of interferon-γ (P = 0.009), tumor necrosis factor-α (P = 0.01), IL-4 (P = 0.024), and IL-2 (P = 0.012) were significantly lower in pneumonia patients with neutrophilic leukocytosis than in those without neutrophilic leukocytosis. Of the five serum chemokine concentrations assessed, only IL-8 was significantly lower in pneumonia patients with neutrophilic leukocytosis than in those without leukocytosis (P = 0.001). These cytokines and chemokines may play important roles in the pathogenesis of childhood pneumonia associated with A/H1N1/2009 influenza virus infection.