Assessment of IL-6 and IL-8 levels in community-acquired pneumonia in children

The search for biomarkers of severe community-acquired pneumonia in children is an urgent clinical task. Cytokines, in particular IL-6 and IL-8, may be considered indices of lung tissue inflammation, being regulators of the immune response. The aim of the study was to evaluate serum levels of IL-6 and IL-8 in children with pneumonia of different severity, and to analyze the relationship of these parameters with origin of the pathology and biomarkers of systemic inflammation. The enzyme immunoassay method was used to determine the concentrations of IL-6, IL-8, and procalcitonin in blood serum samples of 37 children with community-acquired pneumonia of varying severity upon their admission to the hospital. The examined children were divided in 2 groups: (1) patients with severe pneumonia (n = 13); (2), patients with mild pneumonia (n = 24). It was found that the serum levels of both interleukins were higher in children with severe community-acquired pneumonia. Thus, in children with severe disease, the level of IL-6 is 2.2 times, and the level of IL-8 is 3.6 times higher than in patients with mild pneumonia. Positive correlations of moderate strength have been revealed between the severity of the disease and serum levels of IL-6 (r = 0.68, p < 0.0001) and IL-8 (r = 0.57, p < 0.0001). Significant correlations of the studied interleukins were found among the cytokine contents (r = 0.49, p = 0.002), and with other indices of systemic inflammation. IL-6 levels correlated with leukocytosis (r = 0.42, p = 0.009), absolute neutrophil counts (r = 49, p = 0.002), serum procalcitonin (PCT) concentration (r = 0.53, p < 0.001). IL-8 levels correlated with PCT concentrations (r = 0.49, p = 0.002) and CRP (r = 0.35, p < 0.05). Conclusions. The results obtained suggest that the development of severe community-acquired pneumonia in children is associated with increased serum levels of IL-6 and IL-8, as well as laboratory parameters of systemic inflammatory response such as leukocytosis, concentrations of PCT and CRP. The revealed correlations indicate the involvement of IL-6 and IL-8 in development of a systemic inflammatory response associated with this disorder. The data obtained suggest an opportumity of using serum IL-6 and IL-8 levels in children with community-acquired pneumonia as promising biomarkers for assessing the disease severity.