Distribution and Expression of IL-17 and Related Cytokines in Children with Mycoplasma pneumoniae Pneumonia.

The pathogenesis of Mycoplasma pneumoniae pneumonia (MPP), specifically the local immune responses in the lungs, is poorly understood. In this study, flow cytometry was used to analyze IL-17 and related cytokines in plasma and bronchoalveolar lavage fluid (BALF) samples from 18 and 30 pediatric patients with general MPP (GMPP) and refractory MPP (RMPP), respectively. The levels of IL-1Ra, IL-6, IL-8, IL-17, and TNF-α were significantly elevated in the BALF of MPP children compared to the plasma (P < 0.01). Although the plasma IL-6 levels in the children with RMPP were higher than those in the children with GMPP (P < 0.05), the IL-17 levels showed the opposite trend (P < 0.05). The children with RMPP had significantly higher BALF levels of IL-8, IL-17, and TNF-α than the children with GMPP (P < 0.05), and the elevated levels of IL-17 correlated with the increased focal size of the lung lesions (P < 0.05). The elevated levels of IL-17 and related cytokines in the BALF samples could indicate that the local inflammatory response should be distinguished from the systemic inflammatory response in children with MPP. Moreover, RMPP might involve an aggravated inflammatory progression at the site of infection. The levels of IL-17 might correlate with the extent and severity of the lung lesions in MPP.