Imbalance of peripheral blood Th17 and Treg responses in children with refractory Mycoplasma pneumoniae pneumonia.

Mycoplasma pneumoniae (MP) pneumonia is usually a benign self-limiting disease, but some patients suffer from acute lung injury in MP infections who need to use immune-modulators with conventional antibiotic treatment. The imbalance between CD4+CD25+Foxp3+regulatory T (Treg) cells and T helper (Th17) cells has been found in a number of different inflammation and autoimmune disease, while the role of the Th17/Treg balance in MP pneumonia remains largely unknown. The aim of this study was to investigate the Th17/Treg pattern and its impact on disease severity in patients with MP pneumonia. This study involved 36 healthy control and 83 patients including 25 patients with refractory MP pneumonia and 58 patients with macrolide responsive MP pneumonia. The percentages of circulating Th17 cells and Tregs were determined by flow cytometry. The concentrations of serum Th17- and Treg-related cytokines were measured by enzyme-linked immunosorbent assay (ELISA). In comparison with that in the patients with macrolide responsive MP pneumonia and healthy control, significantly higher frequencies of Th17 cells and higher levels of IL-17 were detected in patients with refractory MP pneumonia. But there are no significant difference with the frequencies of Tregs and the levels of TGF-β1 in the patients with refractory MP pneumonia and patients with macrolide responsive MP pneumonia. However the Th17/Treg ratio was found to be significantly higher in the patients with refractory MP pneumonia than the patients with macrolide responsive MP pneumonia. An imbalance of circulating Th17 cells and Tregs is associated with the deterioration of pulmonary injury in patients with MP infections.