Interleukin-23 derived from CD16+ monocytes drives IL-17 secretion by TLR4 pathway in children with mycoplasma pneumoniae pneumonia

The study aimed to investigate whether IL-23 is amplified in monocyte subsets of MP pneumonia and to determine its relevant pathway. We firstly analyze the IL-23p19 expression in monocyte subgroups in MP pneumonia patients and healthy controls subjects by using flow cytometry. Then, we also analyzed the percentage of IL-17+γδT cells and Th17 cells in patients with MP pneumonia and controls subjects. At the same time, the relation between IL-23 and IL-17 were also assessed. Furthermore, we constructed the recombinant community-acquired respiratory distress syndrome (CARDS) toxin and intend to stimulate peripheral blood mononuclear cells and RAW264.7 cells in vitro. IL-23p19 was detected by flow cytometry and the mRNA levels were measured by real-time PCR. Finally, TLR4 pathway was also investigated by TAK242 inhibitor. It turned out that the expression of IL-23p19 was increased in CD14brightCD16+ monocyte of MP pneumonia patients than controls subjects. The patients with MP pneumonia had significantly higher the percentage of IL-17+γδT cells and Th17 cells than controls subjects. Interestingly, the levels of IL-23 were positively related to IL-17 in MP pneumonia patients. CD16+ monocytes and RAW264.7 cells, respectively can be induced by CARDS toxin to secrete IL-23 by TLR4 pathway in vitro. These results indicated that IL-23-IL-17+γδT/Th17 axis may play a role in the pathogenesis of MP pneumonia, whereas IL-23 derived from CD16+ monocytes was expanded in MP pneumonia by TLR4 pathway.