Increased Peripheral TFH Cells and Serum Interleukin-21 in Childhood Mycoplasma Pneumoniae Pneumonia.

Abstract

The aim of this study was to investigate the role of TFH cells and interleukin (IL)-21 in the pathogenesis of childhood Mycoplasma pneumoniae pneumonia (MPP). It was a retrospective study carried out at Yantai Yuhuangding Hospital, China from July 2016 to June 2019. It comprised 46 healthy control (HC) children and 106 pediatric patients, including 60 children with general MPP (GMPP) and 46 children with refractory MPP (RMPP). Flow cytometry was used to detect the frequencies of peripheral TFH cells. The levels of serum IL-21 were tested by ELISA. The transcriptional factors Bcl-6 and Blimp-1 mRNA levels were examined using RT-qPCR. The percentage of TFH cells and expression levels of IL-21 and Bcl-6 in peripheral blood were all significantly elevated in MPP groups compared with HC group (all p <0.001). Furthermore, it was found that a significantly higher percentage of TFH cells and levels of IL-21 and Bcl-6 in RMPP children, compared with GMPP children (all p <0.05). In contrast, lower Blimp-1 levels were observed in MPP groups (p <0.001), especially in RMPP group (p = 0.021). Therefore, the elevated expansion of TFH cells and the increased secretion of IL-21 cytokine may contribute to the pathogenesis of childhood MPP, while its excessive response may be associated with the development of childhood RMPP. Key Words: TFH cells, IL-21, Children, Mycoplasma pneumoniae pneumonia.