Exhausted KLRG1hi CD8+ T and pathogenic GZMA+ Th17 cells are associated with the mild Mycoplasma pneumoniae pneumonia in children

作者：Jing-Ying Zhan, Ren Luo, Chaofan Li, L. Zhong, Qiaoping Wu, Run Wang, Dapeng Chen, Xiao Chen, Kang-yi Ren, Zhengrong Chen, Zhemin Zhou, Enmei Liu, Hong Tang · 发表于：Journal of Infection · 年份：2025 · DOI：10.1016/j.jinf.2025.106642 · 被引用次数：8 · 研究领域：Pneumonia and Respiratory Infections、Microbial infections and disease research、vaccines and immunoinformatics approaches

Mycoplasma pneumoniae (MP) infection in children has recently re-emerged with a higher rate of hospitalization in the post-COVID-19 period. However, understanding of how the adaptive immunity plays a role in the bacterial pneumonia is often restrained by recurrent infection and complex co-infection with M. pneumoniae . Herein, we took advantage of the single-cell RNA sequencing (scRNA-seq) and high-dimensional flow cytometry to characterize the impairment of peripheral T and B lymphocytes in pediatric patients with mild Mycoplasma pneumonia (MMPP). These patients were M. pneumoniae mono-infected at hospitalization, and showed an expansion of both effector and memory CD8 + T cells, with exhausted KLRG1 hi CD8 + T compartments prevailed. Moreover, they exhibited a hyperactivation of IgM + plasma cells and unswitched memory B cells, which could partly explain the IgM seroconversion routinely diagnosed in MMPP. Therefore, the hypo-functional CD8 + T cells and polarization of IgM secreting cells might help explain the ill-controlled bacterial replication in MMPP. Furthermore, compared to the healthy controls, IL-17A producing Th17 cells were reduced in MMPP, but cytotoxic granzymes increased significantly. Reduced IL-17A would suggest elevated M. pneumoniae colonization and reduced bacterial clearance in the respiratory tract, whereas cytotoxic property of this pathogenic Th17 cells might play a role in the pulmonary hyper inflammation. Therefore, this work managed to characterize...