Dysregulated Tfh/B cells and their interactions in neuromyelitis optica spectrum disorder

Liang Wang¹LEI ZHOU¹Zhouzhou Wang¹Jingzi Zhangbao¹Wenjuan Huang¹Hongmei Tan¹Yuxin Fan¹Chuanzhen Lu¹Jian Yu²Min Wang²Jiahong Lu¹Chongbo Zhao¹Jun Wang¹Chao Quan^1*

• ¹Department of Neurology, Huashan Hospital, Fudan University, Shanghai, China
• ²Department of Ophthalmology and Vision Science, Eye and ENT Hospital, Shanghai, China

Background: This study aimed to compare the proportion of circulating follicular helper T (Tfh) and B cell subsets, serum levels of cytokines and chemokines, between neuromyelitis optica spectrum disorder (NMOSD) patients with anti-aquaporin-4 antibody (AQP4-ab) and healthy controls, and to investigate the interaction mechanisms between Tfh and B cells. Methods: AQP4-ab-positive NMOSD patients were enrolled during acute attacks and remission phases, along with age- and sex-matched healthy controls. Flow cytometry was employed to assess circulating Tfh and B cell subsets. Purified CD19+ B cells were cultured alone or co-cultured with CD4+CXCR5+ Tfh cells for 6 days, with various interventions applied to evaluate alterations in Tfh or B cell phenotypes. Serum and supernantant levels of interleukin (IL)-6, IL-21, CXCL13, and AQP4-ab were measured. Results: During acute attacks, NMOSD patients exhibited significantly higher proportions of total Tfh, ICOS+ Tfh, activated Tfh17, switched memory B, double negative B, plasmablasts, and plasma cells, alongside elevated serum levels of IL-6, IL-21, and CXCL13. In contrast, the frequecies of activated Tfh1, naive B and transitional regulatory B cell subsets were significantly reduced. Functional assays revealed that Tfh cells promoted B cell proliferation, differentiation, and AQP4-ab production. Conversely, B cell subsets enhanced Tfh cell proliferation, differentiation, and IL-21 secretion; these effects were attenuated by anti-CD20 and anti-interferon-γ (IFN-γ) monoclonal antibodies, but augmented by anti-IL-10 monoclonal antibody. Conclusions: Circulating Tfh and B cell subsets are dysregulated in AQP4-ab-positive NMOSD, concomitant with increased levels of IL-6, IL-21, and CXCL13. Reciprocal interactions between Tfh and B cells likely contribute to disease pathogenesis.