Age-associated B cells indicate disease activity in rheumatoid arthritis

Age-associated B cells (ABCs) are characterized by CD11c and T-bet expression. ABCs are elevated in several autoimmune diseases and may be associated with RA. This study aimed to investigate ABCs' role in RA and identify potential factors affecting ABCs in RA patients. Peripheral blood mononuclear cells (PBMCs) and plasma samples were collected from 75 RA patients and 27 sex- and age-matched healthy controls. Proportions of ABCs (CD19⁺CD11c⁺T-bet⁺), plasmablasts (CD19⁺CD27⁺CD38^hi), Bregs (CD19⁺IL-10⁺), and T follicular helper (Tfh) cells (CD4⁺CXCR5⁺PD-1^hi) in PBMCs were detected using flow cytometry. Plasma IL-21, IFN-γ, and IL-10 levels were detected by ELISA. Plasma miRNAs (miR-34a, -122, -133a, -142, -146a, -208a, and -155) were detected by RT-PCR. Naïve B cells transfected with different miRNA mimics were deteced after 3 days culture under stimulation of anti-IgM and anti-CD40 or IL-21, IFN-γ, anti-IgM and anti-CD40. ABC proportions in PBMCs were increased in RA patients with higher disease activity and decreased in those with good treatment responses. Additionally, ABC proportions in PBMCs in RA patients were positively correlated with DAS28 scores. Plasma levels of IL-21, miR-142, and miR-146a and proportions of Tfh cells were positively correlated with ABC percentages in PBMCs. Herein, ABCs were identified as potential biological indicators for disease activity and treatment responses. Moreover, miR-142 and miR-146a could induce the differentiation of ABCs in naïve B cells in conjunction with IL-21 and IFN-γ.