Autoantigen Peptide‐8‐Arm Polyethylene Glycol‐Dyes Specifically Recognize Antigen‐Specific B Cells and Improve the Diagnosis of Rheumatoid Arthritis

OBJECTIVES: Rheumatoid arthritis (RA) is a systemic chronic disabling autoimmune disease with high autoantibody production. However, approximately one-third of patients with RA are autoantibodies-negative lacking biomarkers. Antigen-specific B cells are critical participants in RA pathogenesis by producing autoantibodies and driving inflammation and joint damage. Nevertheless, the limited detection methods have impeded in-depth studies on these cells. This study aimed to develop a novel probe to precisely recognize these cells and evaluate their diagnostic potential for RA. METHODS: Autoantigen peptide-8-arm polyethylene glycol (PEG; APP) - dyes, named APP-dyes, were constructed by conjugating classical autoantigens with a multifunctional polymer material, eight-arm PEG-maleimide. The specificity and efficiency of APP-dyes in detecting antigen-specific B cells were analyzed by flow cytometry. The pathogenicity of antigen-specific B cells isolated by APP-dyes was assessed through in vitro culture and adoptive transfer assays. The diagnostic value of APP-dyes in distinguishing RA was also systemically examined. RESULTS: The APP-dyes could efficiently and specifically recognize antigen-specific B cells in patients with RA, experimental arthritis mice, and spontaneous arthritis mice. Antigen-specific B cells isolated by APP-dyes were highly active in autoantibody secretion and arthritis initiation. The sensitivity and/or specificity of mutated citrullinated vimentin-specific B cells and citrullinated Type II collagen-specific B cells identified by the APP-dyes were 73.33% and/or 92.5% and 60.00% and/or 91.25% for RA diagnosis, respectively. Notably, these cells also showed substantial diagnostic performance in anti-cyclic citrullinated peptide-negative and early patients with RA. Moreover, combining antigen-specific B cells with their corresponding autoantibodies further increased the diagnostic accuracy. CONCLUSIONS: These findings indicated APP-dyes as an effective and clinically applicable tool for investigating the mechanisms underlying antigen-specific B cells and distinguishing RA.