AB0025 CITRULLINATED-PEPTIDE SPECIFIC CD4+ T CELL RESPONSES IN RHEUMATOID ARHRITIS

Background: CD4+ T cells reacting to post-translationally modified, citrullinated self-antigens are thought play a central role in the pathogenesis of rheumatoid arthritis (RA) 1 . This is evidenced by strong HLA class II association, success therapeutic co-stimulation blockade and detection autoantigen specific T-cells using multimers 2 These may represent target for antigen-specific, tolerogenic therapies their in-depth phenotyping provide means which monitor such treatment. Objectives: To identify citrullinated-peptide (cit-peptide) induced cytokine repertoire antigen-specific memory both healthy controls (HCs) ACPA positive RA patients intracellular staining flow cytometry. Of note, HLA-types HCs were not known. Methods: Cryopreserved peripheral blood mononuclear (PBMC) from (n = 8) 13) with early (untreated) established disease thawed labelled proliferation tracking dye (PTD). Labelled PBMC then either incubated alone or pool cit-peptides 9-days, followed 5-hour restimulation PMA ionomycin, where secretion was blocked final 4-hours brefeldin-A. Cells harvested, permeabilised stained cell surface markers cytokines including IFN-γ, IL-4, IL-21 IL-17. Stained immediately acquired BD Fortessa X20, identified as viable CD45RO+ (memory) population that had proliferated (PTDlow) response cit-peptides. Stimulation indices (SI) calculated percentage stimulated wells divided unstimulated conditions, cit-peptide responders defined those an SI > 2.0. Net production measured subtracting PTDlow cells, Results: Comparable proliferative responses observed donor groups stimulation pool, 37 % 31 responded 2.0 (Fig. 1A). While little responding HC donors, responsive predominantly IFN-γ producing 1B 1C). In contrast, these donors did produce significant levels IL-17 IL-4 1D 1E). Conclusion: Cit-peptides able induce which, amongst only, Th1/Tfh subtype. while based only on small sample, group, suggesting lack Th17/Th2 responses. Not all peptide possibly reflecting limited number pooled confirmed HLA-DRB1*04:01 peptides selected specificity this basis. Future work will therefore include HLA-typing, well inclusion additional citrullinated-epitopes demonstrate autoreactivity wider cross-section patients. Further be performed, future plans study assay data alongside clinical outcomes assess its value immune monitoring. References: [1]Malmström, V et al Nat Rev Immunol. 2017; 17(1):60-75. [2]Gerstner, C BMC 2020; 21(27):1-14. Disclosure Interests: Jessica Swift: None declared, James Stanway: Ioana Nicorescu: Catharien Hilkens: Frederik Stevenaert Employee of: Janssen, Amy Anderson Grant/research support from: Pfizer, GSK Arthur Pratt John D Isaacs Speakers bureau: Abbvie, Gilead, Roche, UC, Consultant Janssen Figure 1. Citrullinated-peptide (A) net (B), (C), (D) (E) cells.