Session Type: ACR Poster Session A
Session Time: 9:00AM-11:00AM
Background/Purpose: We previously showed that up to 40% of RA synovial recombinant monoclonal antibodies (RA-rmAbs) generated from germinal center-like structure (GC-LS+) RA synovium recognize citrullinated antigens contained in neutrophils extracellular traps (NETs) (1). The cellular source of other potential autoantigens targeted by the majority of locally differentiated B cells remains undefined. Recently, RA-fibroblast-like synoviocytes (RA-FLS) have been implicated in the release of citrullinated antigens (2, 3). However, whether these cells are targeted by RA-rmAbs is still unknown. Here, we aimed to define i) the RA-rmAbs immunoreactivity towards RA-FLS and ii) identify potential stromal-derived autoantigens.
Methods: 67 RA-rmAbs were generated from single CD19+ B cells FACS-sorted from fresh synovial cell suspensions following IgVH+VL genes cloning (1). RA-rmAbs were tested by means of i) cell-based immunofluorescence assays with FLS of RA patients and controls (osteoarthritis (OA)-FLS and RA-dermal fibroblast (RA-DF)), ii) co-localization with stromal specific markers and iii) immunoenzymatic tests with co-localizing antigens. Control rmAbs were also used (Sjögren’s syndrome/healthy donor-IgG rmAbs).
Results: Immunofluorescence on RA-FLS demonstrated reactivity of 22.4% of RA-rmAbs (15/67 rmAbs) towards FLS. Only 4 rmAbs out of 15 were binding both FLS and NETs components. For some RA-rmAbs this reactivity was not specific to RA-FLS since it was also observed for OA-FLS (3% rmAbs). Interestingly, strong co-localization was observed with calreticulin (CRT) which has been shown to bind the RA shared-epitope (SE) ligand and to increase the signalling pathway activated by the SE ligand in its citrullinated form (3). When tested in ELISA for native vs cit-CRT, 20% (14/67 rmAbs) of the FLS-reactive RA clones showed binding to CRT with 6 out of 14 RA-rmAbs displaying increased immunoreactivity towards cit-CRT. Controls rmAbs showed no reactivity to either FLS or CRT. RA-rmAbs binding to CRT was further confirmed in western blot immunoassays.
Conclusion: Here, we provide novel evidence that a subset of locally differentiated B cells within RA synovial GC-LS can react towards RA-FLS derived antigens. Preliminary data suggest that part of this reactivity is directed towards CRT. Identification of immunodominant epitopes within CRT is under investigations.
(1) Corsiero et al, ARD 2015
(2) Sorice et al, Rheumatology 2016
(3) Ling et al, AR 2013
To cite this abstract in AMA style:Corsiero E, Jagemann L, Pitzalis C, Bombardieri M. Characterization of Novel Stromal-Derived Autoantigens Recognized By RA Synovial Monoclonal Antibodies [abstract]. Arthritis Rheumatol. 2017; 69 (suppl 10). https://acrabstracts.org/abstract/characterization-of-novel-stromal-derived-autoantigens-recognized-by-ra-synovial-monoclonal-antibodies/. Accessed September 24, 2023.
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