TY - JOUR
T1 - Cross-reactivity of IgM anti-modified protein antibodies in rheumatoid arthritis despite limited mutational load
AU - Reijm, Sanne
AU - Kissel, Theresa
AU - Stoeken-Rijsbergen, Gerrie
AU - Slot, Linda M.
AU - Wortel, Corrie M.
AU - van Dooren, Hugo J.
AU - Levarht, Nivine E. W.
AU - Kampstra, Arieke S. B.
AU - Derksen, Veerle F. A. M.
AU - Heer, Pleuni Ooijevaar-de
AU - Bang, Holger
AU - Drijfhout, Jan W.
AU - Trouw, Leendert A.
AU - Huizinga, Tom W. J.
AU - Rispens, Theo
AU - Scherer, Hans U.
AU - Toes, René E. M.
N1 - Funding Information: The authors gratefully acknowledge Astrid Brehler for her complement activation experiments during her internship and the Flow cytometry Core Facility (FCF) of the LUMC for technical support and cell sorting assistance. Funding Information: This work has been financially supported by ReumaNederland (15-2-402, 18-1-205 and 17-1-402), the IMI funded project RTCure (777357), ZonMw (91214031, 90714509, 91617107 and 435002030) and Target-to-B! (LSHM18055-SGF). REMT is a recipient of an European Research Council (ERC) advanced grant (AdG2019-884796). Publisher Copyright: © 2021, The Author(s).
PY - 2021/12/1
Y1 - 2021/12/1
N2 - Background: Anti-modified protein antibodies (AMPA) targeting citrullinated, acetylated and/or carbamylated self-antigens are hallmarks of rheumatoid arthritis (RA). Although AMPA-IgG cross-reactivity to multiple post-translational modifications (PTMs) is evident, it is unknown whether the first responding B cells, expressing IgM, display similar characteristics or if cross-reactivity is crucially dependent on somatic hypermutation (SHM). We now studied the reactivity of (germline) AMPA-IgM to further understand the breach of B cell tolerance and to identify if cross-reactivity depends on extensive SHM. Moreover, we investigated whether AMPA-IgM can efficiently recruit immune effector mechanisms. Methods: Polyclonal AMPA-IgM were isolated from RA patients and assessed for cross-reactivity towards PTM antigens. AMPA-IgM B cell receptor sequences were obtained by single cell isolation using antigen-specific tetramers. Subsequently, pentameric monoclonal AMPA-IgM, their germline counterparts and monomeric IgG variants were generated. The antibodies were analysed on a panel of PTM antigens and tested for complement activation. Results: Pentameric monoclonal and polyclonal AMPA-IgM displayed cross-reactivity to multiple antigens and different PTMs. PTM antigen recognition was still present, although reduced, after reverting the IgM into germline. Valency of AMPA-IgM was crucial for antigen recognition as PTM-reactivity significantly decreased when AMPA-IgM were expressed as IgG. Furthermore, AMPA-IgM was 15- to 30-fold more potent in complement-activation compared to AMPA-IgG. Conclusions: We provide first evidence that AMPA-IgM are cross-reactive towards different PTMs, indicating that PTM (cross-)reactivity is not confined to IgG and does not necessarily depend on extensive somatic hypermutation. Moreover, our data indicate that a diverse set of PTM antigens could be involved in the initial tolerance breach in RA and suggest that AMPA-IgM can induce complement-activation and thereby inflammation.
AB - Background: Anti-modified protein antibodies (AMPA) targeting citrullinated, acetylated and/or carbamylated self-antigens are hallmarks of rheumatoid arthritis (RA). Although AMPA-IgG cross-reactivity to multiple post-translational modifications (PTMs) is evident, it is unknown whether the first responding B cells, expressing IgM, display similar characteristics or if cross-reactivity is crucially dependent on somatic hypermutation (SHM). We now studied the reactivity of (germline) AMPA-IgM to further understand the breach of B cell tolerance and to identify if cross-reactivity depends on extensive SHM. Moreover, we investigated whether AMPA-IgM can efficiently recruit immune effector mechanisms. Methods: Polyclonal AMPA-IgM were isolated from RA patients and assessed for cross-reactivity towards PTM antigens. AMPA-IgM B cell receptor sequences were obtained by single cell isolation using antigen-specific tetramers. Subsequently, pentameric monoclonal AMPA-IgM, their germline counterparts and monomeric IgG variants were generated. The antibodies were analysed on a panel of PTM antigens and tested for complement activation. Results: Pentameric monoclonal and polyclonal AMPA-IgM displayed cross-reactivity to multiple antigens and different PTMs. PTM antigen recognition was still present, although reduced, after reverting the IgM into germline. Valency of AMPA-IgM was crucial for antigen recognition as PTM-reactivity significantly decreased when AMPA-IgM were expressed as IgG. Furthermore, AMPA-IgM was 15- to 30-fold more potent in complement-activation compared to AMPA-IgG. Conclusions: We provide first evidence that AMPA-IgM are cross-reactive towards different PTMs, indicating that PTM (cross-)reactivity is not confined to IgG and does not necessarily depend on extensive somatic hypermutation. Moreover, our data indicate that a diverse set of PTM antigens could be involved in the initial tolerance breach in RA and suggest that AMPA-IgM can induce complement-activation and thereby inflammation.
KW - AMPA
KW - B cells
KW - IgM
KW - Rheumatoid arthritis
KW - Somatic hypermutation
UR - http://www.scopus.com/inward/record.url?scp=85114356447&partnerID=8YFLogxK
U2 - https://doi.org/10.1186/s13075-021-02609-5
DO - https://doi.org/10.1186/s13075-021-02609-5
M3 - Article
C2 - 34479638
SN - 1478-6354
VL - 23
JO - Arthritis research & therapy
JF - Arthritis research & therapy
IS - 1
M1 - 230
ER -