Antibodies against citrullinated proteins enhance tissue injury in experimental autoimmune arthritis
Kristine A. Kuhn, … , William H. Robinson, V. Michael Holers
Kristine A. Kuhn, … , William H. Robinson, V. Michael Holers
Published April 3, 2006
Citation Information: J Clin Invest. 2006;116(4):961-973. https://doi.org/10.1172/JCI25422.
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Research Article Autoimmunity

Antibodies against citrullinated proteins enhance tissue injury in experimental autoimmune arthritis

Abstract

Antibodies against citrullinated proteins are specific and predictive markers for rheumatoid arthritis although the pathologic relevance of these antibodies remains unclear. To investigate the significance of these autoantibodies, collagen-induced arthritis (CIA) in mice was used to establish an animal model of antibody reactivity to citrullinated proteins. DBA/1J mice were immunized with bovine type II collagen (CII) at days 0 and 21, and serum was collected every 7 days for analysis. Antibodies against both CII and cyclic citrullinated peptide, one such citrullinated antigen, appeared early after immunization, before joint swelling was observed. Further, these antibodies demonstrated specific binding to citrullinated filaggrin in rat esophagus by indirect immunofluorescence and citrullinated fibrinogen by Western blot. To evaluate the role of immune responses to citrullinated proteins in CIA, mice were tolerized with a citrulline-containing peptide, followed by antigen challenge with CII. Tolerized mice demonstrated significantly reduced disease severity and incidence compared with controls. We also identified novel murine monoclonal antibodies specific to citrullinated fibrinogen that enhanced arthritis when coadministered with a submaximal dose of anti-CII antibodies and bound targets within the inflamed synovium of mice with CIA. These results demonstrate that antibodies against citrullinated proteins are centrally involved in the pathogenesis of autoimmune arthritis.

Authors

Kristine A. Kuhn, Liudmila Kulik, Beren Tomooka, Kristin J. Braschler, William P. Arend, William H. Robinson, V. Michael Holers

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Figure 1

Anti-CCP antibodies appear prior to visible arthritis and in parallel with the appearance of anti-collagen antibodies.

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Anti-CCP antibodies appear prior to visible arthritis and in parallel wi...
(A) Six- to 8-week-old DBA/1J mice were untreated or were immunized at day 0 with CII in CFA or CFA alone and then received booster immunizations 21 days later (black arrows). Sera were collected every 7 days and analyzed for antibody levels. Mice were also observed and scored for development of clinical arthritis. Visible signs of arthritis were measured by adding the number of swollen digits on all 4 paws of each mouse. (B) IgG and (D) isotype-specific antibodies against CII were measured by ELISA as described in Methods. (C) IgG and (E) isotype-specific anti-CCP antibodies were measured by ELISA as described in Methods. IgG3 anti-CCP antibodies were below the limits of detection by ELISA and thus are not shown. The data for each mouse within a group are averaged for that group and represented α SEM. For each group, n = 12. Statistical significance was determined using a 1-way ANOVA. *P < 0.05; **P < 0.01; ***P < 0.001 in CIA mice compared with CFA-immunized and unimmunized mice. (F) Sera from Rag1–/– mice (n = 5) were tested and compared with unimmunized DBA/1J (normal mouse serum (NMS); n = 7 for IgM and n = 23 for IgG). Statistical significance was determined using an unpaired 2-tailed Student’s t test. #P = 0.0004 for IgM anti-CCP antibodies in NMS rsus Rag1–/– mice.