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Open Access Research article

Cartilage oligomeric matrix protein specific antibodies are pathogenic

Hui Geng12, Kutty Selva Nandakumar2, Anna Pramhed4, Anders Aspberg34, Ragnar Mattsson4 and Rikard Holmdahl2*

Author Affiliations

1 Hubei Key Laboratory of Genetic Regulation and Integrative Biology, College of Life Sciences, Central China Normal University, Wuluo Road 152, Wuhan, 430079, China

2 Division of Medical Inflammation Research, Department of Medical Biochemistry and Biophysics, Karolinska Institute, Scheeles väg 2, Stockholm, 17177, Sweden

3 Department of Biology, Cell and developmental biology, University of Copenhagen, Ole Maaløes Vej 5, Copenhagen, DK-2200, Denmark

4 Department of Experimental Medical Sciences, Biomedical Center, Lund University, Sölvegatan 19, Lund, SE-22184, Sweden

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Arthritis Research & Therapy 2012, 14:R191  doi:10.1186/ar4022

Published: 20 August 2012

Abstract

Introduction

Cartilage oligomeric matrix protein (COMP) is a major non-collagenous component of cartilage. Earlier, we developed a new mouse model for rheumatoid arthritis using COMP. This study was undertaken to investigate the epitope specificity and immunopathogenicity of COMP-specific monoclonal antibodies (mAbs).

Methods

B cell immunodominant regions on the COMP molecule were measured with a novel enzyme-linked immunosorbent assay using mammalian expressed full-length mouse COMP as well as a panel of recombinant mouse COMP fragments. 18 mAbs specific to COMP were generated and the pathogenicity of mAbs was investigated by passive transfer experiments.

Results

B cell immunodominant epitopes were localized within 4 antigenic domains of the COMP but with preferential response to the epidermal growth factor (EGF)-like domain. Some of our anti-COMP mAbs showed interactions with the native form of COMP, which is present in cartilage and synovium. Passive transfer of COMP-specific mAbs enhanced arthritis when co-administrated with a sub-arthritogenic dose of a mAb specific to collagen type II. Interestingly, we found that a combination of 5 COMP mAbs was capable of inducing arthritis in naive mice.

Conclusions

We have identified the specificities of mAbs to COMP and their contribution to the development of arthritis. These findings will further improve our understanding of the autoantibody mediated immunopathologies occurring widely in rheumatoid arthritis (RA), as well as in other autoimmune disorders.