Pathogenic Autoreactive B Cells Are Not Negatively Selected toward Matrix Protein Collagen II

Abstract

We have addressed the importance of B cell tolerance to collagen type II, a matrix protein, which is a target in rheumatoid arthritis (RA) and its mouse models. We generated a germline-encoded anti-collagen type II (CII) IgH replacement anti-C1 B cell mouse strain (ACB) to investigate how B cell tolerance to CII, a matrix protein, is subverted and to further understand pathogenesis of RA. Phenotypic analysis revealed that CII-specific B cells were surprisingly neither deleted nor anergized. Instead, they were readily detected in all lymphoid organs. Spontaneously produced autoantibodies could bind directly to cartilage surface without detectable pathology. However, exaggerated arthritis was seen after injection of anti-CII Abs specific for other epitopes. In addition, Abs from CII-specific hybridomas generated from ACB mice induced arthritis. Interestingly, IgH/L chain sequence data in B cell hybridomas revealed a lack of somatic mutations in autoreactive B cells. The ACB model provides the first possibility, to our knowledge, to study B cell tolerance to a matrix protein, and the observations made in the study could not be predicted from previous models. B cell-reactive epitopes on CII are largely shared between human RA and rodent CII-induced arthritis; this study, therefore, has important implications for further understanding of pathological processes in autoimmune diseases like RA.

B‐cell epitope spreading and inflammation in a mouse model of arthritis is associated with a deficiency in reactive oxygen species production

“…Mice with auto-reactive, CII-specific B cells are protected from arthritis B10Q.ACB mice have a high frequency of auto-reactive B cells, naturally producing high titers of anti-CII, C1-epitope specific antibodies but without spontaneous development of arthritis [24], although monoclonal antibodies with the same specificity induced arthritis [25]. To our surprise B10Q.ACB mice were protected even against the development of collagen-induced arthritis (CIA) (Fig.…”

“…In the present study, we have analyzed the role of ROS in B-cell regulation using a newly introduced auto-reactive B-cell model in which the V H VDJ region of a germline encoded and pathogenic antibody binding to the C1 triple helical epitope (GAR-GLTGROGDA, O denotes hydroxyproline, located at position 358-369) of CII was inserted, which led to spontaneous development of highly frequent, CII-specific self-reactive B cells [24].…”

“…This was in contrast to the general belief that ROS promotes inflammation and severity of the disease associated with a number of autoimmune inflammatory diseases [21][22][23]. Alternatively, ROS could also act to regulate lymphocyte activation and B-cell function, thereby being one of the protective factors for the development of autoimmune disease.In the present study, we have analyzed the role of ROS in B-cell regulation using a newly introduced auto-reactive B-cell model in which the V H VDJ region of a germline encoded and pathogenic antibody binding to the C1 triple helical epitope (GAR-GLTGROGDA, O denotes hydroxyproline, located at position 358-369) of CII was inserted, which led to spontaneous development of highly frequent, CII-specific self-reactive B cells [24]. …”

“…Antibodies to the C1 epitope cause arthritis in the mouse and the arthritogenicity is enhanced if antibodies to additional CII epitopes are present [25]. We have earlier documented that CII-specific B cells were neither deleted, receptor edited nor anergized [24], instead they were isotype switched and expanded in the primary and secondary lymphoid organs [24]. In the current study, we show that naïve B10Q.ACB mice failed to develop spontaneous arthritis despite the presence of high titers of autoantibodies indicating their insufficiency to initiate the disease.…”

“…Unexpectedly, high C1-specific antibody titers present in B10Q.ACB mice did not promote arthritis. Even though the presence of endogenous C1-specific antibody in B10Q.ACB mice was found to be an advantage for inducing severe collage antibody induced arthritis (CAIA) [24]. It is possible that auto-reactive B cells in human RA, as well as in the mouse models, could have regulatory functions.…”