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

Abstract

Autoantibody-mediated inflammation contributes to the development of rheumatoid arthritis (RA), and anti-type II collagen (CII) antibodies are present in the serum, synovial fluid, and cartilage of RA patients. We had previously generated and characterized knockin mice expressing a germline-encoded, CII-specific IgH (B10Q.ACB), which demonstrated positive selection of self-reactive B cells. Here, we show that despite the spontaneous production of CII-specific autoantibodies, B10Q.ACB mice are protected from collageninduced arthritis. Introducing a mutation in the Ncf1 gene, leading to ROS deficiency, breaks this strong arthritis resistance. Disease development in Ncf1-mutated B10Q.ACB mice is associated with an enhanced germinal center formation but without somatic mutations of the auto-reactive B cells, increased T-cell responses and intramolecular epitope-spreading. Thus, ROS-mediated B-cell tolerance to a self-antigen could operate by limiting the expansion of the auto-reactive B-cell repertoire, which has important implications for the understanding of epitope spreading phenomena in rheumatoid arthritis and other autoimmune diseases.Keywords: Auto-reactive B cells r Autoantibodies r Arthritis r Epitope spreading r ROS Additional supporting information may be found in the online version of this article at the publisher's web-site IntroductionAutoimmune diseases affect 5% of the worldwide population, and often involve autoantibody-mediated tissue inflammation. The development of rheumatoid arthritis (RA) involves autoantibodies such as rheumatoid factor and antibodies to citrullinated protein antigens. These antibodies appear in the blood of RA patients, many years before the onset of clinical symptoms [1,2], and durCorrespondence: Dr. Rikard Holmdahl e-mail: rikard.holmdahl@ki.se ing the preclinical phase epitope spreading of the antibodies to citrullinated protein antigens occurs [3,4].Anti-type II collagen (CII) antibodies are present in the serum, synovial fluid, and cartilage of RA patients [5,6]. These are directed to both native triple helical (approx. 10% of the patients) and modified citrullinated (approx. 40% of the patients) epitopes [7,8]. The triple helical CII-directed antibodies are detected during the early joint inflammatory phase of RA [9,10]. Interestingly, the identification of the CII epitopes showed that they are highly conserved between mammals [11,12]. Functional analysis of single chain variable fragment antibody [13] Numerous studies identified the prototypes of different pathogenic autoimmune diseases, where the production of hightiter, high affinity autoantibodies to the proposed antigens is generated in germinal centers (GC). GCs in the secondary lymphoid organs are the sites of intense B-cell proliferation and support somatic hyper mutation and the subsequent selection of high affinity B cells. Extra-follicular (non-GC) origin of the autoantibodies was described in many mouse models of autoimmune diseases [19]. We have previously found that Ncf1 polymorphism leads to a lower oxid...

Identification of Ocular Autoantigens Associated With Juvenile Idiopathic Arthritis-Associated Uveitis

“…Consequently, these circumstances may promote the diversification of epitope specificity of the immune response, including the repertoire of antibody specificities, called epitope spreading (33–36). In rheumatoid arthritis (RA), autoantibodies and epitope spreading of antibodies to citrullinated protein antigens are considered to play a critical role in the progression from preclinical to clinical disease states (35, 37, 38). Anti-citrullinated protein/peptide antibodies (ACPA) were also frequently shown in JIA patients.…”

The Role of Reactive Oxygen Species in the Rheumatoid Arthritis-Associated Synovial Microenvironment

“…This strong arthritic resistance is broken by introducing a mutation into the Ncf1 gene that causes ROS deficiency in Ncf1-mutated B10Q. In ACB mice, increased T-cell responses and intramolecular epitope dissemination are linked to disease development, although there are no somatic mutations in autoreactive B cells [ 178 ].…”

Ncf1 polymorphism reveals oxidative regulation of autoimmune chronic inflammation

“…Yet, B cells are activated through interaction with CII‐specific T cells and produce a strong anti‐CII IgG response to the C1 epitope but they do not somatically mutate. Interestingly, introduction of the Ncf1 mutation makes mice susceptible to CIA and the mouse starts to produce anti‐CII antibodies not only to the C1 epitope but also to several epitopes along the CII molecule . Thus, ROS seem to control B‐cell function and epitope spreading toward CII with the production of new pathogenic antibodies.…”