Thus, it is possible that cigarette smoking represents an environmental trigger that induces anti-citrulline antibody responses in genetically susceptible individuals and thereby contributes to the development of RA [13]. Alterations in the citrullination of myelin proteins and autoimmune targeting of citrullinated myelin proteins have been observed in MS. from mice with acute and chronic stages of CIA and EAE. Results In samples from pre-disease CIA and acute-disease EAE, we observed autoantibody targeting of the immunising antigen and responses to a limited set of citrullinated epitopes. Over the course of diseases, the autoantibody responses expanded to target multiple citrullinated epitopes in both CIA and EAE. Using immunoblotting and mass spectrometry analysis, we recognized citrullination of multiple polypeptides in CIA joint and EAE brain tissue that have not previously been described as citrullinated. Conclusions Our results suggest that anti-citrulline antibody responses develop in the early stages of CIA and EAE, and that autoimmune inflammation results in citrullination of joint proteins in CIA and brain proteins in EAE, thereby creating neoantigens that become additional targets in epitope distributing of autoimmune responses. Introduction Post-translational modifications can produce neo-antigens that become targets of autoimmune responses [1,2]. A post-translational modification of importance in rheumatoid arthritis (RA) is the conversion of peptidylarginine to peptidylcitrulline by peptidyl arginine deiminase (PAD) [3,4]. This enzymatic modification is usually termed citrullination, and detection of antibodies targeting citrullinated epitopes has become a important diagnostic marker for the diagnosis of RA, with a sensitivity of about 60% and a specificity of 95% [5-10]. Nevertheless, the mechanisms by which anti-citrullinated protein antibody (ACPA) responses develop remain poorly understood. In Cyproheptadine hydrochloride this study, we used protein microarrays to characterise ACPA responses in rodent models of RA and multiple sclerosis (MS). In RA, ACPA responses are currently assayed in clinical laboratories by detection of antibodies targeting cyclic citrullinated peptides (CCPs) derived from filaggrin [7]. These CCPs probably symbolize molecular mimics of the true citrullinated autoantigens in RA synovium. In RA and other inflammatory arthritides, multiple joint proteins become citrullinated [10-12]. Recent evidence suggests that cigarette smoking induces citrullination of lung proteins, and in patients possessing the shared epitope of human leucocyte antigen (HLA) DR, smoking is usually associated with about a 20-fold increased risk of developing anti-CCP antibody-positive RA [13]. Further, Kuhn and colleagues showed that a monoclonal antibody Cyproheptadine hydrochloride specific for citrullinated fibrinogen exacerbated tissue injury in rodent models of arthritis [14], although it remains possible that this non-affinity matured IgM antibody might cross-react with a native cartilage component as explained for anti-citrulline IgG responses in RA [15]. Thus, it is possible that cigarette smoking represents an environmental trigger that induces anti-citrulline antibody responses Cyproheptadine hydrochloride in genetically susceptible individuals and thereby contributes to the development of RA [13]. Alterations in the citrullination of myelin Cyproheptadine hydrochloride proteins and autoimmune targeting of citrullinated myelin proteins have been observed in MS. Myelin basic protein (MBP) is usually partially citrullinated (C8 isoform) in normal brain tissue, although there is a significant increase in the relative amount of this partially citrullinated form in MS brain tissue [15]. An extensively citrullinated form of MBP is usually associated with Marburg encephalitis, a fulminant autoimmune demyelinating disease [16]. There have also been reports of anti-citrullinated-MBP T cell reactivity in MS [17], as well as evidence that citrullinated MBP can serve as an autoantigen in experimental autoimmune encephalomyelitis (EAE) [18]. In this study we applied synovial and myelin Igf1r protein arrays to investigate the development and development of ACPA responses in rodent models of.