Tryptase Is A Candidate Autoantigen In Rheumatoid Arthritis

Rheumatoid arthritis (RA) is one of the most common autoimmune diseases. Althoughit is a systemic disease, the initiated position is synovial tissue. RA is characterized byinflammatory cell infiltration and synovial cell hyperplasia resulting in joint bone andcartilage rodent destructions. A normal synovium is composed of an intimal lining layer anda synovial sublining. However, in RA patients, CD4+T cells, B cells and macrophagesinvade the synovium causing marked hyperplasia of the intimal lining and massiveinfiltration of the synovial sublining. Moreover, the immunogenic pathways that follow,such as secretion of in flammatory mediators and degradative enzymes, drive thedestruction of local cartilage and bone.Now RA is considered as the consequence of synthetic action of genetic factors,environmental pressure and miacrobe infection. Although the exact mechanism of RApathogenesis is still not fully understood, autoimmune responses are considered to play animportant role in this process. It has been hypothesized that autoantigens, presented byRA-associated HLA-DR molecular, activate self-reactive antigen-specific immune cells toinitiate synovial inflammation. Currently, the autoantigens is purposed to induceautoimmune responses in RA remain unclear. For the past few years, a variety of candidateautoantigens have been studied and categorized into three major groups:(1) Antigensderived from the origin of the joint, such as type II collagen, human chondrocyteglycoprotein39, and proteoglycan;(2) Highly conserved foreign antigens with humanhomologs, including heat shock proteins, EBV trans-acting factor and Escherichia coli dnaJ;and (3) Post-translationally modified proteins, such as citrullinated, filaggrin andimmunoglobulin G. While these putative autoantigens are specifically detected in the joint,many of them lack a definite association with clinical RA pathogenesis. For example, whiletype II collagen is found in the joints of some RA patients, they generally lack anti-type IIcollagen antibodies. Furthermore, levels of type II collagen in the joints ofantibody-positive patients do not correlate well with the duration, activity or severity of RA. Therefore, there is a need to identify novel RA-associated autoantigens that will not onlyinform the detailed mechanisms of RA pathogenesis, but also provide diagnostic value.In recent years, great progress has been made in the theory and technology ofproteomics. As embranchment of proteomics, serum proteomics technology has been payedmore and more attention also to screen autoantigens. This technology is used to seek thedifferent protein spot of serum in objective people based on creating normal proteinexpression profiles in order to search the structure and function of disease associated protein.Therefore, in this study, we apply to serum proteomics strategy to uncover novel candidateautoantigen in RA patients.Firstly, we screened proteins from synovium of the RA patients by cross comparisonsof synovium-serum proteomics approach, and choose these proteins responsed to RA serumto matrix-assisted laser desorption/ionization time-of-flight mass spectrometry(MALDI-TOF-MS). Further, we confirmed these proteins by co-immunofluorescenceanalysis and ELISA. Finally, we performed a correlation analysis of clinical indexes andserum protein levels in early and late RA patients in order to understand the relationshipbetween protein levels and RA disease activity.Results should that tryptase might be a candidate RA autoantigen by analyzing proteinsfrom synovial tissues of RA patients using two-dimensional electrophoresis (2-DE) andmatrix-assisted laser desorption/ionization time-of-flight mass spectrometry(MALDI-TOF-MS). We detected high levels of tryptase protein and its cognate antibody insynovial tissues and sera of RA patients. Furthermore, tryptase in synovial tissuescolocalized with IgG complexes as determined by co-immunofluorescence analysis.Importantly, tryptase levels were markedly associated with key indexes for RA disease,including the Disease Activity Score using28joint counts (DAS28), rheumatoid factor (RF),and autoantibodies against cyclic citrullinated peptide (anti-CCP). Our results implicatetryptase in the pathogenesis of RA and suggest its presence in serum or synovium may serveas a diagnostic indicator of RA.