Immunoglobulin heavy chain variable region gene utilization by B cell hybridomas derived from rheumatoid synovial tissue.

Rheumatoid arthritis (RA) is a chronic inflammatory disease that primarily affects synovial joints. Activated B lymphocytes and plasma cells are present in the synovial tissue and are thought to contribute to the immunopathology of the rheumatoid joint. To investigate rheumatoid synovial B lymphocytes, we have generated B cell hybridomas from synovial tissue of an RA patient. Here we describe the immunoglobulin VH gene repertoire of eight IgM- and 10 IgG-secreting synovial-derived hybridomas. The VH4 gene family is highly represented (38.5%) in this panel of hybridomas compared with the frequency of VH4 gene expression in circulating B lymphocytes reported previously (19-22%) and with the VH4 gene frequency we observed in a panel of hybridomas derived in the same manner from the spleen and tonsil of normal individuals (19%). The increased frequency of VH4 gene expression was not due to the expansion of a single B cell clone in vivo as none of these hybridomas was clonally related. Two synovial-derived hybridomas secreted autoantibodies; one (VH3+) secreted an IgM-rheumatoid factor (RF) and the other (VH4+) secreted IgM with polyreactive binding to cytoskeletal proteins and cardiolipin. The antibodies secreted by the remaining synovial-derived hybridomas were not reactive with the autoantigens tested. The VH gene usage in a proportion (5/17) of synovial-derived hybridomas that expressed CD5 antigen provided preliminary evidence that CD5+ B cells in RA synovium have a similar increase of VH4 gene expression reported for CD5+ B cells from normal individuals and patients with chronic lymphocytic leukaemia.     

Autoantibodies to GPI in rheumatoid arthritis: linkage between an animal model and human disease

In K/BxN T cell receptor-transgenic mice, spontaneous inflammatory arthritis exhibiting many of the features of human rheumatoid arthritis (RA) is initiated by T cells, but is almost entirely sustained by antibodies to the self-antigen glucose-6-phosphate isomerase (GPI). The relevance of these observations to human disease has been questioned. Here we show that 64% of humans with RA, but not controls, had increased concentrations of anti-GPI immunoglobulin G (IgG) in serum and synovial fluid. In addition, the concentrations of soluble GPI in the sera and synovial fluids of RA patients were also elevated, which led to immune complex formation. Using phage-display methods, we cloned a panel of specific high-affinity human monoclonal anti-GPI IgGs from a patient with RA. These antibodies were highly somatically mutated, which was indicative of an affinity-matured response that was antigen driven. Immunohistochemistry of RA synovium showed high concentrations of GPI on the surface of the synovial lining and on the endothelial cell surface of arterioles; this indicated a mechanism by which antibodies to GPI may precipitate joint disease. The results indicate that the immunological events that lead to the development of autoimmune disease in the K/BxN mouse model may also occur in human RA. This data may be used to develop new strategies for therapeutic intervention.     

The exploration of joint-specific immunoreactions on immunoglobulins G of anti-glucose-6-phosphate isomerase antibody-positive patients with rheumatoid arthritis

The pathogenic role of autoantibodies in rheumatoid arthritis (RA) remains elusive. Anti-glucose-6-phosphate isomerase (GPI) antibodies (Abs) are candidates for arthritogenic Abs because they directly induce arthritis in mice. High titers of anti-GPI Abs are found in some RA patients with severe forms. The aim of this study was to analyze the role of IgG, including anti-GPI Abs, in the joints of RA patients. Synovial tissue was obtained from 6 patients with RA (3 anti-GPI Abs- positive and 3 anti-GPI Abs- negative) and compared histologically and immunohistochemically for IgG and C3 deposition. IgG fractions were separated from the sera of anti-GPI Abs-positive RA patients and healthy subjects, and injected into the metacarpophalangeal joints of 4 cynomolgus monkeys. On day 16, the joints were harvested and examined histologically and immunohistochemically. The expression of the C5a receptor (C5aR) molecule in the synovium was quantified by real-time PCR using cDNA from the monkeys' joints. The synovia of anti-GPI Abs-positive RA patients showed diffuse infiltration of cells, including mast cells, and strong deposition of IgG and C3. In monkeys, IgG from RA patients, including anti-GPI Abs, resulted in recruitment of granulocytes and mononuclear cells, strong deposition of IgG on the articular surface, and overexpression of C5aR, but no joint swelling. No infiltrated cells or IgG deposition were observed in monkeys injected with IgGs from healthy subjects. Our results suggest that IgG fraction from RA patients, including that of anti-GPI Abs, may play a role in the synovitis of RA, although the pathogenesis of human anti-GPI Abs is still uncertain.     

Proliferating Cells in the Synovial Fluid in Rheumatic Disease

The subtype of the proliferating cells in the synovial fluid of patients with rheumatoid arthritis (RA), ankylopoietic spondylarthrosis (SPA), and osteoarthritis (OA) was studied with autoradiography-immunoperoxidase double staining. Of all spontaneously proliferating synovial fluid cells in chronic arthritis, 59 +/- 4% displayed T8 differentiation marker, whereas T4 (21 +/- 4%) and B (2 +/- 1%) cells were few. Of all T4+ and all T8+ lymphocytes, 0.55 +/- 0.1% and 0.90 +/- 0.1%, respectively, incorporated [3H]thymidine. The [3H]thymidine labelling index for B cells was 0.30 +/- 0.1%. This was in contrast to OA, in which no proliferating lymphocytes were observed in the synovial fluid. Our findings suggest that the predominance of proliferating T8+ cells in the synovial fluid reflects an underlying chronic inflammation. Because RA and SPA synovium is a site of intense immunoglobulin production, our finding of the predominance of activated, proliferating T8+ cells may also reflect a dissociation between phenotype and function as a reason for the chronicity of the joint inflammation.     

Usefulness of serum S100B as a marker for the acute phase of aquaporin-4 autoimmune syndrome

The aquaporin-4 (AQP4) water channel antibody is used in the diagnosis of neuromyelitis optica (NMO) due to its high sensitivity and high specificity. However, some patients are reported to have neither optic neuritis nor myelitis despite being positive for the AQP4-autoantibody (AQP4-Ab). Therefore, recent reports suggest that such patients should be diagnosed as having 'AQP4-autoimmune syndrome'. In this study, we quantified the levels of glial fibrillar acidic protein (GFAP) and S100B by enzyme-linked immunosorbent assay (ELISA) in CSF and serum samples simultaneously obtained in the acute phase of ten AQP4-autoantibody (AQP4Ab)-positive and seven AQP4Ab-negative patients. Serum levels of S100B were significantly higher in the acute phase of the AQP4Ab-positive patients (2.92±1.22pg/ml) than in the AQP4Ab-negative patients (0.559±0.180pg/ml, p=0.0250), while serum levels of GFAP were not different between the two groups (AQP4Ab-positive vs. AQP4Ab-negative: 0.120±0.113ng/ml vs. 0.00609±0.00609ng/ml, p=0.193). Furthermore, the CSF and serum levels of S100B had a significant positive correlation in AQP4Ab-positive patients (n=10, r=0.673, p=0.0390). Our results raise the possibility that serum levels of S100B, but not GFAP, examined in the acute phase of the disease might be a useful biomarker for the relapse of AQP4 autoimmune syndrome.     

Immunoglobulin G from anti-glucose-6-phosphate isomerase antibodies positive patient with rheumatoid arthritis induces synovitis in cynomolgus monkeys

Anti-glucose-6-phosphate isomerase (GPI) antibodies (Abs) solely induce arthritis in mice. High titers of anti-GPI Abs are found in some patients with rheumatoid arthritis (RA), but their pathogenic role remains elusive. The aim of this study was to evaluate the pathogenic role of anti-GPI Abs in cynomolgus monkeys. IgG fractions were separated from sera of anti-GPI Abs-positive RA patients and healthy subjects and directly injected into the metacarpophalangeal joints of 4 cynomolgus monkeys. At day 16, the joints were harvested and examined histologically and immunohistochemically. The expression of C5a receptor (C5aR) molecule in the synovium was quantified by real-time PCR using cDNA from monkey joints. In monkey joints, IgG including anti-GPI Abs resulted in recruitment of granulocytes and mononuclear cells, strong deposition of human IgG on the articular surface, and overexpression of C5aR, but no joint swelling. No infiltrated cells or IgG deposition were observed in monkeys injected with IgGs from healthy subjects. Our results suggest that IgG fraction from RA patients including anti-GPI Abs may play a crucial role in the generation of synovitis in monkeys, although the pathogenesis of anti-GPI Abs in RA patients is still uncertain.     

T cell immunophenotypes and DR antigen expression in intravenous drug users. Relationship to human immunodeficiency virus serology

Thirty-six intravenous drug users were studied for peripheral blood mononuclear cell (PBMC) immunophenotypes and human immunodeficiency virus (HIV) serological profiles. This population has a high risk for developing HIV infection. Half (18/36) were HIV antibody (Ab) negative (-) and half were positive (+). Total T lymphocytes (CD3+ and CD2+) were not different between HIV Ab-negative and HIV-positive groups. Unactivated T(CD3+DR-) cells/mm3 were less (p = 0.003) in HIV Ab-positive patients (1,467 +/- 628) compared to HIV Ab-negative patients (2,190 +/- 695). T-helper (CD4+) cells/mm3 were also less in HIV Ab-positive patients (762 +/- 344 vs. 1,161 +/- 419, p = 0.005). The most significant difference was in activated T lymphocyte CD3+DR+) percentages where the mean was 9.6% in those HIV Ab-positive compared to 3.8% in seronegatives (p less than 0.001). Preliminary studies showed that in vitro naloxone treatment of PBMC had no effects on immunophenotypic expression except for CD3+DR+ lymphocytes, where a significant reduction was observed in the HIV Ab-positive group (p = 0.022) but not in the HIV ab-negative group. These findings suggest that in certain populations, activated T cells may be an early manifestation of HIV infection.     

Autoantibody production by severe combined immunodeficient mice reconstituted with synovial cells from rheumatoid arthritis patients

In an attempt to characterize the heterogeneity of the human autoantibody response, mice with severe combined immunodeficiency were reconstituted with synovial or blood lymphocytes from patients with rheumatoid arthritis (RA). Mononuclear cells extracted from synovial fluid or tissue (SMC) were a greatly enriched source of IgM rheumatoid factor (RF)-producing cells compared to the peripheral blood mononuclear cells (PBMC) of rheumatoid arthritis patients or normal donors. Six to nine weeks after reconstitution of mice with synovial mononuclear cells, 0%-39.3% (mean = 11.4%) of total IgM consisted of IgM RF compared to 0%-0.15% (mean = 0.02%) in mice given RA PBMC and 0%-1.2% (mean = 0.34%) in mice given normal PBMC. Detectable levels of IgM RF were maintained in some mice for as long as 20 weeks after transfer. Mice reconstituted with synovial membrane or synovial fluid lymphocytes produced a heterogeneous mixture of immunoglobulins. These included other autoantibodies, such as anti-nuclear and anti-cytoplasmic antibodies, and antibodies to exogenous antigens such as the Epstein-Barr virus nuclear antigen-1 (EBNA-1). This heterogeneity is further illustrated by the demonstration that the sera from mice given synovial cells also contained IgG antibodies possessing all three major VH families (VH1, VH3 and VH4) and the four major V kappa families (V kappa 1 to V kappa 4). Autoantibody production gradually decreased with time even under circumstances where total immunoglobulin levels increased, and elevated production could not be induced by antigenic stimulation. These findings describe a new model for the analysis of human autoantibody production.     

IL-38 抑制LPS / TLR4 诱导炎症减轻类风湿关节炎的机制研究

目的:探讨IL-38 和TLR4 在类风湿关节炎中的潜在关联及其在类风湿性关节炎中致病的机制。方法:选取2013 年1 月至2016 年2 月间本院收治的41 例类风湿关节炎患者(观察组)及45 例本院实施创伤后滑膜切除术的患者(对照组)为研究对象。收集观察组和对照组的外周血单个核细胞(PBMCs)、滑膜组织及血清。荧光定量PCR 检测PBMCs 及滑膜组织中IL-38 及TLR4 的mRNA 水平。ELISA 检测滑膜液及血清中IL-38 的表达,Western blot 检测滑膜组织中IL-38 及TLR4的表达。LPS 和/ 或IL-38 刺激RAW264.7 细胞,ELISA 检测RAW264.7 细胞上清中IL-6、IL-8 及TNF-α的含量,荧光定量PCR检测RAW264.7 细胞TLR4、IL-6、IL-8 及TNF-α的表达。NF-κB 激活-核转运试剂盒及Western blot 检测NF-κB 信号的激活水平。结果:与对照组相比,类风湿关节炎患者PBMCs、血清及滑膜组织和滑膜液中IL-38 水平显著升高,而TLR4 水平也显著升高,Pearson 相关分析显示二者呈负相关。LPS 和/ 或IL-38 刺激RAW264.7 细胞后,IL-38 能够抑制LPS 诱导的TLR4、IL-6、IL-8 及TNF-α表达,进一步的分析显示,IL-38 能抑制NF-κB 信号途径激活,因此推测IL-38 可能是通过抑制NF-κB 信号途径激活从而抑制LPS/ TLR4 信号诱导的炎症因子表达。结论:IL-38 能抑制LPS/ TLR4 诱导炎症减轻类风湿关节炎,其机制可能是通过抑制NF-κB 信号途径的激活。     

Analysis of the immunoglobulin heavy chain gene variable region of intravascular large B-cell lymphoma

Intravascular large B-cell lymphoma (IVLBL) is a rare neoplasm characterized by proliferation of lymphoma cells within the blood vessels. The cell origin of IVLBL has not yet been determined. We examined cell lineage, with immunohistochemical staining and molecular analysis, using polymerase chain reaction (PCR) of the variable region of the immunoglobulin heavy chain (Ig-VH) gene. We also investigated the cell origin using direct sequence analysis of the complementary-determining region 2 (CDR2) and framework region 3 (FR3) in six cases, consisting of two male and four female patients. The sequences in five cases showed frequent mutations. The percent homology to their closest germline genes ranged from 74.7 to 91.8%. However, one case showed a percent homology of 99.4% in CDR2 and FR3 of Ig-VH. All cases showed rearrangements of VH3 family genes. Interestingly, three of the IVLBL cases with hypermutated IgH genes showed the expression of CD5. Therefore, expression of CD5 in lymphoma cells does not indicate that the origin of IVLBL is the same as mantle cell lymphoma having the character of CD5 expression, which develops in pre-germinal center cells. Our results indicate that most IVLBLs may originate in the post-germinal center cells, based on the presence of somatic mutation in VH genes, although some heterogeneous cases are intermingled within IVLBL.     

Rheumatoid arthritis synovial macrophage-osteoclast differentiation is osteoprotegerin ligand-dependent

Osteoprotegerin ligand (OPGL) is a newly discovered molecule which is essential for osteoclast differentiation. Both OPGL and its soluble decoy receptor, osteoprotegerin (OPG), which inhibits osteoclast formation, are known to be produced by osteoblasts and inflammatory cells found in the rheumatoid arthritis (RA) synovium. In this study, RA synovial macrophages were incubated in the presence or absence of OPGL, macrophage-colony stimulating factor (M-CSF), and dexamethasone for various time points. The results indicated that osteoclast formation from RA synovial macrophages is OPGL-dependent and that OPGL and M-CSF are the only humoral factors required for RA synovial macrophage-osteoclast differentiation. OPG was found to inhibit osteoclast formation by RA synovial macrophages in a dose-dependent manner. This study has shown that macrophages isolated from the synovium of RA patients are capable of differentiating into osteoclastic bone-resorbing cells; this process is OPGL- and M-CSF-dependent and is modulated by corticosteroids. Cellular (T and B cells, dendritic cells) and humoral factors in RA synovium and bone may influence osteoclast formation and bone resorption by controlling OPGL/OPG production.     

IL-17 increases cadherin-11 expression in a model of autoimmune experimental arthritis and in rheumatoid arthritis

IL-17 plays important roles in synovial inflammation and bone destruction in the mouse model of autoimmune arthritis and in rheumatoid arthritis (RA). Cadherin-11 determines the behavior of synovial cells in their proinflammatory and destructive tissue response in inflammatory arthritis, and promotes the invasive behavior of fibroblast-like synoviocytes (FLS). The purpose of this study was to examine the effect of IL-17 on the expression of cadherin-11 in autoimmune experimental arthritis and in RA synovium. The severity of synovial inflammation and bone destruction were examined in IL-17-injected knee joints of mice with collagen-induced arthritis (CIA). Cadherin-11 expression was examined in the synovium of mice with CIA, of IL-1 receptor antagonist (IL-1Ra)-deficient mice and of patients with RA and osteoarthritis (OA). Cadherin-11 expression was also examined in the synovium of IL-17 injected knee joints from CIA mice and in IL-17-stimulated FLS of CIA mice and RA patients. IL-17 aggravated synovial inflammation and bone destruction in CIA. By immunohistochemistry, cadherin-11 expression was increased in the synovium of mice with CIA and IL-1Ra-deficient mice and in patients with RA. Synovial cadherin-11 expression in IL-17-injected knee joints, measured by real-time RT-PCR, Western blot and immunohistochemistry, was increased in CIA. Cadherin-11 expression was significantly increased by IL-17 in cultured FLS of CIA mice and RA patients, and these increases were blocked by NF-κB inhibitors. IL-17 increased the expression of cadherin-11 in vivo and in vitro, which implies that an IL-17-induced increase of cadherin-11 is involved in IL-17-induced aggravation of joint destruction and inflammation.     

CD4+ T-cell-mediated cytotoxicity against staphylococcal enterotoxin B-pulsed synovial cells.

Apoptosis of synovial cells in rheumatoid arthritis (RA) synovium determined in vivo is suggested to counteract the overgrowth of synovium. Immunohistological examination has revealed the infiltration of activated CD4+ T cells, which express Fas ligand (FasL), in RA synovium. The presence of a putative antigen (Ag) of autoimmune disorders in a target organ may induce the activation of specific T cells in the inflammatory region such as RA synovium. We examined the possible role of CD4+ T cells activated by synovial cells in a staphylococcal enterotoxin B (SEB)-dependent manner, inducing synovial cell apoptosis. Synovial cells were cultured with or without interferon-gamma (IFN-gamma) and further incubated with CD4+ T cells in the presence of SEB. After the cocultivation, both the cytotoxicity and FasL expression of CD4+ T cells were investigated. Constitutive Fas expression was detected on both unstimulated and IFN-gamma-stimulated synovial cells. CD4+ T cells did not kill SEB-pulsed unstimulated synovial cells efficiently. In contrast, when CD4+ T cells were incubated with IFN-gamma-stimulated synovial cells with SEB whose human leucocyte antigen (HLA)-DR and -DQ expression was markedly induced, significant cytotoxicity by these cells against synovial cells was detected. The addition of anti-HLA-DR and -DQ monoclonal antibodies (mAbs) or human Fas chimeric protein (hFas-Fc) reduced this cytotoxicity. FasL expression of CD4+ T cells cocultured with IFN-gamma-stimulated synovial cells with SEB was significantly induced. Furthermore, the addition of mAbs against CD54, CD58 and CD106 inhibited both the cytotoxicity and FasL expression of CD4+ T cells induced by IFN-gamma-stimulated synovial cells in the presence of SEB, indicating the importance of costimulatory molecules on synovial cells in activating CD4+ T cells. Our results suggest that CD4+ T cells are activated by synovial cells by an SEB-dependent manner and express FasL, inducing Fas-mediated apoptosis of the latter cells. These phenomena may regulate the overgrowth of synovial cells in RA synovium.     

B7-H3在类风湿关节炎患者滑膜组织内的表达及分布研究

探讨B7家族共刺激分子B7-H3在类风湿关节炎(RA)患者滑膜组织内的表达及分布。方法:使用免疫组化法检测RA患者滑膜组织B7-H3的表达,并使用免疫荧光法检测B7-H3在细胞中的定位及分布。结果:免疫组化结果证实,RA患者滑膜组织中有大量的B7-H3阳性细胞,形态观察提示这些阳性的细胞主要为毛细血管细胞、滑膜细胞、局部淋巴结处的T细胞及巨噬细胞;免疫荧光分析进一步表明这些B7-H3+细胞主要为CD68+巨噬细胞,CD31+内皮细胞及CK-18+上皮细胞。此外,对比其他B7家族共刺激分子在滑膜组织中的分布,免疫荧光发现B7-H3共表达于B7-DC+及HVEM+血管,但不表达于B7-H1+及B7-H4+细胞。类风湿关节炎滑膜组织内有大量B7-H3阳性细胞,提示B7-H3有可能参与并调节关节炎的病理进程。     

Characterization of human hybridoma clones isolated from hemophilia patients with specificity for different domains of coagulating factor VIII

Hemophilia A patients treated with human coagulating factor VIII (FVIII) may develop inhibitory antibodies (inhibitors). Characterization of the inhibitors at the clonal level may help exploring new therapeutic strategies. We have generated lymphoblastoid cell lines (LCLs) producing anti-FVIII antibodies from peripheral blood lymphocytes of hemophilia A patients with high inhibitor titers. We fused the anti-FVIII-positive LCLs with a heteromyeloma, to produce FVIII specific hybridomas. We determined the specificity, isotype, idiotypic and immunoglobulin (Ig) variable region heavy (VH) chain gene family profiles of the secreted antibodies (Ab) by ELISA, immunoblotting and RT-PCR. We established eight hybridomas which produced high titers of anti-FVIII Ab. All hybridomas secreted IgM Ab, associated with either kappa(5/8) or lambda(3/8) light chain. Analysis of the expressed VH genes by RT-PCR revealed that the hybridomas utilized only the VH1 (63%) or the VH3 (37%) gene families. Among the cross-reactive idiotypes (CRIs) we tested, only the VH1 and VK3b-associated CRIs were expressed by 3 hybridomas. Immunoblotting of thrombin-digested FVIII demonstrated distinct patterns of reactivity of the monoclonal Ab (MAb) secreted by the hybridomas, which recognized either the A2 domain of the Fvm heavy chain, or the light chain, or both. Our findings suggest that: a) the isotype of the anti-FVIII Ab secreted by LCLs and hybridoma clones (IgM) differs from that of anti-FVIII Ab in vivo, which are predominantly IgG4: this suggests a negative selection of the isotype-switched FVIII-specific B-cells in the periphery of these patients; b) the anti-FVIII Ab have a biased representation of the VH1 gene family, and c) somatic mutations in the VH genes coding for FVIII specificity occur in the anti-FVIII Ab response, as evidenced by lack of expression of the VH-associated CRI.     

Expansion of a unique macrophage subset in rheumatoid arthritis synovial lining layer

The Z39Ig protein (complement receptor for C3b and iC3b) is expressed on resident tissue macrophages in various tissues. This study was undertaken to examine the distribution of Z39Ig+cells and their phenotypic features in rheumatoid arthritis (RA) synovium, in comparison with those of osteoarthritis (OA) and psoriatic arthritis (PsA) synovium. Monoclonal anti-Z39Ig antibody was produced by immunizing Z39Ig transfected murine pre B cells and used for the identification of Z39Ig+cells. Z39Ig+cells were further stained with antibodies to macrophages, fibroblast-like synoviocytes, complement receptors and dendritic cells by using the double immunostaining method in normal, RA, OA and PsA synovium. RA synovial mononuclear cells were double-stained using anti-Z39Ig and anti-CD11c antibodies and sorted into Z39Ig+CD11c+cells and Z39Ig+CD11c-cells. These cell populations were then analysed by electron microscopy. The expression of the Z39Ig protein was limited to intimal macrophages in normal, RA, OA and PsA synovium. The numbers of Z39Ig+CD11c+cells and the ratios of Z39Ig+CD11c+cells to Z39Ig+cells were increased in the synovial lining layer of RA as compared with those of OA and PsA. The ultrastructural analysis of Z39Ig+CD11c+cells showed the character of macrophages with many secondary lysosomes and swelling of mitochondria. Z39Ig+ cells appeared to be useful for identification of resident tissue macrophages in normal synovium and the corresponding macrophages in the synovial lining layer of inflammatory arthritis. Expansion of Z39Ig+CD11c+cells was characteristic of RA synovial lining layer.     

Morphological and molecular pathology of the B cell response in synovitis of rheumatoid arthritis

The synovitis of rheumatoid arthritis (RA) was long regarded merely as an unspecific chronic inflammatory process of minor diagnostic value and therefore did not play a major role in the understanding of the pathogenesis of RA. It is only in recent years, along with the observation that T and B cells are expanded oligoclonally in synovial tissue and that B cells are able to undergo a local germinal center (GC) reaction, that the synovial tissue has come to be regarded as a site of specific immune processes. The analysis of the immunoglobulin (Ig) gene repertoire had great impact on the understanding of B cell response in lymphatic organs and was subsequently applied to B cells from RA patients. The analyses of the variable (V) regions of the Ig heavy (H) and light (lambda) chains suggested that an antigen specific activation and differentiation of B cells into plasma cells (Plc) takes place in the chronically inflamed synovial tissue of patients with RA. It seems that in a subset of RA patients the synovial tissue develops into an ectopic lymphoid tissue that supports a local GC reaction. Ectopic GC are characteristic of RA; however, they are in general absent from synovitis of osteoarthritis (OA). Here the accumulation of Plc follows a different mechanism. Highly mutated VH genes suggest that in OA memory B cells migrate into the synovial tissue with subsequent differentiation into Plc but without further V gene diversification. Therefore in synovitis two patterns of B cell activation can be differentiated: the maturative and the accumulative type. These two patterns are not definitely disease linked. The maturative type is only found in RA whereas the accumulative type occurs in both diseases. Clinically RA is defined via serum antibodies to the constant region of Ig, so-called rheumatoid factor. However, the spectrum of autoreactive B cells in RA patients is wide and is based on the study of antibody specificities in serum, in synovial fluid and B cell lines derived from peripheral blood, bone marrow, synovial fluid and synovial tissue. These analyses defined non-organ-specific and organ-specific antigens. One can reasonably assume that the disease is far too complex to be explained by only a single antigen. There is a whole combination of antigens acting in a multistep manner that is responsible for RA pathogenesis. It can be hypothesized that chronic synovitis, which is the underlying mechanism of joint destruction, follows a three-step process: (a) initiation, (b) destruction, and (c) perpetuation. The characterization of antigens driving the local synovial B cell maturation and accumulation could lead to an understanding of the process perpetuating the disease. Identification of arthritogenic antigens may yield new avenues for diagnostics and immunotherapy but also a new approach for prevention by vaccines with antigens probably defined by synovial B cell reactivity.