Production of nitric oxide in the synovial membrane of rheumatoid and osteoarthritis patients

We have demonstrated spontaneous nitric oxide (NO) production by primary synovial cultures from rheumatoid (RA) and osteoarthritis patients. Increased NO production followed addition of staphylococcal enterotoxin B. Immunochemical double staining with specific anti-human inducible NO synthase (iNOS) and nonspecific esterase (NSE), or anti- CD68 (markers for tissue macrophages) showed that although many lining layer cells in RA synovium expressed iNOS, most (approximately 90%) were NSE- and CD68-, with only a minor population (approximately 10%) which were iNOS+, CD68+/NSE+. These data demonstrate the capacity for high output of NO by human synovial tissue and show that, although human macrophages can express high levels of iNOS, the majority of cells expressing iNOS are fibroblasts. We also report that synoviocytes, and macrophage cell lines, cultured with the NO donor, S- nitroso-acetyl penicillamine, produced high concentrations of tumor necrosis factor (TNF)-alpha. These results suggest that NO may mediate pathology in RA through the induction of TNF-alpha production.     

类风湿性关节炎患者关节滑膜组织蛋白质组学

背景:已有研究表明滑膜炎持久反复发作,最终导致关节内软骨和骨的破坏,国内关于类风湿性关节炎滑膜组织的蛋白质组学研究报道较少。目的:通过比较类风湿性关节炎患者和无关节滑膜损伤患者滑膜组织蛋白质表达的差异,探讨类风湿性关节炎可能的发病机制,寻找类风湿性关节炎致病相关蛋白。方法:选取6例无关节滑膜损伤患者及6例活动期类风湿性关节炎患者行关节镜手术得到的滑膜组织,提取总蛋白质后进行双向凝胶电泳,考马斯亮蓝染色,PDQUEST软件分析,对差异蛋白质点采用基质辅助激光解析电离质谱(MALDI-TOF-MS)技术进行鉴定,并用Mascot软件在SwissProt和NCBInr数据库中进行同源比较和分析鉴定。结果与结论:建立了类风湿性关节炎组及对照组滑膜组织双向凝胶电泳图谱,获得130个差异在2倍以上的蛋白质点数,选取其中分辨清楚的39个点进行鉴定,初步鉴定出29个蛋白质,其中21个蛋白质点在类风湿性关节炎组中表达上调,8个表达下调,其功能涉及功能代谢、细胞信号传导、抗氧化、分子伴侣等。结果表明类风湿关节炎滑膜病变是一个多种蛋白质参与的复杂过程,这些表达差异蛋白质可能是类风湿性关节炎发病的内在因素。     

Synovium as a source of increased amino-terminal parathyroid hormone-related protein expression in rheumatoid arthritis. A possible role for locally produced parathyroid hormone-related protein in the pathogenesis of rheumatoid arthritis.

Proinflammatory cytokines, including tumor necrosis factor (TNF) and interleukin 1 (IL-1), mediate the joint destruction that characterizes rheumatoid arthritis (RA). Previous studies have shown that parathyroid hormone-related protein (PTHrP) is a member of the cascade of proinflammatory cytokines induced in parenchymal organs during lethal endotoxemia. To test the hypothesis that NH2-terminal PTHrP, a potent bone resorbing agent, could also be a member of the synovial cascade of tissue-destructive cytokines whose expression is induced in RA, PTHrP expression was examined in synovium and synoviocytes obtained from patients with RA and osteoarthritis (OA). PTHrP production, as determined by measurement of immunoreactive PTHrP(1-86) in tissue explant supernatants, was increased 10-fold in RA versus OA synovial tissue. Synovial lining cells and fibroblast-like cells within the pannus expressed both PTHrP and the PTH/PTHrP receptor, findings that were confirmed by in vitro studies of cultured synoviocytes. TNF-alpha and IL-1beta stimulated PTHrP expression in synoviocytes, while dexamethasone and interferon-gamma, agents with some therapeutic efficacy in the treatment of RA, inhibited PTHrP release. Treatment of synoviocytes with PTHrP(1-34) stimulated IL-6 secretion. These results suggest that proinflammatory cytokine-stimulated production of NH2-terminal PTHrP by synovial tissue directly invading cartilage and bone in RA may mediate joint destruction through direct effects on cartilage or bone, or, indirectly, via the induction of mediators of bone resorption in the tumor-like synovium.     

Intra-articular adenoviral-mediated gene transfer of trail induces apoptosis of arthritic rabbit synovium

Rheumatoid arthritis (RA) is an inflammatory autoimmune disease that primarily affects joints. In rheumatoid joints there is extensive synovial proliferation with diseased synovium becoming highly aggressive, attaching to the articular cartilage and bone to form what is termed a pannus. The formation of active pannus is central to erosive disease and resulting joint destruction. In this study, we examined the ability to eliminate the hyperplastic synovium by adenoviral-mediated gene transfer of human TNF-related apoptosis-inducing ligand (TRAIL), a member of the TNF family that is able to induce apoptosis through interaction with receptors containing death domains, DR4 and DR5. Infection of synovial cells derived from RA patients with Ad.TRAIL resulted in significant apoptosis in three out of five lines. Moreover, primary rabbit synovial fibroblasts were also sensitive to Ad.TRAIL-mediated gene transfer. In a rabbit model of arthritis, intra-articular gene transfer of TRAIL induced apoptosis in cells within the synovial lining, reduced leukocytic infiltration and stimulated new matrix synthesis by cartilage. These results demonstrate that TRAIL can affect the viability of the cells populating the activated synovium in arthritic joints and suggest that the delivery of TRAIL to arthritic joints may represent a non-invasive mechanism for inducing pannus regression.     

A novel spleen tyrosine kinase inhibitor blocks c-Jun N-terminal kinase-mediated gene expression in synoviocytes

Spleen tyrosine kinase (Syk) is a key regulator of cell signaling induced by cytokines or Fc receptor engagement. However, the role of Syk in rheumatoid arthritis (RA) is not known yet. We investigated the pathways activated by Syk in tumor necrosis factor-alpha (TNFalpha)-stimulated fibroblast-like synoviocytes (FLS) using the novel Syk inhibitor N4-(2,2-dimethyl-3-oxo-4H-pyrid[1,4]oxazin-6-yl)-5-fluoro-N2-(3,4,5-trimethoxyphenyl)-2,4-pyrimidinediamine (R406). Using immunohistochemistry, Syk was detected in RA synovial tissue (ST), primarily in the synovial intimal lining. Western blot analysis demonstrated significantly greater amounts of phospho-Syk expression in RA ST compared with osteoarthritis ST. The kinase was expressed and functionally activated by TNFalpha in FLS and was blocked by R406. Western blot analysis demonstrated that Syk inhibition by R406 markedly suppressed TNFalpha-induced c-Jun N-terminal kinase (JNK) phosphorylation in FLS, with a modest decrease in extracellular signal-regulated kinase phosphorylation. Surprisingly, p38 activation was not affected by R406. The Syk inhibitor also decreased TNFalpha-induced mitogen-activated protein kinase kinase (MKK) 4 phosphorylation but not MKK3 and MKK6 phosphorylation, which is consistent with its selective sparing of p38. The connection between Syk and JNK was confirmed by demonstrating decreased phospho-c-Jun protein expression and complete inhibition of JNK function in R406-treated cells. R406 also suppressed downstream actions of JNK, as determined by activator protein 1 binding, as well as matrix metalloproteinase 3 gene expression. These data demonstrate that Syk activation plays an essential role in TNFalpha-induced cytokine and matrix metalloproteinase production in RA FLS, especially by suppressing activation of the JNK pathway.     

Expression and functional significance of alternatively spliced CS1 fibronectin in rheumatoid arthritis microvasculature.

Expression of fibronectin (FN) isoforms containing CS1, a 25-amino acid sequence present within the alternatively spliced IIICS region of FN, has been analyzed in rheumatoid arthritis (RA) synovium. Unexpectedly, CS1-containing FN variants were exclusively found on endothelium but not extracellular matrix (ECM) of RA synovium. Lumenal expression of CS1 on RA endothelial cells, as observed by electron microscopy, correlated with inflammation in RA, since normal synovium expressed little CS1 without appreciable decrease in ECM FN. CS1 expression on human endothelial cells was further shown by FN mRNA analyses. In adhesion assays on frozen RA synovial sections, T lymphoblastoid cells expressing functionally activated alpha 4 beta 1 integrin specifically attached to the intravascular surface of RA endothelium. Binding was abrogated by both anti-alpha 4 integrin and CS1 peptides. Our observations suggest direct involvement of CS1-containing FN in recruitment of alpha 4 beta 1-expressing mononuclear leukocytes in synovitis, and provide basis for therapeutic intervention in RA.     

Nitric oxide production and inducible nitric oxide synthase expression in inflammatory arthritides.

In this study, we have identified the source of nitric oxide (NO) produced in the human inflammatory joints by analyzing expression of inducible NO synthase. In ex vivo organ cultures, both inflammatory synovium and cartilage from patients with rheumatoid arthritis produced NO. The NO production was suppressed by NG-monomethyl-L-arginine, an inhibitor of NO synthase. The amount of NO produced by the synovium correlated with the proportion of CD14+ cells in the corresponding tissue (r = 0.8, P < 0.05). Immunohistochemical analysis as well as in situ hybridization showed that inducible NO synthase was predominantly expressed in synovial lining cells, endothelial cells, chondrocytes, and to a lesser extent, in infiltrating mononuclear cells and synovial fibroblasts. The synovial lining cells and the infiltrating cells expressing inducible NO synthase were identified where CD14+ cells were located. Together with morphological features, this suggests that they are type A synoviocytes. NO production from freshly isolated synoviocytes and chondrocytes was up-regulated by in vitro stimulation with a combination of IL-TNF-beta, TNF-alpha, and LPS. In summary, the present results suggest that NO is produced primarily by CD14+ synoviocytes, chondrocytes, and endothelial cells in inflammatory joints of arthritides. NO production can be upregulated by cytokines present in inflamed joints. The increased NO production may thus contribute to the pathological features in inflammatory arthritides.     

Apoptosis in rheumatoid arthritis synovium.

RA synovial tissue (ST) was studied to determine if and where apoptosis occurs in situ. Genomic DNA was extracted from 5 RA and 1 osteoarthritis ST samples. Agarose gel electrophoresis demonstrated DNA ladders characteristic for apoptosis from each tissue. In situ and labeling (ISEL) was used to identify DNA strand breaks consistent with apoptosis in frozen sections. 12 RA and 4 osteoarthritis ST were studied by ISEL and all were positive, but only 2 of 4 normal tissues were positive. The primary location of apopotic cells was the synovial lining. Some sublining cells were also positive, but lymphoid aggregate staining was conspicuously absent. Immunohistochemistry and ISEL were combined and showed that the lining cells with DNA strand breaks were mainly macrophages, although some fibroblastlike cells were also labeled. Sublining cells with fragmented DNA included macrophages and fibroblasts, but T cells in lymphoid aggregates, which expressed large amounts of bcl-2, were spared. DNA strand breaks in cultured fibroblastlike synoviocytes was assessed using ISEL. Apoptosis could be induced by actinomycin D, anti-fas antibody, IL-1, and TNF-alpha but not by IFN-gamma. Fas expression was also detected on fibroblast-like synoviocytes using flow cytometry. Therefore, DNA strand breaks occur in synovium of patients with arthritis. Cytokines regulate this process, and the cytokine profile in RA (high IL-1/TNF; low IFN-gamma) along with local oxidant injury might favor induction of apoptosis.     

Enhanced production of monocyte chemoattractant protein-1 in rheumatoid arthritis.

Cells within the synovial tissue may recruit mononuclear phagocytes into the synovial fluid and tissues of arthritic patients. We investigated the production of the chemotactic cytokine monocyte chemoattractant protein-1 (MCP-1) using sera, synovial fluid, synovial tissue, as well as macrophages and fibroblasts isolated from synovial tissues from 80 arthritic patients. MCP-1 levels were significantly higher (P less than 0.05) in synovial fluid from RA patients (mean 25.5 +/- 8.1 ng/ml [SE]) compared to synovial fluid from osteoarthritis (OA) patients (0.92 +/- 0.08), or from patients with other arthritides (2.9 +/- 1.5). MCP-1 levels in RA sera (8.44 +/- 2.33) were significantly greater than MCP-1 in normal sera (0.16 +/- 0.06). The quantities of RA synovial fluid IL-8, which is chemotactic for neutrophils and lymphocytes, and MCP-1 were strongly positively correlated (P less than 0.05). To examine the cellular source of MCP-1, RA synovial tissue macrophages and fibroblasts were isolated. Synovial tissue fibroblasts did not express MCP-1 mRNA, but could be induced to produce MCP-1 by stimulation with either IL-1 beta, tumor necrosis factor-alpha (TNF-alpha), or LPS. In contrast, unlike normal peripheral blood monocytes or alveolar macrophages, RA synovial tissue macrophages constitutively expressed MCP-1 mRNA and antigen. Immunohistochemical analysis of synovial tissue showed that a significantly greater percentage of RA macrophages (50 +/- 8%) as compared to either OA macrophages (5 +/- 2) or normal macrophages (1 +/- 0.3) reacted with anti-MCP-1 antibodies. In addition, the synovial lining layer reacted with MCP-1 in both RA and OA synovial tissues. In contrast, only a minority of synovial fibroblasts (18 +/- 8%) from RA synovium were positive for immunolocalization of MCP-1. These results suggest that synovial production of MCP-1 may play an important role in the recruitment of mononuclear phagocytes during inflammation associated with RA and that synovial tissue macrophages are the dominant source of this cytokine.     

双向电泳和质谱技术在类风湿关节炎滑膜细胞差异蛋白分析中的应用及意义

目的 采用2-DE和质谱技术分析RA患者和创伤件关节炎患者关节滑膜组织中FLS蛋白质组学的变化,寻找RA关节滑膜特异性自身抗原.方法 采用2-DE分离6例创伤性关节炎患者及3例RA患者关节滑膜组织中FLS总蛋白质,凝胶经银染显色和图像数据分析识别差异蛋白质点,并用MALDI-TOF-MS对筛选出的差异蛋白质点进行鉴定.结果 RA患者与创伤性关节炎患者中的FLS蛋白质通过2-DE检测,分别检出1 633、1 603个蛋白质点;对2组相互匹配的蛋白质点进行差异分析后,其中蛋白质差异量大于3倍的差异点共有92个,从中选取在RA患者FLS中表达上调的33个差异蛋白质点进行MALDI-TOF-MS 鉴定分析,并与IPI和Swiss-Prot数据库进行比对,共鉴定出包括肿瘤型丙酮酸激酶、α-烯醇化酶、二硫键异构酶A3 前体、谷胱甘肽转移酶、泛素结合酶E2K、血小板活化因子乙酰水解酶、二氢嘧啶酶样2、腺苷酸酶、转醛醇酶、乙酰基辅酶A异构酶、26S蛋白调节亚单位S6a、膜联蛋白A11、过氧化物还原酶1、人色氨酰tRNA合成酶、核纤层蛋白、肌间蛋白、核基质蛋白、肌动蛋白、T-复合物多肽1、葡萄糖调节蛋白75、αB-晶体蛋白、葡萄糖调节蛋白78、未知蛋白:如PSMFA和SELENBP1等30个与RA发病有关的蛋白.结论 RA患者与创伤性关节炎患者FLS间存在差异表达的蛋白质,这些差异蛋白有可能是构成RA关节滑膜的相关自身抗原,并可能在诱导RA自身免疫反应中发挥一定作用.     

Rheumatoid arthritis synovial membrane contains a 62,000-molecular-weight protein that shares an antigenic epitope with the Epstein-Barr virus-encoded associated nuclear antigen.

A monoclonal antibody, selected for reactivity with the Epstein-Barr virus (EBV)-encoded antigen EBNA-1, exhibited strong reactivity with the synovial lining cells in joint biopsies from 10 of 12 patients with rheumatoid arthritis (RA) and adherent cells eluted from these tissues. No staining of RA synovial membrane frozen tissue sections or eluted synovial-lining cells was obtained with monoclonal antibodies directed against other EBV-encoded antigens (anti-p160, anti-gp200/350) or with monoclonal antibodies directed against antigens encoded by cytomegalovirus, herpes simplex viruses, or human T cell leukemia virus type I. Among 12 osteoarthritis and normal synovial biopsies only rare reactive cells were noted. Characterization of the antigen(s) in RA synovium by the Western immunoblotting technique revealed a 62,000-molecular-weight (mol-wt) protein, in contrast to the 70,000-85,000-mol-wt EBNA-1 antigen found in EBV-transformed cells. The structural basis for the cross-reactivity of the RA synovial membrane 62,000-mol-wt protein and the EBNA-1 antigen appears to reside in the glycine-alanine rich region of these molecules. A rabbit antibody directed against a synthetic peptide (IR3-VI-2) derived from the glycine-alanine-rich region of EBNA-1 reacted with the 70,000-85,000-mol-wt EBNA-1 antigen in EBV-infected cells and with the 62,000-mol-wt molecule in RA synovial membrane extracts. Since strong antibody responses to EBNA-1 are known to exist in RA patients, these results suggest that immune responses to a cross-reactive antigen may play a role in the pathogenesis of RA.     

Novel gene therapy for rheumatoid arthritis by FADD gene transfer: induction of apoptosis of rheumatoid synoviocytes but not chondrocytes

Synovial cells in the rheumatoid synovium show abnormal proliferation, leading to joint destruction. Rheumatoid synovial cells express functional Fas antigen and are susceptible to Fas-mediated apoptosis. We have proposed the induction of apoptosis by Fas/Fas ligand system of proliferative rheumatoid synovium as a novel therapy for rheumatoid arthritis (RA). We have recently reported that Fas-associated death domain protein (FADD) plays a key role in Fas-mediated apoptosis of synovial cells in patients with RA. In this study, we determined whether FADD gene transfer could induce apoptosis of RA synoviocytes in vitro and in vivo. Transfection of FADD gene by adenoviral vector into cultured RA synoviocytes induced up-regulation of FADD expression and apoptosis. In addition, local injection of FADD adenovirus (Ad-FADD) eliminated synoviocytes in vivo by induction of apoptosis of proliferating human rheumatoid synovium engrafted in severe combined immunodeficiency mouse, which is the most suitable animal model of RA for the evaluation of treatment strategy in vivo. In addition, Ad-FADD-induced apoptosis was limited to cells of the synovium tissue and did not affect chondrocytes. Our results strongly suggest that FADD gene transfer can induce apoptosis of RA synoviocytes both in vitro and in vivo, suggesting that FADD gene transfer might be effective in the treatment of RA.     

沙利度胺对类风湿关节炎滑膜成纤维样细胞影响的体外研究

目的研究沙利度胺(Thalidomide)对类风湿关节炎(RA)滑膜成纤维样细胞(FLS)体外培养时的增生殖分化特性的影响。方法关节镜、关节活检针取RA患者滑膜组织,分离培养和鉴定FLS,MTT法和反转录-聚合酶链反应(RT-PCR)方法观察沙利度胺对FLS细胞存活分数(SF)和c-fos、COX-2mRNA表达。结果RA-FLS体外培养呈良性增生。沙利度胺对RA-FLS的SF值的抑制作用最强(P<0.05)。生理剂量的沙利度胺干预时的浓度与FLS的SF值呈负相关。RA-FLS的c-fos、环氧化酶2(COX-2)mRNA表达率高,加入沙利度胺共孵育3天后c-fos和COX-2mRNA的表达率均明显下降。结论培养和鉴定RA滑膜细胞,证实体外培养传代的RA-FLS为非恶性无限制增生。实验剂量下沙利度胺通过抑制c-fos、COX-2的表达、降低FLS增殖能力等不同途径,发挥对RA滑膜细胞的免疫调节作用。     

Epithelial neutrophil activating peptide-78: a novel chemotactic cytokine for neutrophils in arthritis.

We and others have shown that cells obtained from inflamed joints of rheumatoid arthritis (RA) patients produce interleukin-8, a potent chemotactic cytokine for neutrophils (PMNs). However, IL-8 accounted for only 40% of the chemotactic activity for PMNs found in these synovial fluids. Currently, we have examined the production of the novel PMN chemotactic cytokine, epithelial neutrophil activating peptide-78 (ENA-78), using peripheral blood, synovial fluid, and synovial tissue from 70 arthritic patients. RA ENA-78 levels were greater in RA synovial fluid (239 +/- 63 ng/ml) compared with synovial fluid from other forms of arthritis (130 +/- 118 ng/ml) or osteoarthritis (2.6 +/- 1.8 ng/ml) (P < 0.05). RA peripheral blood ENA-78 levels (70 +/- 26 ng/ml) were greater than normal peripheral blood levels (0.12 +/- 0.04 ng/ml) (P < 0.05). Anti-ENA-78 antibodies neutralized 42 +/- 9% (mean +/- SE) of the chemotactic activity for PMNs found in RA synovial fluids. Isolated RA synovial tissue fibroblasts in vitro constitutively produced significant levels of ENA-78, and this production was further augmented when stimulated with tumor necrosis factor-alpha (TNF-alpha). In addition RA and osteoarthritis synovial tissue fibroblasts as well as RA synovial tissue macrophages were found to constitutively produce ENA-78. RA synovial fluid mononuclear cells spontaneously produced ENA-78, which was augmented in the presence of lipopolysaccharide. Immunohistochemical localization of ENA-78 from the synovial tissue of patients with arthritis or normal subjects showed that the predominant cellular source of this chemokine was synovial lining cells, followed by macrophages, endothelial cells, and fibroblasts. Synovial tissue macrophages and fibroblasts were more ENA-78 immunopositive in RA than in normal synovial tissue (P < 0.05). These results, which are the first demonstration of ENA-78 in a human disease state, suggest that ENA-78 may play an important role in the recruitment of PMNs in the milieu of the inflamed joint of RA patients.     

TNF-α和CRT双信号对RA患者滑膜组织NLRP3炎症小体的活化作用

目的研究肿瘤坏死因子-α(TNF-α)和钙网织蛋白(CRT)双信号对类风湿性关节炎(RA)患者成纤维样滑膜细胞(FLS)中核苷酸结合寡聚化结构域受体3(NLRP3)炎症小体活化的影响。方法采用间接免疫荧光染色法检测12例RA和10例骨性关节炎(OA)患者滑膜组织NLRP3、衔接蛋白凋亡相关斑点样蛋白(ASC)的表达,并与滑膜衬里层和衬里下层FLS标志物进行共定位研究。采用胶原酶消化法分离RA患者滑膜组织中FLS并进行体外培养。分别用不同浓度的TNF-α或脂多糖(LPS)(刺激剂)处理细胞,采用免疫印迹法和实时荧光定量聚合酶链反应(qRT-PCR)检测细胞NLRP3、白细胞介素1β前体(pro-IL-1β)和白细胞介素18前体(pro-IL-18)的蛋白和mRNA表达。加入尼日利亚菌素(Nigericin)或CRT后采用免疫印迹法检测FLS中半胱氨酸天冬氨酸特异性蛋白酶1(Caspase-1)活化片段p20的表达;收集细胞培养上清液,采用酶联免疫吸附试验(ELISA)检测分泌型白细胞介素(IL)-1β和IL-18水平。结果 RA患者滑膜组织中NLRP3炎症小体的主要成分NLRP3和ASC的平均荧光强度高于OA患者(P<0.01)。NLRP3、ASC和IL-1β裂解片段(cleaved IL-1β)与RA患者滑膜衬里层FLS表面标志物PDPN和衬里下层FLS表面标志物CD248均有共定位。体外细胞实验结果显示TNF-α可以促进FLS中NLRP3和pro-IL-1β的蛋白表达;与对照组(无刺激剂)相比,二者的mRNA表达显著增加(P<0.05、P<0.001),而LPS对RA患者FLS中NLRP3炎症小体的预活化无影响。TNF-α/Nigericin或TNF-α/CRT双信号能够促进FLS中Caspase-1的活化,导致Caspase-1活化片段p20呈浓度依赖性升高;与对照组相比,TNF-α/CRT组分泌型IL-1β显著升高(P<0.05)。结论 TNF-α/CRT双信号可促进RA患者FLS中NLRP3炎症小体的活化。     

Upregulated expression and function of VLA-4 fibronectin receptors on human activated T cells in rheumatoid arthritis.

The VLA-4 (CD49d/CD29) integrin is a cell surface receptor involved in the interaction of lymphoid cells with both extracellular matrix (ECM) and endothelial cells. We have investigated the expression and function of VLA-4 fibronectin (FN) receptors on T cells localized in the inflammed synovium of patients with rheumatoid arthritis (RA). A high proportion of T cells in both synovial membrane (SM) and synovial fluid (SF) expressed the activation antigens AIM (CD69) and gp95/85 (Ea2) as well as an increased number of VLA-4 alpha and beta 1 adhesion molecules, as compared with peripheral blood (PB) T cells from the same patients. Furthermore, the majority of these activated SF T cells were able to adhere to a 38-kD FN proteolytic fragment containing the connecting segment-1 (CS-1) specifically through VLA-4 receptors, whereas a significantly lower proportion of PB T cells displayed this capacity. Therefore, our results show that activated T cells selectively localize at sites of tissue injury in RA disease and provide evidence for the in vivo regulation of the expression and function of the VLA-4 integrin. This regulatory mechanism may enable T cells either to facilitate migration or to persist at sites of inflammation.