Mesenchymal stem cells control alloreactive CD8+CD28− T cells

CD28/B7 co-stimulation blockade with belatacept prevents alloreactivity in kidney transplant patients. However, cells lacking CD28 are not susceptible to belatacept treatment. As CD8⁺CD28⁻ T-cells have cytotoxic and pathogenic properties, we investigated whether mesenchymal stem cells (MSC) are effective in controlling these cells. In mixed lymphocyte reactions (MLR), MSC and belatacept inhibited peripheral blood mononuclear cell (PBMC) proliferation in a dose-dependent manner. MSC at MSC/effector cell ratios of 1:160 and 1:2·5 reduced proliferation by 38·8 and 92·2%, respectively. Belatacept concentrations of 0·1 μg/ml and 10 μg/ml suppressed proliferation by 20·7 and 80·6%, respectively. Both treatments in combination did not inhibit each other''s function. Allostimulated CD8⁺CD28⁻ T cells were able to proliferate and expressed the cytolytic and cytotoxic effector molecules granzyme B, interferon (IFN)-γ and tumour necrosis factor (TNF)-α. While belatacept did not affect the proliferation of CD8⁺CD28⁻ T cells, MSC reduced the percentage of CD28⁻ T cells in the proliferating CD8⁺ T cell fraction by 45·9% (P = 0·009). CD8⁺CD28⁻ T cells as effector cells in MLR in the presence of CD4⁺ T cell help gained CD28 expression, an effect independent of MSC. In contrast, allostimulated CD28⁺ T cells did not lose CD28 expression in MLR–MSC co-culture, suggesting that MSC control pre-existing CD28⁻ T cells and not newly induced CD28⁻ T cells. In conclusion, alloreactive CD8⁺CD28⁻ T cells that remain unaffected by belatacept treatment are inhibited by MSC. This study indicates the potential of an MSC–belatacept combination therapy to control alloreactivity.     

Increased autophagy in CD4+ T cells of rheumatoid arthritis patients results in T‐cell hyperactivation and apoptosis resistance

Rheumatoid arthritis (RA) is an autoimmune disease hallmarked by aberrant cellular homeostasis, resulting in hyperactive CD4⁺ T cells that are more resistant to apoptosis. Both hyperactivation and resistance to apoptosis may contribute to the pathogenicity of CD4⁺ T cells in the autoimmune process. A better knowledge of the mechanisms determining such impaired homeostasis could contribute significantly to both the understanding and the treatment of the disease. Here we investigated whether autophagy, is dysregulated in CD4⁺ T cells of RA patients, resulting in disturbed T‐cell homeostasis. We demonstrate that the rate of autophagy is significantly increased in CD4⁺ T cells from RA patients, and that increased autophagy is also a feature of in vitro activated CD4⁺ T cells. The increased apoptosis resistance observed in CD4⁺ T cells from RA patients was significantly reversed upon autophagy inhibition. These mechanisms may contribute to RA pathogenesis, as autophagy inhibition reduced both arthritis incidence and disease severity in a mouse collagen induced arthritis mouse model. Conversely, in Atg5^flox/flox‐CD4‐Cre⁺ mice, in which all T cells are autophagy deficient, T cells showed impaired activation and proliferation. These data provide novel insight into the pathogenesis of RA and underscore the relevance of autophagy as a promising therapeutic target.     

Elevated circulating Th17 and follicular helper CD4+ T cells in patients with rheumatoid arthritis

It remains not fully elucidated the potential functions of Th17 cells and follicular helper T (Tfh) cells and secreting cytokines in the pathogenesis of rheumatoid arthritis (RA) and their association with disease activity. In this study, the frequencies of Th17 and Tfh cells were determined by flow cytometry, and the levels of interleukin (IL)‐17, IL‐21, and IL‐22 were measured by ELISA in RA patients with different disease activities. The dynamic changes of cell subsets were also detected in response to disease‐modify antirheumatic drugs (DMARDs) therapy. The percentages of CD3⁺CD4⁺IL‐17A⁺ (Th17) cells and CD3⁺CD4⁺CXCR5⁺ICOS^high (Tfh) cells, as well as the concentrations of IL‐17, IL‐21, and IL‐22 were significantly elevated in RA patients than those in healthy individuals. Furthermore, Tfh cells, IL‐21, and IL‐22 in the serum was positively correlated with the values of disease activity score. Concentrations of IL‐21 and IL‐22 in the serum were remarkably reduced following the DMARDs therapies. Our data suggested that Th17 cells, Tfh cells as well as the secreting cytokines may be involved in the pathogenesis of RA. The frequency of circulating Tfh cells and the productions of IL‐21 and IL‐22 were associated with the disease activity of RA patients, and might be potential therapeutic targets for treatment of RA.     

Increased frequency of CD56Bright NK‐cells,CD3−CD16+CD56− NK‐cells and activated CD4+T‐cells or B‐cells in parallel with CD4+CDC25High T‐cells control potentially viremia in blood donors with HCV

A detailed phenotypic analysis of major and minor circulating lymphocyte subsets is described in potential blood donors with markers of hepatitis C virus (HCV), including non‐viremic and viremic groups. Although there were no changes in the hematological profile of either group, increased the levels of pre‐NK cells (CD3^?CD16⁺CD56^?) and a lower frequency of mature NK cells (CD3^?CD16⁺CD56⁺) characterized innate immunity in the non‐viremic group. Both non‐viremic and viremic groups displayed significantly increased levels of CD56^Bright NK cells. Furthermore, this subset was significantly elevated in the viremic subgroup with a low viral load. In addition, an increase in the NKT2 subset was observed only in this subgroup. An enhanced frequency of activated CD4⁺ T‐cells (CD4⁺HLA‐DR⁺) was a characteristic feature of the non‐viremic group, whereas elevated CD19⁺ B‐cells and CD19⁺CD86⁺ cell populations were the major phenotypic features of the viremic group, particularly in individuals with a low viral load. Although CD4⁺CD25^High T‐cells were significantly elevated in both the viremic and non‐viremic groups, it was particularly evident in the viremic low viral load subgroup. A parallel increase in CD4⁺CD25^High T‐cells, pre‐NK, and activated CD4⁺ T‐cells was observed in the non‐viremic group, whereas a parallel increase in CD4⁺CD25^High T‐cells and CD19⁺ B‐cells was characteristic of the low viral load subgroup. These findings suggest that CD56^Bright NK cells, together with pre‐NK cells and activated CD4⁺ T‐cells in combination with CD4⁺CD25^High T‐cells, might play an important role in controlling viremia. Elevated CD56^Bright NK cells, B‐cell responses and a T‐regulated immunological profile appeared to be associated with a low viral load. J. Med. Virol. 81:49–59, 2009. © 2008 Wiley‐Liss, Inc.     

DRB1*0402 may influence arthritis by promoting naive CD4+ T‐cell differentiation in to regulatory T cells

HLA‐DRB1*0401 expression in humans has been associated with a predisposition to developing rheumatoid arthritis (RA) and collagen‐induced arthritis (CIA), while HLA‐DRB1*0402 is not associated with susceptibility. Here, we determined if mice transgenic (Tg) for human *0401 have a CD4⁺ T‐cell repertoire that predetermines proinflammatory cytokine production. The data show that both *0401 and *0402 Tg mice can produce TH1/TH17 cytokines, although the kinetics of response may be different. However, in the context of antigen‐specific responses in a CIA model, *0402 Tg mice generate a TH2 response that may explain their resistance to developing arthritis. In addition, a significant subset of naïve CD4⁺ T cells from *0402 Tg mice can be activated in polarizing conditions to differentiate into Treg cells that produce IFN‐γ. *0401 Tg mice harbor memory CD4⁺ T cells that differentiate into IL‐17⁺ cells in various polarizing conditions. Our data suggest that *0401 Tg mice generate a strong immune response to lipopolysaccharide and may be efficient in clearing infection, and may *0401 have been evolutionarily selected for this ability. Autoimmunity, such as RA, could likely be a bystander effect of the cytokine storm that, along with the presence of low Treg‐cell numbers in *0401 Tg mice, causes immune dysregulation.     

Correlation between miR-126 expression and DNA hypomethylation of CD4+ T cells in rheumatoid arthritis patients

It has been known that the occurrence of rheumatoid arthritis (RA) was closely correlated with DNA hypomethylation in CD4+ T cells, in which DNA methyltransferase plays a certain role. This study therefore investigated the effect of miR-126 on CD4+ T cell subgroup in RA patients and the alternation of DNA hypomethylation, in an attempt to provide new sights into the pathogenesis and treatment of RA. CD4+ T cells separated from RA patients were transfected with miRNA (miR)-126 expression vector or miR-126 inhibitor expression vector. The expression levels of CD11a, CD70 and DNMT1 mRNA were examined by real-time PCR. Protein levels of CD11a and CD70 were tested by flow cytometry while DNMT1 protein level was quantified by Western blotting. DNA was modified by sodium bisulfite and was sequenced for the methylation status of promoters of CD11a and CD70 genes. Both mRNA and protein expressions of CD11a and CD70 genes in CD4+ T cells were elevated by miR-126 transfection, along with decreased DNMT1 protein level but not mRNA level. The methylation degree of promoters of both CD11a and CD70 genes were significantly depressed after miR-126 transfection. The transfection by miR-126 inhibitor effectively reversed such effects. In RA patients, elevated miR-126 may promote the expression of CD11a and CD70 via the induction of hypomethylation of gene promoters by depressing DNMTI1 protein levels.     

Ligand dimensions are important in controlling NK‐cell responses

Size‐dependent protein segregation at the cell–cell contact interface has been suggested to be critical for regulation of lymphocyte function. We investigated the role of ligand dimensions in regulation of mouse NK‐cell activation and inhibition. Elongated forms of H60a, a mouse NKG2D ligand, were generated and expressed stably in the RMA cell line. RMA cells expressing the normal size H60a were lysed efficiently by both freshly isolated and IL‐2 stimulated C57BL/6 mouse‐derived NK cells; however the level of lysis decreased as the H60a ligand size increased. Importantly, H60a elongation did not affect NKG2D binding, as determined by soluble NKG2D tetramer staining, and by examining NK‐cell target cell conjugate formation. CHO cells are efficient at activating NK cells from C57BL/6 mice, and expression of a single chain form of H‐2K^b, a ligand for the mouse inhibitory receptor Ly49C, strongly inhibited such activation of Ly49C/I positive NK cells. Elongation of H‐2K^b resulted in decreased inhibition of both lysis and IFN‐γ production by NK cells. These results establish that small ligand dimensions are important for both NK‐cell activation and inhibition, and suggest that there are shared features between the mechanisms of receptor triggering on different types of lymphocytes.     

Co-stimulatory pathways controlling activation and peripheral tolerance of human CD4+CD28− T cells

Co-stimulation mediated by the CD28 molecule is considered critical in the activation of CD4⁺ T cells. In patients with rheumatoid arthritis and infrequently in normal individuals, CD4⁺ T cells lacking CD28 expression are expanded and contain clonogenic populations. To analyze whether these cells are independent of co-stimulatory requirements or whether they use co-stimulatory signals distinct from the CD28 pathway, we have compared CD4⁺ CD28⁺ and CD4⁺ CD28^?T cell clones isolated from rheumatoid arthritis patients. Accessory cells supported the induction of CD25 expression as well as of proliferative responses after anti-CD3 cross-linking and prevented the induction of anergy in CD4⁺ CD28^? T cell clones. In contrast to CD4⁺CD28⁺ T cells, the presence of accessory cells did not enhance the secretion of interleukin (IL)-2, interferon-γ, or IL-4. The co-stimulatory signals did not involve CD28/CTLA-4–CD80/CD86 receptor-ligand interactions. The proliferative response of CD4⁺CD28^? T cells could not be blocked by anti-CD2, anti-CD18, and anti-CD58 antibodies, suggesting that these receptor-ligand interactions cannot provide CD28^? independent co-stimulation. Our data suggest that CD4⁺CD28^? T cells require co-stimulatory signals for optimal induction of cell growth and CD25 expression as well as for the prevention of anergy. The co-stimulatory receptor-ligand interaction is independent of the CD28 pathway and may be involved in the oligoclonal expansion of the CD4⁺ CD28^? T cell subset in rheumatoid arthritis.     

CD8‐β ADP‐ribosylation affects CD8+ T‐cell function

The CD8αβ coreceptor is crucial for effective peptide: MHC‐I recognition by the TCR of CD8⁺ T cells. Adenosine diphosphate ribosyl transferase 2.2 (ART2.2) utilizes extracellular NAD⁺ to transfer ADP‐ribose to arginine residues of extracellular domains of surface proteins. Here, we show that in the presence of extracellular NAD⁺, ART2.2 caused ADP‐ribosylation of CD8‐β on murine CD8⁺ T cells in vitro and in vivo. Treatment with NAD⁺ prevented binding of anti‐CD8‐β mAb YTS156.7.7 but not of mAb H35–17.2, indicating that NAD⁺ caused modification of certain epitopes and not a general loss of CD8‐β. Loss of antibody binding was strictly dependent on ART2.2, because it was not observed on ART2‐deficient T cells or in the presence of inhibitory anti‐ART2.2 single‐domain antibodies. ADP‐ribosylation of CD8‐β occurred during cell isolation, particularly when cells were isolated from CD38‐deficient mice. Incubation of ART2‐expressing, but not of ART2‐deficient, OVA‐specific CD8⁺ T cells with NAD⁺ interfered with binding of OVA_257–264:MHC‐I tetramers. In line with this result, treatment of WT mice with NAD⁺ resulted in reduced CD8⁺ T‐cell mediated cytotoxicity in vivo. We propose that ADP‐ribosylation of CD8‐β can regulate the coreceptor function of CD8 in the presence of elevated levels of extracellular NAD⁺.     

类风湿关节炎患者外周血CD4+T细胞亚群的分析

目的 研究类风湿性关节炎(RA)患者不同时期外周血Treg和Th1、Th2、Th17细胞以及中性粒细胞上CD64的表达水平,及它们与RA的活动性指标和自身抗体的相关性.方法 采集78例RA患者和21例健康人外周静脉血,采用流式细胞术检测淋巴细胞亚群(Treg,Th1、Th2、Th17细胞)的变化.结果 RA的CD3+ CD4+T细胞和CD4+ CD25+T细胞增多,活动期RA组Treg比率高于缓解期RA组和健康对照组,缓解期RA组Th2细胞减少,RA中Th1,TH17细胞与健康对照组相比无统计学意义,Treg和Th1、Th2、Th17细胞与RA的活动性指标(ESR,CRP和PLT)均无关联.结论 CD4+T细胞亚群数量异常可能与RA疾病发展有关.     

Critical stoichiometric ratio of CD4+ CD25+ FoxP3+ regulatory T cells and CD4+ CD25− responder T cells influence immunosuppression in patients with B‐cell acute lymphoblastic leukaemia

Regulatory T (Treg) cells act to suppress activation of the immune system and thereby maintain immunological homeostasis and tolerance to self-antigens. The frequency and suppressing activity of Treg cells in general are high in different malignancies. We wanted to identify the role and regulation of CD4⁺ CD25⁺ FoxP3⁺ Treg cells in B-cell acute lymphoblastic leukaemia (B-ALL). We have included patients at diagnosis (n = 54), patients in clinical remission (n = 32) and normal healthy individuals (n = 35). These diagnosed patients demonstrated a lower number of CD4⁺ CD25⁺ cells co-expressing a higher level of FoxP3, interleukin-10, transforming growth factor-β and CD152/CTLA-4 than the normal population. Treg cells from patients showed a higher suppressive capability on CD4⁺ CD25⁻ responder T (Tresp) cells than normal. The frequency and immunosuppressive potential of CD4⁺ CD25⁺ FoxP3⁺ Treg cells became high with the progression of malignancy in B-ALL. Relative distribution of Tresp and Treg cells was only ˜5 : 1 in B-ALL but ˜35 : 1 in normal healthy individuals, further confirming the elevated immunosuppression in patients. A co-culture study at these definite ex vivo ratios, indicated that Treg cells from B-ALL patients exhibited higher immunosuppression than Treg cells from normal healthy individuals. After chemotherapy using the MCP841 protocol, the frequency of CD4⁺ CD25⁺ cells was gradually enhanced with the reduction of FoxP3, interleukin-10 positivity corresponded with disease presentation, indicating reduced immunosuppression. Taken together, our study indicated that the CD4⁺ CD25⁺ FoxP3⁺ Treg cells played an important role in immunosuppression, resulting in a positive disease-correlation in these patients. To the best of our knowledge, this is the first detailed report on the frequency, regulation and functionality of Treg cells in B-ALL.     

Interleukin-15 selectively expands CD57+ CD28- CD4+ T cells, which are increased in active rheumatoid arthritis

Proinflammatory cytokines as well as CD4(+) T cells play critical roles in the pathogenesis of rheumatoid arthritis (RA). Recently, an increase of CD57(+) or CD28(-)CD4(+) T cells was demonstrated in RA, although the mechanism of the increase of these T cells is unclear. In this study, we first examined the relationship between CD57(+)CD4(+) T cells and CD28(-)CD4(+) T cells and found CD57(+)CD28(-)CD4(+) T cells, but neither CD57(+)CD28(+) nor CD57(-)CD28(+) cells, expanded in the peripheral blood of active RA. In vitro experiments revealed that CD57(+)CD28(-)CD4(+) T cells selectively expanded in response to IL-15. Furthermore IL-15-stimulated CD57(+)CD28(-)CD4(+) T cells induced TNF-alpha production from monocytes. These results suggest that CD57(+)CD28(-)CD4(+) T cells are involved in the pathogenesis of RA by responding to IL-15.     

HIV gag‐specific immune response mediated by double negative (CD3+CD4−CD8−) T cells in HIV‐exposed seronegative individuals

Double negative (DN) T cells are CD3⁺, CD4^?, CD8^? cells with either T‐cell receptors (TCR) αβ or TCR γδ whose importance on protection against HIV infection is unknown. Since HIV‐exposed seronegative individuals correspond to an ideal group in whom correlates of protection are expected, the role of these cells was studied in 13 HIV‐serodiscordant couples in a stable relationship and reporting unprotected sexual intercourses. HIV‐specific immune responses mediated by DN T‐cells were evaluated by measuring intracellular IFNγ and MIP1β (CCL4) production in response to HIV‐Gag peptides. Thirty‐five healthy controls not exposed to HIV were tested similarly and used to define a threshold for positive responses. Interestingly, Gag‐specific DN T‐cell responses were found in 3/13 (23%) HIV‐exposed seronegative individuals (Group A), involving both DN/αβ⁺ and DN/γδ⁺ T‐cells through MIP1β and IFNγ production. 4/13 (30%) of partners infected with HIV (Group B) also showed Gag‐specific responses but were mediated exclusively by DN/γδ⁺ T‐cells, mainly through IFNγ production. DN T‐cells in Group A individuals can display differential HIV‐specific immune responses, which might contribute to the low susceptibility to infection with HIV shown by individuals in Group A. J. Med. Virol. 85:200–209, 2013. © 2012 Wiley Periodicals, Inc.     

Lactobacillus rhamnosus reduces CD8+T cell mediated inflammation in patients with rheumatoid arthritis

BackgroundThe T cells, components of adaptive immunity participate in immune pathology of the autoimmune inflammatory disorder called rheumatoid arthritis (RA). The presence of TLRs on the surface of the CD8⁺ T cells and their ability to recognize bacterial moieties adds to the inflammatory burden in case of RA. It has been reported that the gut microbiome is necessary for the crucial shift in the balance between proinflammatory and anti-inflammatory cytokines. The altered gut microbiome and the presence of TLRs emphasizes on the microbiome driven inflammatory responses in case of RA.MethodsEighty-nine RA patients participated in this study. Clinical variations like disease duration, number of actively inflamed joints, number and type of bone deformities, CRP, RF, Anti-CCP, ESR, DAS 28 score were recorded for each patient. Co-culture of CD8⁺T cells and bacteria has been performed with proper culture condition. TLRs and inflammatory mediators’ expression level were checked by both qPCR and flow cytometry analysis.ResultsWe observed in the suppression of pro-inflammatory molecules like Granzyme B and IFNƳ and expression of TLR2 in CD8 + T cells upon treatment with Lactobacillus rhamnosus (L. rhamnosus). Moreover, L. rhamnosus activated CD8⁺T cells such that they could induce FOXP3 expression in CD4⁺T cells thereby skewing T cell population towards a regulatory phenotype. On the contrary, TLR4 engagement on CD8⁺T cell by Escherichia coli (E.coli) increased in inflammatory responses following ERK activation.ConclusionsThus, we conclude that L. rhamnosus can effectively suppress CD8⁺T cell mediated inflammation by a simultaneous decrease of Th1 cells that may potentiate better treatment modalities for RA.     

类风湿关节炎患者外周血Tfh及Th9的变化及临床意义

目的 观察类风湿关节炎(RA)患者外周血中滤泡辅助性T细胞(Tfh)及T辅助细胞9(Th9)的变化,并与病情活动性及脏器受累等临床资料进行相关性分析,探讨Tfh及Th9在RA发病过程中可能的免疫学发病机制.方法 选择36例RA患者和22例健康对照.根据病情活动度不同将病例组分为病情高度活动组(22例)、病情中度活动组(14例),流式细胞仪检测RA和正常对照组外周血单个核细胞( PBMCs)中CD4-FITC、CXCR5-PE、ICOS-APC标记的CD4+ CXCR5+ ICOS+(Tfh)及CD8-FITC、CD3-APC、IL9-PE标记的CD3+CD8-IL-9+( Th9)比例.分析Tfh及Th9与RA患者的血沉(ESR)、C反应蛋白(CRP)、类风湿因子(RF)、关节压痛数、肿胀数及骨质破坏等指标的相关性;分析Tfh与Th9的关系.结果 RA患者的Tfh表达率明显高于对照组(Z=-6.082,P=0.000),RA患者Th9的表达率亦高于对照组(0.989±0.498 vs 0.213 ±0.084,t=13.063,P=0.000);RA重度活动组Tfh表达率亦高于中度活动患者的表达率(3.880±1.255 vs 2.678±1.022,t=2.990,P=0.005),且两组Tfh的表达率均高于对照组(P均＜0.01);RA重度活动患者Th9表达率高于中度患者(1.181±0.523 vs 0.686±0.254,t=4.043,P=0.000),且两组Th9的表达率亦均高于对照组(P均＜0.01); Tfh 细胞数与RA患者DAS28(r=0.571,P=0.000)、ESR(r=0.375,P=0.029)、CRP(r=0.357,P=0.032)、关节压痛数(r=0.598,P=0.000)、RF(r=0.421,P=0.023)及抗CCP滴度(r=0.421,P=0.023)正相关;与病程、晨僵、关节肿胀数、骨质破坏、心电图异常无相关性.Th9表达的百分率与RA患者的DAS28( r=0.461,P=0.005)、ESR(r=0.347,P=0.042)、CRP(r=0.384,P=0210)、关节压痛数(r=0.341,P=0.042)、关节肿胀数(r=0.347,P=0.038)及RF(r=0.379,P=0.025)正相关,与病程、晨僵时间、抗CCP滴度、心电图异常及骨质破坏无相关性;Tfh与Th9在外周血中的表达率呈正相关(r=0.727,P=0.000).结论 RA患者外周血Tfh及Th9的比例显著升高,且与疾病活动度及相关炎症指标明显相关,提示Tfn及Th9可能参与RA的发病及病情发展.     

CD40L demethylation in CD4(+) T cells from women with rheumatoid arthritis

We have previously demonstrated that DNA demethylation of CD40L on the X chromosome is responsible for female susceptibility to systemic lupus erythematosus (SLE). It is unknown whether aberrant methylation of the CD40L gene also contributes to the higher incidence of rheumatoid arthritis (RA) in females. In this study, we used real-time RT-PCR and flow cytometry to compare CD40L expression levels, and bisulfite sequencing to assess the methylation status of the CD40L promoter region. The results show that CD40L is upregrulated in CD4(+) T cells of female patients with RA. In addition, the CD40L promoter region in CD4(+) T cells from female RA patients was found to be demethylated, which corresponded with increased CD40L mRNA expression. These findings suggest that DNA demethylation contributes to CD40L expression in RA CD4(+) T cells and may in part explain the female preponderance of this disease.     

Clonally expanded CD4+CD28null T cells in rheumatoid arthritis use distinct combinations of T cell receptor BV and BJ elements

Clonally expanded, autoreactive CD4(+)CD28(null) cells can be found in the peripheral blood of patients with rheumatoid arthritis and have been shown to be associated with severeextra-articular disease manifestations. We investigated the size of the CD4(+)CD28(null) compartment and the TCR beta chain repertoire of expanded CD4(+) clonotypes in 94 rheumatoid arthritis patients by complementarity-determining region 3 (CDR3) length analysis (spectratyping) in the BV6 and BV14 TCR families, with primers specific for three arbitrarily chosen beta chain joining elements (BJ1S2, BJ2S3 and BJ2S7). The spectratyping results showed a strong correlation of the size of the CD4(+)CD28(null) compartment with the detected number of BV14 clonotypes, whereas no association with BV6 oligoclonality was found. Only clones using the BV14-BJ1S2 and BV14-BJ2S3 combinations contributed to this correlation, however, whereas BV14-BJ2S7 clones did not. This preferential correlation implies a role for the TCR beta chain in stimulating clonal outgrowth and argues against the previously suggested superantigenic stimulation of in-vivo-expanded clones. Instead, since no evidence for shared antigen specificity could be detected, clonal expansion of T cells in rheumatoid arthritis might be influenced by the BJ elements because of changes in the flexibility of the protein backbone of the beta-chain.