T-cell responses in rheumatoid arthritis: systemic abnormalities-local disease

The impact of CD4+CD28null T lymphocytes on atrial fibrillation: a potential pathophysiological pathway

Introduction

Atrial fibrillation (AF) represents the most common cardiac arrhythmia in daily clinical practice and substantially impacts affected patients by elevation of both morbidity and mortality. Previous investigations proved that inflammatory processes are closely linked to this multifactorial pathogenesis—especially autoreactive CD4⁺CD28^null T cells received in-depth attention.

Purpose

Consequently, a potential pathophysiological pathway of the impact of CD4⁺CD28null T lymphocytes on the development and progression AF can be outlined.

Conclusion

Considering the available data in the literature, it needs to be assumed that CD4⁺CD28^null T lymphocytes are mainly involved in the development of AF and disease progression. Of utmost importance, it can be considered as the result of a T-cell-mediated auto-immune reaction among myocardial tissue. However, mechanisms which recruit CD4⁺CD28^null cells in cardiac tissue remain unclear and need further investigation.

S100A4 regulates the Src-tyrosine kinase dependent differentiation of Th17 cells in rheumatoid arthritis

OBJECTIVES

To evaluate the role of S100A4, a calcium-binding regulator of nonmuscle myosin assembly, for T-cell responses in rheumatoid arthritis.

METHODS

Arthritis was induced in the methylated bovine serum albumin (mBSA)-immunized mice lacking the entire S100A4 protein (S100A4KO) and in wild-type counterparts treated with short hairpin ribonucleic acid (shRNA)-lentiviral constructs targeting S100A4 (S100A4-shRNA). The severity of arthritis was evaluated morphologically. T-cell subsets were characterized by the expression of master transcription factors, and functionally by proliferation activity and cytokine production. The activity of the Scr-kinases Fyn and Lck was assessed by the autophosphorylation of C-terminal thyrosine and by the phosphorylation of the CD5 cytodomain. The interaction between S100A4 and the CD5 cytodomain was analysed by nuclear magnetic resonance spectrophotometry.

RESULTS

S100A4-deficient mice (S100A4KO and S100A4-shRNA) had significantly alleviated morphological signs of arthritis and joint damage. Leukocyte infiltrates in the arthritic joints of S100A4-deficient mice accumulated Foxp3(+) Treg cells, while the number of RORγt(+) and (pTyr705)STAT3(+) cells was reduced. S100A4-deficient mice had a limited formation of Th17-cells with low retinoic acid orphan receptor gamma t (RORγt) mRNA and IL17 production in T-cell cultures. S100A4-deficient mice had a low expression and activity of T-cell receptor (TCR) inhibitor CD5 and low (pTyr705)STAT3 (signal transducer and activator of transcription 3), which led to increased (pTyr352)ZAP-70 (theta-chain associated protein kinase of 70kDa), lymphocyte proliferation and production of IL2. In vitro experiments showed that S100A4 directly binds Lck and Fyn and reciprocally regulates their kinase activity towards the CD5 cytodomain. Spectrometry demonstrates an interaction between the CD5 cytodomain and EF2-binding sites of S100A4.

CONCLUSION

The present study demonstrates that S100A4 plays an important part in the pathogenesis of arthritis. It controls CD5-dependent differentiation of Th17 cells by regulating the activity of the Src-family kinases Lck and Fyn.

Bacteria in the adventitia of cardiovascular disease patients with and without rheumatoid arthritis

The incidence of atherosclerosis is significantly increased in rheumatoid arthritis (RA). Infection is one factor that may be involved in the pathogenesis of both diseases. The cause of RA and atherosclerosis is unknown, and infection is one of the factors that may be involved in the pathogenesis of both diseases. The aims of this study were to identify bacteria in the aortic adventitia of patients with cardiovascular disease (CVD) in the presence and absence of RA, and to determine the effect of identified candidate pathogens on Toll-like receptor (TLR)-dependent signalling and the proinflammatory response. The aortic adventitia of 11 CVD patients with RA (RA+CVD) and 11 CVD patients without RA (CVD) were collected during coronary artery bypass graft surgery. Bacteria were detected in four samples from CVD patients and three samples from RA+CVD patients and identified by 16S rRNA gene sequencing. Methylobacterium oryzae was identified in all three RA+CVD samples, representing 44.1% of the bacterial flora. The effect of M. oryzae on TLR-dependent signalling was determined by transfection of HEK-293 cells. Although mild TLR2 signalling was observed, TLR4 was insensitive to M. oryzae. Human primary macrophages were infected with M. oryzae, and a TLDA qPCR array targeting 90 genes involved in inflammation and immune regulation was used to profile the transcriptional response. A significant proinflammatory response was observed, with many of the up-regulated genes encoding proinflammatory cytokines (IL-1α, IL-1β, IL-6, TNF-α) and chemokines (CCR7, IL-8). The aortic adventitia of CVD patients contains a wide range of bacterial species, and the bacterial flora is significantly less diverse in RA+CVD than CVD patients. M. oryzae may stimulate an proinflammatory response that may aggravate and perpetuate the pathological processes underlying atherosclerosis in RA patients.

Baseline numbers of circulating CD28-negative T cells may predict clinical response to abatacept in patients with rheumatoid arthritis

OBJECTIVE

To evaluate the number of circulating CD28-negative (CD28-) T cells as a predictor of clinical response to abatacept in patients with rheumatoid arthritis (RA).

METHODS

Peripheral blood CD28- T cell subsets were evaluated by flow cytometry at baseline in 32 patients with RA treated with abatacept. Receiver-operator curves were applied to examine the predictive value of T cell populations and to choose the cutoff for the best performance of the test. Remission was defined using the Disease Activity Score 28 based on C-reactive protein.

RESULTS

The overall predictive values of the CD8+CD28- and CD4+CD28- cells for remission after 6 months of abatacept therapy were 0.802 (SE 0.078) and 0.743 (SE 0.089), respectively. Cutoff values of < 87 CD8+CD28- cells/μl and < 28 CD4+CD28- cells/μl had 80.0% sensitivity and 81.8% specificity (Fisher test: p = 0.001), and 60.0% sensitivity and 77.3% specificity (p = 0.043), respectively, for prediction of remission at 6 months. Patients having low baseline numbers of CD8+CD28- T cells had a more than 4-fold higher probability of achieving remission within 6 months than patients with higher levels of these cells.

CONCLUSION

A simple laboratory measure, the baseline number of circulating CD28- T cells, predicted remission after 6 months of abatacept treatment in patients with RA.

Association of CD4 enhancer gene polymorphisms with rheumatoid arthritis in Egyptian female patients

CD4 is a candidate gene in autoimmune diseases, including rheumatoid arthritis (RA). Because the CD4 receptor is crucial for appropriate antigen responses of CD4+ T cells, changes in CD4 expression and CD4+ T-cell activity may influence tolerance or tissue destruction in autoimmune diseases and contribute to their risk. We analyzed two polymorphisms of the CD4 in 172 female Egyptian patients with RA and in 112 matched healthy control. Genotyping of CD4-11743 and CD4-10845 was determined by restriction fragment length polymorphism-polymerase chain reaction (PCR-RFLP). Subjects with the CC genotype of CD4-11743 were significantly more likely to develop RA (OR = 2.7, P = 0.03) and more likely to have sever RA (OR = 2.7, P = 0.024). Carrier of A allele of CD4-10845 was significantly more likely to develop sever RA (OR = 3.7, P = 0.000). CD4-11743 genetic polymorphisms are associated with the susceptibility and severity of RA, and CD4-10845 genetic polymorphisms are associated with the severity of RA.

Varying expression of four genes sharing a common regulatory sequence may differentiate rheumatoid arthritis from ageing effects on the CD4(+) lymphocytes

The CD28 gene is similarly down-regulated in CD4(+) lymphocytes from both healthy elderly people and patients with rheumatoid arthritis (RA) because of impaired protein-binding activity of the 'α' sequence in its promoter region. Other genes important for the CD4(+) cell function may share that sequence and may be similarly regulated and affected. We searched GenBank for possible 'α' homologues and then compared transcriptional activities of the respective genes in the CD4(+) cells of young and older healthy individuals and those with RA by real-time PCR. We show here that genes encoding one of the zinc finger proteins (ZNF334), the 'aging hormone' Klotho, the retinoid acid receptor β2 (RARβ2) and the T-cell adapter protein GRAP-2, contain sequences with various (exceeding 70%) degrees of homology to the 'α' sequence near their promoters. These genes are transcribed in human CD4(+) lymphocytes; the expressions of RARβ2, KLOTHO and ZNF334 are significantly decreased in a correlated manner in the cells of patients with RA compared with those of healthy individuals. In RA patients, the extremely reduced expression of ZNF334 does not depend on the individual's age, apparently constituting a disease-related phenomenon; whereas that of RARβ2 and KLOTHO occurs mostly in the cells of relatively younger patients, making them similar to the lymphocytes of healthy elderly in this aspect.

Gamma/delta T cells are the predominant source of interleukin-17 in affected joints in collagen-induced arthritis, but not in rheumatoid arthritis

OBJECTIVE

Although interleukin-17 (IL-17)-producing gamma/delta T cells were reported to play pathogenic roles in collagen-induced arthritis (CIA), their characteristics remain unknown. The aim of this study was to clarify whether gamma/delta T cells or CD4+ T cells are the predominant IL-17-producing cells, and to determine what stimulates gamma/delta T cells to secret IL-17 in mice with CIA. The involvement of IL-17-producing gamma/delta T cells in SKG mice with autoimmune arthritis and patients with rheumatoid arthritis (RA) was also investigated.

METHODS

IL-17-producing cells in the affected joints of mice with CIA were counted by intracellular cytokine staining during 6 distinct disease phases, and these cells were stimulated with various combinations of cytokines or specific antigens to determine the signaling requirements. Similar studies were performed using SKG mice with arthritis and patients with RA.

RESULTS

Gamma/delta T cells were the predominant population in IL-17-producing cells in the swollen joints of mice with CIA, and the absolute numbers of these cells increased in parallel with disease activity. IL-17-producing gamma/delta T cells expressed CC chemokine receptor 6, were maintained by IL-23 but not by type II collagen in vitro, and were induced antigen independently in vivo. Furthermore, IL-17 production by gamma/delta T cells was induced by IL-1beta plus IL-23 independently of T cell receptor. In contrast to what was observed in mice with CIA, IL-17-producing gamma/delta T cells were nearly absent in the affected joints of SKG mice and patients with RA, and Th1 cells were predominant in the joints of patients with RA.

CONCLUSION

Gamma/delta T cells were antigen independently stimulated by inflammation at affected joints and produced enhanced amounts of IL-17 to exacerbate arthritis in mice with CIA but not in SKG mice with arthritis or patients with RA.

Altered naive and memory CD4+ T-cell homeostasis and immunosenescence characterize younger patients with myelodysplastic syndrome

Response to immunosuppressive therapy (IST) in younger patients with myelodysplastic syndrome (MDS) has been linked to a T-cell-dominant autoimmune process that impairs hematopoiesis. Analysis of the age-adjusted CD4:CD8 ratio in 76 MDS patients compared with 54 healthy controls showed that inadequate CD4+, rather than expansion of CD8+ T cells, was associated with a lower ratio in a group that included both lower and higher risk MDS patients defined by the International Prognostic Scoring System. In younger MDS patients, naive and memory phenotypes defined by CD45RA and CD62L display showed depletion of naive CD4+ and CD8+ T cells, suggesting a possible relationship to IST responsiveness. To determine the correlation between T-cell subset distribution, T-cell turnover and autoimmunity, a cohort of 20 patients were studied before and after IST. The CD4:CD8 ratio correlated inversely with the proliferative T-cell index before treatment in IST-responsive patients, suggesting that proliferation may be linked to accelerated CD4+ T-cell turnover and hematopoietic failure. Our data show seminal findings that both CD4+ and CD8+ T-cell subsets are dysregulated in MDS. Association between these T-cell defects and response to IST suggests that aberrant T-cell homeostasis and chronic activation are critical determinants influencing autoimmune hematopoietic suppression in younger patients.

Will Jill come tumbling after? The case for a JAK2-type mutation as a prequel to the connective tissue disorders

The JAK2 [V617F] mutation has recently been recognised as critical to the pathogenesis of the myeloproliferative disorders (MPDs). Thus, a common mutation affecting a haematopoietic precursor stem cell is capable of giving rise to diverse clinical phenotypes. In this hypothesis paper, we propose that a similar mutation affecting a stem cell precursor, most likely of the B cell lineage, could underlie the development of the connective tissue disorders which could be regarded as "lymphoproliferative" disorders. Consistent with this hypothesis is the observation that there are similarities between the myeloproliferative disorders and the connective tissue disorders in terms of their biological behaviour. Diseases within each family can transform into each other and sometimes into haematological malignancies (most often B cell origin non-Hodgkins lymphoma for the connective tissue disorders and acute myeloid leukemia for the myeloproliferative disorders). The timecourse for development of the connective tissue disorders involves a long latent period when autoantibodies are present (anti-CCP and ANA) possibly reflecting production by a B cell clone. A similar time-dependent increase in clonal dominance has been described in erythroblastic clones taken from the bone marrow of polycythemia vera patients, long before the onset of clinical disease. Evidence of B cell clonality has been described in bone marrow samples from rheumatoid arthritis patients and from glandular biopsies from those with Sjogren's syndrome. Moreover, pseudofollicles containing activated B cells are features of rheumatoid synovial membrane and have also recently been described in subchondral bone where they are associated with macrophages, T cells and osteoclasts. The success of B cell depletion therapy in rheumatoid arthritis and systemic lupus erythematosus is also strong circumstantial evidence for this hypothesis.

CD4+ CD28 null T cells in coronary artery disease: when helpers become killers

The crucial role of T cells in atherosclerosis and coronary artery disease (CAD) has been highlighted by recent observations. Helper CD4(+) T cells can both aggravate or attenuate the atherogenic process and the development of CAD. CD4(+)CD28(null) T cells are an unusual subset of helper cells which expand and have deleterious effects in CAD. In this review, we discuss the current issues on the generation of CD4(+)CD28(null) T cells and focus on their phenotypic and functional characteristics relevant to the development of cardiovascular events. The possible effects of the present day therapies for CAD on the CD4(+)CD28(null) T cells are also explored. Targeting the CD4(+)CD28(null) T cell subset in CAD could provide novel therapeutic strategies to prevent acute life-threatening coronary events.

The Immunology of Rheumatoid Arthritis

Rheumatoid arthritis (RA) is represents the most common chronic inflammatory joint disease and is still a major medical challenge because of unsolved issues related to the etiologic and pathogenetic questions. Intensive research has been conducted over the last years that focused on the inappropriate activation of the immune system: although T cells have long been deemed to play a central role in the origin and propagation of joint inflammation, data accumulated so far have widened this perspective recognizing the contribution of other cells, as well as the major histocompatibility complex class II proteins and a composite set of costimulatory signals responsible for the production of proinflammatory cytokines and other soluble mediators implicated in tissue destruction typical of the disease. This paper will provide an insight into the immune system in RA, dissecting cellular and humoral aspects both in serum and in synovium of patients.

Klotho--a common link in physiological and rheumatoid arthritis-related aging of human CD4+ lymphocytes

Human CD4(+) T lymphocytes undergo aging-related changes leading to decreased immunity to infections and neoplasms, and to increased frequency of autoimmune diseases including rheumatoid arthritis (RA). Certain changes, observed in the CD4(+) cells of RA patients, resemble those observed during physiological aging, but occur at earlier age. Underlying cellular mechanism(s) of these similarities are so far largely unknown. Here we show that KLOTHO, a beta-glucuronidase gene whose activity changes are associated with aging phenotype, is down-regulated at the mRNA, protein, and enzymatic (beta-glucuronidase) activity levels both in the healthy elderly and especially in RA CD4(+) lymphocytes. Although the exact role of Klotho activity for CD4(+) cell function is unknown, we propose here that it might be involved in anti-inflammatory processes occurring in the young and healthy individuals, but reduced in both healthy elderly and RA patients. To support this hypothesis, we show here that the reduction of Klotho expression and activity in both elderly and patients' lymphocytes occurs in concert with the down-regulation of T cell costimulatory molecule CD28, the latter known to be dependent on increased levels of TNF-alpha. Thus, a common mechanism of KLOTHO down-regulation, but executed at various times in life, may underlie both physiological and disease-related T cell aging. Klotho activity might become a target of anti-RA drug development as well as a tool to help increase the immune system efficiency in the elderly.

Rosmarinic acid induces apoptosis of activated T cells from rheumatoid arthritis patients via mitochondrial pathway

T cells play an important role in the initiation and the progression of rheumatoid arthritis (RA) and depletion of potentially pathogenic T cells was suggested as an important therapeutic protocol. We determined if rosmarinic acid (RosA), known as a secondary metabolite from herbal plants, had apoptotic activity toward T cells from RA patients and further verified target T-cell subsets. CD3(+)CD25(+) activated T-cell subsets from most of the RA patients displayed significantly higher apoptosis rates than did the PBMCs and total CD3(+) T cells. Furthermore, activated and effector CD4(+) T cells, including CD4(+)CD25(+) and CD4(+)CD45RO(+) T cells, had a tendency of being more susceptible to RosA-induced apoptosis than that of resting and naïve T-cell subsets. RosA induced the release of cytochrome c from mitochondria and the blockage of mitochondrial depolarization inhibited apoptosis. Taken together, these results suggest that RosA induces apoptosis of activated T-cell subsets from RA patients via a mitochondrial pathway.

Rheumatoid arthritis

Therapeutic efficacy of depleting B cells or blocking T-cell costimulation in rheumatoid arthritis (RA) has confirmed the critical pathogenic role of adaptive immune responses. Yet, RA preferentially affects elderly individuals, in whom adaptive immunity to exogenous antigens begins to fail. Here, we propose that senescence of the immune system is a risk factor for RA, with chronic inflammation resulting from the accumulation of degenerate T cells that have a low threshold for activation and utilize a spectrum of novel receptors to respond to microenvironmental cues. The process of immunosenescence is accelerated in RA and precedes the onset of disease, the acceleration, in part, being conferred by the HLA-DR4 haplotype. Naive CD4(+) T cells in RA are contracted in diversity and restricted in clonal burst. Senescence of effector CD4(+) T cells is associated with the loss of CD28 and the de novo expression of KIR2DS2, NKG2D, and CX(3)CR1, all of which function as costimulatory molecules and reduce the threshold for T-cell activation. The synovial microenvironment promotes chronic persistent immune responses by facilitating ectopic lymphoid neogenesis, such as the formation of aberrant germinal centers. With the propensity to develop complex lymphoid architectures and to provide optimal activation conditions for senescent CD4(+) T cells, the synovium becomes a natural target for pathogenic immune responses in prematurely aged individuals.

Endothelial cell dysfunction in systemic vasculitis: new developments and therapeutic prospects

PURPOSE OF REVIEW

The role of the endothelium as an active player rather than a passive victim of inflammation has received considerable interest in atherosclerosis, but less so in systemic vasculitis (SV). However, the accumulating multi-organ damage seen in SV probably includes the endothelium. Assessment of endothelial function is now a standard clinical research tool in cardio-vascular departments. The exciting insights provided by their application to SV, in both primary disease and connective tissue diseases (CTD), is reviewed here.

RECENT FINDINGS

Diffuse endothelial cell dysfunction (ECD) documented by several techniques occurs commonly in adult and childhood SV. Similar ECD is also seen in CTD. The mechanisms probably relate to inflammatory cytokines such as TNF. The particular role of vasculitic, as opposed to synovial or internal organ inflammation, may be release of secondary mediators directly into the blood stream- whence they can reach distant endothelial beds to induce this diffuse ECD.

SUMMARY

Endothelial injury is the first step in atherosclerosis, where peripheral abnormalities correlate with coronary artery responses. The diffuse ECD in CTD suggests that vascular inflammation may initiate the accelerated CVS disease there. The new findings of similar ECD in primary SV predicts enhanced atherosclerosis here too. In Kawasaki syndrome, persistent late ECD correlates with abnormal coronary responses. In adult SV, initial data also suggests increased subclinical atherosclerosis. The role of endothelial function in the clinical outcome of SV deserves more attention. Research to pinpoint the mechanisms of ECD should lead to more specific therapies that may ameliorate the continuing late morbidity and mortality of SV.

Modulating co-stimulation: a rational strategy in the treatment of rheumatoid arthritis?

Rheumatoid arthritis (RA) is a common destructive inflammatory disease that affects 0.5-1% of the population in many countries. Even though several new treatments have been introduced for patients with RA, a considerable proportion of patients do not benefit from these, and the need for alternative treatment strategies is clear. This review explores the potential for a therapy targeting the adaptive immune system by modulating co-stimulation of T cells with a CTLA4-Ig fusion protein (abatacept).

Peripheral blood but not synovial fluid natural killer T cells are biased towards a Th1-like phenotype in rheumatoid arthritis

Natural killer T (NKT) cells have been implicated in the regulatory immune mechanisms that control autoimmunity. However, their precise role in the pathogenesis of rheumatoid arthritis (RA) remains unclear. The frequency, cytokine profile and heterogeneity of NKT cells were studied in peripheral blood mononuclear cells (PBMCs) from 23 RA patients and 22 healthy control individuals, including paired PBMC–synovial fluid samples from seven and paired PBMC–synovial tissue samples from four RA patients. Flow cytometry revealed a decreased frequency of NKT cells in PBMCs from RA patients. NKT cells were present in paired synovial fluid and synovial tissue samples. Based on the reactivity of PBMC-derived NKT cells toward α-galactosylceramide, RA patients could be divided into responders (53.8%) and nonresponders (46.2%). However, NKT cells isolated from synovial fluid from both responders and nonresponders expanded upon stimulation with α-galactosylceramide. Analysis of the cytokine profile of CD4⁺ and CD4^- PBMC derived NKT cell lines from RA patients revealed a significantly reduced number of IL-4 producing cells. In contrast, synovial fluid derived NKT cell lines exhibited a Th0-like phenotype, which was comparable to that in healthy control individuals. This suggests that synovial fluid NKT cells are functional, even in patients with nonresponding NKT cells in their blood. We conclude that, because the number of Vα24⁺Vβ11⁺CD3⁺ NKT cells is decreased and the cytokine profile of blood-derived NKT cells is biased toward a Th1-like phenotype in RA patients, NKT cells might be functionally related to resistance or progression of RA. Providing a local boost to the regulatory potential of NKT cells might represent a useful candidate therapy for RA.

T-cell senescence: a culprit of immune abnormalities in chronic inflammation and persistent infection

Long-lived clonal T cells deficient in CD28 expression are commonly found in patients with inflammatory syndromes and persistent infections. Considering that CD28 loss is the most consistent immunological marker of aging, we propose that, in pathological states, CD28(null) T cells represent prematurely senescent cells resulting from persistent immune activation. These unusual lymphocytes have aberrant functions that contribute to disease-related immune abnormalities, and the degree of accumulation of CD28(null) T cells predicts the severity of clinical manifestations. We suggest that understanding of the biological properties of T cells that have reached replicative senescence will influence the future management of certain diseases. Indeed, studies on the molecular basis for the loss of CD28 are already providing information on methods to functionally rescue senescent T cells.

CD28nullCD4+ T cells--characterization of an effector memory T-cell population in patients with rheumatoid arthritis

CD4+ T cells lacking the costimulatory molecule CD28 have been described both in elderly individuals and in chronic inflammatory disorders, one being rheumatoid arthritis (RA). We, in this study, provide a comprehensive characterization of cell surface markers on and function of such CD28nullCD4+ T cells, as well as correlations with clinical parameters. We conclude that of all surface markers associated with these cells, only CD57 and CD11b are expressed on the majority of them. This CD28null population occurred in one-third of patients with RA and was independent of clinical characteristics. The population was persistent and expanded in peripheral blood, but was excluded from the joint in most patients. Functionally, CD28nullCD4+ T cells were potent effector memory cells with regard to their proliferation and cytokine-secretion profiles. This capacity correlated with a hitherto unpublished surface phenotype, the cells being uniformly CCR7- and CD43high. Moreover, a new terminally differentiated CD45RA+CCR7- population of CD4+ T cells was identified. We would like to suggest that in the unbalanced immune system of patients with autoimmune disease and chronic infection an expanded CD28nullCD4+ T-cell population able to secrete high levels of cytokines is likely to contribute to disease manifestations.

The expression of urotensin II receptor (U2R) is up-regulated by interferon-gamma

Urotensin-II (U-II) was identified as the natural ligand of the G protein-coupled receptor GPR14, which has been correspondingly renamed Urotensin-II receptor (U2R). The tissue distribution of U2R and the pharmacological effects of U-II suggest a novel neurohormonal system with potent cardiovascular effects. We here report the human rhabdomyosarcoma cell line TE-671 as the first natural and endogenous source of functional U2R in an immortalized cell line. In TE-671 cells, U-II stimulated extracellular signal regulated kinase phosphorylation and increased c-fos mRNA expression. Furthermore, we demonstrate that the expression of U2R mRNA and functional U-II high affinity binding sites are serum-responsive and that they are specifically up-regulated by interferon gamma (IFNgamma). We propose that IFNgamma contributes to the previously observed increase of U2R density in the heart tissue of congestive heart failure (CHF) patients and we suggest that U2R up-regulation, as a consequence of an inflammatory response, could lead to a clinical worsening of this disease.

Multiple functions for CD28 and cytotoxic T lymphocyte antigen-4 during different phases of T cell responses: implications for arthritis and autoimmune diseases

Chronic T cell responses, as they occur in rheumatoid arthritis, are complex and are likely to involve many mechanisms. There is a growing body of evidence that, in concert with the T cell antigen receptor signal, CD28 and cytotoxic T-lymphocyte antigen-4 (CTLA-4; CD152) are the primary regulators of T cell responses. Whereas CD28 primarily activates T cell processes, CTLA-4 inhibits them. The mechanism for this dichotomy is not fully understood, especially as CD28 and CTLA-4 recruit similar signalling molecules. In addition, recent studies demonstrate that CD28 and CTLA-4 have multiple functions during T cell responses. In particular, CTLA-4 exerts independent distinct effects during different phases of T cell responses that could be exploited for the treatment of rheumatoid arthritis.

Suppression of T cell responses by chondromodulin I, a cartilage-derived angiogenesis inhibitory factor: Therapeutic potential in rheumatoid arthritis

OBJECTIVE

Chondromodulin I (ChM-I), a cartilage matrix protein, promotes the growth and proteoglycan synthesis of chondrocytes. However, it also inhibits angiogenesis. Since ChM-I is expressed not only in cartilage, but also in the thymus, we investigated the modulation of T cell function by ChM-I to assess its therapeutic potential in rheumatoid arthritis (RA).

METHODS

The localization of ChM-I expression in mouse thymus tissue was examined by in situ hybridization. The proliferative response of peripheral blood T cells and synovial cells obtained from patients with RA was evaluated by (3)H-thymidine incorporation assay. The effects of ChM-I were examined using recombinant human ChM-I (rHuChM-I). Modulation of the antigen-specific immune response was evaluated by the recall response of splenic T cells and the delayed-type hypersensitivity response induced in the ear of mice primed with ovalbumin (OVA). Antigen-induced arthritis (AIA) was induced in mice by injecting methylated bovine serum albumin into the ankle joints 2 weeks after the priming.

RESULTS

ChM-I was expressed in the cortex of the thymus. Recombinant human ChM-I suppressed the proliferative response of mouse splenic T cells and human peripheral blood T cells stimulated with anti-CD3/CD28 antibodies, in a dose-dependent manner. Production of interleukin-2 was decreased in rHuChM-I-treated mouse CD4 T cells. Ten micrograms of rHuChM-I injected intraperitoneally into OVA-primed mice suppressed the induction of the antigen-specific immune response. Finally, rHuChM-I suppressed the development of AIA, and also suppressed the proliferation of synovial cells prepared from the joints of patients with RA.

CONCLUSION

These results suggest that ChM-I suppresses T cell responses and synovial cell proliferation, implying that this cartilage matrix protein has a therapeutic potential in RA.

Augmented production of chemokines by the interaction of type II collagen-reactive T cells with rheumatoid synovial fibroblasts

OBJECTIVE

To determine the impact of type II collagen (CII)-reactive T cells on the production of chemokines in the joints of patients with rheumatoid arthritis (RA).

METHODS

T cell proliferative responses to bovine CII were assayed in synovial fluid (SF) mononuclear cells and peripheral blood mononuclear cells. CII-stimulated T cells were cocultured with fibroblast-like synoviocytes (FLS). The expression of interleukin-8 (IL-8), monocyte chemoattractant protein 1 (MCP-1), and macrophage inflammatory protein 1 alpha (MIP-1 alpha) in the sera, SF, and supernatant of the CII-stimulated T cells and FLS coculture was measured by enzyme-linked immunosorbent assays.

RESULTS

The levels of IL-8, MCP-1, and MIP-1 alpha in SF were significantly higher than those in paired sera of RA patients. IL-8, MCP-1, and MIP-1 alpha levels in SF were strongly correlated with T cell responses to CII. When FLS were cocultured with CII-stimulated T cells, the production of IL-8, MCP-1, and MIP-1 alpha was significantly increased. This increase correlated well with the T cell proliferative response to CII. Chemokine production by coculture of CII-stimulated T cells and FLS was mediated mainly by direct cell-cell contact through CD40 ligand-CD40 engagement.

CONCLUSION

Our data indicate that the presence of CII-reactive T cells in RA joints can increase the production of chemokines such as IL-8, MCP-1, and MIP-1 alpha through interaction with FLS. This chemokine production is mediated by cell-cell contact, including CD40 ligand-CD40 engagement. These results suggest that CII-reactive T cells play a crucial role in the amplification and perpetuation of the inflammatory process in the rheumatoid synovium.

Targeting autoantigen-specific T cells and suppression of autoimmune encephalomyelitis with receptor-modified T lymphocytes

We demonstrate here the feasibility of antigen-specifically redirecting T cells against autoreactive T lymphocytes and thereby treating a model autoimmune disease. We created and transgenically expressed on T cells a heterodimeric chimeric receptor that genetically links an autoantigenic peptide, its restricting MHC, and the signal transduction domain of the T-cell receptor (TCR) zeta-chain. Engagement of the chimeric receptor by the TCR of autoreactive T cells activated the receptor-modified T cells in vitro and in vivo, inducing proliferation and cytolysis. Adoptively transferred receptor-modified T cells prevented and treated a model autoimmune disease, experimental allergic encephalomyelitis (EAE), even after epitope spreading had diversified the autoantigenic response. Treatment reduced disease severity and increased survival of affected animals, and was durable for >75 days. The receptor-modified cells acted both by strongly attenuating T-cell response to autoantigen as well as by shifting the residual response from an immunopathologic Th1 to a protective Th2 format.

Inducible nitric oxide synthase is expressed in synovial fluid granulocytes

The objective of the study was to evaluate the NO-producing potential of synovial fluid (SF) cells. SF from 15 patients with arthritis was compared with blood from the same individuals and with blood from 10 healthy controls. Cellular expression of inducible nitric oxide synthase (iNOS) was analysed by flow cytometry. High-performance liquid chromatography was used to measure l-arginine and l-citrulline. Nitrite and nitrate were measured colourimetrically utilizing the Griess' reaction. Compared to whole blood granulocytes in patients with chronic arthritis, a prominent iNOS expression was observed in SF granulocytes (P < 0.001). A slight, but statistically significant, increase in iNOS expression was also recorded in lymphocytes and monocytes from SF. l-arginine was elevated in SF compared to serum (257 +/- 78 versus 176 +/- 65 micro mol/l, P = 0.008), whereas a slight increase in l-citrulline (33 +/- 11 versus 26 +/- 9 micro mol/l), did not reach statistical significance. Great variations but no significant differences were observed comparing serum and SF levels of nitrite and nitrate, respectively, although the sum of nitrite and nitrate tended to be elevated in SF (19.2 +/- 20.7 versus 8.6 +/- 6.5 micro mol/l, P = 0.054). Synovial fluid leucocytes, in particular granulocytes, express iNOS and may thus contribute to intra-articular NO production in arthritis.

Characterization of autoreactive T cells to the autoantigens heterogeneous nuclear ribonucleoprotein A2 (RA33) and filaggrin in patients with rheumatoid arthritis

The role of autoimmune reactions in the pathogenesis of rheumatoid arthritis (RA) is poorly understood. To address this issue we have investigated the spontaneous T cell response to two well-characterized humoral autoantigens in RA patients and controls: 1) the heterogeneous nuclear ribonucleoprotein A2, i.e., the RA33 Ag (A2/RA33), and 2) filaggrin in unmodified and citrullinated forms. In stimulation assays A2/RA33 induced proliferative responses in PBMC of almost 60% of the RA patients but in only 20% of the controls (patients with osteoarthritis or psoriatic arthritis and healthy individuals), with substantially stronger responses in RA patients (p < 0.00002). Furthermore, synovial T cells of seven RA patients investigated were also clearly responsive. In contrast, responses to filaggrin were rarely observed and did not differ between RA patients and controls. Analysis of A2/RA33-induced cytokine secretion revealed high IFN-gamma and low IL-4 production in both RA and control PBMC, whereas IL-2 production was mainly observed in RA PBMC (p < 0.03). Moreover, A2/RA33-specific T cell clones from RA patients showed a strong Th1 phenotype and secreted higher amounts of IFN-gamma than Th1 clones from controls (p < 0.04). Inhibition experiments performed with mAbs against MHC class II molecules showed A2/RA33-induced T cell responses to be largely HLA-DR restricted. Finally, immunohistochemical analyses revealed pronounced overexpression of A2/RA33 in synovial tissue of RA patients. Taken together, the presence of autoreactive Th1-like cells in RA patients in conjunction with synovial overexpression of A2/RA33 may indicate potential involvement of this autoantigen in the pathogenesis of RA.

Characterization of CD28(-)CD4(+) T cells in living kidney transplant patients with long-term allograft acceptance

CD28(-)CD4(+) T-cell subpopulation is expanded in kidney allograft patients with long graft survival. To seek for the roles of CD28(-)CD4(+) T cells in the long-term acceptance of kidney allografts, we characterized this population by analyzing cell surface molecules, TCR V(beta) repertoire, mixed lymphocyte reaction (MLR), and cytokine production. The number of CD28(-)CD4(+) T cells increased correlatively with time after transplantation in this group of patients. The CD28(-)CD4(+) T cells did not express detectable levels of CD25, CD69, V(alpha)24, or CTLA-4 but expressed heterogeneous amounts of CD45 RA on the surface. Freshly sorted CD28(-)CD4(+) T cells revealed a restricted V(beta) repertoire, whereas the V(beta) usage of CD28(+)CD4(+) T cells from the same patients was much diversified. Expression levels of TGF-beta and IFNgamma gene were significantly higher in the CD28(-) CD4(+) T cells than in the CD28(+)CD4(+) T cells from the kidney allograft patients. These findings suggest that an oligoclonal CD28(-) CD4(+) T-cell population is continuously activated in patients with long allograft survival, which may be linked with the long-term acceptance.

Clonal biases of peripheral CD8 T cell repertoire directly reflect local inflammation in polymyositis

Polymyositis (PM) involves destruction of striated muscles by autoaggressive CD8 T cells, which accumulate and secrete cytotoxic effector molecules in the affected muscles. Previous studies of peripheral T cell repertoires from normal individuals and patients with viral infections have shown that primed CD8 T cells, unlike CD4 T cells, are prone to expand clonally and persist as large populations in the peripheral blood. These facts made us assume that autoaggressive myocytotoxic CD8 T cells would expand clonally in the peripheral blood from patients with PM. By clonal analyses of peripheral T cells from patients and age-matched controls, we show here that clonal expansion of CD8 T cells was more frequent in patients. This was not significant in CD4 T cells. In analogy to virus-specific T cells, the expanded T cells persisted as large populations over time. Analysis of the muscle biopsy specimens revealed that some of the expanded clones were infiltrating in the affected muscles from the same patients. These results provide the first evidence that local autoimmune reaction directly elicits significant biases in peripheral T cell repertoire. The expanded cells, which should be candidate autoaggressive T cells, were readily isolated from the peripheral blood for analysis of expressed genes including perforin. Thus, our findings should give us an immediate clue to analysis of the pathogenic T cells in PM.

T-cell receptor repertoire in human germinal centres

A search for an antigen-driven expansion of T lymphocytes in the inflamed joints in rheumatoid arthritis (RA) patients have been going on for decades. We here analyzed the human germinal centre T-cell receptor (TCR) Vbeta gene usage with polymerase chain reaction (PCR) combined with sequence analysis, to address the question of clonality in tonsils and synovial tissue from RA patients. Our data show a large degree of TCR heterogeneity in both these histological structures. Furthermore, clonally related T cells were found within different closely located germinal centres indicating either an active T-cell migration between germinal centres (GC) or that a T-cell clone may seed more than one GC.

Shift toward T helper 1 cytokines by type II collagen-reactive T cells in patients with rheumatoid arthritis

OBJECTIVE

To investigate the impact of type II collagen (CII)-reactive T cells on the Th1/Th2 cytokine balance in patients with rheumatoid arthritis (RA).

METHODS

T cell proliferative responses to bovine CII were examined in synovial fluid mononuclear cells (SFMC) and peripheral blood mononuclear cells (PBMC) by mixed lymphocyte culture. CII-reactive T cell lines were generated from the SFMC and PBMC. Interferon-gamma (IFNgamma), interleukin-12 (IL-12), and IL-4 were measured by enzyme-linked immunosorbent assay in the SF, sera, and culture supernatants of PBMC and SFMC that had been stimulated with CII.

RESULTS

The frequency of CII-reactive T cells was higher in the PBMC from RA patients than in that from osteoarthritis patients and healthy control subjects. In RA patients, CII-reactive T cells were more prevalent in SFMC than in PBMC. The mean level of IFNgamma and the ratio of IFNgamma to IL-4 were significantly higher in the culture supernatants of T cells stimulated with CII; these differences were more prominent in SFMC. Levels of IL-12 in the culture supernatants of SFMC and PBMC stimulated with CII were significantly higher than those in unstimulated supernatants. T cell responsiveness correlated well with the level of type 1 cytokines in culture supernatants from RA T cells stimulated with CII. In the CII-reactive cell lines, the increased production of IFNgamma was consistent with clonal expansion.

CONCLUSION

CII-reactive T cells are more abundant in SFMC than in PBMC and are strongly associated with a shift toward Thl cytokine in the inflamed joints of RA patients. Our results suggest that a skewing toward type 1 cytokines by CII-reactive T cells may play an important role in the chronic inflammatory process of RA.

Clonality and longevity of CD4+CD28null T cells are associated with defects in apoptotic pathways

CD4(+)CD28(null) T cells are oligoclonal lymphocytes rarely found in healthy individuals younger than 40 yr, but are found in high frequencies in elderly individuals and in patients with chronic inflammatory diseases. Contrary to paradigm, they are functionally active and persist over many years. Such clonogenic potential and longevity suggest altered responses to apoptosis-inducing signals. In this study, we show that CD4(+)CD28(null) T cells are protected from undergoing activation-induced cell death. Whereas CD28(+) T cells underwent Fas-mediated apoptosis upon cross-linking of CD3, CD28(null) T cells were highly resistant. CD28(null) T cells were found to progress through the cell cycle, and cells at all stages of the cell cycle were resistant to apoptosis, unlike their CD28(+) counterparts. Neither the activation-induced up-regulation of the IL-2R alpha-chain (CD25) nor the addition of exogenous IL-2 renders them susceptible to Fas-mediated apoptosis. These properties of CD28(null) T cells were related to high levels of Fas-associated death domain-like IL-1-converting enzyme-like inhibitory protein, an inhibitor of Fas signaling that is normally degraded in T cells following activation in the presence of IL-2. Consistent with previous data showing protection of CD28(null) cells from spontaneous cell death, the present studies unequivocally show dysregulation of apoptotic pathways in CD4(+)CD28(null) T cells that favor their clonal outgrowth and maintenance in vivo.

The down-regulation of HLA-DM gene expression in rheumatoid arthritis is not related to their promoter polymorphism

HLA-DM molecule, a class II-like heterodimer, is a critical factor of HLA class II-dependent Ag presentation. It acts as a molecular chaperone and also functions as a peptide editor favoring the presentation of high-stability peptides. Thus, it appears to skew the peptide repertoire presented to T cells. Variation in HLA-DM expression has considerable effect on Ag presentation and regulation of these genes is likely to be a prerequisite to prevent autoimmunity. In this study, rheumatoid arthritis (RA) was chosen as a model of human autoimmune disease since its genetic susceptibility is known to be associated with the HLA-DR and -DM components. We described a limited nucleotide polymorphism in the HLA-DM promoters with functional impact on basal transcriptional activity and IFN-gamma induction as assessed in vitro. However, no difference of allele frequencies was found between controls and RA patients. Despite of this lack of association, expression of HLA-DM molecules was also investigated. Interestingly, an underexpression of HLA-DM transcripts and protein was shown in peripheral blood B cells from RA patients compared with controls or inflammatory arthritis patients. This underexpression does not affect HLA-DR genes and is responsible for a decrease of the DM:DR ratio in RA patients. This specific HLA-DM down-regulation is likely to have important consequences on Ag presentation and could participate in the autoimmune process in RA.

T lymphocyte costimulatory molecules in host defense and immunologic diseases

BACKGROUND

Costimulation is an essential component for the optimal induction of T cell-mediated immune responses. Manipulation of the costimulatory pathway with antibodies or genetically-engineered fusion proteins is an important strategy to treat immune-related diseases including allergy, asthma, transplantation and cancer. Recent advances have revealed several new costimulatory molecules, and the functional characteristics of each costimulatory pathway are now becoming clearer.

LEARNING OBJECTIVES

In this review, we summarize basic outlines of the costimulatory systems in terms of molecular structure, expression kinetics and immunological function. We further discuss involvement and therapeutic manipulation of costimulation in several clinical diseases.

DATA SOURCE

The MEDLINE database was used to review the literature related to costimulation.

CONCLUSION

Costimulatory pathways play an essential role in the activation and regulation of T cell immune responses and the induction of T cell tolerance. Therapeutic manipulation of the costimulatory system demonstrates beneficial effects to treat immunological diseases in murine models as well as some clinical situations.

Central role of thrombospondin-1 in the activation and clonal expansion of inflammatory T cells

Thrombospondin-1 (TSP) is a transiently expressed matricellular protein known to promote chemotaxis of leukocytes to inflammatory sites. However, TSP and its receptor CD36 are abundantly expressed in chronically inflamed tissues such as the rheumatoid synovium. Here, we show that TSP provides the costimulatory signal that is necessary for the activation of autoreactive T cells. Data presented reveal that TSP-mediated costimulation is achieved through its independent interaction with CD36 on APCs and with CD47 on T cells. We propose that a CD47-TSP-CD36 trimolecular complex is a novel costimulatory pathway that significantly decreases the threshold of T cell activation. Consistent with the paradigm that lesions in rheumatoid synovitis are sites of antigenic recognition, the characteristic focal expression of TSP on APCs such as macrophages and fibroblast-like synoviocytes suggest a central role of TSP in the expansion of tissue-infiltrating T cells.

Association of MHC and rheumatoid arthritis. Association of RA with HLA-DR4: the role of repertoire selection

Most patients with rheumatoid arthritis (RA) express HLA-DR4, HLA-DR1 or HLA-DR10. These alleles share a common amino acid motif in their third hypervariable regions: the shared epitope. In normals and patients with RA, HLA-DR genes exert a major influence on the CD4 alpha beta T-cell repertoire, as shown by studies of AV and BV gene usage and by BV BJ gene usage by peripheral blood CD4 alpha beta T-cells. However, the rheumatoid T-cell repertoire is not entirely under HLA-DR influence, as demonstrated by discrepancies in VB JB gene usage between identical twins discordant for RA and by contraction of the CD4 alpha beta T-cell repertoire in RA patients. Shared epitope positive HLA-DR alleles may shape the T-cell repertoire by presenting self peptides to CD4 T cells in the thymus. Peptides processed from HLA-DR molecules and encompassing the shared epitope may also be presented by HLA-DQ and select CD4 alpha beta T cells in the thymus. Thus, shared epitope-positive alleles impose a frame on the T-cell repertoire. This predisposing frame is further modified (by unknown factors) to obtain the contracted rheumatoid repertoire.

Characterization of the cytokine network at a single cell level in mice with collagen-induced arthritis using a dual color ELISPOT assay

Collagen-induced arthritis (CIA) in mice has been classified as a Thl-mediated disease. However, most evidence for this has been obtained by indirect experiments; for example, the administration of neutralizing anti-interferon-gamma (IFN-gamma) antibody reduced the severity of arthritis. To obtain direct evidence about the cytokine balance in CIA mice, we analyzed the cytokine-secreting cell in CIA mice at the single cell level using a dual color enzyme-linked immunospot (ELISPOT) assay, which enabled us to analyze interleukin-2 (IL-2)-secreting cells or IL-4-secreting cells or both simultaneously. Furthermore, to characterize the cytokine network in the pathogenesis of CIA, the frequency of the cells secreting IL-12, which induced the development of naive Th cells into Th1 cells, was analyzed. The results show that in the prearthritic phase, the number of IL-12-secreting cells in spleen and peritoneal exuded cells is increased, and Th1 cells in lymph node and spleen are dominant. In contrast, after the onset of clinical arthritis, the number of IL-12-secreting cells in spleen, lymph node, and peritoneal exuded cells is decreased, and there is a shift from a Thl-dominant to a Th2-dominant state in lymph node and spleen. The results indicated that the pathogenesis of CIA is associated with a disruption in the normal ratio of Th1/Th2 at cell level.

Characterization of tissue outgrowth developed in vitro in patients with rheumatoid arthritis: involvement of T cells in the development of tissue outgrowth

BACKGROUND

The aim of this study was to analyze cellular and cytokine interactions governing the development of synovial tissue outgrowth in patients with rheumatoid arthritis (RA).

METHODS

A single-cell suspension of dissociated synovial tissues of RA patients was cultured for a long period to develop tissue outgrowth. The resulting tissue outgrowth was characterized by immunohistochemical staining and ELISA.

RESULTS

The tissue outgrowth developed in vitro included various cell types, such as macrophage-like synovial cells, fibroblast-like synovial cells and lymphocytes. Even after prolonged cultivation, synovial cells devoid of infiltrating T lymphocytes did not form tissue outgrowth. The outgrowth contained CD3+ cells, LeuM3 (CD14)+ cells and HLA-DR+ cells. The T cells expressed lymphocyte function-associated antigen (LFA)-1 and CD2, and the synovial cells expressed intracellular adhesion molecule (ICAM)-1 and LFA-3, suggesting possible interactions via LFA-1/ICAM-1 and CD2/LFA-3. Production of T-cell derived IFN-gamma and IL-17 and synovial-cell-derived fibroblast growth factor (FGF)-1 and IL-15 was confirmed in the tissue outgrowth as well as in RA synovial tissue. These cell types stimulate each other by secreting cytokines, leading to the secretion of proinflammatory cytokines and matrix metalloproteinase (MMP)-1 by the tissue outgrowth and proliferation of both lymphocytes and synovial cells.

CONCLUSION

This study emphasizes the importance of cellular interactions between T cells and synovial cells, via adhesion molecules and the secretion of cytokines with stimulatory activity towards other cell types, for the hyperactivity of RA synovial cells.