Proinflammatory mediator–induced reversal of CD4+,CD25+ regulatory T cell–mediated suppression in rheumatoid arthritis

Objective

We previously demonstrated that CD4+,CD25+ regulatory T (Treg) cells are present in increased numbers in the synovial fluid (SF) of rheumatoid arthritis (RA) patients and display enhanced suppressive activity as compared with their peripheral blood (PB) counterparts. Despite the presence of these immunoregulatory cells in RA, chronic inflammation persists. The purpose of the present study was to investigate whether particular proinflammatory mediators that are associated with RA could abrogate CD4+,CD25+ Treg–mediated suppression.

Methods

Monocyte phenotype was determined by flow cytometry and cytokine levels by enzyme‐linked immunosorbent assay. Magnetically sorted CD4+,CD25– and CD4+,CD25+ T cells derived from the PB and SF obtained from RA patients were stimulated alone or in coculture with anti‐CD3 monoclonal antibody (mAb) and autologous antigen‐presenting cells, in the absence or presence of anti‐CD28 mAb or the proinflammatory cytokines interleukin‐6 (IL‐6), tumor necrosis factor α (TNFα), or IL‐7.

Results

Monocytes from the SF of RA patients displayed increased expression of HLA class II molecules, CD80, CD86, and CD40 as compared with PB‐derived monocytes, indicating their activated status. Mimicking this increased costimulatory potential, addition of anti‐CD28 mAb to cocultures of CD4+,CD25– and CD4+,CD25+ T cells resulted in reduced CD4+,CD25+ Treg–mediated suppression in both PB and SF. Furthermore, IL‐7 and, to a limited extent, TNFα, both of which are produced by activated monocytes and were detected in SF, abrogated the CD4+,CD25+ Treg–mediated suppression. In contrast, IL‐6 did not influence Treg‐mediated suppression.

Conclusion

Our findings suggest that the interaction of CD4+,CD25+ Treg cells with activated monocytes in the joint might lead to diminished suppressive activity of CD4+,CD25+ Treg cells in vivo, thus contributing to the chronic inflammation in RA.

     

Impaired suppression of synovial fluid CD4+CD25− T cells from patients with juvenile idiopathic arthritis by CD4+CD25+ Treg cells

Objective

Natural CD4+CD25+FoxP3+ Treg cells play a crucial role in maintaining immune homeostasis and controlling autoimmunity. In patients with juvenile idiopathic arthritis (JIA), inflammation occurs despite the increased total numbers of Treg cells in the synovial fluid (SF) compared to the peripheral blood (PB). This study was undertaken to investigate the phenotype of CD4+ T cells in PB and SF from JIA patients, the function of synovial Treg cells, and the sensitivity of PB and SF CD4+CD25− effector T cells to the immunoregulatory properties of Treg cells, and to study the suppression of cytokine secretion from SF effector T cells by Treg cells.

Methods

The phenotypes of effector T cells and Treg cells of PB and SF from JIA patients and healthy donors were determined by flow cytometry. The functionality of isolated Treg cells and effector T cells was quantified in ³H‐thymidine proliferation assays. Cytokine levels were analyzed using Bio‐Plex Pro assay.

Results

Compared to PB, SF showed significantly elevated numbers of activated and differentiated CD4+CD45RO+ T cells. Sensitivity of SF effector T cells to the suppressive effects of Treg cells from both PB and SF was impaired, correlating inversely with the expression of CD69 and HLA–DR. However, SF effector T cell cytokine secretion was partly suppressed by SF Treg cells.

Conclusion

Our findings indicate that regulation is impaired in the SF of patients with JIA, as shown by the resistance of effector T cells to immunoregulation by functional Treg cells. This resistance of the SF effector T cells might be due to their activated phenotype.

     

ANTI‐CD3 therapy expands the numbers of CD4+ and CD8+ treg cells and induces sustained amelioration of collagen‐induced arthritis

Objective

To assess the therapeutic potential of anti‐CD3 monoclonal antibodies (mAb) for rheumatoid arthritis, using collagen‐induced arthritis as an animal model.

Methods

Arthritis was induced in DBA/1 mice by immunization with type II collagen. After disease onset, a single injection of anti‐CD3 mAb (20 μg/mouse) was administered, and arthritis severity was monitored over a 10‐day period.

Results

Anti‐CD3 mAb treatment resulted in a sustained reduction in disease activity, which was associated with an increase in the proportion of naturally occurring CD4+CD25+FoxP3+ regulatory T (Treg) cells and the generation of a population of CD8+CD25+FoxP3+ Treg cells. Anti‐CD3 mAb treatment did not alter the capacity of CD4+ Treg cells to suppress effector T cell proliferation and interferon‐γ (IFNγ) production in vitro. However, CD4+ Treg cells from both anti‐CD3 mAb–treated and control mice were unable to suppress interleukin‐17 (IL‐17) production. In contrast, CD8+ Treg cells induced by anti‐CD3 therapy suppressed IL‐17 production as well as CD4+ T cell proliferation and IFNγ production.

Conclusion

These results show that anti‐CD3 mAb treatment has important therapeutic potential for rheumatoid arthritis and has the capacity to generate antiarthritic CD8+ Treg cells and expand the relative numbers of CD4+ Treg cells.

     

Reduced expression of decay‐accelerating factor 1 on CD4+ T cells in murine systemic autoimmune disease

Objective

Deficiency of decay‐accelerating factor 1 (termed Daf1 in mice) has been shown to exacerbate autoimmunity, and recent studies have suggested that this may be explained by Daf1 acting as a regulator of T cell immunity. The aim of this study was to determine whether Daf1 expression on T cells is modulated during development of autoimmunity in mice.

Methods

To test this hypothesis, we examined Daf1 levels in NZB, DBA/2, and B10.S mice before and after induction of murine mercury‐induced autoimmunity (mHgIA). Daf1 was measured by real‐time polymerase chain reaction and flow cytometry, and levels of Daf1 were correlated with markers of lymphocyte activation and cytokine production.

Results

Autoimmune‐prone NZB mice had low endogenous levels of Daf1 irrespective of the induction of mHgIA. Induction of autoimmunity reduced Daf1 expression in mHgIA‐sensitive B10.S mice, particularly on activated/memory (CD44^high) CD4+ T cells that accumulate as a result of exposure to mercury. Murine mercury‐induced autoimmunity–resistant DBA/2 mice, which fail to accumulate CD44^high T cells, showed no change in Daf1 expression. Modulation of Daf1 expression was found to require CD4+ T cell costimulation, since B10.S mice deficient in CD28 were unable to down‐regulate Daf1 or accumulate activated/memory CD4+ T cells. In B10.S mice exposed to mercury, the production of interleukin‐4 (IL‐4), but not that of IL‐2 or interferon‐γ, in the spleen was associated with CD44^high,Daf1^low,CD4+ T cells.

Conclusion

These findings demonstrate that reduction of Daf1 expression is closely associated with CD4+ T cell activation and the accumulation of CD44^high(activated/memory),CD4+ T cells in both spontaneous and induced systemic autoimmune disease.

     

Pregnancy in patients with ankylosing spondylitis: Do regulatory T cells play a role?

Objective

To investigate the numerical and functional changes of CD4+CD25^high regulatory T (Treg) cells during pregnancy and postpartum in patients with ankylosing spondylitis (AS).

Methods

The frequency of CD4+CD25^high T cells was determined by flow cytometry in 10 pregnant and 5 nonpregnant patients with AS as well as in 14 pregnant and 4 nonpregnant healthy controls. Pregnant individuals were investigated at the third trimester and 8 weeks postpartum. Treg cells and CD4+CD25? effector T (Teff) cells separated by fluorescence‐activated cell sorting were stimulated with anti‐CD3 and anti‐CD28 monoclonal antibodies, alone or in coculture, to investigate proliferation and cytokine secretion.

Results

The frequency of CD4+CD25^high Treg cells was significantly higher during pregnancy than postpartum in both healthy control subjects and patients with AS. In contrast to Treg cells in healthy pregnant women, Treg cells in pregnant women with AS secreted only small amounts of interleukin‐10 and showed lower suppression of tumor necrosis factor α and interferon‐γ secretion by CD4+CD25? Teff cells. At the postpartum time point, proinflammatory cytokine levels in the Treg/Teff cell cocultures and Teff cell monocultures were significantly higher in patients with AS than in healthy controls.

Conclusion

Pregnancy influenced the expansion and cytokine secretion of Treg cells in both patients with AS and control subjects. However, the Treg cells of pregnant patients with AS failed to support an antiinflammatory cytokine milieu, thereby possibly contributing to the persistent disease activity of AS during pregnancy.

     

Expression of toll‐like receptor 2 on CD16+ blood monocytes and synovial tissue macrophages in rheumatoid arthritis

Objective

CD16 (IgG Fcγ receptor type IIIA [FcγRIIIA])–expressing CD14+ monocytes express high levels of Toll‐like receptor 2 (TLR‐2) and are able to efficiently produce proinflammatory cytokines such as tumor necrosis factor α (TNFα). To understand the role of CD16 and TLR‐2 in monocyte and macrophage activation in rheumatoid arthritis (RA), we investigated the expression of TLR‐2 on CD16+ blood monocytes and synovial tissue macrophages and the effect of CD16 and TLR‐2 activation on cytokine production.

Methods

The expression of CD14, CD16, TLR‐2, and TLR‐4 on blood monocytes was measured by flow cytometric analysis. CD16 and TLR‐2 expression in RA synovial tissue was detected by 2‐color immunofluorescence labeling. CD16+ mature monocytes were prepared by incubating blood monocytes in plastic plates for 24 hours. These adhered monocytes were stimulated with lipoteichoic acid (LTA), anti‐FcγRIII antibody, and Hsp60 for 5 hours, and culture supernatants were measured for various cytokines by immunoassay. The activation of NF‐κB was detected by electrophoretic mobility shift assay.

Results

The frequency of CD16+ cells in all blood monocytes was significantly increased in patients with RA compared with healthy controls. TLR‐2 was expressed at higher levels on CD16+ monocytes than on CD16− monocytes, while TLR‐4 was expressed similarly on both monocytes. In RA synovial tissue, CD16+/TLR‐2+ cells were distributed mainly in the lining layer. TLR‐2 expression on monocytes was enhanced by macrophage colony‐stimulating factor (M‐CSF) and interleukin‐10 (IL‐10), but was reduced by transforming growth factor β1, while CD16 expression was inducible by these cytokines. Adhered monocytes (∼50% CD16+) produced TNFα, IL‐1β, IL‐6, IL‐8, IL‐12 p40, IL‐1 receptor antagonist, and IL‐10 after LTA stimulation. This cytokine response was inhibited significantly by anti–TLR‐2 antibody and partly by anti–TLR‐4 antibody. Anti‐FcγRIII antibody stimulation markedly enhanced the LTA‐induced TNFα response. Hsp60 could stimulate TNFα production by adhered monocytes, which was inhibited similarly by anti–TLR‐2 antibody and anti–TLR‐4 antibody. NF‐κB activation in adhered monocytes was induced by LTA, but this NF‐κB activity was not augmented by anti‐FcγRIII antibody stimulation.

Conclusion

These results suggest that CD16+ monocytes and synovial tissue macrophages with high TLR‐2 expression may be induced by M‐CSF and IL‐10, and their production of TNFα could be simulated by endogenous TLR ligands such as Hsp60 and FcγRIIIA ligation by small immune complexes in RA joints.

     

Large‐scale extraction and characterization of CD271+ multipotential stromal cells from trabecular bone in health and osteoarthritis: Implications for bone regeneration strategies based on uncultured or minimally cultured multipotential stromal cells

Objective

To test the hypothesis that CD45^lowCD271+ bone marrow multipotential stromal cells (MSCs) are abundant in the trabecular bone niche and to explore their functional “fitness” in health and osteoarthritis (OA).

Methods

Following enzymatic extraction, MSC release was evaluated using colony‐forming unit–fibroblast (CFU‐F) and colony‐forming unit–osteoblast assays, flow cytometry, and confocal microscopy. CD45^lowCD271+ cells isolated by fluorescence‐activated cell sorting were enumerated and expanded under standard and clonal conditions. Their proliferative and osteogenic potencies were assessed in relation to donor age and compared with those of aspirated CD45^lowCD271+ cells. In vitro and in vivo MSC “aging” was measured using quantitative polymerase chain reaction–based telomere length analysis, and standard differentiation assays were utilized to demonstrate multipotentiality.

Results

Cellular isolates from trabecular bone cavities contained ∼65‐fold more CD45^lowCD271+ cells compared with aspirates (P < 0.0001) (median 1.89% [n = 39] and 0.029% [n = 46], respectively), concordant with increased CFU‐F release. Aspirated and enzymatically released CD45^lowCD271+ cells had identical MSC phenotypes (∼100% CD73+CD105+CD13+, ∼50–60% CD146+CD106+CD166+) and contained large proportions of highly clonogenic multipotential cells. In vitro osteogenic potency of freshly isolated CD45^lowCD271+ cells was comparable with, and often above, that of early‐passage MSCs (8–14%). Their frequency and in vivo telomere status in OA bone were similar to those in bone from age‐matched controls.

Conclusion

Our findings show that CD45^lowCD271+ MSCs are abundant in the trabecular bone cavity and indistinguishable from aspirated CD45^lowCD271+ MSCs. In OA they display aging‐related loss of proliferation but no gross osteogenic abnormality. These findings offer new opportunities for direct study of MSCs in musculoskeletal diseases without the requirement for culture expansion. They are also relevant for direct therapeutic exploitation of prospectively isolated, minimally cultured MSCs in trauma and OA.

     

Interleukin‐17–producing T cells are enriched in the joints of children with arthritis,but have a reciprocal relationship to regulatory T cell numbers

Objective

To identify interleukin‐17 (IL‐17)–producing T cells from patients with juvenile idiopathic arthritis (JIA), and investigate their cytokine production, migratory capacity, and relationship to Treg cells at sites of inflammation, as well as to test the hypothesis that IL‐17+ T cell numbers correlate with clinical phenotype in childhood arthritis.

Methods

Flow cytometry was used to analyze the phenotype, cytokine production, and chemokine receptor expression of IL‐17–producing T cells in peripheral blood and synovial fluid mononuclear cells from 36 children with JIA, in parallel with analysis of forkhead box P3 (FoxP3)–positive Treg cells. Migration of IL‐17+ T cells toward CCL20 was assessed by a Transwell assay. Synovial tissue was analyzed by immunohistochemistry for IL‐17 and IL‐22.

Results

IL‐17+ T cells were enriched in the joints of children with JIA as compared with the blood of JIA patients (P = 0.0001) and controls (P = 0.018) and were demonstrated in synovial tissue. IL‐17+ T cell numbers were higher in patients with extended oligoarthritis, the more severe subtype of JIA, as compared with patients with persistent oligoarthritis, the milder subtype (P = 0.046). Within the joint, there was an inverse relationship between IL‐17+ T cells and FoxP3+ Treg cells (r = 0.61, P = 0.016). IL‐17+,CD4+ T cells were uniformly CCR6+ and migrated toward CCL20, but synovial IL‐17+ T cells had variable CCR4 expression. A proportion of IL‐17+ synovial T cells produced IL‐22 and interferon‐γ.

Conclusion

This study is the first to define the frequency and characteristics of “Th17” cells in JIA. We suggest that these highly proinflammatory cells contribute to joint pathology, as indicated by relationships with clinical phenotypes, and that the balance between IL‐17+ T cells and Treg cells may be critical to outcome.

     

Increased intraarticular interleukin‐7 in rheumatoid arthritis patients stimulates cell contact–dependent activation of CD4+ T cells and macrophages

Objective

To determine the level of intraarticular expression of interleukin‐7 (IL‐7) in patients with rheumatoid arthritis (RA) and to investigate the mechanisms by which IL‐7 facilitates activation of CD4+ T cells and monocyte/macrophages in RA.

Methods

IL‐7 levels were measured in synovial fluid obtained from patients with RA and patients with osteoarthritis (OA). Immunohistologic analysis was used to assess the expression of IL‐7 in synovial tissue from patients with RA. Proliferation and activation markers were determined in order to measure the effect of IL‐7 on mononuclear cells, isolated CD4+ T cells, and monocyte/macrophages from the peripheral blood and synovial fluid. Cocultures of CD4+ T cells and monocytic cells in the absence or presence of a semipermeable membrane were performed to assess the extent to which IL‐7 induces its effects, either contact dependently or via soluble mediators.

Results

IL‐7 levels were increased in synovial fluid from patients with RA compared with the levels in synovial fluid from patients with OA. Macrophages, fibroblasts, and endothelial cells in the joint lining tissue expressed abundant IL‐7. In vitro, synovial fluid CD4+ T cells and macrophages were hyperresponsive to IL‐7 when compared with peripheral blood cells. Furthermore, IL‐7 enhanced cell contact–dependent activation of CD4+ T cells and monocyte/macrophages.

Conclusion

The abundant intraarticular expression of IL‐7 and the stimulation by IL‐7 of contact‐dependent activation of CD4+ T cells and monocytic cells indicate that this cytokine plays an important proinflammatory role in RA synovitis. Further identification of IL‐7–induced pathways may improve understanding of the important interactive role of CD4+ T cells and monocytic cells in RA.

     

Suppression of collagen‐induced arthritis in growth arrest and DNA damage–inducible protein 45β–deficient mice

Objective

Growth arrest and DNA damage–inducible protein 45β (GADD45β) is involved in stress responses, cell cycle regulation, and oncogenesis. Previous studies demonstrated that GADD45β deficiency exacerbates K/BxN serum–induced arthritis and experimental allergic encephalomyelitis (EAE) in mice, indicating that GADD45β plays a suppressive role in innate and adaptive immune responses. To further understand how GADD45β regulates autoimmunity, we evaluated collagen‐induced arthritis in GADD45β^–/– mice.

Methods

Wild‐type (WT) and GADD45β^–/– DBA/1 mice were immunized with bovine type II collagen (CII). Serum anticollagen antibody levels were quantified by enzyme‐linked immunosorbent assay. Expression of cytokines and matrix metalloproteinases in the joint and spleen was determined by quantitative polymerase chain reaction. The in vitro T cell cytokine response to CII was measured by multiplex analysis. CD4+CD25+ Treg cells and Th17 cells were quantified using flow cytometry.

Results

GADD45β^–/– mice showed significantly lower arthritis severity and joint destruction compared with WT mice. MMP‐3 and MMP‐13 expression was also markedly reduced in GADD45β^–/– mice. However, serum anti‐CII antibody levels were similar in both groups. FoxP3 and interleukin‐10 (IL‐10) expression was increased 2–3‐fold in splenocytes from arthritic GADD45β^–/– mice compared with those from WT mice. Flow cytometric analysis showed greater numbers of CD4+CD25+ Treg cells in the spleen of GADD45β^–/– mice than in the spleen of WT mice. In vitro studies showed that interferon‐γ and IL‐17 production by T cells was significantly decreased in GADD45β^–/– mice.

Conclusion

Unlike passive K/BxN arthritis and EAE, GADD45β deficiency in CIA was associated with lower arthritis severity, elevated IL‐10 expression, decreased IL‐17 production, and increased numbers of Treg cells. The data suggest that GADD45β plays a complex role in regulating adaptive immunity and, depending on the model, either enhances or suppresses inflammation.

     

CD28‐dependent differentiation into the effector/memory phenotype is essential for induction of arthritis in interleukin‐1 receptor antagonist–deficient mice

Objective

Interleukin‐1 receptor antagonist (IL‐1Ra)–deficient mice on a BALB/c background spontaneously develop a chronic inflammatory polyarthropathy closely resembling that of rheumatoid arthritis in humans. To elucidate the role of CD28 costimulatory signals in the development of this disease, we studied IL‐1Ra/CD28–double‐deficient mice.

Methods

We crossed IL‐1Ra–deficient mice with CD28–deficient mice and observed the incidence and severity of arthritis. To investigate functions of IL‐1Ra/CD28–double‐deficient T cells, cells were stimulated with CD3 monoclonal antibody or allogeneic antigen‐presenting cells (APCs) and their proliferative responses and levels of cytokine production were measured.

Results

Disease severity was lower in IL‐1Ra/CD28–double‐deficient mice than in mice that were deficient only in IL‐1Ra, although incidence of arthritis was not affected by the presence or absence of CD28. When pathogenic IL‐1Ra–KO T cells were transferred into nude mice, severe arthritis developed. Even though T cells from double‐deficient mice showed the same diminished proliferative capacity as was seen in T cells from CD28–single‐deficient animals, nude mice into which double‐deficient T cells were transferred never developed arthritis.

Conclusion

These findings indicate that IL‐1Ra/CD28–double‐deficient T cells can be activated by IL‐1Ra–deficient activated APCs, resulting in induction of arthritis; however, these T cells did not induce the disease under normal conditions, because they did not differentiate into effector/memory phenotype.

     

Increased bone density and resistance to ovariectomy‐induced bone loss in FoxP3‐transgenic mice based on impaired osteoclast differentiation

Objective

Immune activation triggers bone loss. Activated T cells are the cellular link between immune activation and bone destruction. The aim of this study was to determine whether immune regulatory mechanisms, such as naturally occurring Treg cells, also extend their protective effects to bone homeostasis in vivo.

Methods

Bone parameters in FoxP3‐transgenic (Tg) mice were compared with those in their wild‐type (WT) littermate controls. Ovariectomy was performed in FoxP3‐Tg mice as a model of postmenopausal osteoporosis, and the bone parameters were analyzed. The bones of RAG‐1^–/– mice were analyzed following the adoptive transfer of isolated CD4+CD25+ T cells. CD4+CD25+ T cells and CD4+ T cells isolated from FoxP3‐Tg mice and WT mice were cocultured with monocytes to determine their ability to suppress osteoclastogenesis in vitro.

Results

FoxP3‐Tg mice developed higher bone mass and were protected from ovariectomy‐induced bone loss. The increase in bone mass was found to be the result of impaired osteoclast differentiation and bone resorption in vivo. Bone formation was not affected. Adoptive transfer of CD4+CD25+ T cells into T cell–deficient RAG‐1^–/– mice also increased the bone mass, indicating that Treg cells directly affect bone homeostasis without the need to engage other T cell lineages.

Conclusion

These data demonstrate that Treg cells can control bone resorption in vivo and can preserve bone mass during physiologic and pathologic bone remodeling.

     

The spontaneous remission of juvenile idiopathic arthritis is characterized by CD30+ T cells directed to human heat‐shock protein 60 capable of producing the regulatory cytokine interleukin‐10

Objective

To test the hypothesis that T cell reactivity to self heat‐shock protein 60 (Hsp60) in patients with remitting juvenile idiopathic arthritis (JIA) is part of an antiinflammatory, regulatory mechanism.

Methods

Using peripheral blood–derived mononuclear cells (PBMCs) and synovial fluid–derived mononuclear cells (SFMCs) obtained from patients with JIA, we analyzed the expression of CD30 and the induction of regulatory cytokines in response to human and mycobacterial Hsp60.

Results

In oligoarticular JIA patients, in vitro activation of PBMCs and SFMCs with Hsp60 induced a high expression of CD30 on CD4+, activated (HLA–DR–positive), memory (CD45RO+) T cells. The expression of CD30 induced by human Hsp60 was much higher than that induced by mycobacterial Hsp60. In oligoarticular JIA patients with active disease, the expression of CD30 in response to human Hsp60 was paralleled by a high interleukin‐10 (IL‐10):interferon‐γ (IFNγ) ratio. In addition, restimulated human Hsp60–specific T cell lines from oligoarticular JIA patients showed a high production of IL‐10 and a low production of IFNγ. In contrast, PBMCs and SFMCs from polyarticular JIA patients responded to human Hsp60 with virtually no expression of CD30 and a low IL‐10:IFNγ ratio.

Conclusion

The results show that T cells responding to human Hsp60 in oligoarticular JIA patients express CD30, and during active phases of the disease, these T cells have a cytokine profile with a high IL‐10:IFNγ ratio. These findings suggest that in oligoarticular JIA patients, human Hsp60–specific CD4+ cells have a regulatory function and contribute to disease remission.

     

Systemic lupus erythematosus monocytes are less responsive to interleukin‐10 in the presence of immune complexes

Objective

Systemic lupus erythematosus (SLE) is a systemic inflammatory disease characterized by autoantibody production and immune complex deposition. The level of interleukin‐10 (IL‐10), predominantly an antiinflammatory cytokine, is paradoxically elevated in patients with SLE. The aim of this study was to examine the hypothesis that the antiinflammatory function of IL‐10 is impaired in monocytes from patients with SLE with long‐term exposure to immune complexes.

Methods

CD14+ monocytes were isolated from healthy donors and patients with SLE. Cultured CD14+ cells were treated with heat‐aggregated human IgG (325 μg/ml) in the presence or absence of IL‐10 (20 ng/ml). To study gene expression, RNA was extracted 3 hours after treatment. To study cytokine production, supernatants were harvested after 8 hours. To study IL‐10 signaling, cell lysates were obtained from CD14+ cells treated with human IgG (325 μg/ml) for 1 hour followed by IL‐10 (20 ng/ml) treatment for 10 minutes. Western blot analysis was used to assess STAT‐3 phosphorylation. All experiments were performed in pairs.

Results

When stimulated with human IgG, SLE monocytes produced more tumor necrosis factor α (TNFα) and IL‐6 than did control cells. The suppressive effect of IL‐10 on human IgG–induced TNFα and IL‐6 production was lower in SLE monocytes compared with control monocytes, although IL‐10 receptor expression was similar in SLE and control monocytes. Human IgG suppressed IL‐10 receptor expression and altered IL‐10 signaling in control monocytes. Like SLE monocytes, interferon‐α (IFNα)–primed control monocytes stimulated with human IgG were also less responsive to IL‐10.

Conclusion

Human IgG and IFNα modulate IL‐10 function. In SLE monocytes, which are considered to be IFNα primed and persistently exposed to immune complexes, responses to IL‐10 are abnormal, limiting the antiinflammatory effect of this cytokine.

     

Interleukin‐13–producing CD8+ T cells mediate dermal fibrosis in patients with systemic sclerosis

Objective

Fibrosis is a major contributor to morbidity and mortality in systemic sclerosis (SSc). T cells are the predominant inflammatory infiltrate in affected tissue and are thought to produce cytokines that drive the synthesis of extracellular matrix (ECM) proteins by fibroblasts, resulting in excessive fibrosis. We have previously shown that aberrant interleukin‐13 (IL‐13) production by peripheral blood effector CD8+ T cells from SSc patients correlates with the extent of skin fibrosis. The present study was undertaken to investigate the role of IL‐13 production by CD8+ T cells in dermal fibrosis, an early and specific manifestation of SSc.

Methods

ECM protein production by normal dermal fibroblasts cocultured with SSc CD8+ T cell supernatants was determined by quantitative polymerase chain reaction and Western blotting. Skin‐homing receptor expression and IL‐13 production by CD8+ T cells in the peripheral blood of SSc patients were measured by flow cytometry. IL‐13+ and CD8+ cells in sclerotic skin were identified by immunohistochemistry.

Results

IL‐13–producing circulating CD8+ T cells from patients with SSc expressed skin‐homing receptors and induced a profibrotic phenotype in normal dermal fibroblasts, which was inhibited by an anti–IL‐13 antibody. High numbers of CD8+ T cells and IL‐13+ cells were found in the skin lesions of SSc patients, particularly during the early inflammatory phase of the disease.

Conclusion

These findings show that IL‐13–producing CD8+ T cells are directly involved in modulating dermal fibrosis in SSc. The demonstration that CD8+ T cells homing to the skin early in the course of SSc are associated with accumulation of IL‐13 is an important mechanistic contribution to the understanding of the pathogenesis of dermal fibrosis in SSc and may represent a potential target for therapeutic intervention.

     

Presence of CD4+CD8+ double‐positive T cells with very high interleukin‐4 production potential in lesional skin of patients with systemic sclerosis

Objective

Fibrotic skin changes in systemic sclerosis (SSc) are preceded by the appearance of an inflammatory infiltrate rich in T cells. Since no direct comparison with T cells in normal skin has been performed previously, this study was undertaken to functionally characterize T cells in the skin of patients with early active SSc and in normal skin.

Methods

We characterized coreceptor expression, T cell receptor (TCR) usage, cytokine production, and helper and cytolytic activity of T cell lines and clones established from skin biopsy specimens from 6 SSc patients and 4 healthy individuals. Immunofluorescence analysis of skin biopsy and peripheral blood samples was performed to confirm the presence of specific subsets in vivo.

Results

A distinct subset expressing both CD4 and CD8α/β coreceptors at high levels (double‐positive [DP]) was present in T cell lines from SSc and normal skin. DP T cells actively transcribed both accessory molecules, exerted clonally distributed cytolytic and helper activity, and expressed TCR clonotypes distinct from those in CD4+ or CD8+ single‐positive (SP) T cells. In SSc skin, DP T cells produced very high levels of interleukin‐4 (IL‐4) compared with CD4+ SP T cells. Furthermore, DP T cells were directly identified in SSc skin, thus providing evidence that they are a distinct subset in vivo.

Conclusion

The present findings show that T cells with the unusual CD4+CD8+ DP phenotype are present in the skin. Their very high level of IL‐4 production in early active SSc may contribute to enhanced extracellular matrix deposition by fibroblasts.