Decrease of regulatory T cells in patients with systemic lupus erythematosus

Regulatory T-cells in systemic lupus erythematosus and rheumatoid arthritis

Regulatory T-cells (Tregs) are the guardians of peripheral tolerance acting to prevent autoimmune diseases such as systemic lupus erythomatosus (SLE) and rheumatoid arthritis (RA). Defects in Tregs have been reported in these two diseases despite significant differences in their clinical phenotype and pathogenesis. In both diseases the potency of Treg fails to keep pace with the activation of effector cells and are unable to resist the ensuing inflammation. This review will discuss the phenotypic, numeric, and functional abnormalities in Tregs and their role in patients and murine models of SLE and RA.

T-cell specific defect in expression of the NTPDase CD39 as a biomarker for lupus

Regulatory T cells (T(regs)) are critical for maintenance of peripheral tolerance via suppression of T-cell responses, and absence of T(regs) results in autoimmunity. The role of aberrations in the T(reg) pool for the development of systemic lupus erythematosus (SLE, lupus) remains uncertain. T(reg)-mediated generation of adenosine, dependent on the ectonucleotidase CD39, is an important mechanism for suppression of T-cell responses. We tested whether decreases in numbers of T(regs), and specifically CD39-expressing T(regs), are associated with human lupus. We studied 15 SLE patients, six patients with rheumatoid arthritis (RA) and 24 healthy controls. T(reg) phenotypic markers, including CD39 expression, were studied by flow cytometry. Varying numbers of sorted T(regs) cells were co-cultured with responder T (T(resp)) cells, with proliferation assessed by (3)H-thymidine incorporation. The proportion of T(regs) as defined by Foxp3(+) CD25(+high) CD127(-/low) was similar in lupus and control populations. CD39-expressing T(regs) comprised 37±13% of the T(reg) population in healthy controls and 36±21% in lupus subjects using nonsteroidal immunosuppressants to control active disease, but was nearly absent in five of six lupus subjects with minimally active disease. In contrast to healthy controls and lupus subjects without the CD39 defect, in SLE subjects with the CD39 defect, adenosine-dependent T(reg)-mediated suppression was nearly absent. These results suggest that functional defects in T(regs), rather than reduced T(reg) numbers, are important for the loss of peripheral tolerance in lupus. Presentation of this defect may serve as a biomarker for untreated disease.

Human FoxP3+ regulatory T cells in systemic autoimmune diseases

Since the characterization of CD4(+)CD25(+) regulatory T (Treg) cells in mice, significant progress has been made in the definitions of the phenotype and the function of human Treg cells in health and in pathological conditions. Recent advances in the field leading to a better molecular definition of Treg subsets in humans and the description of the dynamics of differentiation of Treg cells should bring new insights in the understanding of human chronic systemic autoimmune diseases. How Treg cells are compromised in these diseases is a challenging issue because the elucidation of the mechanisms leading to such anomaly might lead to promising novel therapeutic approaches.

Elevated Th17 cells are accompanied by FoxP3+ Treg cells decrease in patients with lupus nephritis

To investigate the variations of T-helper 17 (Th17) and regulatory T (Treg) cells in patients with lupus nephritis (LN), a total of 60 systemic lupus erythematosus patients and 28 healthy controls (HCs) were enrolled. The frequency of Th17 cells and Treg cells in peripheral blood mononuclear cells (PBMCs) was evaluated by flow cytometric analysis. The serum concentrations of interleukin-17 (IL-17) and transforming growth factor-beta 1 (TGF-β1) were measured by enzyme-linked immunosorbent assay (ELISA). The results demonstrated in LN patients a significant decrease in the frequency of CD4+CD25(high) and CD4+CD25+FoxP3+ T cells and a significant increase in the frequency of Th17 cells in peripheral blood, and the ratio of Th17 to Treg cell frequency was significantly increased along with increased SLEDAI scores. LN patients had a lower percentage and expression of FoxP3 in CD4+CD25(high) T cells than SLE patients without nephritis. The concentration of TGF-β1 was found decreased in SLE patients compared with that from healthy controls, though no significant difference was found between LN patients and SLE patients without nephritis. The expression of IL-17 levels in LN patients exhibited a significant increase compared with patients without nephritis and healthy controls. Based on our results, the significantly elevated Th17 cells are accompanied by FoxP3+ Treg cells decrease in lupus nephritis, suggesting that Th17/Treg functional imbalance may be involved in the pathogenesis of renal damage in SLE patients.

Mechanisms of impaired regulation by CD4(+)CD25(+)FOXP3(+) regulatory T cells in human autoimmune diseases

A lack of regulatory T (T(Reg)) cells that express CD4, CD25 and forkhead box P3 (FOXP3) results in severe autoimmunity in both mice and humans. Since the discovery of T(Reg) cells, there has been intense investigation aimed at determining how they protect an organism from autoimmunity and whether defects in their number or function contribute to the development of autoimmunity in model systems. The next phase of investigation - that is, to define the role that defects in T(Reg) cells have in human autoimmunity - is now underway. This Review summarizes our progress so far towards understanding the role of CD4(+)CD25(+)FOXP3(+) T(Reg) cells in human autoimmune diseases and the impact that this knowledge might have on the diagnosis and treatment of these diseases.

Natural regulatory T cells in autoimmunity

The suppressive/immunomodulatory function of CD4(+)CD25(+)FOXP3(+) regulatory T (Treg) cells is crucial for the maintenance of immune homeostasis, which helps to prevent autoimmunity and reduce the inflammation induced by pathogens and environmental insults. This review summarizes the current knowledge on the types and mechanisms of action of Treg cells and their role in the immune tolerance to self-antigens, with a particular focus on naturally occurring Treg cells.

Association of single-nucleotide polymorphisms in FOXP3 gene with systemic lupus erythematosus susceptibility: a case-control study

Foxp3, encoded by the human FOXP3 gene, is a transcription factor that regulates regulatory T-cell (Treg) development and function. Associations have been reported between FOXP3 gene variants and autoimmune endocrinopathy and non-endocrine autoimmune disease. The aim of this study was to investigate the possible influence of single nucleotide polymorphisms (SNP) in the FOXP3 gene on genetic predisposition to systemic lupus erythematosus (SLE). The study cohort comprised 172 SLE patients and 181 controls, who were genotyped for the FOXP3 gene variants. Of five SNPs identified, the FOXP3 -6054 ATT carrier was shown to be associated with renal disorder (odds ratio [OR] 3.26, 95% confidence interval [95% CI] 1.33-8.03, p = 0.0077). Furthermore, lower anti-dsDNA levels were found in patients with the -3279 A carrier (p = 0.0109). To the authors' knowledge, this is the first study to investigate the association of FOXP3 SNPs with susceptibility to SLE, as well as sub-phenotype susceptibility. Although the exact role of Foxp3 and FOXP3 gene variations in SLE is still not clear, the present data support the importance of variations in the FOXP3 gene region for the etiology of certain manifestations of SLE.

The associations of circulating CD4+CD25high regulatory T cells and TGF-β with disease activity and clinical course in patients with adult-onset Still's disease

OBJECTIVE

To determine circulating levels of CD4(+)CD25(high) regulatory T (Treg) cells and transforming growth factor-β (TGF-β) in patients with adult-onset Still's disease (AOSD) and to examine the associations with disease activity and clinical course of this disease.

METHODS

The frequencies of circulating CD4(+)CD25(high) Treg cells in 52 active AOSD patients, 42 active systemic lupus erythematosus (SLE) patients, and 22 healthy controls (HCs) were determined using flow cytometry analysis. Levels of serum TGF-β and soluble interleukin-2 receptor (sIL-2R) were measured by enzyme-linked immunosorbent assay.

RESULTS

Significantly lower levels of circulating CD4(+)CD25(high) Treg cells and serum TGF-β were found in AOSD patients and SLE patients than those found in HCs. Levels of circulating CD4(+)CD25(high) Treg cells and TGF-β were inversely correlated with disease activity scores for AOSD patients and SLE patients. Circulating CD4(+)CD25(high) Treg cell frequencies were positively correlated with serum TGF-β levels for patients with both diseases. Levels of circulating CD4(+)CD25(high) Treg cells and TGF-β significantly increased, paralleling clinical remission and the decrease in levels of C-reactive protein and soluble interleukin-2 receptor after effective therapy in AOSD patients. AOSD patients with monocyclic course had significantly higher levels of circulating CD4(+)CD25(high) Treg cells and TGF-β compared to those with polycyclic and chronic articular course.

CONCLUSION

Diminished levels of circulating CD4(+)CD25(high) Treg cells and TGF-β, and inverse correlation with disease activity in patients with AOSD and SLE might be involved in the pathogenesis of both diseases. Increased levels of circulating CD4(+)CD25(high) Treg cells or TGF-β might be associated with a favorable clinical course in AOSD patients.

Alfacalcidol treatment restores derailed immune-regulation in patients with undifferentiated connective tissue disease

Vitamin D deficiency may contribute to pathological changes in the number and function of CD4+ T helper cell subsets (CD4+Th1, CD4+Th17, CD4+CD25(bright)Foxp3-natural regulatory T cells-nTreg) in patients with undifferentiated connective tissue disease (UCTD). The aim of the present study was to evaluate, whether alfacalcidol could restore immune-regulatory changes in patients with UCTD. We assessed the optimal dose of alfacalcidol that could normalize the elevated levels of IFN-γ expressed by the CD4+Th1 cells and the IL-17 expressed by Th17 cells. Furthermore alfacalcidol decreased the Th1 and Th17 related cytokine levels, repaired the nTreg/Th7 balance, and restored the functional activity of nTreg cells. Twenty one UCTD patients with Vitamin D deficiency (<30 ng/ml) were administered with three different daily doses of alfacalcidol. Seven patients were supplemented with 0.5 μg/day, 7 patients with 1.0 μg/day, and 7 patients with 1.5 μg/day alfacalcidol treatment during 5 weeks. Our results indicated that 1.0 μg/day alfacalcidol during 5 weeks was the optimal therapeutic regime to increase the vitamin D levels, repair the nTreg/Th17 balance and raise the capacity of nTreg cells to suppress the proliferation of autologous CD4+CD25- cells. 1.5 μg daily dose alfacalcidol was not more effective than the 1.0 μg/day treatment. In this study we described that vitamin D deficiency can contribute to the complex immune-regulatory abnormalities in patients with UCTD and vitamin D substitution therapy can improve the fine balance of pro- and anti-inflammatory processes in the disease.

Role of CD27/CD70 pathway of activation in immunity and tolerance

The CD70/CD27 axis has gained increasing interest among the immunologists, because of its capacity to regulate immunity versus tolerance. Recent studies clearly show that expression of CD70 may prevent tolerance induced by antigen presentation in the steady-state, i.e., by nonactivated DCs. In addition, CD27 signaling appears critical for T cell expansion and survival and therefore, induction of long-term memory. It contributes to germinal center formation, B cell activation, and production of neutralizing antibodies but can also be subverted by viruses, in particular, during chronic infections. The potential role of the CD27/CD70 pathway in the course of inflammatory diseases, as in EAE, arthritis, and inflammatory bowel disease models, suggests that CD70 may be a target for immune intervention. Conversely, the potency of costimulation through CD27 suggests that the CD27/CD70 axis could be exploited for the design of anti-cancer vaccines.

Role of regulatory T cells in rheumatoid arthritis: facts and hypothesis

Regulatory T cells (Treg) are a CD4⁺ lymphocyte subset involved in self-tolerance and autoimmunity prevention. There is evidence for a phenotypic and/or functional impairment of this cell subset during the natural history of several chronic autoimmune/inflammatory diseases, including rheumatoid arthritis (RA). Although the intracellular transcription factor FoxP3 is thought to be the master regulator of Treg cell function, a number of other molecules expressed on the cell surface have been proposed for the identification of Treg cells. This is important in order to favour their possible selective isolation and in the development of new therapeutic strategies. In the present paper, available data on phenotypic and functional characterization of Treg cells in both peripheral blood and synovial fluid from RA patients are reviewed and their possible pathogenic role in triggering and perpetuating rheumatoid joint inflammation is discussed.

Impaired regulatory T-cell homeostasis due to vitamin D deficiency in undifferentiated connective tissue disease

OBJECTIVE

The aim of this study was to perform a quantitative and functional analysis of natural CD4+CD25(high)Foxp3+ regulatory T cells (nTregs) and CD4+IL-17+ T cells, and to assess the serum levels of proinflammatory cytokines in patients with undifferentiated connective tissue disease (UCTD) before and after 5 weeks of 0.5 μg/day alfacalcidol supplementation.

METHODS

Twenty-five patients with UCTD were enrolled in an open-label trial of alfacalcidol. Plasma levels of 25-hydroxyvitamin D [25(OH)D] were assessed by a high-performance liquid chromatography (HPLC) method. Flow cytometry was used for the quantification of nTregs and the IL-17 expression of T-helper (Th)17 cells. The serum concentrations of cytokines interleukin (IL)-12, interferon (IFN)-γ, IL-23, IL-17, IL-6, and IL-10 were measured by an enzyme-linked immunosorbent assay (ELISA).

RESULTS

Treatment with alfacalcidol raised 25(OH)D levels from a mean of 23.5 ± 5.6 to 34.5 ± 7.4 ng/mL (p = 0.059; NS). Alfacalcidol treatment decreased both Th1- (IL-12 and IFN-γ) and Th17-related (IL-23, IL-17, IL-6) cytokine levels in UCTD patients, while the soluble IL-10 level increased (IL-12: 156.7 ± 75.2 vs. 87.5 ± 42.1 pg/mL, p < 0.001; IFN-γ: 41.5 ± 12.0 vs. 21.7 ± 9.9 pg/mL, p < 0.001; IL-23: 385.2 ± 82.2 vs. 210.0 ± 69.3 pg/mL, p < 0.001; IL-17: 37.8 ± 9.6 vs. 17.8 ± 4.5 pg/mL, p = 0.009; IL-6: 39.4 ± 11.3 vs. 23.5 ± 6.3 pg/mL, p < 0.001, IL-10: 8.4 ± 3.0 vs. 21.4 ± 9.7 pg/mL, p < 0.001). Alfacalcidol improved the Th17/nTreg imbalance, as it inhibited the IL-17 expression of Th17 cells, and increased the number of nTregs. The alfacalcidol might increase the capacity of nTreg cells to suppress the proliferation of autologous CD4+CD25⁻ cells.

CONCLUSION

Our findings support the idea that vitamin D influences the Th17/nTreg imbalance in vitamin D-insufficient patients with UCTD and could be beneficial in the management of the disease.

The imbalance between regulatory and IL-17-secreting CD4+ T cells in lupus patients

It has been well recognized that a deficit of numbers and function of CD4+CD25+Foxp3+ cells (Treg) is attributed to the development of some autoimmune diseases; however, there are controversial data regarding the suppressive effect of Treg cells on the T cell response in systemic lupus erythematosus (SLE). Additionally, IL-17-producing cells (Th17) have been recently emerged as a new pathogenic cell, but their role in lupus remains unclear. In this study, we studied the connection between Treg and Th17 cells in lupus patients. We observed that, while Treg or Th17 cells alone were not correlated to SLE development, the ratio of Treg to Th17 cells in active SLE patients is significantly lower than that in inactive SLE patients and healthy controls, and we also found corticosteroid treatment increased the ratio of Treg to Th17 cells in active SLE patients. Moreover, this ratio is inversely correlated with the severity of active SLE. The present study indicates that active SLE appears to exist as an imbalance between Treg and Th17 cells. Correction of this Treg/Th17 imbalance may have therapeutic impact for patients with SLE.

[Regulatory T cells and systemic autoimmune diseases: systemic lupus erythematosus, rheumatoid arthritis, primary Sjögren's syndrome]

Regulatory/suppressor T cells (Tregs) maintain immunologic homeostasis and prevent autoimmunity. They are the guardians of dominant tolerance. Recent research reveals quantitative and/or functional defect of Tregs in systemic autoimmune diseases. In this article, past and recent studies of Tregs in human systemic lupus erythematosus (SLE), rheumatoid arthritis (RA) and primary Sjögren's syndrome (pGSS) are reviewed. Most studies report that Tregs are decreased in peripheral blood of subjects with active SLE. A population of CD4+CD25-Foxp3+ is specifically described in SLE. Tregs functions are still discussed. Tregs counts in peripheral blood of RA patients vary across studies. Enrichment of synovial fluid in Tregs contrasts with inflammation. Tregs suppressive effects are altered in vivo in RA secondary to proinflammatory cytokines environment and resistance of effector T cells to Tregs. In pGSS, the conflicting place of Tregs in the balance prevention of autoimmunity/antitumor immunity is unspecified. Immunosuppressive treatments, like corticosteroids and anti-TNF, modulate Tregs cells population. There is increasing interest in the use of Tregs as a biological therapy to preserve and restore tolerance to self-antigen. However, difficulties to characterize these lymphocytes and controversies in the results of studies refrain their use in current clinical practice.

Regulatory T cell (Treg) subsets return in patients with refractory lupus following stem cell transplantation, and TGF-beta-producing CD8+ Treg cells are associated with immunological remission of lupus

Compared with conventional drug therapy, autologous hemopoietic stem cell transplantation (HSCT) can induce very-long-term remission in refractory lupus patients. Herein, we show that in posttransplant patients, both CD4(+)CD25(high)FoxP3(+) and an unusual CD8(+)FoxP3(+) Treg subset return to levels seen in normal subjects; accompanied by almost complete inhibition of pathogenic T cell response to critical peptide autoepitopes from histones in nucleosomes, the major lupus autoantigen from apoptotic cells. In addition to a stably sustained elevation of FoxP3, posttransplant CD8 T cells also maintained markedly higher expression levels of latency-associated peptide (LAP), CD103, PD-1, PD-L1, and CTLA-4, as compared with pretransplant CD8 T cells that were identically treated by a one-time activation and rest in short-term culture. The posttransplant CD8 regulatory T cells (Treg) have autoantigen-specific and nonspecific suppressive activity, which is contact independent and predominantly TGF-beta dependent. By contrast, the pretransplant CD8 T cells have helper activity, which is cell contact dependent. Although CD4(+)CD25(high) Treg cells return during clinical remission of conventional drug-treated lupus, the posttransplant patient's CD8 Treg cells are considerably more potent, and they are absent in drug-treated patients in whom CD4 T cell autoreactivity to nucleosomal epitopes persists even during clinical remission. Therefore, unlike conventional drug therapy, hemopoietic stem cell transplantation generates a newly differentiated population of LAP(high)CD103(high) CD8(TGF-beta) Treg cells, which repairs the Treg deficiency in human lupus to maintain patients in true immunological remission.

Monocytes and T lymphocytes contribute to a predominance of interleukin 6 and interleukin 10 in systemic lupus erythematosus

OBJECTIVE

To investigate the contribution of T lymphocytes and monocytes to cytokine production in systemic lupus erythematosus (SLE).

METHODS

Forty-five SLE patients and 19 healthy volunteers were included. Serum levels of tumor necrosis factor alpha (TNFalpha), interferon gamma (IFN gamma), interleukin (IL)-6, and IL10 were quantified by ELISA. The cytokine production capacities of peripheral blood mononuclear cells were assessed by culturing in vitro with PMA+Ionomycin or LPS. The intracellular cytokine expression was measured by flow cytometry in T lymphocytes and monocytes, respectively. The influence of the disease activity (measured as the SLE-disease activity index; SLEDAI) and the treatment the patients were receiving was evaluated.

RESULTS

Serum IL10, IL6, and TNFalpha levels were increased in patients (P <or= 0.01), and a higher spontaneous (without stimuli) intracellular expression of IL10 in CD4+ and CD8+ T lymphocytes (P < 0.05) and of IL6 in monocytes (P = 0.01) were found. After stimulation, patients presented a higher percentage of CD4+ and CD8+ T lymphocytes producing IL4 and IL10 (P <or= 0.01), and of monocytes producing IL6 (P = 0.04) and IL10 (P = 0.008). The SLEDAI score was positively correlated with the percentage of CD4+IL10+ and CD8+IL10+ T lymphocytes (P < 0.01), and inversely correlated with CD8+TNFalpha+ (P= 0.02), CD4+IFN gamma+ (P = 0.04) and CD8+ IFN gamma+ (P = 0.002) T lymphocytes. Patients receiving high dose prednisone produced higher IL10, but they also were the patients with a more active disease.

CONCLUSION

Monocytes and T lymphocytes (CD4+ and CD8+) contribute to an overproduction of IL6 and IL10 in SLE; this correlates with the disease activity but is independent of the treatment the patients are receiving.

Identification of regulatory T cells in systemic lupus erythematosus

The concept that regulatory T cells (Treg) play a key role in both development and maintenance of autoimmune response in rheumatic diseases is well accepted. In recent years, several studies analyzed Treg cell phenotype and function in systemic lupus erythematosus (SLE), the prototypical systemic autoimmune disorder in humans. Although qualitative and/or quantitative abnormalities of Treg cells have been shown, data are often conflicting. This may depend on the selection of patients with different degrees of disease activity or on immunosuppressive treatments that can alter Treg cell findings. Among several proposed surface or intracellular Treg cell markers, CD25 at high level of expression and the transcription factor Foxp3 are the two most investigated in SLE. Despite the glucocorticoid-induced TNF receptor-related protein (GITR) represents a reliable phenotypic marker of murine Treg cells, little is known about its role in humans, in particular in the course of systemic autoimmune disorders. Preliminary data seems to suggest that this marker may represent a good tool to identify cell populations included within Treg cell subsets.

Regulatory T cells and their role in rheumatic diseases: a potential target for novel therapeutic development

Regulatory T cells have an important role in limiting immune reactions and are essential regulators of self-tolerance. Among them, CD4+CD25high regulatory T cells are the best-described subset. In this article, we summarize current knowledge on the phenotype, function, and development of CD4+CD25high regulatory T cells. We also review the literature on the role of these T cells in rheumatic diseases and discuss the potential for their use in immunotherapy.

Regulatory T cells in systemic lupus erythematosus: past, present and future

Regulatory/suppressor T cells (Tregs) maintain immunologic homeo-stasis and prevent autoimmunity. In this article, past studies and recent studies of Tregs in mouse models for lupus and of human systemic lupus erythematosus are reviewed concentrating on CD4⁺CD25⁺Foxp3⁺ Tregs. These cells consist of thymus-derived, natural Tregs and peripherally induced Tregs that are similar phenotypically and functionally. These Tregs are decreased in young lupus-prone mice, but are present in normal numbers in mice with established disease. In humans, most workers report CD4⁺Tregs are decreased in subjects with active systemic lupus erythematosus, but the cells increase with treatment and clinical improvement. The role of immunogenic and tolerogenic dendritic cells in controlling Tregs is discussed, along with new strategies to normalize Treg function in systemic lupus erythematosus.

CD4(+)CD25 (+) regulatory T cells in human lupus erythematosus

Natural CD4(+)CD25(+) regulatory T cells (T(reg)) show a potent immunosuppressive function and contribute to immunologic self-tolerance by suppressing potentially auto-reactive T cells. Depletion of these cells leads to the induction of severe autoimmune diseases in animal models; more recently, several studies have also reported an impairment of T(reg) number and/or function in various human autoimmune diseases. For example, aberrant numbers of circulating CD4(+)CD25(+) T(reg) have been seen in patients with type I diabetes, mycosis fungoides, graft-versus-host-reaction, and rheumatoid arthritis. Moreover, increased numbers of functionally active CD4(+)CD25(+) T(reg) have been detected in the synovial fluid of patients with rheumatoid arthritis. In systemic lupus erythematosus (SLE), conflicting data on the role of CD4(+)CD25(+) T(reg) in human autoimmune diseases have been presented in the literature. Decreased numbers of peripheral blood T(reg) have been reported by most studies on SLE patients with active disease, but non-impaired or even increased CD4(+)CD25(+) T(reg) numbers have also been described. In addition, both deficient and normal suppressive capacity of isolated T(reg) have been observed in SLE. Analysis of CD4(+)FoxP3(+) T(reg) in skin lesions of patients with a primarily cutaneous manifestation of the disease showed a significant reduction in cell numbers as compared to other inflammatory skin diseases, suggesting the importance of analyzing T(reg) numbers in the affected tissue. In this review, we discuss the role of CD4(+)CD25(+) T(reg) in autoimmunity and recent published data on SLE. Furthermore, we highlight the need for additional studies that address specific gaps of knowledge regarding the pathophysiological mechanisms as well as the identification of future therapeutic strategies for autoimmune diseases.

Reduced proportions of natural killer T cells are present in the relatives of lupus patients and are associated with autoimmunity

Introduction

Systemic lupus erythematosus is a genetically complex disease. Currently, the precise allelic polymorphisms associated with this condition remain largely unidentified. In part this reflects the fact that multiple genes, each having a relatively minor effect, act in concert to produce disease. Given this complexity, analysis of subclinical phenotypes may aid in the identification of susceptibility alleles. Here, we used flow cytometry to investigate whether some of the immune abnormalities that are seen in the peripheral blood lymphocyte population of lupus patients are seen in their first-degree relatives.

Methods

Peripheral blood mononuclear cells were isolated from the subjects, stained with fluorochrome-conjugated monoclonal antibodies to identify various cellular subsets, and analyzed by flow cytometry.

Results

We found reduced proportions of natural killer (NK)T cells among 367 first-degree relatives of lupus patients as compared with 102 control individuals. There were also slightly increased proportions of memory B and T cells, suggesting increased chronic low-grade activation of the immune system in first-degree relatives. However, only the deficiency of NKT cells was associated with a positive anti-nuclear antibody test and clinical autoimmune disease in family members. There was a significant association between mean parental, sibling, and proband values for the proportion of NKT cells, suggesting that this is a heritable trait.

Conclusions

The findings suggest that analysis of cellular phenotypes may enhance the ability to detect subclinical lupus and that genetically determined altered immunoregulation by NKT cells predisposes first-degree relatives of lupus patients to the development of autoimmunity.

Immunological mechanisms and clinical implications of regulatory T cell deficiency in a systemic autoimmune disorder: roles of IL-2 versus IL-15

Regulatory T cell deficiency is evident in patients with lupus, but the casual [corrected] relationship and underlying mechanism leading to Treg deficiency are unclear. We analyzed the Treg profile, induction and functions of Treg in a lupus mouse model. A characteristic age-dependent biphasic change of Treg frequency was observed in the MRL/lpr mice, which developed a spontaneous lupus-like disease. After an early increase, Treg frequency in the peripheral lymphoid organs rapidly declined with age. Functionally, Treg from both young and old MRL/lpr mice were fully competent in suppressing the wild-type MRL/+ T effector cell (Teff) responses. Adoptive transfer of MRL/+ Treg markedly suppressed clinical disease in the MRL/lpr mice. We demonstrated that the reduced Treg frequency was a result of insufficient peripheral Treg expansion due to defective MRL/lpr Teff in IL-2 production, and the associated defects in dendritic cells, which could be fully restored by exogenous IL-2. In the absence of IL-2, MRL/lpr Teff but not MRL/lpr Treg were highly responsive to IL-15 and could expand rapidly due to enhanced IL-15R expression and IL-15 synthesis. These findings thus provide a clear causal relationship and immunological mechanism underlying Treg deficiency and systemic autoimmunity.

Pathogenesis of cutaneous lupus erythematosus

Although for decades sunlight was suspected to be involved in the development of cutaneous lupus erythematosus (CLE), only in recent years research on the effects of ultraviolet irradiation on the skin of patients with CLE has resulted in a more comprehensive model for the pathogenesis of the disease. In this model, exposure to UV light induces apoptosis of keratinocytes and the release of pro-inflammatory cytokines. In susceptible patients, the presence or even accumulation of apoptotic cells results in the induction of characteristic inflammatory skin lesions, which might be due to a delayed and pro-inflammatory clearance of these apoptotic cells. Many other factors, in part genetically determined, are involved in CLE resulting in a very heterogeneous clinical manifestation. Among these factors, presence of autoantibodies, a decreased number of regulatory T cells at the site of inflammation and increased expression of pro-inflammatory cytokines like TNFalpha and IFN-inducible protein myxovirus protein A have been shown to play a role in the pathogenesis of CLE.

T-regulatory cells in systemic lupus erythematosus

Thymus-derived CD4(+)CD25(high)Foxp3(+) T-regulatory cells (Tregs) have an important role in the mechanisms of peripheral immune tolerance and in the prevention of pathogenic autoimmunity through the suppression of proliferation and production of pro-inflammatory cytokines in effector immune cells. Some studies have shown that in systemic lupus erythematosus (SLE) the number of circulating Tregs may be decreased during active disease, and that the extent of such decrease may correlate with severity of the disease. Recent data in murine models of lupus have suggested the possibility to target Tregs for the modulation of SLE, and Treg-based intervention has been proposed as a novel therapeutic mean for a better management of the disease. This review provides an update on the role of Tregs in SLE, discussing new findings in relation to possible targeting of Tregs for immune modulation in lupus.

Low number of regulatory T cells in skin lesions of patients with cutaneous lupus erythematosus

OBJECTIVE

To define the phenotype and function of CD4+,CD25+ regulatory T cells (Treg) in patients with cutaneous lupus erythematosus (CLE), a heterogeneous autoimmune disease characterized primarily by inflammatory skin lesions.

METHODS

The number of Treg in skin specimens obtained from patients with various subtypes of CLE was investigated by immunohistochemical analysis, using anti-Foxp3 and anti-CD4 monoclonal antibodies. Furthermore, characterization of peripheral blood CD4+,CD25+ Treg from normal healthy donors and patients with CLE was carried out by flow cytometry, analyzing the expression of Foxp3 and Treg subpopulations. We also purified CD4+,CD25(high) Treg obtained from patients with CLE and tested the sensitivity of these cells to CD95L-mediated apoptosis.

RESULTS

Quantitative analysis of CD4+ T cells in skin lesions from patients with CLE revealed that the number was similar to that in lesions from patients with other chronic inflammatory diseases, but the number of Foxp3+ Treg in CLE was significantly reduced. There was no correlation between disease subtype and the frequency of Foxp3+ Treg in the skin of patients with CLE. In peripheral blood, no significant differences were observed in the number and phenotype of CD4+,CD25+ Treg or in the sensitivity to apoptosis of CD4+,CD25(high) Treg derived from patients with CLE and those derived from normal healthy donors.

CONCLUSION

These data suggest that an organ-specific abnormality of Treg in the skin underscores the importance of analyzing Treg in the affected tissue. Such a local process might give insight into the pathogenic mechanisms of CLE and differs from a global peripheral dysfunction as reported for patients with a systemic manifestation of the disease.