Regulatory T cell defects in rheumatoid arthritis

Therapy with regulatory T-cell infusion in autoimmune diseases and organ transplantation: A review of the strengths and limitations

In the last decade, cell therapies have revolutionized the treatment of some diseases, earning the definition of being the "third pillar" of therapeutics. In particular, the infusion of regulatory T cells (Tregs) is explored for the prevention and control of autoimmune reactions and acute/chronic allograft rejection. Such an approach represents a promising new treatment for autoimmune diseases to recover an immunotolerance against autoantigens, and to prevent an immune response to alloantigens. The efficacy of the in vitro expanded polyclonal and antigen-specific Treg infusion in the treatment of a large number of autoimmune diseases has been extensively demonstrated in mouse models. Similarly, experimental work documented the efficacy of Treg infusions to prevent acute and chronic allograft rejections. The Treg therapy has shown encouraging results in the control of type 1 diabetes (T1D) as well as Crohn's disease, systemic lupus erythematosus, autoimmune hepatitis and delaying graft rejection in clinical trials. However, the best method for Treg expansion and the advantages and pitfalls with the different types of Tregs are not fully understood in terms of how these therapeutic treatments can be applied in the clinical setting. This review provides an up-to-date overview of Treg infusion-based treatments in autoimmune diseases and allograft transplantation, the current technical challenges, and the highlights and disadvantages of this therapeutic approaches."

Post-Translational Regulations of Foxp3 in Treg Cells and Their Therapeutic Applications

Regulatory T (Treg) cells are indispensable for immune homeostasis due to their roles in peripheral tolerance. As the master transcription factor of Treg cells, Forkhead box P3 (Foxp3) strongly regulates Treg function and plasticity. Because of this, considerable research efforts have been directed at elucidating the mechanisms controlling Foxp3 and its co-regulators. Such work is not only advancing our understanding on Treg cell biology, but also uncovering novel targets for clinical manipulation in autoimmune diseases, organ transplantation, and tumor therapies. Recently, many studies have explored the post-translational regulation of Foxp3, which have shown that acetylation, phosphorylation, glycosylation, methylation, and ubiquitination are important for determining Foxp3 function and plasticity. Additionally, some of these targets have been implicated to have great therapeutic values. In this review, we will discuss emerging evidence of post-translational regulations on Foxp3 in Treg cells and their exciting therapeutic applications.

Regulatory T cell heterogeneity and therapy in autoimmune diseases

Regulatory T (Treg) cells are a group of CD4⁺ T cell with high expression of CD25 and cell linage specific transcription factor forkhead box P3 (Foxp3) and play a vital role in maintaining immune homeostasis. In the last two decades, researchers have shown that Treg cells involved in the occurrence, development and prognosis of many diseases, especially in autoimmune diseases. Treg targeted therapies, such as low-dose interleukin-2 (IL-2) treatment and Treg infusion therapy, which are aimed at restoring the number or function of Treg cells, have become a hot topic in clinical trials of these diseases. It is believed that Treg cells are heterogeneous. Different subsets of Treg cells have various functions and play different parts in immunomodulatory. Gaining insights into Treg heterogeneity will help us further understand the function of Treg cells and provide news ideas for the selective therapeutic manipulation of Treg cells. In this review, we mainly summarize the heterogeneity of Treg cells and their potential therapeutic value in autoimmune diseases.

The regulation of immune tolerance by FOXP3

The proper restraint of the destructive potential of the immune system is essential for maintaining health. Regulatory T (T_reg) cells ensure immune homeostasis through their defining ability to suppress the activation and function of other leukocytes. The expression of the transcription factor forkhead box protein P3 (FOXP3) is a well-recognized characteristic of T_reg cells, and FOXP3 is centrally involved in the establishment and maintenance of the T_reg cell phenotype. In this Review, we summarize how the expression and activity of FOXP3 are regulated across multiple layers by diverse factors. The therapeutic implications of these topics for cancer and autoimmunity are also discussed.

Foxp3, Regulatory T Cell, and Autoimmune Diseases

Regulatory T cells (Tregs) represent a cell type that promotes immune tolerance to autologous components and maintains immune system homeostasis. The abnormal function of Tregs is relevant to the pathogenesis of systemic lupus erythematosus (SLE), rheumatoid arthritis (RA), and other autoimmune diseases. Therefore, therapeutic modulation of Tregs could be a potent means of treating autoimmune diseases. Human Tregs are diverse, however, and not all of them have immunosuppressive effects. Forkhead box P3 (Foxp3), a pivotal transcription factor of Tregs that is crucial in maintaining Treg immunosuppressive function, can be expressed heterogeneously or unstably across Treg subpopulations. Insights into modulating Treg differentiation on the level of DNA transcription or protein modification may improve the success of Treg modifying immunotherapies. In this review, we will summarize three main prospects: the regulatory mechanism of Foxp3, the influence on Foxp3 and Tregs in autoimmune diseases, then finally, how Tregs can be used to treat autoimmune diseases.

Arthritis models: usefulness and interpretation

Animal models of arthritis are used to better understand pathophysiology of a disease or to seek potential therapeutic targets or strategies. Focusing on models currently used for studying rheumatoid arthritis, we show here in which extent models were invaluable to enlighten different mechanisms such as the role of innate immunity, T and B cells, vessels, or microbiota. Moreover, models were the starting point of in vivo application of cytokine-blocking strategies such as anti-TNF or anti-IL-6 treatments. The most popular models are the different types of collagen-induced arthritis and arthritis in KBN mice. As spontaneous arthritides, human TNF-α transgenic mice are a reliable model. It is mandatory to use animal models in the respect of ethical procedure, particularly regarding the number of animals and the control of pain. Moreover, design of experiments should be of the highest level, animal models of arthritis being dedicated to exploration of well-based novelties, and never used for confirmation or replication of already proven concepts. The best interpretations of data in animal models of arthritis suppose integrated research, including translational studies from animals to humans.

Expression of tyrosine hydroxylase in CD4+ T cells contributes to alleviation of Th17/Treg imbalance in collagen-induced arthritis

Tyrosine hydroxylase (TH), a rate-limiting enzyme for the synthesis of catecholamines, is expressed in T lymphocytes. However, the role of T cell-expressed TH in rheumatoid arthritis (RA) is less clear. Herein, we aimed to show the contribution of TH expression by CD4⁺ T cells to alleviation of helper T (Th)17/regulatory T (Treg) imbalance in collagen-induced arthritis (CIA), a mouse model of RA. CIA was prepared by intradermal injection of collagen type II (CII) at tail base of DBA1/J mice. Expression of TH in the spleen and the ankle joints was measured by real-time polymerase chain reaction and Western blot analysis. Percentages of TH-expressing Th17 and Treg cells in splenic CD4⁺ T cells were determined by flow cytometry. Overexpression and knockdown of TH gene in CD4⁺ T cells were taken to evaluate effects of TH on Th17 and Treg cells in CIA. TH expression was upregulated in both the inflamed tissues (spleen and ankle joints) and the CD4⁺ T cells of CIA mice. In splenic CD4⁺ T cells, the cells expressing TH were increased during CIA. These cells that expressed more TH in CIA were mainly Th17 cells rather than Treg cells. TH gene overexpression in CD4⁺ T cells from CIA mice reduced Th17 cell percentage as well as Th17-related transcription factor and cytokine expression and secretion, whereas TH gene knockdown enhanced the Th17 cell activity. In contrast, TH gene overexpression increased Treg-related cytokine expression and secretion in CD4⁺ T cells of CIA mice, while TH gene knockdown decreased the Treg cell changes. Collectively, these findings show that CIA induces TH expression in CD4⁺ T cells, particularly in Th17 cells, and suggest that the increased TH expression during CIA represents an anti-inflammatory mechanism.

Dopamine D2 Receptor Is Involved in Alleviation of Type II Collagen-Induced Arthritis in Mice

Human and murine lymphocytes express dopamine (DA) D2-like receptors including DRD2, DRD3, and DRD4. However, their roles in rheumatoid arthritis (RA) are less clear. Here we showed that lymphocyte DRD2 activation alleviates both imbalance of T-helper (Th)17/T-regulatory (Treg) cells and inflamed symptoms in a mouse arthritis model of RA. Collagen-induced arthritis (CIA) was prepared by intradermal injection of chicken collagen type II (CII) in tail base of DBA/1 mice or Drd2 (-/-) C57BL/6 mice. D2-like receptor agonist quinpirole downregulated expression of proinflammatory Th17-related cytokines interleukin- (IL-) 17 and IL-22 but further upregulated expression of anti-inflammatory Treg-related cytokines transforming growth factor- (TGF-) β and IL-10 in lymphocytes in vitro and in ankle joints in vivo in CIA mice. Quinpirole intraperitoneal administration reduced both clinical arthritis score and serum anti-CII IgG level in CIA mice. However, Drd2 (-/-) CIA mice manifested more severe limb inflammation and higher serum anti-CII IgG level and further upregulated IL-17 and IL-22 expression and downregulated TGF-β and IL-10 expression than wild-type CIA mice. In contrast, Drd1 (-/-) CIA mice did not alter limb inflammation or anti-CII IgG level compared with wild-type CIA mice. These results suggest that DRD2 activation is involved in alleviation of CIA symptoms by amelioration of Th17/Treg imbalance.

The impact of biological therapy on regulatory T cells in rheumatoid arthritis

Regulatory T cells (Treg) are functionally defective in patients with RA. Restoring their function may not only control inflammation but also restore tolerance in these patients. Biologic therapies have been tremendously successful in treating RA. Here we review numerous reports suggesting that these immunomodulatory therapies have an impact on Treg and that this may contribute to their beneficial effects. Better understanding of their mode of action may not only lead to improvements in therapies and sustained remission but also enable the development of biomarkers of response, which would be the first steps towards personalized medicine.

Cytokine expression and cytokine-based T cell profiling in South Indian rheumatoid arthritis

Rheumatoid arthritis (RA), a chronic inflammatory disease affects up to 1% of the general population. Early diagnosis and treatment are limited by the absence of specific and reliable diagnostic/prognostic biomarkers. This study was carried out in 48 Tamil South Indian RA patients and 49 healthy controls (HC) to identify any cytokine signature(s) that could potentially serve as biomarkers. Expression profiles of Th1, Th2, Th17 and Tregs cell type-specifying cytokines and transcription factors were analyzed using real time quantitative PCR (qPCR) assay. To explore if such expression profiles mirror their steady state plasma levels, a bead-based multiplex fluorescent assay was carried out. We found that the expression of transcription factors T-bet (for Th1), GATA-3 (for Th2) and FoxP3 (for Tregs) were significantly lower in patients than in healthy controls (P<0.0001) similar to lowering of IFNγ (P=0.004) and IL-10 (P=0.04). The transcript levels of IL-12p40 and TNF-α were higher among patients as compared to HC (P<0.0001 and P=0.02, respectively). Circulating levels of assessed cytokines were in general higher in RA patients as compared to controls. These alterations in the expression of transcription factors and cytokines highlight the underlying dysregulation of T cell subsets in RA that reflects a predominantly inflammatory phenotype. Despite dissecting these cellular and molecular processes, no specific signature that could be of diagnostic and/or prognostic value was identified. Additional longitudinal follow-up studies, especially on newly diagnosed treatment-naïve patients are warranted to uncover clinically useful biomarkers of RA.

FOXP3⁺ T regulatory cell modifications in inflammatory bowel disease patients treated with anti-TNFα agents

Treg modulation has been hypothesized as one of the mechanisms by which antitumor necrosis factor α (TNFα) agents exert their action in rheumatoid arthritis (RA) and inflammatory bowel disease (IBD). However, data in IBD are still conflicting. We evaluated CD4⁺CD25⁺FOXP3⁺ (Tregs) by flow cytometry in peripheral blood from 32 adult IBD patient before (T0) and after the induction of anti-TNFα therapy (T1). Eight healthy controls (HCs) were included. We also evaluated the number of FOXP3⁺ cells in the lamina propria (LP) in biopsies taken in a subset of patients and controls. Treg frequencies were significantly increased in peripheral blood from our patients after anti-TNFα therapy compared to T0. T1 but not T0 levels were higher than HC. The increase was detectable only in clinical responders to the treatment. A negative correlation was found among delta Treg levels and the age of patients or disease duration and with the activity score of Crohn's disease (CD). No significant differences were found in LP FOXP3⁺ cells. Our data suggest the possibility that in IBD patients the treatment with anti-TNFα may affect Treg percentages and that Treg modifications may correlate with clinical response, but differently in early versus late disease.

Effect of a cocoa flavonoid-enriched diet on experimental autoimmune arthritis

Previously we established that a cocoa-enriched diet in young rats reduces specific antibody production and the T helper (Th) lymphocyte proportion in lymphoid tissues. The aim of the present study was to ascertain the modulatory ability of a cocoa flavonoid-enriched diet on collagen-induced arthritis (CIA), which is mediated by anti-collagen autoantibody response and Th lymphocyte activation. Female Louvain (LOU) rats were fed with a cocoa-enriched diet, beginning 2 weeks before CIA induction. Hind-paw swelling and serum cytokine and anti-collagen antibody concentrations were determined. Anti-collagen antibody-secreting cell counts and lymphocyte subset proportions were established in inguinal lymph nodes (ILN). Reactive oxygen species (ROS), nitric oxide (NO) and TNFα produced by peritoneal macrophages were determined. Although arthritic cocoa-fed rats showed a similar hind-paw swelling time course as the arthritic animals fed a standard diet, the cocoa intake was able to decrease specific IgG2a, IgG2b and IgG2c titres. Moreover, cocoa intake in CIA rats reduced ROS production, TNFα and NO release from peritoneal macrophages, and decreased the Th:cytotoxic T cell ratio in ILN. In conclusion, a cocoa flavonoid-enriched diet in LOU rats with CIA produced no effect on hind-paw swelling but was able to modulate the specific antibody response and also the Th lymphocyte proportion, as well as the synthesis of pro-inflammatory mediators from peritoneal macrophages. Therefore, a cocoa-enriched diet could be a good adjuvant therapy in disorders with oxidative stress or autoimmune pathogenesis.

Effect of cocoa-enriched diets on lymphocytes involved in adjuvant arthritis in rats

Cocoa and its flavonoids have potential anti-inflammatory properties in vitro and in acute inflammation models in vivo. The aim of the present study was to ascertain the effects of two cocoa-enriched diets on adjuvant arthritis (AA) in rats, considering not only clinical and biochemical inflammatory indices, but also antibody response and lymphocyte composition. Female Wistar rats were fed with a 5 or 10 % cocoa-enriched diet beginning 2 weeks before arthritis induction and until the end of the study. AA was induced by an intradermal injection of heat-killed Mycobacterium butyricum suspension. The hind-paw swelling (plethysmometry), serum anti-mycobacterial antibody concentration (ELISA), blood and inguinal lymph node lymphocyte subset percentage (flow cytometry), and IL-2, interferon γ and PGE₂ released from splenocytes (ELISA) were assessed. Although the cocoa diets had no significant effect on hind-paw swelling, a tendency to reduce it was observed at the end of the study. Cocoa-enriched diets were able to decrease the serum anti-mycobacterial antibody concentration and the splenocyte PGE2 production, as well as the proportion of T-helper (Th) lymphocytes in blood and regional lymph nodes, which probably includes cells responsible for the arthritic process. The cocoa diets prevented a decrease in the proportion of regulatory T-cells in blood and a disequilibrium between inguinal lymph node natural killer (NK) CD8⁺ and NK CD8⁻ subsets. In conclusion, the cocoa-enriched diets during AA were not able to significantly decrease joint inflammation but modified Th-cell proportions and prevented specific antibody synthesis.

Decreased mRNA expression of two FOXP3 isoforms in peripheral blood mononuclear cells from patients with rheumatoid arthritis and systemic lupus erythematosus

Both the number and functional capacity of T-regulatory (Treg) cells are known to be decreased in various autoimmune diseases. FOXP3, an essential transcription factor for Treg cells, has three isoforms in humans, wild, and exon 2- and exon 2-exon 7-lacking, although their role in autoimmunity is not clearly understood. Here, we investigated the messenger RNA (mRNA) expression of the major wild and exon-2 isoforms in peripheral mononuclear cells by quantitative PCR methods in 56 subjects, consisting of 23 rheumatoid arthritis (RA) and 25 systemic lupus erythematosus (SLE) patients, and 8 healthy controls (HCs). Although mRNA expression of the two isoforms did not directly correlate with clinical disease activity, relative expression of both was significantly lower in SLE and RA patients than in HCs. Furthermore, we found a significant statistical correlation between the two isoforms, suggesting that they are similarly regulated. Decreased expression of these isoforms in RA and SLE may reflect Treg cell abnormalities in these autoimmune diseases.

An altered peptide ligand corresponding to a novel epitope from heat-shock protein 60 induces regulatory T cells and suppresses pathogenic response in an animal model of adjuvant-induced arthritis

Induction of immune tolerance as therapeutic approach for autoimmune diseases constitutes a current research focal point. In this sense, we aimed to evaluate an altered peptide ligand (APL) for induction of peripheral tolerance in patients with rheumatoid arthritis (RA). A novel T-cell epitope from human heat-shock protein 60 (Hsp60), an autoantigen involved in the pathogenesis of RA, was identified by bioinformatics tools and an APL was design starting from this epitope. We investigated the ability of this APL for inducing regulatory T cells (Treg cells) in mice and evaluated the therapeutic effect of this peptide in an adjuvant-induced arthritis (AA) rat model. Clinical score, TNFα levels and histopathology were monitored, as well as the capacity of this APL for inducing Treg cells. Finally, the potentialities of the APL for inducing Treg cells were evaluated in ex vivo assays using mononuclear cells isolated from peripheral blood (PBMC). The APL induced an increase of the proportions of Treg cells in the draining lymph nodes of the injected site in mice. The APL efficiently inhibited the course of AA, with significant reduction of the clinical and histopathology score. This effect was associated with an increase of the proportions of Treg cells and a decrease of TNFα levels in spleen. Finally, stimulation of PBMCs from RA patients by the APL increases the proportions of the CD4(+)CD25(high)FoxP3(+) Treg cells. These results indicate a therapeutic potentiality of APL and support further investigation of this candidate drug for treatment of RA.

Quantification and phenotype of regulatory T cells in rheumatoid arthritis according to disease activity score-28

Here we studied and characterized different peripheral blood (PB) regulatory T cell (Treg) subsets in rheumatoid arthritis (RA) patients and tested the hypothesis that changes in these cells can be linked to the degree of inflammation and relapsing/remission periods. PB cells were examined from RA subjects (n = 60) with different disease activity score-28 (DAS28) and from healthy controls (n = 40). Frequencies of Treg subsets expressing characteristic membrane antigens, FoxP3 or intracellular cytokines were quantified by flow cytometry. We observed a decrease in the percentages of CD4(+)CD25(high), CD4(+)CD25(int), CD4(+)CD25(int/high)FoxP3(+), CD4(+)CD38(+), CD4(+)CD62L(+), CD8(+)CD25(high)CD45RA(+) and CD8(+)CD25(int)CD45RA(+) T cells in PB of RA patients compared to healthy controls. In addition, we found increased percentages of cells expressing membrane/intracellular regulatory antigens such as OX40 (CD134), CD45RB(low) or CTLA-4 (CD152), and a higher proportion of other T cell subsets including CD4(+)CTLA-4(+), CD4(+)IL10(+), CD4(+)CD25(int)IL10(+), CD4(+)CD25(int) TGFbeta(+), CD4(+)CD25(low) TGFbeta(+) and CD8(+)CD28(- ). We show that most of these changes parallel the intensity of inflammation, with lowest or highest values in patients with moderately/very active disease compared to healthy controls and at times to patients with inactive RA. The balance between these cell subsets and their antigen expression would determine the inflammation levels and could thus be linked to the relapsing/remission periods of the disease.

The numbers of Foxp3 + Treg cells are positively correlated with higher grade of infiltration at the salivary glands in primary Sjogren's syndrome

This study was designed to investigate whether Foxp3( +) regulatory T (Treg) cells play a role in the histopathologic changes of primary Sjögren's Syndrome (pSS) and to evaluate other factors possibly associated with Foxp3(+) Treg cells in pSS patients. The number of FoxP3-expressing T cells in peripheral blood (PB) of 39 patients with pSS, 40 patients with rheumatoid arthritis (RA), and 28 healthy controls was measured by flow-cytometer analysis. FoxP3-expressing CD4(+)CD25(+) Treg cells were analyzed in minor salivary gland (SG) tissues of 39 pSS patients. Histopathologic changes were examined by light microscopy according to Chisholm's classification. Immunohistochemistry and immunofluorescence were performed to assess the Foxp3(+) Treg in SG biopsy specim-ens. The numbers of CD4(+) T cells and FoxP3-expressing CD4(+) T cells in PB were similar in all groups. Expression of CD25 on CD4(+) T cells in PB of patients with pSS and RA was significantly higher than in healthy controls, especially for RA patients. Immunohistochemistry and immunofluorescence showed that FoxP3(+) Treg were enriched in the SGs of pSS patients, with a positive correlation between the increase in FoxP3(+) Treg in SG and the Chisholm score in pSS (p < 0.001, r = +0.605). The increase of FoxP3( +) Treg cells in the SGs of pSS patients, which is correlated with gland infiltration, suggests that natural regulatory T cells play an important role in the pathogenesis of pSS. Further studies are required to explore the mechanisms that mediate the relationship between Treg and the pathogenesis of pSS.

Influenza vaccine administration in rheumatoid arthritis patients under treatment with TNFalpha blockers: safety and immunogenicity

Twenty-eight patients with low-moderate, stable rheumatoid arthritis (RA), under treatment with tumor necrosis factor (TNF) alpha blockers, were immunized at least once with non-adjuvanted trivalent influenza vaccine during three consecutive influenza seasons. Antibodies toward A influenza antigens significantly increased and reached protective levels, still detectable 6 months after vaccination, both in RA patients and healthy controls. Response to B antigen instead was only observed from the second year for healthy controls and in the third year for patients. No significant difference in disease activity and anti-nuclear antibodies was observed as a consequence of vaccine administration, whereas T regulatory cells showed a significant increase 30 days after immunization in RA patients. This study confirms safety of influenza vaccine administration in RA patients treated with TNFalpha blockers. The cohort follow-up revealed the overcoming of poor B vaccine antigen immunogenicity via repeated vaccinations. Finally, protective antibody response was still observed 6 months after vaccination.

CTLA4-Ig modifies dendritic cells from mice with collagen-induced arthritis to increase the CD4+CD25+Foxp3+ regulatory T cell population

Cytotoxic T lymphocyte antigen-4 (CTLA4) and IgG fusion protein, CTLA4-Ig, is a therapeutic agent used for rheumatoid arthritis. It binds B7 molecules on dendritic cells (DCs) and thereby blocks B7/CD28 costimulatory interaction and inhibits effective T cell proliferation. However, the effect of CTLA4-Ig on the regulatory T cell (Treg) is still not known. In this study, we investigated the influence of CTLA4-Ig on the CD4+CD25+Foxp3+ Treg population in collagen-induced arthritis (CIA) mouse model. CTLA4-Ig suppressed CIA and increased the CD4+CD25+Foxp3+ Treg population in joint and spleen. When CD11c + DCs and CD4+T cells from CIA mice were cultured with anti-CD3, CTLA4-Ig increased the CD4+CD25 + Foxp3+ Treg population in a TGF-beta-dependent manner. When CD11c + DCs from CIA mice were treated with CTLA4-Ig and adoptively transferred into CIA-induced mice, arthritis did not develop in association with the increase in CD4+CD25+Foxp3+ Treg population. However, in CTLA4-Ig-untreated DC-transferred CIA mice, arthritis developed and then rapidly progressed. Our study demonstrated that CTLA4-Ig suppressed CIA by modifying DCs from CIA mice into tolerogenic DCs to increase the CD4+CD25+Foxp3+ Treg population and this seems to be the new immune regulatory mechanism of CTLA4-Ig.

Infliximab in the treatment of rheumatoid arthritis

Infliximab was the first monoclonal antibody to human necrosis factor alpha (TNFalpha) developed for treating rheumatoid arthritis (RA). This chimeric antibody binds with high affinity to both soluble and trans-membrane TNF and is able to reduce synovial inflammation, bone resorption and cartilage degradation. The efficacy of infliximab has been observed in active RA despite treatment with multiple disease modifying anti-rheumatic drugs (DMARDs), and in early disease with no prior treatment by methotrexate (MTX). Infliximab has been shown to reduce joint inflammation and to slow radiographic progression, in both clinical and non-clinical responders. Recent data suggest that using infliximab early in RA treatment increases the percentage of clinical remission and allows infliximab discontinuation. The recommended dosage of 3 mg/kg could be increased up to 10 mg/kg with partial efficacy of the dose escalation. Antibodies to infliximab have been observed in 7% to 61% of patients and are associated with a low trough level of infliximab and secondary response failure. Their occurrence could be prevented by co-medication with MTX. The combination of DMARDs other than MTX with infliximab was found to be safe and efficacious. Infections, principally tuberculosis, are increased in treated patients, and the risk is greater at higher dose. Even if the treatment is generally safe and well tolerated, patients treated with infliximab should be closely monitored.

Interleukin-23/Th17 pathways and inflammatory bowel disease

The IL-23/Th17 pathway has recently been identified to play a critical role in a number of chronic inflammatory diseases including inflammatory bowel disease (IBD). The identification in IBD patients of associations in IL23R and regions that include other genes in the IL-23/Th17 pathway has highlighted the importance of proper IL-23/Th17 pathway regulation in intestinal immune homeostasis. IL-23 plays a role in CD4+ Th17 lineage cells, characterized by IL-17 secretion and the expression of the transcription factor retinoic acid-related orphan receptor (ROR)gamma tau, and in other immune and nonimmune cells. The balance between effector T cell subsets, such as Th17 cells, and CD4+ T regulatory subsets is finely regulated; dysregulation of this balance can lead to inflammation and autoimmunity. As such, the IL-23/Th17 pathway contributes to immune responses that play a role in defenses to microbial infection, as well as in the intestinal inflammation observed in both animal models of colitis and human IBD.

Role of regulatory T-cells in autoimmunity

There has been considerable historical interest in the concept of a specialist T-cell subset which suppresses over-zealous or inappropriate T-cell responses. However, it was not until the discovery that CD4(+)CD25(+) T-cells had suppressive capabilities both in vitro and in vivo that this concept regained credibility and developed into one of the most active research areas in immunology today. The notion that in healthy individuals there is a subset of T(reg)-cells (regulatory T-cells) involved in 'policing' the immune system has led to the intensive exploration of the role of this subset in disease resulting in a number of studies concluding that a quantitative or qualitative decline in T(reg)-cells is an important part of the breakdown in self-tolerance leading to the development of autoimmune diseases. Although T(reg)-cells have subsequently been widely postulated to represent a potential immunotherapy option for patients with autoimmune disease, several studies of autoimmune disorders have demonstrated high numbers of T(reg)-cells in inflamed tissue. The present review highlights the need to consider a range of other factors which may be impairing T(reg)-cell function when considering the mechanisms involved in the breakdown of self-tolerance rather than focussing on intrinsic T(reg)-cell factors.

Current concepts in the pathogenesis of early rheumatoid arthritis

Rheumatoid arthritis (RA) is a systemic inflammatory disease with a predilection for symmetrically distributed diarthroidal joints. It is clinically heterogeneous, with particular disease phenotypes defined according to a complex interplay of genes and the environment. In this chapter we first summarize current knowledge of RA genetic susceptibility, a field which has been transformed in recent years by powerful modern genotyping technologies. The importance of a recently described subclassification for the disease based upon the presence or absence of circulating autoantibodies to citrullinated peptides has further informed genetic studies, and we consider the implications for our understanding of RA pathogenesis. We then review the cellular and molecular processes that initiate and perpetuate joint destruction.

Frequency of regulatory T cells is not affected by transient B cell depletion using anti-CD20 antibodies in rheumatoid arthritis

Objectives

Transient B cell depletion with the monoclonal anti-CD20 antibody rituximab has shown favourable clinical responses in patients with rheumatoid arthritis (RA). Recently a characteristic regeneration pattern of B cell subpopulations has been reported. However, little is known about the impact of B-cell depletion on peripheral T cells in particular regulatory T cells.

Materials and Methodology

17 patients with RA having failed anti-TNF were treated with rituximab. Four colour staining was performed using CD19, CD3, CD4, CD8, CD16, CD56, CD25, HLA-DR, HLA-G and intracellular Foxp3 at five time points spanning up to 12 months after rituximab. In addition, quantification of the soluble form of the HLA class I molecule HLA-G by ELISA has been performed.

Results

Peripheral B cell depletion lasted 6 to 9 months. The absolute number of CD3+, CD4+ and CD8+ lymphocytes showed no significant changes up to 1 year after B-cell depletion compared to before therapy. Only the relative frequency for CD3 and CD4 showed a significant increase (p < 0.05). In particular, CD4+CD25++ and Foxp3 positive regulatory T cells remained constant. The percentage of HLA-G positive cells in the CD4+ or CD8+ population did not change significantly either. The amount of sHLA-G remained without significant changes.

Conclusion

Absolute T cell counts showed no significant changes after rituximab compared to the time point before therapy.In particular, the frequency of regulatory T cells with a CD4+CD25++ phenotype as well as positive Foxp3 expression were numerically stable. Additionally, HLA-G positive regulatory T cells and soluble levels of HLA-G showed no significant changes.

Stored red blood cell transfusion induces regulatory T cells

BACKGROUND

Allogeneic blood transfusion mediates immunosuppression in transfused recipients by an unknown mechanism. Regulatory T cells (T(regs)) are suppressive CD4(+)CD25(+)Foxp3(+) cells with a central role in immunosuppression in trauma victims, cancer patients, and transplant recipients. We hypothesized that transfusion-related immunosuppression is, in part, mediated by induction of T(regs), and this induction is attenuated with prestorage leukoreduction and accentuated with prolonged storage.

STUDY DESIGN

Packed red blood cell (PRBC) units were obtained and 50% of PRBCs were leukoreduced (LR) before routine storage for 1 day or 42 days and the supernatant was collected. Normal human peripheral blood mononuclear cells (PBMCs) were exposed to 1-day NLR, 42-day NLR, 1-day LR, or 42-day LR PRBC supernatants or to PRBC storage solution or washed PRBC supernatant +/- anti-CD3 stimulation, and analyzed by flow cytometry for Foxp3(+) T(regs) or CD25(+)-activated T cells. PRBC supernatants and cell culture supernatants were analyzed by immunoassay for interleukin (IL)-1beta, IL-2, IL-4, IL-10, interferon-gamma, tumor necrosis factor-alpha, and transforming growth factor-beta. T(reg) activity was evaluated by suppression assay.

RESULTS

All PRBC groups induced T(regs) compared with control media in anti-CD3-stimulated PBMCs, without alteration by LR or prolonged storage. PRBC supernatant did not alter nonspecific T-cell activation from control media. PRBC-induced T(regs) were suppressive, inhibiting proliferation of T-responder cells. All cytokines measured decreased with storage in LR PRBC units and no cytokines were substantially elevated in cell supernatants exposed to PRBC supernatant. PRBC storage solution did not reproduce the effects of PRBC supernatant, and washed PRBC supernatant attenuated T(reg) induction.

CONCLUSIONS

PRBC supernatant induces T(regs), but this induction is not altered by LR or prolonged storage. This induction appears to be independent of cytokines and is attenuated with washed PRBCs, implicating the plasma fraction.

Delineating the role of the HLA-DR4 "shared epitope" in susceptibility versus resistance to develop arthritis

In humans, HLA-DR alleles sharing amino acids at the third hypervariable region with DRB1*0401(shared epitope) are associated with a predisposition to rheumatoid arthritis, whereas DRB1*0402 is not associated with such a predisposition. Both DRB1*0402 and DRB1*0401 occur in linkage with DQ8 (DQB1*0302). We have previously shown that transgenic (Tg) mice expressing HLA-DRB1*0401 develop collagen-induced arthritis. To delineate the role of "shared epitope" and gene complementation between DR and DQ in arthritis, we generated DRB1*0402, DRB1*0401.DQ8, and DRB1*0402.DQ8 Tg mice lacking endogenous class II molecules, AE(o). DRB1*0402 mice are resistant to develop arthritis. In double-Tg mice, the DRB1*0401 gene contributes to the development of collagen-induced arthritis, whereas DRB1*0402 prevents the disease. Humoral response to type II collagen is not defective in resistant mice, although cellular response to type II collagen is lower in *0402 mice compared with *0401 mice. *0402 mice have lower numbers of T cells in thymus compared with *0401 mice, suggesting that the protective effect could be due to deletion of autoreactive T cells. Additionally, DRB1*0402 mice have a higher number of regulatory T cells and show increased activation-induced cell death, which might contribute toward protection. In DRB1*0401.DQ8 mice, activated CD4(+) T cells express class II genes and can present DR4- and DQ8-restricted peptides in vitro, suggesting a role of class II(+) CD4 T cells locally in the joints. The data suggest that polymorphism in DRB1 genes determines predisposition to develop arthritis by shaping the T cell repertoire in thymus and activating autoreactive or regulatory T cells.

Foxp3+ T-regulatory cells in Sjogren's syndrome: correlation with the grade of the autoimmune lesion and certain adverse prognostic factors

Sjögren's syndrome (SS) is a chronic autoimmune exocrinopathy associated with variable lymphocytic infiltration of the affected organs (primarily salivary and lacrimal glands) and broad clinical manifestations, including lymphoma development. To investigate the potential implication of Foxp3(+) T-regulatory cells in the regulation of SS inflammatory responses, we studied their incidence in the minor salivary glands (MSGs) and their relationship with histopathological and clinical disease parameters. Similar percentages of infiltrating Foxp3(+) cells were observed in the MSG lesions of all SS patients (n = 30) and non-SS sialadenitis controls (n = 7). Foxp3(+) cells were not detected in sicca-complaining controls with negative biopsy (n = 6). In SS patients, Foxp3(+) cell frequency varied according to lesion severity, with the highest and lowest frequencies obtained in intermediate and mild MSG lesions, respectively. In the peripheral blood of these patients, reverse distribution of Foxp3(+) cells was observed. Furthermore, the frequency of Foxp3(+) cells in the MSG lesions and peripheral blood was negatively associated (r = -0.6679, P = 0.0065). MSG-infiltrating Foxp3(+) cells were found to positively correlate with biopsy focus score (P = 0.05), infiltrating mononuclear cells, dendritic cells, and macrophages (P </= 0.024 each), and serum C4 levels (P = 0.0328), whereas lower Foxp3(+) cell incidence correlated with adverse predictors for lymphoma development, such as the presence of C4 hypocomplementemia (P = 0.012) and SG enlargement (tendency, P = 0.067). Our findings suggest that the Foxp3(+) T-regulatory cell frequency in the MSG lesions of SS patients correlates with inflammation grade and certain risk factors for lymphoma development.

Immunoregulatory properties of vasoactive intestinal peptide in human T cell subsets: implications for rheumatoid arthritis

Rheumatoid arthritis (RA) is a chronic inflammatory autoimmune disease whose pathogenesis is not completely understood. Unbalanced Th1/Th2 T-cell polarization has been suggested to play a pathogenetic role and therefore, modulation of T-cell polarization is a potential therapeutic target. Vasoactive intestinal peptide (VIP) is a broadly distributed peptide that exerts anti-inflammatory and immunomodulatory effects, in the collagen-induced arthritis (CIA) murine model of RA, and ex vivo, in synovial cells from RA patients. In the present study, we have found that polyclonal stimulation of peripheral blood lymphocytes (PBL) from RA patients produces higher levels of inflammatory mediators and lower levels of Th1 cytokines than PBL from healthy controls; moreover, VIP has negligible effects on inflammatory mediators and Th1 cytokines produced by PBL from healthy controls but favours Th2 profile and enhanced IL-10 production after stimulation. VIP increases the levels of IL-10 and IL-4 in the supernatant of human CD4(+)CD45RA(+) cells cultured in a non-conditioned or a Th2-conditioned situation. In contrast, VIP does not modify the production of these cytokines in a Th1-conditioned medium. In summary, VIP can differentially modify the functional capacity of human lymphocytes by inducing Th2/Treg differentiation depending on their previous phenotype.