IL-35 is a novel cytokine with therapeutic effects against collagen-induced arthritis through the expansion of regulatory T cells and suppression of Th17 cells

Adoptive transfer of all-trans-retinal-induced regulatory T cells ameliorates experimental autoimmune arthritis in an interferon-gamma knockout model

Maintaining an appropriate balance between subsets of CD4(+) helper T cells and T regulatory cells (Tregs) is a critical process in immune homeostasis and a protective mechanism against autoimmunity and inflammation. To identify the role of vitamin A-related compounds, we investigated the regulation of interleukin (IL)-17-producing helper T cells (Th17 cells) and Tregs treated with all-trans-retinal (retinal). CD4(+)T cells or total cells from the spleens of C57BL/6 mice were stimulated under Treg-polarizing (anti-CD3/CD28 and TGF-β) or Th17-polarizing (anti-CD3/CD28, TGF-β, and IL-6) conditions in the presence or absence of retinal. To analyze their suppressive abilities, retinal-induced Tregs or TGF-β-induced Tregs were co-cultured with responder T cells. Collagen-induced arthritis (CIA) was established in interferon (IFN)-γ knockout mice. On day 13, retinal-induced Tregs were adoptively transferred to mice with established CIA after second immunizations. Compared with TGF-β-induced Treg cells, retinal-induced Tregs showed increased Foxp3 expression and mediated stronger suppressive activity. Under Th17-polarizing conditions, retinal inhibited the production of IL-17 and increased the expression of Foxp3.Retinal-induced Tregs showed therapeutic effects in IFN-γ knockout CIA mice. Thus, we demonstrated that retinal reciprocally regulates Foxp3(+) Tregs and Th17 cells. These findings suggest that retinal, a vitamin A metabolite, can regulate the balance between pro- and anti-inflammatory immunity. A better understanding of the manipulation of Foxp3 and Tregs may enable the application of this tremendous therapeutic potential in various autoimmune diseases.

Aberrant expression of Treg-associated cytokine IL-35 along with IL-10 and TGF-β in acute myeloid leukemia

Acute myeloid leukemia (AML) is the most common hematological malignancy in adults, characterized by distorted proliferation and the development of myeloid cells and their precursors in the blood and bone marrow. Interleukin 35 (IL-35), a novel inhibitory cytokine secreted by regulatory T (Treg) cells is a novel potential target used for the therapeutic manipulation of Treg activity in order to treat cancer and autoimmune diseases. To investigate the role and imbalance of Treg-related cytokines in the pathogenesis of AML, we measured the plasma concentration of three Treg-associated cytokines [IL-35, IL-10 and transforming growth factor-β (TGF-β)] and evaluated their clinical relevance. The concentration of IL-35, IL-10 and TGF-β in plasma specimens from 55 patients with AML [27 newly diagnosed (ND) patients and 28 in complete remission (CR)] and 24 controls was analyzed using the enzyme-linked immunosorbent assay method. Significantly higher levels of plasma IL-35 and IL-10 were observed in AML ND patients compared with healthy controls or AML CR patients. IL-10 concentrations were positively correlated with TGF-β, whereas no correlations were found between the other cytokines. IL-10 levels were positively correlated with white blood cell (WBC) and neutrophil (NEU) count but there were no correlations between IL-35 and TGF-β with WBC and NEU count. In conclusion, we demonstrated for the first time that AML ND patients have increased plasma concentrations of IL-35, suggesting that this cytokine is involved in the pathophysiological process of the disease, and that further research is required to address this issue.

T regulatory cells in B-cell malignancy - tumour support or kiss of death?

It is well established that T regulatory (Treg) cells counteract tumour immunity. However, conflicting results describing the role of Treg cells in haematological tumours warrant further investigations to clarify the interactions between Treg cells and the tumour. B-cell malignancy derives from different stages of B-cell development and differentiation in which T cells play a profound role. The transformed B cell may still be in need of T-cell help to thrive but simultaneously they may be recognized and destroyed by cytotoxic lymphocytes. Recent reports demonstrate that Treg cells can suppress and even kill B cells as part of their normal function to rescue the body from autoimmunity. An emerging body of evidence points out that Treg cells not only inhibit tumour-specific T cells but may also have a role in suppressing the progression of the B-cell tumour. In this review, we discuss the origin and function of Treg cells and their role in patients with B-cell tumours.

Distinct subunit pairing criteria within the heterodimeric IL-12 cytokine family

The heterodimeric IL-12 cytokine family is characterized by the sharing of three α (p19, p28, p35) and two β (p40 and Ebi3) subunits, and includes IL-12 (p35/p40), IL-23 (p19/p40), IL-27 (p28/Ebi3) and IL-35 (p35/Ebi3). In this study, the dimerization interfaces of IL-12 family members were characterized, with emphasis on IL-35. Ebi3 and p35 subunits from human and mouse paired effectively with each other, indicating there is no species barrier to IL-35 dimerization and suggesting a conserved dimerization interface. Specific p35 residues that contribute to formation of the IL-12 interface were assessed for their contribution to the IL-35 interface, and candidate Ebi3 residues were screened for their contribution to both IL-27 and IL-35 interfaces. Several residues were identified as critical to the IL-12 or IL-27 interfaces. Conversely, no single mutation was identified that completely disrupts p35/Ebi3 pairing. Linear alanine scanning mutagenesis on both p35 and Ebi3 subunits was performed, focusing on residues that are conserved between the mouse and human proteins. Additionally, a structure-based alanine-scanning approach in which mutations were clustered based on proximitiy was performed on the p35 subunit. Both approaches suggest that IL-35 has distinct criteria for subunit pairing and is remarkabley less sensitive to structural perturbation than IL-12 and IL-27. Additionally, studies using a panel of anti-p35 and anti-Ebi3 antibodies indicate differential availability of epitopes within IL-12 family members that share these subunits, suggesting that IL-35 has distinct structural features, relative to IL-12 and IL-27. These results may be useful in future directed therapeutic targeting of IL-12 family members.

IL-35 is a novel responsive anti-inflammatory cytokine--a new system of categorizing anti-inflammatory cytokines

It remains unknown whether newly identified anti-inflammatory/immunosuppressive cytokine interleukin-35 (IL-35) is different from other anti-inflammatory cytokines such as IL-10 and transforming growth factor (TGF)-β in terms of inhibition of inflammation initiation and suppression of full-blown inflammation. Using experimental database mining and statistical analysis methods we developed, we examined the tissue expression profiles and regulatory mechanisms of IL-35 in comparison to other anti-inflammatory cytokines. Our results suggest that in contrast to TGF-β, IL-35 is not constitutively expressed in human tissues but it is inducible in response to inflammatory stimuli. We also provide structural evidence that AU-rich element (ARE) binding proteins and microRNAs target IL-35 subunit transcripts, by which IL-35 may achieve non-constitutive expression status. Furthermore, we propose a new system to categorize anti-inflammatory cytokines into two groups: (1) the house-keeping cytokines, such as TGF-β, inhibit the initiation of inflammation whereas (2) the responsive cytokines including IL-35 suppress inflammation in full-blown stage. Our in-depth analyses of molecular events that regulate the production of IL-35 as well as the new categorization system of anti-inflammatory cytokines are important for the design of new strategies of immune therapies.

Increased Th17 and regulatory T cell responses in EBV-induced gene 3-deficient mice lead to marginally enhanced development of autoimmune encephalomyelitis

EBV-induced gene 3 (EBI3)-encoded protein can form heterodimers with IL-27P28 and IL-12P35 to form IL-27 and IL-35. IL-27 and IL-35 may influence autoimmunity by inhibiting Th17 differentiation and facilitating the inhibitory roles of Foxp3(+) regulatory T (Treg) cells, respectively. In this study, we have evaluated the development of experimental autoimmune encephalomyelitis (EAE) in EBI3-deficient mice that lack both IL-27 and IL-35. We found that myelin oligodendrocyte glycoprotein peptide immunization resulted in marginally enhanced EAE development in EBI3-deficient C57BL6 and 2D2 TCR-transgenic mice. EBI3 deficiency resulted in significantly increased Th17 and Th1 responses in the CNS and increased T cell production of IL-2 and IL-17 in the peripheral lymphoid organs. EBI3-deficient and -sufficient 2D2 T cells had equal ability in inducing EAE in Rag1(-/-) mice; however, more severe disease was induced in EBI3(-/-)Rag1(-/-) mice than in Rag1(-/-) mice by 2D2 T cells. EBI3-deficient mice had increased numbers of CD4(+)Foxp3(+) Treg cells in peripheral lymphoid organs. More strikingly, EBI3-deficient Treg cells had more potent suppressive functions in vitro and in vivo. Thus, our data support an inhibitory role for EBI3 in Th17, Th1, IL-2, and Treg responses. Although these observations are consistent with the known functions of IL-27, the IL-35 contribution to the suppressive functions of Treg cells is not evident in this model. Increased Treg responses in EBI3(-/-) mice may explain why the EAE development is only modestly enhanced compared with wild-type mice.

Mechanisms of allergen-specific immunotherapy

Allergen-specific immunotherapy (allergen-SIT) is a potentially curative treatment approach in allergic diseases. It has been used for almost 100 years as a desensitizing therapy. The induction of peripheral T cell tolerance and promotion of the formation of regulatory T-cells are key mechanisms in allergen-SIT. Both FOXP3⁺CD4⁺CD25⁺ regulatory T (Treg) cells and inducible IL-10- and TGF-β-producing type 1 Treg (Tr1) cells may prevent the development of allergic diseases and play a role in successful allergen-SIT and healthy immune response via several mechanisms. The mechanisms of suppression of different pro-inflammatory cells, such as eosinophils, mast cells and basophils and the development of allergen tolerance also directly or indirectly involves Treg cells. Furthermore, the formation of non-inflammatory antibodies particularly IgG4 is induced by IL-10. Knowledge of these molecular basis is crucial in the understanding the regulation of immune responses and their possible therapeutic targets in allergic diseases.

The immunobiology of IL-27

Like many cytokines, IL-27 has pleiotropic properties that can limit or enhance ongoing immune responses depending on context. Thus, under certain circumstances, IL-27 can promote TH1 differentiation and has been linked to the activation of CD8(+) T cells and enhanced humoral responses. However, IL-27 also has potent inhibitory properties and mice that lack IL-27 mediated signaling develop exaggerated inflammatory responses in the context of infection or autoimmunity. This chapter reviews in depth the biology of IL-27, including the initial discovery, characterization, and signaling mediated by IL-27 as well as more recent insights into the molecular and cellular basis for its pleiotropic effects. Many of these advances are relevant to human diseases and highlight the potential of therapies that harness the regulatory properties of IL-27.

Regulatory T-cell-associated cytokines in systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is an autoimmune disease characterized by autoantibody production, complement activation, and immune complex deposition, resulting in tissue and organ damage. An understanding of the mechanisms responsible for homeostatic control of inflammation, which involve both innate and adoptive immune responses, will enable the development of novel therapies for SLE. Regulatory T cells (Treg) play critical roles in the induction of peripheral tolerance to self- and foreign antigens. Naturally occurring CD4⁺CD25⁺ Treg, which characteristically express the transcription factor forkhead box protein P3 (Foxp3), have been intensively studied because their deficiency abrogates self-tolerance and causes autoimmune disease. Moreover, regulatory cytokines such as interleukin-10 (IL-10) also play a central role in controlling inflammatory processes. This paper focuses on Tregs and Treg-associated cytokines which might regulate the pathogenesis of SLE and, hence, have clinical applications.

New directions in the basic and translational biology of interleukin-27

Interleukin (IL)-27 is a member of the IL-6 and IL-12 family composed of the IL-27p28 and Epstein-Barr virus-induced gene 3 (EBI3) subunits. Although IL-27 was originally identified as a proinflammatory factor, subsequent studies have revealed the pleiotropic nature of this cytokine. This review discusses recent work that has explored the effect of IL-27 on CD4(+) T cell subsets, including T regulatory type 1 (Tr-1) cells, T follicular helper cells (Tfhs), and forkhead box P3 (Foxp3)(+) T regulatory cells (Tregs). Additionally, we highlight studies that have identified a role for the IL-27p28 subunit as a cytokine receptor antagonist. Much of the recent work on IL-27 has been relevant to human disease states characterized by inappropriate or excessive inflammation, and this review discusses potential opportunities to use IL-27 as a therapeutic agent.

A cytokine-centric view of the pathogenesis and treatment of autoimmune arthritis

Cytokines are immune mediators that play an important role in the pathogenesis of rheumatoid arthritis (RA), an autoimmune disease that targets the synovial joints. The cytokine environment in the peripheral lymphoid tissues and the target organ (the joint) has a strong influence on the outcome of the initial events that trigger autoimmune inflammation. In susceptible individuals, these events drive inflammation and tissue damage in the joints. However, in resistant individuals, the inflammatory events are controlled effectively with minimal or no overt signs of arthritis. Animal models of human RA have permitted comprehensive investigations into the role of cytokines in the initiation, progression, and recovery phases of autoimmune arthritis. The discovery of interleukin-17 (IL-17) and its association with inflammation and autoimmune pathology has reshaped our viewpoint regarding the pathogenesis of arthritis, which previously was based on a simplistic T helper 1 (Th1)-Th2 paradigm. This review discusses the role of the newer cytokines, particularly those associated with the IL-17/IL-23 axis in arthritis. Also presented herein is the emerging information on IL-32, IL-33, and IL-35. Ongoing studies examining the role of the newer cytokines in the disease process would improve understanding of RA as well as the development of novel cytokine inhibitors that might be more efficacious than the currently available options.

Interleukin-35 mediates mucosal immune responses that protect against T-cell-dependent colitis

BACKGROUND & AIMS

The soluble hematopoietin receptor Epstein-Barr virus-induced protein (EBI)-3 is an immune regulator that has been associated with the pathogenesis of inflammatory bowel disease. However, the concept that EBI3 is part of an interleukin (IL)-27 heterodimer that mediates chronic inflammatory and autoimmune diseases has been challenged by the description of IL-35, a bioactive cytokine comprising EBI3 and IL-12 p35. We investigated the roles of IL-27 and IL-35 in chronic inflammation of the intestine.

METHODS

We analyzed EBI3-deficient mice and IL-27p28-deficient mice with spontaneous or T-cell transfer-induced colitis and compared outcomes with wild-type mice (controls). We constructed vectors that express EBI3 covalently linked to the IL-12p35 chain (recombinant [r]IL-35).

RESULTS

Intestines of EBI3-deficient mice had increased pathologic features of colitis, compared with IL-27p28-deficient or control mice; they also had shorter survival times, indicating that IL-35, rather than IL-27, protects the intestine from immune responses in mice. The mucosa of EBI3-deficient mice accumulated subsets of activated CD4+ T cells that produced T-helper (Th)1 and Th17 cytokines. Adoptive transfer of these T cells induced colitis in RAG-deficient mice. The rIL-35 significantly reduced the development of several forms of experimental colitis and reduced levels of markers of Th1 and Th17 cells.

CONCLUSIONS

IL-35 controls the development of T-cell-dependent colitis in mice. It might be developed as a therapeutic target for patients with chronic intestinal inflammation.

Cell therapy with autologous tolerogenic dendritic cells induces allograft tolerance through interferon-gamma and epstein-barr virus-induced gene 3

Innovative therapeutic strategies are needed to diminish the impact of harmful immunosuppression in transplantation. Dendritic cell (DC)-based therapy is a promising approach for induction of antigen-specific tolerance. Using a heart allograft model in rats, we analyzed the immunoregulatory mechanisms by which injection of autologous tolerogenic DCs (ATDCs) plus suboptimal immunosuppression promotes indefinite graft survival. Surprisingly, we determined that Interferon-gamma (IFNG), a cytokine expected to be propathogenic, was threefold increased in the spleen of tolerant rats. Importantly, its blockade led to allograft rejection [Mean Survival Time (MST) = 25.6 ± 4 days], showing that IFNG plays a critical role in immunoregulatory mechanisms triggered by ATDCs. IFNG was expressed by TCRαβ(+) CD3(+) CD4(-) CD8(-) NKRP1(-) cells (double negative T cells, DNT), which accumulated in the spleen of tolerant rats. Interestingly, ATDCs specifically induced IFNG production by DNT cells. ATDCs expressed the cytokinic chain Epstein-Barr virus-induced gene 3 (EBI3), an IL-12 family member. EBI3 blockade or knock-down through siRNA completely abolished IFNG expression in DNT cells. Finally, EBI3 blockade in vivo led to allograft rejection (MST = 36.8 ± 19.7 days), demonstrating for the first time a role for EBI3 in transplantation tolerance. Taken together our results have important implications in the rationalization of DC-based therapy in transplantation as well as in the patient immunomonitoring follow-up.

Cytokines in autoimmunity: role in induction, regulation, and treatment

Cytokines play a pivotal role in the pathogenesis of autoimmune diseases. The precise triggers for the breakdown of self-tolerance and the subsequent events leading to the induction of pathogenic autoimmune responses remain to be defined for most of the naturally occurring autoimmune diseases. Studies conducted in experimental models of human autoimmune diseases and observations in patients have revealed a general scheme in which proinflammatory cytokines contribute to the initiation and propagation of autoimmune inflammation, whereas anti-inflammatory cytokines facilitate the regression of inflammation and recovery from acute phase of the disease. This idea is embodied in the T helper (Th) 1/Th2 paradigm, which over the past two decades has had a major influence on our thinking about the role of cytokines in autoimmunity. Interestingly, over the past decade, the interleukin (IL)-17/IL-23 axis has rapidly emerged as the new paradigm that has compelled us to critically re-examine the cytokine-driven immune events in the pathogenesis and treatment of autoimmunity. In this 2-volume special issue of the journal, leading experts have presented their research findings and viewpoints on the role of cytokines in the context of specific autoimmune diseases.

IL-35 production by inducible costimulator (ICOS)-positive regulatory T cells reverses established IL-17-dependent allergic airways disease

BACKGROUND

Recent evidence suggests that IL-17 contributes to airway hyperresponsiveness (AHR); however, the mechanisms that suppress the production of this cytokine remain poorly defined.

OBJECTIVE

We sought to identify the regulatory cells and molecules that suppress IL-17-dependent allergic airways disease.

METHODS

Mice were sensitized by means of airway instillations of ovalbumin together with low levels of LPS. Leukocyte recruitment to the lung and AHR were assessed after daily challenges with aerosolized ovalbumin. Flow cytometry, quantitative PCR, and gene-targeted mice were used to identify naturally arising subsets of regulatory T (Treg) cells and their cytokines required for the suppression of established allergic airway disease.

RESULTS

Allergic sensitization through the airway primed both effector and regulatory responses. Effector responses were initially dominant and led to airway inflammation and IL-17-dependent AHR. However, after multiple daily allergen challenges, IL-17 production and AHR decreased, even though pulmonary levels of T(H)17 cells remained high. This loss of AHR was reversible and required the expansion of a Treg cell subset expressing both forkhead box protein 3 and inducible costimulator. These Treg cells also expressed the regulatory cytokines IL-10, TGF-β, and IL-35. Whereas IL-10 and TGF-β were dispensable for suppression of AHR, IL-35 was required.

CONCLUSION

IL-35 production by inducible costimulator-positive Treg cells can suppress IL-17 production and thereby reverse established, IL-17-dependent AHR in mice. Targeting this pathway might therefore be of therapeutic value for treating allergic asthma in human subjects.

The role of cytokines and chemokines in Histoplasma capsulatum infection

Histoplasma capsulatum is a prevalent fungal pathogen in the United States, infecting approximately 500,000 individuals each year. Host protection requires an intact cell-mediated immune response. In this review, we will discuss how cytokines and chemokines influence protective immunity in H. capsulatum infection.

IL-12p35 subunit contributes to autoimmunity by limiting IL-27-driven regulatory responses

Contrasting results have emerged from studies performed using IL-12p35(-/-) mice. Animals lacking the IL-12p35 subunit can either be protected from or develop exacerbated autoimmune diseases, intracellular infections, and delayed-type hypersensitivity responses. In this study, we report that mice lacking the IL-12p35 subunit develop a significantly milder Ag-induced arthritis compared with wild-type (WT) mice. Lack of severe inflammation is accompanied by an increase in the mRNA levels of the Ebi-3 and p28 subunits and increased secretion of IL-27 and IL-10. This anti-inflammatory environment contributed to increased differentiation of regulatory T and B cells with intact suppressive function. Furthermore, IL-12p35(-/-) mice display reduced numbers of Th17 cells compared with WT arthritic mice. Neutralization of IL-27, but not the systemic administration of IL-12, restored inflammation and Th17 to levels seen in WT mice. The restoration of disease phenotype after anti-IL-27 administration indicates that the IL-12p35 subunit acts as negative regulator of the developing IL-27 response in this model of arthritis.

Cytokines in autoimmune uveitis

Autoimmune uveitis is a complex group of sight-threatening diseases that arise without a known infectious trigger. The disorder is often associated with immunological responses to retinal proteins. Experimental models of autoimmune uveitis targeting retinal proteins have led to a better understanding of the basic immunological mechanisms involved in the pathogenesis of uveitis and have provided a template for the development of novel therapies. The disease in humans is believed to be T cell-dependent, as clinical uveitis is ameliorated by T cell-targeting therapies. The roles of T helper 1 (Th1) and Th17 cells have been major topics of interest in the past decade. Studies in uveitis patients and experiments in animal models have revealed that Th1 and Th17 cells can both be pathogenic effectors, although, paradoxically, some cytokines produced by these subsets can also be protective, depending on when and where they are produced. The major proinflammatory as well as regulatory cytokines in uveitis, the therapeutic approaches, and benefits of targeting these cytokines will be discussed in this review.

Progesterone promotes differentiation of human cord blood fetal T cells into T regulatory cells but suppresses their differentiation into Th17 cells

Progesterone, a key female sex hormone with pleiotropic functions in maintenance of pregnancy, has profound effects on regulation of immune responses. We report in this work a novel function of progesterone in regulation of naive cord blood (CB) fetal T cell differentiation into key T regulatory cell (Treg) subsets. Progesterone drives allogeneic activation-induced differentiation of CB naive, but not adult peripheral blood, T cells into immune-suppressive Tregs, many of which express FoxP3. Compared with those induced in the absence of progesterone, the FoxP3(+) T cells induced in the presence of progesterone highly expressed memory T cell markers. In this regard, the Treg compartment in progesterone-rich CB is enriched with memory-type FoxP3(+) T cells. Moreover, CB APCs were more efficient than their peripheral blood counterparts in inducing FoxP3(+) T cells. Another related function of progesterone that we discovered was to suppress the differentiation of CB CD4(+) T cells into inflammation-associated Th17 cells. Progesterone enhanced activation of STAT5 in response to IL-2, whereas it decreased STAT3 activation in response to IL-6, which is in line with the selective activity of progesterone in generation of Tregs versus Th17 cells. Additionally, progesterone has a suppressive function on the expression of the IL-6 receptor by T cells. The results identified a novel role of progesterone in regulation of fetal T cell differentiation for promotion of immune tolerance.

Regulation of type 17 helper T-cell function by nitric oxide during inflammation

Type 17 helper T (Th17) cells are implicated in the pathogenesis many of human autoimmune diseases. Development of Th17 can be enhanced by the activation of aryl hydrocarbon receptor (AHR) whose ligands include the environmental pollutant dioxin, potentially linking environmental factors to the increased prevalence of autoimmune disease. We report here that nitric oxide (NO) can suppress the proliferation and function of polarized murine and human Th17 cells. NO also inhibits AHR expression in Th17 cells and the downstream events of AHR activation, including IL-22, IL-23 receptor, and Cyp1a1. Conversely, NO did not affect the polarization of Th17 cells from mice deficient in AHR. Furthermore, mice lacking inducible nitric oxide synthase (Nos2(-/-)) developed more severe experimental autoimmune encephalomyelitis than WT mice, with elevated AHR expression, increased IL-17A, and IL-22 synthesis. NO may therefore represent an important endogenous regulator to prevent overexpansion of Th17 cells and control of autoimmune diseases caused by environmental pollutants.

Interleukins, from 1 to 37, and interferon-γ: receptors, functions, and roles in diseases

Advancing our understanding of mechanisms of immune regulation in allergy, asthma, autoimmune diseases, tumor development, organ transplantation, and chronic infections could lead to effective and targeted therapies. Subsets of immune and inflammatory cells interact via ILs and IFNs; reciprocal regulation and counter balance among T(h) and regulatory T cells, as well as subsets of B cells, offer opportunities for immune interventions. Here, we review current knowledge about ILs 1 to 37 and IFN-γ. Our understanding of the effects of ILs has greatly increased since the discoveries of monocyte IL (called IL-1) and lymphocyte IL (called IL-2); more than 40 cytokines are now designated as ILs. Studies of transgenic or knockout mice with altered expression of these cytokines or their receptors and analyses of mutations and polymorphisms in human genes that encode these products have provided important information about IL and IFN functions. We discuss their signaling pathways, cellular sources, targets, roles in immune regulation and cellular networks, roles in allergy and asthma, and roles in defense against infections.

Airway inflammation and IgE production induced by dust mite allergen-specific memory/effector Th2 cell line can be effectively attenuated by IL-35

CD4(+) memory/effector T cells play a central role in orchestrating the rapid and robust immune responses upon re-encounter with specific Ags. However, the immunologic mechanism(s) underlying these responses are still not fully understood. To investigate this, we generated an allergen (major house dust mite allergen, Blo t 5)-specific murine Th2 cell line that secreted IL-4, IL-5, IL-10, and IL-13, but not IL-9 or TNF-α, upon activation by the cognate Ag. These cells also exhibited CD44(high)CD62L(-) and CD127(+) (IL-7Rα(+)) phenotypes, which are characteristics of memory/effector T cells. Experiments involving adoptive transfer of this Th2 cell line in mice, followed by three intranasal challenges with Blo t 5, induced a dexamethasone-sensitive eosinophilic airway inflammation. This was accompanied by elevation of Th2 cytokines and CC- and CXC-motif chemokines, as well as recruitment of lymphocytes and polymorphic mononuclear cells into the lungs. Moreover, Blo t 5-specific IgE was detected 4 d after the last intranasal challenge, whereas elevation of Blo t 5-specific IgG1 was found at week two. Finally, pulmonary delivery of the pVAX-IL-35 DNA construct effectively downregulated Blo t 5-specific allergic airway inflammation, and i.m. injection of pVAX-IL-35 led to long-lasting suppression of circulating Blo t 5-specific and total IgE. This model provides a robust research tool to elucidate the immunopathogenic role of memory/effector Th2 cells in allergic airway inflammation. Our results suggested that IL-35 could be a potential therapeutic target for allergic asthma through its attenuating effects on allergen-specific CD4(+) memory/effector Th2 cell-mediated airway inflammation.

Interleukin-35 enhances Lyme arthritis in Borrelia-vaccinated and -infected mice

Interleukin-35 (IL-35) has been reported to inhibit the production of interleukin-17 (IL-17) as a means of preventing arthritis and other inflammatory diseases. We previously showed that treatment of Borrelia-vaccinated and -infected mice with anti-IL-17 antibody at the time of infection prevented the development of arthritis. The anti-IL-17 antibody-treated mice lacked the extensive tissue damage, such as bone and cartilage erosion, that occurred in the tibiotarsal joints of untreated Borrelia-vaccinated and -infected control mice. We hypothesized that IL-35 would reduce the severity of arthritis by suppressing the production of IL-17 in Borrelia-vaccinated and -infected mice. Here, we show that administration of recombinant IL-35 (rIL-35) to Borrelia-vaccinated and -infected mice augments the development of severe arthritis compared to the results seen with untreated control mice. Borrelia-vaccinated and -infected mice treated with rIL-35 had significantly (P < 0.05) greater hind paw swelling and histopathological changes from day 4 through day 10 than non-rIL-35-treated Borrelia-vaccinated and -infected mice. In addition, the treatment with IL-35 only slightly decreased the production of IL-17 in Borrelia-primed immune cells and did not prevent the development of borreliacidal antibody. Our data do not support a role for IL-35 as a potential therapeutic agent to reduce inflammation in Lyme arthritis.

Transfer of cell membrane components via trogocytosis occurs in CD4+ Foxp3+ CD25+ regulatory T-cell contact-dependent suppression

A key component of the immune system is its ability to establish and maintain peripheral tolerance. Naturally occurring CD4+ CD25+ Foxp3+ regulatory T (nTreg) cells represent an important means by which this is accomplished, through their potent ability to suppress the actions of both CD4+ and CD8+ effector (Teff) cells in vitro and in vivo. We hypothesized that direct contact between nTreg and Teff cells is sufficient for nTreg cell-contact suppression. We first show that nTreg cell suppression is independent of APCs and their derived co-stimulatory signals. We then used a two-colour, lipid dye labelling and quantification approach to formally demonstrate that nTreg cells specifically form cell conjugates with responding T (Tresp) cells only under TCR activating conditions. Strikingly, activated CD4+ nTreg cells undergo progressive trogocytosis, a process by which membrane fragments are transferred from one cell subset to another, with Tresp cells more readily than Teff cells. These results are the first to show that nTreg cell cognate interactions with Tresp cells leads to trogocytosis between the cells, and the first to relate the degree of trogocytosis with the level of nTreg-mediated suppression.

Use of cytokine immunotherapy to block CNS demyelination induced by a recombinant HSV-1 expressing IL-2

We previously have described a model of multiple sclerosis (MS) in which constitutive expression of murine interleukin (IL)-2 by herpes simplex virus type 1 (HSV-1) (HSV-IL-2) causes central nervous system (CNS) demyelination in different strains of mice. In the current study, we investigated whether this HSV-IL-2-induced demyelination can be blocked using recombinant viruses expressing different cytokines or by injection of plasmid DNA. We have found that coinfection of HSV-IL-2-infected mice with recombinant viruses expressing IL-12p35, IL-12p40 or IL-12p35+IL-12p40 did not block the CNS demyelination, and that coinfection with a recombinant virus expressing interferon (IFN)-γ exacerbated it. In contrast, coinfection with a recombinant virus expressing IL-4 reduced demyelination, whereas coinfection of HSV-IL-2-infected mice with a recombinant HSV-1 expressing the IL-12 heterodimer (HSV-IL-12p70) blocked the CNS demyelination in a dose-dependent manner. Similarly, injection of IL-12p70 DNA blocked HSV-IL-2-induced CNS demyelination in a dose-dependent manner and injection of IL-35 DNA significantly reduced CNS demyelination. Injection of mice with IL-12p35 DNA, IL-12p40 DNA, IL-12p35+IL-12p40 DNA or IL-23 DNA did not have any effect on HSV-IL-2-induced demyelination, whereas injection of IL-27 DNA increased the severity of the CNS demyelination in the HSV-IL-2-infected mice. This study demonstrates for the first time that IL-12p70 can block HSV-IL-2-induced CNS demyelination and that IL-35 can also reduce this demyelination, whereas IFN-γ and IL-27 exacerbated the demyelination in the CNS of the HSV-IL-2-infected mice. Our results suggest a potential role for IL-12p70 and IL-35 signaling in the inhibition of HSV-IL-2-induced immunopathology by preventing development of autoaggressive T cells.

Effect of exercise training intensity on murine T-regulatory cells and vaccination response

To understand the underlying mechanism(s) for the effect of exercise at different intensities on T cell and DNA vaccination responses, we treated mice in a training protocol with regular moderate-intensity exercise (MIE) or prolonged, exhaustive high-intensity exercise (HIE). After 6 weeks of training, splenocytes were isolated to evaluate cytokine expression and T-regulatory (Treg) cell proportion by RT-PCR and FACS, respectively. Another set of mice that completed the same training protocol were used to determine DNA vaccination responses. These mice were immunized three times with HBV DNA vaccine at 2-week intervals and euthanized on day 14 after the last immunization. Serum and splenocytes were isolated to determine humoral and cell-mediated immunity (CMI). Results showed that HIE increased anti-inflammatory cytokine expression and CD4(+) CD25(+) Treg cell proportion. Further, HIE decreased IFN-γ expression, T-lymphocyte proliferation, and antigen-specic cytotoxic response in HBV DNA vaccine-immunized mice. MIE did not change anti-inflammatory cytokine expression or CD4(+) CD25(+) Treg cell proportion but increased pro-inflammatory cytokine expression and augmented antigen-specific CMI. Thus, MIE lower the risk of cancer and infectious illness through enhancing the pro-inflammatory responses. By contrast, HIE might increase the risk of common infections, such as upper respiratory tract infection, due to an up-regulation of CD4(+) CD25(+) Treg cells and anti-inflammatory responses.

Increased frequencies of T helper type 17 cells in tuberculous pleural effusion

Th17 cells have emerged as an important mediator in inflammatory and autoimmune diseases. Recent studies suggest a potential impact of Th17 cells on tuberculosis (TB) infection. This study was designed to investigate the possible involvement of Th17 cells in tuberculous pleural effusion. Compared with healthy volunteers, patients with TB had a higher proportion of Th17 cells in peripheral blood mononuclear cells (PBMCs). Moreover, the percentage of Th17 cells in pleural effusions of TB patients was obviously higher than that in PBMC from TB patients or healthy controls. Furthermore, the mRNA and protein expression levels of IL-17 and IL-6 were significantly increased in the patients with tuberculous pleural effusion, while expression level of TGF-β was decreased in the pleural effusion. Correlation analysis showed a significant correlation between IFN-γ concentrations and the frequencies of Th17 cells in tuberculous pleural effusion. These results indicate that Th17 cells may contribute to the immunopathogenesis of tuberculous pleural effusion.

Evolutionary divergence and functions of the human interleukin (IL) gene family

Cytokines play a very important role in nearly all aspects of inflammation and immunity. The term 'interleukin' (IL) has been used to describe a group of cytokines with complex immunomodulatory functions -- including cell proliferation, maturation, migration and adhesion. These cytokines also play an important role in immune cell differentiation and activation. Determining the exact function of a particular cytokine is complicated by the influence of the producing cell type, the responding cell type and the phase of the immune response. ILs can also have pro- and anti-inflammatory effects, further complicating their characterisation. These molecules are under constant pressure to evolve due to continual competition between the host's immune system and infecting organisms; as such, ILs have undergone significant evolution. This has resulted in little amino acid conservation between orthologous proteins, which further complicates the gene family organisation. Within the literature there are a number of overlapping nomenclature and classification systems derived from biological function, receptor-binding properties and originating cell type. Determining evolutionary relationships between ILs therefore can be confusing. More recently, crystallographic data and the identification of common structural motifs have led to a more accurate classification system. To date, the known ILs can be divided into four major groups based on distinguishing structural features. These groups include the genes encoding the IL1-like cytokines, the class I helical cytokines (IL4-like, γ-chain and IL6/12-like), the class II helical cytokines (IL10-like and IL28-like) and the IL17-like cytokines. In addition, there are a number of ILs that do not fit into any of the above groups, due either to their unique structural features or lack of structural information. This suggests that the gene family organisation may be subject to further change in the near future.

Immunoregulatory cytokines are associated with protection from immunopathology following Mycobacterium avium subspecies paratuberculosis infection in red deer

Although the causative agent of Johne's disease, Mycobacterium avium subsp. paratuberculosis, is well known, the etiology of disease and the immune responses generated in response to infection are still poorly understood. Knowledge of definitive markers of protective immunity, infection, and the establishment of chronic granulomatous Johne's disease is necessary to advance vaccine and diagnostic development. We sought to profile the immune responses occurring within jejunal lymph nodes of experimentally challenged red deer (Cervus elaphus). Quantitative PCR was utilized to measure a range of cytokines, signaling molecules, and transcription factors involved in Th1, Th2, Treg, and Th17 immune responses. Significant differences in gene expression were observed between control, minimally diseased, and severely diseased animals, with severely diseased animals showing elevated proinflammatory transcripts and reduced anti-inflammatory transcripts. We identified a proinflammatory cytokine milieu of gamma interferon, interleukin-1α (IL-1α), and IL-17, which may contribute to the immunopathology observed during clinical Johne's disease and suggest that Th2 and Treg immune responses may play an important role in controlling the development of immunopathology in infected animals.

Interleukins and cancer immunotherapy

Cancer is a complex disease with interactions between normal and neoplastic cells. Since current therapies for cancer largely rely on drugs or radiation that kill dividing cells or block cell division, these treatments may have severe side effects on normal proliferating cells in patients with cancer. Therefore, the potential for treatment of cancer patients by immunologic approaches, which may be specific for tumors and will not injure most normal cells, has great promise. Cancer immunotherapy aims to augment the weak host immune response to developing tumors. One strategy is to utilize cytokines such as IL-2. More recently, several exciting new interleukins have been characterized that have considerable promise for future immunotherapy. The promise of cancer immunotherapy largely depends upon the identification of these novel interleukins. This review provides an overview of the antitumor effects of relatively new interleukins as potential therapeutic agents applicable for cancer immunotherapy.

Detectable expression of IL-35 in CD4+ T cells from peripheral blood of chronic hepatitis B patients

Epstein-Barr virus-induced gene 3 (Ebi3) and the p35 subunit of IL-12 have been reported to form a heterodimeric cytokine, named IL-35, in human and mouse. In mice, IL-35 has been shown to be constitutively expressed by CD4(+)CD25(+)Foxp3(+) regulatory T cells (Tregs) and suggested to contribute to their suppressive activity. However, human CD4(+)CD25(+)Foxp3(+) Tregs do not constitutively express detectable amounts of IL-35 in both mRNA and protein levels. Circulating CD4(+)CD25(+) Treg frequency of chronic Hepatitis B patients significantly correlates with serum viral load. In this study, we investigated whether IL-35 expression could be detected in CD4(+) T cells from peripheral blood of chronic Hepatitis B patients. Using both RT-PCR and immunoprecipitation plus Western blot analysis, we demonstrated that IL-35 expression could be detected in the CD4(+) T cells from peripheral blood of Chronic Hepatitis B patients.

EAE mediated by a non-IFN-γ/non-IL-17 pathway

Previous studies have shown that EAE can be elicited by the adoptive transfer of either IFN-γ-producing (Th1) or IL-17-producing (Th17) myelin-specific CD4(+) T-cell lines. Paradoxically, mice deficient in either IFN-γ or IL-17 remain susceptible to EAE following immunization with myelin antigens in CFA. These observations raise questions about the redundancy of IFN-γ and IL-17 in autoimmune demyelinating disease mediated by a diverse, polyclonal population of autoreactive T cells. In this study, we show that an atypical form of EAE, induced in C57BL/6 mice by the adoptive transfer of IFN-γ-deficient effector T cells, required IL-17 signaling for the development of brainstem infiltrates. In contrast, classical EAE, characterized by predominant spinal cord inflammation, occurred in the combined absence of IFN-γ and IL-17 signaling, but was dependent on GM-CSF and CXCR2. Our findings contribute to a growing body of data, indicating that individual cytokines vary in their importance across different models of CNS autoimmunity.

Regulatory ripples

Regulatory T cells come in many different forms depending on their mode of action or developmental origin. Data now show that interleukin 35, an immunomodulatory cytokine secreted by regulatory T cells, and interleukin 10 induce so-called 'iTR35 cells', which may have an important role in the phenomenon of infectious tolerance.

Regulatory T cells: overcoming suppression of T-cell immunity

Regulatory T cells inhibit cellular immunity and represent an obstacle for the development of cancer immunotherapy. The understanding of Treg cellular biology has exponentially increased during the last 10 years, driven primarily by elegant in vivo studies of mouse models systems and in vitro studies of human cells. Numerous clinical strategies are under active investigation to achieve Treg depletion or inhibition in patients with cancer, including low-dose cyclophosphamide and interleukin-2 or anti-interleukin-2R immunotoxins. To date, only modest results have been reported in patients. Our preliminary data suggest that the antihuman CD25 monoclonal daclizumab may be useful as an alternative approach for in vivo Treg depletion, but the mechanism of action of this effect remains to be elucidated. Certain immune modulatory agents may indirectly affect Tregs in patients with cancer but not necessarily in the desired direction for the therapeutic setting. More sophisticated techniques that have become available for Treg analysis in patients will assist in this important translational effort.

A role for IL-27p28 as an antagonist of gp130-mediated signaling

The heterodimeric cytokine interleukin 27 (IL-27) signals through the IL-27Rα subunit of its receptor, combined with gp130, a common receptor chain used by several cytokines, including IL-6. Notably, the IL-27 subunits p28 (IL-27p28) and EBI3 are not always expressed together, which suggests that they may have unique functions. Here we show that IL-27p28, independently of EBI3, antagonized cytokine signaling through gp130 and IL-6-mediated production of IL-17 and IL-10. Similarly, the ability to generate antibody responses was dependent on the activity of gp130-signaling cytokines. Mice transgenic for expression of IL-27p28 showed a substantial defect in the formation of germinal centers and antibody production. Thus, IL-27p28, as a natural antagonist of gp130-mediated signaling, may be useful as a therapeutic for managing inflammation mediated by cytokines that signal through gp130.

FoxP3+ CD4+ T cells in systemic autoimmune diseases: the delicate balance between true regulatory T cells and effector Th-17 cells

Breakdown of tolerance is a hallmark of autoimmune diseases. Over the past 10 years, there has been increased interest in the role of FoxP3(+) regulatory T cells (T(Regs)) in maintaining peripheral tolerance. Dysfunction of these cells is considered to play a major role in the development of autoimmune diseases. Besides their suppressive function, a fraction of these cells has the capacity to differentiate into IL-17-producing cells (Th-17), a phenomenon associated with autoimmune inflammation. The revealed plasticity of T(Regs), therefore, has obvious implications when designing therapeutic strategies for restoring tolerance in autoimmune diseases using T(Regs). In this review, we discuss development, classification, molecular characterization and mechanisms of suppression by T(Regs). In addition, we describe recent data on their potential conversion into Th-17 cells in human systemic autoimmune diseases. We also outline a new strategy for T(Reg)-based therapy via isolation, expansion and re-infusion of highly pure FoxP3(+) T(Regs) free of contaminating effector T cells.

The role of the IL-12 cytokine family in directing T-cell responses in oral candidosis

Candida albicans is an opportunistic fungal pathogen that normally exists as a harmless commensal in humans. In instances where host debilitation occurs, Candida can cause a range of clinical infections, and whilst these are primarily superficial, effecting mucosal membranes, systemic infections can develop in severely immunocompromised individuals. The mechanism of host immunity during commensal carriage of C. albicans has been intensively studied. In this paper, we present the most recent information concerning host recognition of C. albicans leading to cytokine production and the subsequent T-cell responses generated in response to C. albicans. Particular focus is given to the role of the IL-12 cytokine family including IL-12, IL-23, IL-27, and IL-35, in host immunity to Candida. CD4⁺ T-cells are considered crucial in the regulation of immunity and inflammation. In this regard, the role of Th1/2, helper cells, together with the recently identified Th17 and Treg cells in candidosis will be discussed. Understanding the detailed mechanisms that underlie host immunity to Candida not only will be of benefit in terms of the infections caused by this organism but could also be exploited in the development of therapeutic interventions for other diseases.

Grape seed proanthocyanidin extract (GSPE) differentially regulates Foxp3(+) regulatory and IL-17(+) pathogenic T cell in autoimmune arthritis

Grape seed proanthocyanidin extract (GSPE), which is the antioxidant derived from grape seeds, has been reported to possess a variety of potent properties. We have previously shown that GSPE attenuates collagen-induced arthritis. However the mechanism by which GSPE regulates the immune response remains unclear, although it may involve effects on the regulation of pathogenic T cells in autoimmune arthritis. To clarify this issue, we have assessed the effects of GSPE on differential regulation of Th17 and regulatory T (Treg) cells subsets in vitro in mouse and human CD4(+) T cells. We observed that GSPE decreased the frequency of IL-17(+)CD4(+)Th17 cells and increased induction of CD4(+)CD25(+)forkhead box protein 3 (Foxp3)(+) Treg cells. In vivo, GSPE effectively attenuated clinical symptoms of established collagen-induced arthritis in mice with concomitant suppression of IL-17 production and enhancement of Foxp3 expression (type II collagen-reactive Treg cells) in CD4(+) T cells of joints and splenocytes. The presence of GSPE decreased the levels of IL-21, IL-22, IL-26 and IL-17 production by human CD4(+) T cells in a STAT3-dependent manner. In contrast, GSPE induces Foxp3(+) Treg cells in humans. Our results suggest that GSPE possesses a reciprocal control over IL-17 and Foxp3. By potently regulating inflammatory T cell differentiation, GSPE may serve as a possible novel therapeutic agent for inflammatory and autoimmune diseases, including rheumatoid arthritis.

Transcriptional characteristics of CD4+ T cells in multiple sclerosis: relative lack of suppressive populations in blood

BACKGROUND

Multiple sclerosis (MS) is hypothetically caused by autoreactive Th1 and Th17 cells, whereas Th2 and regulatory T cells may confer protection. The development of Th subpopulations is dependant on the expression of lineage-specific transcription factors.

OBJECTIVE

The aim of this study was to assess the balance of CD4(+)T cell populations in relapsing-remitting MS.

METHODS

Blood mRNA expression of TBX21, GATA3, RORC, FOXP3 and EBI3 was assessed in 33 patients with relapsing-remitting MS and 20 healthy controls. In addition, flow cytometry was performed to assess T lymphocyte numbers.

RESULTS

In relapsing-remitting MS, diminished expression of FOXP3 (Treg) was found (p < 0.05), despite normal numbers of CD4(+)CD25(hi)Treg. Immunoregulatory EBI3 and Th2-associated GATA3 ([a-z]+) was also decreased in MS (p < 0.005 and p < 0.05, respectively). Expression of TBX21 (Th1) and RORC (Th17) did not differ between patients and controls. Similar changes were observed when analysing beta-interferon treated (n = 12) or untreated (n = 21) patients. Analysis of transcription factor ratios, comparing TBX21/GATA3 and RORC/FOXP3, revealed an increase in the RORC/FOXP3 ratio in patients with relapsing-remitting MS (p < 0.005).

CONCLUSION

Our findings indicate systemic defects at the mRNA level, involving downregulation of beneficial CD4(+)phenotypes. This might play a role in disease development by permitting activation of harmful T cell populations.

Innate IFN-gamma production by subsets of natural killer cells, natural killer T cells and gammadelta T cells in response to dying bacterial-infected macrophages

Interferon-gamma (IFN-gamma) activation of macrophages is a crucial step in the early innate defence against bacterial infection. This innate IFN-gamma is thought to be produced mainly by natural killer (NK) cells through activation with interleukin (IL)-12p70 secreted by macrophages and dendritic cells (DCs) that have sensed bacterial products. However, a number of reports have shown that bacterial stimuli are unable to induce macrophages and/or DCs to produce sufficient amounts of IL-12p70 unless these cells are primed by IFN-gamma. It remains, therefore, unsettled how initial IFN-gamma is produced. In a previous study, we reported a novel IFN-gamma production pathway that was associated with cell death in macrophages caused by intracellular bacteria like Listeria monocytogenes (LM) and Shigella flexneri. In this study, we showed that cell death of bone-marrow-derived macrophage (BMM) cells following in vitro infection with Staphylococcus aureus (SA), an extracellular bacterium, can also stimulate this IFN-gamma production pathway. We also unequivocally demonstrated by using BMM cells from IL-12-deficient mice that the bacterial-infected macrophage cell death-mediated IFN-gamma production can occur without IL-12 although the magnitude of the response is much smaller than that in the presence of IL-12. The enhancing effect of IL-12 on this response proved to be attributable to the negligible amounts (0.5 approximately 1.5 pg/ml) of IL-12p70 but not to the large amounts of IL-12p40 that were both secreted by SA- and LM-infected macrophages. Taken all together, we propose that macrophage cell death caused by bacteria may trigger the initial IFN-gamma production at an early stage of bacterial infection.

IL-23 in the pathogenesis of rheumatoid arthritis

Interleukin-23 (IL-23) is a heterodimeric cytokine belonging to the IL-6/IL-12 family that plays a key role in several of autoimmune and inflammatory disorders. This family contains the 34 type I cytokine receptor chains and 27 ligands, which share structural and functional similarities, but on the other hand they display distinct roles in shaping Th cells responses. IL-12 family cytokines have not only proinflammatory effects but they also promote inflammatory responses. IL-23 is composed of the p40 subunit in common with IL-12, and with a unique p19 subunit. IL-23 binding to an IL-23 receptor expressed on dendritic cells, macrophages and monocytes triggers the activation of Jak2 and Tyk2, which in turn phosphorylates STAT1, STAT3, STAT4 and STAT5 as well as induce formation of STAT3-STAT4 heterodimers. IL-23 is one of the essential factors required for the survival and/or expansion of Th17 cells, which produce IL-17, IL-17F, IL-6 and TNF-alpha. Th17 cells stimulated by the IL-23 promote osteoclastogenesis through production of IL-17, which induce receptor activator of NF-kappa B ligand on mesenchymal cells. The IL-23-IL-17 axis includes Th17 cells and plays a key role in the development of autoimmune arthritis.

CD4+CD25+ regulatory T cells in autoimmune arthritis

CD4(+)CD25(+) regulatory T (Treg) cells can play a critical role in the prevention of autoimmunity, as evidenced by the cataclysmic autoimmune disease that develops in mice and humans lacking the key transcription factor forkhead box protein 3 (Foxp3). At present, however, how and whether Treg cells participate in the development of rheumatoid arthritis (RA), which has both systemic manifestations and a joint-targeted pathology that characterizes the disease, remains unclear. In this review, we describe work that has been carried out aimed at determining the role of Treg cells in disease development in RA patients and in mouse models of inflammatory arthritis. We also describe studies in a new model of spontaneous autoimmune arthritis (TS1 x HACII mice), in which disease is caused by CD4(+) T cells recognizing a neo-self-antigen expressed by systemically distributed antigen-presenting cells. We show that TS1 x HACII mice develop arthritis despite the presence of CD4(+)CD25(+)Foxp3(+) Treg cells that recognize this target autoantigen, and we outline steps in the development of arthritis at which Treg cells might potentially act, or fail to act, in the development of inflammatory arthritis.

IL-35 stimulation of CD39+ regulatory T cells confers protection against collagen II-induced arthritis via the production of IL-10

IL-35 is produced by regulatory T cells, and this novel cytokine can downregulate Th17 cell development and inhibit autoimmune inflammation. In this work, an rIL-35, as a single-chain fusion between murine IL-12p35 and EBV-induced gene 3, was expressed in yeast. This rIL-35 inhibited OVA-specific cellular and Ab responses in OVA-challenged recipients of DO11.10 CD4+ T cells. Likewise, IL-35 inhibited clinical manifestation of collagen-induced arthritis or could cease further disease exacerbation upon initiation of IL-35 treatment. Exogenous IL-35 treatments suppressed Th1 and Th17 cells and promoted CD39 expression by CD4+ T cells. Sorted CD25-CD39+CD4+ T cells from IL-35-treated mice produced IL-10 and, upon adoptive transfer, were sufficiently potent to inhibit subsequent development of inflammation in mice with collagen-induced arthritis, whereas sorted CD25+CD39+CD4+ T cells showed reduced potency. IL-35 treatments of IL-10-/- mice failed to induce protective CD39+CD4+ T cells, demonstrating the effector role of IL-10 by IL-35 immunosuppression.

A pivotal role for interleukin-27 in CD8+ T cell functions and generation of cytotoxic T lymphocytes

Cytotoxic T lymphocytes (CTLs) play a critical role in the control of various cancers and infections, and therefore the molecular mechanisms of CTL generation are a critical issue in designing antitumor immunotherapy and vaccines which augment the development of functional and long-lasting memory CTLs. Interleukin (IL)-27, a member of the IL-6/IL-12 heterodimeric cytokine family, acts on naive CD4+ T cells and plays pivotal roles as a proinflammatory cytokine to promote the early initiation of type-1 helper differentiation and also as an antiinflammatory cytokine to limit the T cell hyperactivity and production of pro-inflammatory cytokines. Recent studies revealed that IL-27 plays an important role in CD8+ T cells as well. Therefore, this article reviews current understanding of the role of IL-27 in CD8+ T cell functions and generation of CTLs.

Regulation in chronic obstructive pulmonary disease: the role of regulatory T-cells and Th17 cells

COPD (chronic obstructive pulmonary disease) is an inflammatory disorder of the airways, which is associated with irreversible airway obstruction. The pathological hallmarks of COPD are destruction of the lung parenchyma (pulmonary emphysema), inflammation of the central airways (chronic bronchitis) and inflammation of the peripheral airways (respiratory bronchiolitis). Tobacco smoking is established as the main aetiological factor for COPD. A maladaptive modulation of inflammatory responses to inhalation of noxious particles and gases is generally accepted as being a key central pathogenic process; however, the precise regulatory mechanisms of the disease are poorly understood. Two cell types are known to be important in immune regulation, namely regulatory T-cells and the newly identified Th17 (T-helper 17) cells. Both types of cells are subsets of CD4 T-lymphocytes and modulate the immune response through secretion of cytokines, for example IL (interleukin)-10 and IL-17 respectively. The present review will begin by describing the current understanding of inflammatory cell involvement in the disease process, and then focus on the possible role of subsets of regulatory and helper T-cells in COPD.

Tolerance to the foetal allograft?

In this review, we will detail the concept of tolerance and its history in reproductive immunology. We will then consider whether it applies to the foetal-maternal relationship and discuss the mechanisms involved in non-rejection of the foeto-placental unit.

Human rhinoviruses induce IL-35-producing Treg via induction of B7-H1 (CD274) and sialoadhesin (CD169) on DC

IL-35 is a heterodimer of EBV-induced gene 3 and of the p35 subunit of IL-12, and recently identified as an inhibitory cytokine produced by natural Treg in mice, but not in humans. Here we demonstrate that DC activated by human rhinoviruses (R-DC) induce IL-35 production and release, as well as a suppressor function in CD4(+) and CD8(+) T cells derived from human peripheral blood but not in naïve T cells from cord blood. The induction of IL-35-producing T cells by R-DC was FOXP3-independent, but blocking of B7-H1 (CD274) and sialoadhesin (CD169) on R-DC with mAb against both receptors prevented the induction of IL-35. Thus, the combinatorial signal delivered by R-DC to T cells via B7-H1 and sialoadhesin is crucial for the induction of human IL-35(+) Treg. These results demonstrate a novel pathway and its components for the induction of immune-inhibitory T cells.