Revisiting the role of IL-2 in autoimmunity

Vitamin D Presented In Vitro Immunomodulatory Property on T Lymphocyte-Related Cytokines in Systemic Lupus Erythematosus

Inflammatory T lymphocyte cytokines contribute to tissue damage in SLE patients. Vitamin D (Vit D) has a well-established immunomodulatory action, but few studies have addressed the effect of 1,25 dihydroxyvitamin D3 (1,25 (OH)2D3) on peripheral blood mononuclear cells (PBMCs) in SLE patients. The aim of this study was to evaluate the immnunomodulatory effect of 1,25 (OH)2D3 on T lymphocyte-related cytokines. Blood from 27 female SLE patients was collected for PBMC isolation and anti-DNA, complement, and serum 25 (OH)D3 level measurements. PBMCs were stimulated with anti-CD3/anti-CD28 in the presence or absence of dexamethasone or various concentrations of 1,25 (OH)2D3 for 48 h. We assessed IL-17A, IL-22, IL-21, IL-9, IFN-γ, IL-4, IL-10, IL-2, IL-6, and TNF by cytometric bead assay (CBA) and enzyme immune assay (ELISA) on culture supernatant. The mean age of patients was 36.2 (± 10.5 years) and the median Systemic Lupus Erythematosus Disease Activity Index (SLEDAI) was 4 (0-6). The addition of 1,25 (OH)2D3 in PBMC culture reduced IL-17 A, IL-22, IL-9, and IFN-γ levels at 100 nM (p ≤ 0.0001). Furthermore, the addition of 1,25 (OH)2D3 at all concentrations increased IL-4 (p ≤ 0.0006), and 0.1 and 1 nM increased IL-10 (p ≤ 0.0004) and 0.1 nM increased IL-2 levels (p ≤ 0.0001). There was no difference regarding IL-21 and TNF levels. The addition of 1,25 (OH)2D3 in PBMC culture presented an inhibitory effect on proinflammatory cytokines and increased immunoregulatory cytokines in SLE patients, suggesting the beneficial effect of this vitamin.

Dynamically modeling the effective range of IL-2 dosage in the treatment of systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is a complex systemic autoimmune disease characterized by an overactive immune response to self-antigen. The overactivation of CD4⁺ Foxp3⁻ conventional T cells (Tcons) and the inactivation of CD4⁺ CD25⁺ Foxp3⁺ regulatory T cells (Tregs) play important roles in the progression of SLE. Clinical trials showed that low-dose interleukin-2 (IL-2) is effective in treating SLE. Here, we developed a mathematical model involving Tcons, Tregs, natural killer (NK) cells, and IL-2 to simulate the dynamic processes involved in the treatment of SLE. We found an effective range of IL-2 dosage defined by the Tcon/Treg ratio in SLE treatment, termed the IL-2 dosage therapeutic window (IDTW). Our results showed that high levels of self-antigen result in a narrow IDTW and high post-treatment Tcon/Treg ratio. Furthermore, we proposed a classification method based on the ratio of pre-treatment Treg to CD4⁺ T cells to predict the treatment outcome of SLE patients.

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Tcon/Treg ratio can be an indicator to define the IL-2 dosage therapeutic window in SLE treatment

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SLE patients with high levels of self-antigen are predicted to have a narrow IL-2 therapeutic window

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High-dose IL-2 should overactivate Tcons and increase the Tcon/Treg ratio in SLE patients

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SLE patients with lower pre-treatment Treg are more likely to benefit from IL-2 administration

Role of maternal interleukin-8 (IL-8) in normal-term birth in the human

Cytokines are the main factors involved in the normal functions of the placenta and delivery process. The aim of this project was to compare serum levels of interleukin-8 (IL-8), IL-6, tumour necrosis factor α (TNF-α) and transforming growth factor β (TGF-β) in term and prolonged-pregnancy mothers and their neonates. This study was performed on 240 participants including 60 term and prolonged-pregnancy neonates and their corresponding mothers. Serum levels of IL-8, IL-6, TNF-α and TGF-β were evaluated by the enzyme-linked immunosorbent assay technique. The results revealed that IL-8 serum levels were significantly lower in the prolonged-pregnancy mothers and their neonates when compared with term mothers and their neonates. Data analysis also revealed a negative correlation between TGF-β and age of prolonged-pregnancy mothers. A poor positive correlation between IL-6 and head circumference of term neonates was also observed. IL-8 may play crucial roles in the process of on-time delivery and age may significantly affect TGF-β production in prolonged-pregnancy mothers. Pro-inflammatory cytokines, such as IL-6, can also be considered as main factors involved in fetal growth.

Genetic and Environmental Interaction in Type 1 Diabetes: a Relationship Between Genetic Risk Alleles and Molecular Traits of Enterovirus Infection?

PURPOSE OF REVIEW

We provide an overview of the current knowledge regarding the natural history of human type 1 diabetes (T1D) and the documented associations between virus infections (in particular the enteroviruses) and disease development. We review studies that examine whether T1D-specific risk alleles in genes involved in the function of the immune system can alter susceptibility to virus infections or affect the magnitude of the host antiviral response. We also highlight where the major gaps in our knowledge exist and consider possible implications that new insights gained from the discussed gene-environment interaction studies may bring.

RECENT FINDINGS

A commonality between several of the studied T1D risk variants studied is their role in modulating the host immune response to viral infection. Generally, little support exists indicating that the risk variants increase susceptibility to infection and moreover, they usually appear to predispose the immune system towards a hyper-reactive state, decrease the risk of infection, and/or favor the establishment of viral persistence. In conclusion, although the current number of studies is limited, this type of research can provide important insights into the mechanisms that are central to disease pathogenesis and further describe how genetic and environmental factors jointly influence the risk of T1D development. The latter may provide genetic markers that could be used for patient stratification and for the selection of method(s) for disease prevention.

Decreased erythrocyte CD44 and CD58 expression link e-waste Pb toxicity to changes in erythrocyte immunity in preschool children

Lead (Pb) toxicity damages blood cells and disturbs the immune micro-environment. When Pb enters the circulatory system, >95% of Pb accumulates in erythrocytes. We therefore conducted this study to explore the long-term effect of Pb exposure on expression of erythrocyte adhesion molecules (CD44 and CD58) and related downstream cytokine concentrations. We enrolled a total of 267 preschool children, 2-7 years of age, from Guiyu (e-waste-exposed group, n = 132) and Haojiang (reference group, n = 135) in November and December 2015. We measured child blood Pb, biomarkers including erythrocyte CD44 and CD58, erythrocyte count, leukocyte count and inflammatory cytokines (IL-1β, IL-12p70 and IFN-γ), and calculated erythrocyte Pb levels. Regression model demonstrated that higher erythrocyte Pb was associated with lower CD44 and CD58. Compared to low erythrocyte Pb levels (quartile 1), high erythrocyte Pb levels (quartile 4) were related to lower levels of erythrocyte CD44 and CD58. Elevated blood Pb correlated with higher IL-12p70 and IFN-γ, and lower IL-2. The mediation effect of erythrocyte CD44 on the relationship of erythrocyte Pb with IL-1β and IL-12p70 was significant, and the effect of erythrocyte Pb on IFN-γ was mediated by erythrocyte CD58. The data provides novel translational insight into the relationship between elevated Pb exposure and the change of erythrocyte immunity and downstream cytokine secretion in preschool children.

The role of FOXP3+ regulatory T cells in human autoimmune and inflammatory diseases

CD4⁺ regulatory T cells (T_reg ) expressing the forkhead box protein 3 (FOXP3) transcription factor (T_regs ) are instrumental for the prevention of autoimmune diseases. There is increasing evidence that the human T regulatory population is highly heterogeneous in phenotype and function. Numerous studies conducted in human autoimmune diseases have shown that T_reg cells are impaired either in their suppressive function, in number, or both. However, the contribution of the FOXP3⁺ T_reg subpopulations to the development of autoimmunity has not been delineated in detail. Rare genetic disorders that involve deficits in T_reg function can be studied to develop a global idea of the impact of partial or complete deficiency in a specific molecular mechanism involved in T_reg function. In patients with reduced T_reg numbers (but no functional deficiency), the expansion of autologous T_reg cells could be a suitable therapeutic approach: either infusion of in-vitro autologous expanded cells, infusion of interleukin (IL)-2/anti-IL-2 complex, or both. T_reg biology-based therapies may not be suitable in patients with deficits of T_reg function, unless their deficit can be corrected in vivo/in vitro. Finally, it is critical to consider the appropriate stage of autoimmune diseases at which administration of T_reg cellular therapy can be most effective. We discuss conflicting data regarding whether T_reg cells are more effectual at preventing the initiation of autoimmunity, ameliorating disease progression or curing autoimmunity itself.

Contemporary issues and future directions in autoimmune hepatitis

Autoimmune hepatitis (AIH) is a severe life-threatening hepatopathy of unknown etiology, affecting both pediatric and adult populations, and characterised by inflammatory liver histology, circulating non-organ-specific autoantibodies, and hypergammaglobulinaemia. AIH is a very heterogeneous disease with a variety of clinical presentations, ranging from asymptomatic liver test abnormalities to acute severe hepatitis or even acute liver failure. It responds very well to immunosuppressive treatment with prednisolone with or without azathioprine. Patients who are intolerant or fail to respond to standard therapy are candidates for alternative immunosuppressive regimens, the combination of steroids with mycophenolate mofetil or calcineurin inhibitors being the most frequently reported. The pathogenesis of AIH remains not completely understood, although there is evidence that genetic predisposition, molecular mimicry and defective immunoregulatory mechanisms contribute to the autoimmune liver damage. Areas covered: A literature search was conducted using the key-words 'autoimmune hepatitis', 'immunogenetics', 'regulatory T-cells' and 'immunosuppression'. The aim of this review is to discuss recent breakthroughs in the understanding AIH pathogenesis, diagnosis and treatment. Expert commentary: Progress in the understanding of AIH pathogenesis is likely to contribute to the development of novel therapeutic strategies, such as the adoptive transfer of autologous expanded antigen-specific regulatory T-cells.

Functional Modulation of Regulatory T Cells by IL-2

The suppressive function of regulatory T cells (Tregs) is critical to the maintenance of immune homeostasis in vivo and yet, the specific identification of Tregs by phenotypic markers is not perfect. Tregs were originally identified in the CD4+CD25+ fraction of T cells, but FoxP3 expression was later included as an additional marker of Tregs as FoxP3 expression was identified as being critical to the development and function of these cells. Intracellular expression of FoxP3 makes it difficult in using to isolate live and not permeabilized cells for functional assays. As such CD4+CD25+ fraction is still frequently used for functional assays of Tregs. Although, the CD4+CD25+ fraction substantially overlaps with the FoxP3+ fraction, the minor mismatch between CD4+CD25+ and FoxP3+ fractions may confound the functional characteristics of Tregs. In this study, we isolated CD4+FoxP3+ as well as CD4+CD25+ fractions from Foxp3 knock-in mice, and compared their proliferative and suppressive activity in the presence or absence of various concentrations of IL-2. Our results showed comparable patterns of proliferative and suppressive responses for both fractions, except that contrary to the CD4+CD25+ fraction the FoxP3+ fraction did not proliferate in an autocrine fashion even in response to a strong stimulation. In presence of exogenous IL-2, both CD4+CD25+ and CD4+FoxP3+ fractions were more sensitive than the CD4+CD25- responder cells in proliferative responsiveness. In addition, a low dose IL-2 enhanced whereas a high dose abrogated the suppressive activities of the CD4+CD25+ and CD4+FoxP3+ fractions. These results may provide an additional understanding of the characteristics of the various fractions of isolated Tregs based on phenotype and function and the role of varying levels of exogenous IL-2 on the suppressive activity of these cells.

Inhibition of G-Protein βγ Signaling Decreases Levels of Messenger RNAs Encoding Proinflammatory Cytokines in T Cell Receptor-Stimulated CD4(+) T Helper Cells

Background: Inhibition of G-protein βγ (Gβγ) signaling was found previously to enhance T cell receptor (TCR)-stimulated increases in interleukin 2 (IL-2) mRNA in CD4⁺ T helper cells, suggesting that Gβγ might be a useful drug target for treating autoimmune diseases, as low dose IL-2 therapy can suppress autoimmune responses. Because IL-2 may counteract autoimmunity in part by shifting CD4⁺ T helper cells away from the Type 1 T helper cell (TH1) and TH17 subtypes towards the TH2 subtype, the purpose of this study was to determine if blocking Gβγ signaling affected the balance of TH1, TH17, and TH2 cytokine mRNAs produced by CD4⁺ T helper cells.

Methods: Gallein, a small molecule inhibitor of Gβγ, and siRNA-mediated silencing of the G-protein β₁ subunit (Gβ₁) were used to test the effect of blocking Gβγ on mRNA levels of cytokines in primary human TCR-stimulated CD4⁺ T helper cells.

Results: Gallein and Gβ₁ siRNA decreased interferon-γ (IFN-γ) and IL-17A mRNA levels in TCR-stimulated CD4⁺ T cells grown under TH1-promoting conditions. Inhibiting Gβγ also decreased mRNA levels of STAT4, which plays a positive role in TH1 differentiation and IL-17A production. Moreover, mRNA levels of the STAT4-regulated TH1-associated proteins, IL-18 receptor β chain (IL-18Rβ), mitogen-activated protein kinase kinase kinase 8 (MAP3K8), lymphocyte activation gene 3 (LAG-3), natural killer cell group 7 sequence (NKG7), and oncostatin M (OSM) were also decreased upon Gβγ inhibition. Gallein also increased IL-4, IL-5, IL-9, and IL-13 mRNA levels in TCR-stimulated memory CD4⁺ T cells grown in TH2-promoting conditions.

Conclusions: Inhibiting Gβγ to produce these shifts in cytokine mRNA production might be beneficial for patients with autoimmune diseases such as rheumatoid arthritis (RA), Crohn’s disease (CD), psoriasis, multiple sclerosis (MS), and Hashimoto’s thyroiditis (HT), in which both IFN-γ and IL-17A are elevated.

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.

The effect of the novel tellurium compound AS101 on autoimmune diseases

Tellurium is a rare element, which has been regarded as a non-essential trace element despite its relative abundance in the human body. The chemistry of tellurium supports a plethora of activities, but its biochemistry is not clearly established to date. The small tellurium(IV) compound, ammonium trichloro (dioxoethylene-o,o')tellurate (AS101) developed and initially investigated by us, is currently being evaluated in Phase II clinical trials in psoriasis patients. AS101 is the first tellurium compound to be tested for clinical efficacy. This compound is a potent immunomodulator both in vitro and in vivo with a variety of potential therapeutic applications. The present review will focus on the immunomodulatory properties of AS101, and specifically, its effects in mitigating autoimmune diseases. AS101 has several activities that act on the immune system, including: 1) its ability to reduce IL-17 levels and to inhibit the function of Th17 cells; 2) its specific unique redox-modulating activities enabling the inhibition of specific leukocyte integrins such as α4β1 and α4β7, that are pivotal for diapedesis of macrophages and CD4(+) T inflammatory/auto-reactive cells into the autoimmune tissues; and 3) its ability to enhance the activity of regulatory T cells (Treg). These activities coupled with its excellent safety profile suggest that AS101 may be a promising candidate for the management of autoimmune diseases.

Ultra-low dose interleukin-2 promotes immune-modulating function of regulatory T cells and natural killer cells in healthy volunteers

Low-dose interleukin-2 (IL-2) expands regulatory T cells (Tregs) and natural killer (NK) cells after stem cell transplantation (SCT) and may reduce graft-versus-host disease (GVHD). We hypothesized that ultra-low dose (ULD) IL-2 could serve as an immune-modulating agent for stem cell donors to prevent GVHD following SCT. However, the safety, dose level, and immune signatures of ULD IL-2 in immune-competent healthy subjects remain unknown. Here, we have characterized the phenotype and function of Tregs and NK cells as well as the gene expression and cytokine profiles of 21 healthy volunteers receiving 50,000 to 200,000 units/m(2)/day IL-2 for 5 days. ULD IL-2 was well tolerated and induced a significant increase in the frequency of Tregs with increased suppressive function. There was a marked expansion of CD56(bright) NK cells with enhanced interferon-γ (IFN-γ) production. Serum cytokine profiling demonstrated increase of IFN-γ induced protein 10 (IP-10). Gene expression analysis revealed significant changes in a highly restricted set of genes, including FOXP3, IL-2RA, and CISH. This is the first study to evaluate global immune-modulating function of ULD IL-2 in healthy subjects and to support the future studies administrating ULD IL-2 to stem cell donors.

T cells from autoimmune patients display reduced sensitivity to immunoregulation by mesenchymal stem cells: role of IL-2

Mesenchymal stem cells (MSCs) are multipotent progenitor cells which have been shown to possess broad immunoregulatory and anti-inflammatory capabilities, making them a promising tool to treat autoimmune diseases (AIDs). Nevertheless, as in recent years T cells from AID patients have been found to resist suppression by regulatory T cells, the question of whether they could be regulated by MSCs arises. To use MSCs as a therapeutic tool in human autoimmune diseases, one prerequisite is that T cells from autoimmune patients will be sensitive to these stem cells. The aim of this work was to investigate the ability of healthy donor derived MSCs to inhibit the proliferation of T cells from two pathophysiologically different AIDs: Multiple Sclerosis (MS) and Myasthenia Gravis (MG). We show that MSC-induced inhibition of interferon-γ production and surface expression of the CD3, CD4 and CD28 receptors by activated lymphocytes was similar in the AID patients and healthy controls. Contrarily, the MSCs' ability to suppress the proliferation of T cells of both diseases was significantly weaker compared to their ability to affect T cells of healthy individuals. Although we found that the inhibitory mechanism is mediated through CD14+ monocytes, the faulty cellular component is the patients' T cells. MSC-treated MS and MG lymphocytes were shown to produce significantly more IL-2 than healthy subjects while coupling of the MSC treatment with neutralizing IL-2 antibodies resulted in inhibition levels similar to those of the healthy controls. MSCs were also found to down-regulate the lymphocyte surface expression of the IL-2 receptor (CD25) through both transcription inhibition and induction of receptor shedding. Addition of IL-2 to MSC-inhibited lymphocytes restored proliferation thus suggesting a key role played by this cytokine in the inhibitory mechanism. Taken together, these results demonstrate the potential of a MSC-based cellular therapy for MS, MG and possibly other autoimmune diseases but also highlight the need for a better understanding of the underlying mechanisms for development and optimization of clinical protocols.

Tregs are dysfunctional in vivo in a spontaneous murine model of Crohn's disease

Although regulatory T cells (Tregs) have been implicated in inflammatory bowel disease, Tregs from Crohn's disease (CD) patients are increased in number and function normally in vitro. To clarify this disparity, we studied Treg function in vivo using a spontaneous model of CD-like ileitis. We first administered anti-CD25-depleting antibodies to SAMP1/YitFc (SAMP) mice to assess ileitis; mesenteric lymph node cells were then transferred into SCID (severe combined immunodeficient) recipients to induce colitis. CD25 depletion increased the severity of both spontaneous ileitis and adoptively transferred colitis. Interestingly, a second transfer of CD4(+)CD25(+) cells from untreated AKR control mice was able to ameliorate the induced colitis, whereas CD4(+)CD25(+) cells from untreated SAMP mice were not, suggesting a functional abnormality in SAMP Tregs. Anti-CD25 treatment in SAMP mice also induced proliferation of CD25(-)Foxp3(+) Tregs, which had a proinflammatory intestinal T helper type 1/ T helper type 2 (Th1/Th2) effector phenotype. These studies demonstrate Treg dysfunction in a spontaneous model of CD-like ileitis.

Ontogeny and localization of the cells produce IL-2 in healthy animals

IL-2 is a growth factor for activated T cells and is required for maintenance of naturally arising regulatory T cells (nTregs). Mice defective in IL-2/IL-2 receptor signaling pathways have impaired nTregs and suffer from lymphoproliferative disorders, suggesting that IL-2 is present and functional in healthy animals. However, the cellular source of IL-2 is currently unknown. To determine which cells produce IL-2 in healthy animals, we established mice carrying cre gene knock in at the il-2 locus (termed IL-2(cre)). When IL-2(cre) mice were crossed with EGFP reporter mice, EGFP was exclusively expressed by a fraction of CD4 T cells present in both lymphoid and non-lymphoid tissues. Live imaging of IL-2(cre) mice that carry the luciferase reporter showed concentrated localization of luciferase(+) cells in Peyer's patches. These cells were not observed in new born mice but appeared within 3days after birth. Reduction of antigen receptor repertoire by transgene expression reduced their number, indicating that recognition of environmental antigens is necessary for generation of these IL-2 producers in healthy animals. A substantial fraction of EGFP(+) cells also produce IL-10 and IFN-γ, a characteristic profile of type 1 regulatory T cells (Tr1). The data suggest that a group of Tr1 cells have addition roles in immune homeostasis by producing IL-2 along with other cytokines and help maintaining Tregs.

Inflammatory cytokines in systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is an autoimmune disease of unknown origin affecting virtually all organ systems. Beyond genetic and environmental factors, cytokine imbalances contribute to immune dysfunction, trigger inflammation, and induce organ damage. The key cytokine that is involved in SLE pathogenesis is interferon alpha. Interferon secretion is induced by immune complexes and leads to upregulation of several inflammatory proteins, which account for the so-called IFN signature that can be found in the majority of SLE PBMCs. Additionally IL-6 and IFN-y as well as T-cell-derived cytokines like IL-17, IL-21, and IL-2 are dysregulated in SLE. The latter induce a T-cell phenotype that is characterized by enhanced B-cell help and enhanced secretion of proinflammatory cytokines but reduced induction of suppressive T cells and activation-induced cell death. This paper will focus on these cytokines and highlights pathophysiological approaches and therapeutic potential.

Opposing functions of IL-2 and IL-7 in the regulation of immune responses

Regulation of the magnitude and quality of immune responses is dependent on the integration of multiple signals which typically operate through positive and negative feedback loops. Cytokines that promote or limit T cell expansion and differentiation are often both present in the complex lymphoid environment where antigen-initiated T cell responses take place. The nature and strength of the cytokine signal received by the responding cell, as well as by surrounding regulatory cells, will determine the extent of clonal expansion and the progression towards effector and memory cell differentiation. The mechanisms that determine how much cytokine is produced and how cytokine activities are controlled by receptor expression and intracellular regulators of signaling are not fully understood. Here we discuss the opposing functions of two members of the common receptor gamma chain (γc) cytokines, IL-2 and IL-7 in the generation and regulation of immune responses in vivo.

CTLA-4-Ig therapy diminishes the frequency but enhances the function of Treg cells in patients with rheumatoid arthritis

Rheumatoid arthritis (RA) is an autoimmune and inflammatory disease. Natural T regulatory (nTreg) cells, which constitutively express the CTLA-4 molecule, have an important role in the pathogenesis of autoimmune conditions. Although it has been reported that biological agents are able to modulate the levels or function of Treg lymphocytes, the possible effect of Abatacept (CTLA-4-Ig) therapy on these cells has not been studied in autoimmune conditions. We explored the effect of Abatacept therapy on Treg cells in patients with RA. The number of different subsets of Treg cells was analyzed by flow cytometry in the peripheral blood from 45 patients with RA that were (n = 30) or not (n = 15) under Abatacept therapy as well as in 20 healthy controls. The function of Treg cells was assessed by an assay of inhibition of lymphocyte proliferation. We found that Abatacept therapy was associated with a significant diminution in the levels of CD4+CD25(bright)Foxp3+, and CD4+CTLA-4+ nTreg cells. In contrast, the regulatory function of CD4+CD25+ lymphocytes was significantly enhanced after the administration of Abatacept. Our data suggest that CTLA-4-Ig exerts a complex and interesting effect on Treg cells in patients with RA.

IL-2-controlled expression of multiple T cell trafficking genes and Th2 cytokines in the regulatory T cell-deficient scurfy mice: implication to multiorgan inflammation and control of skin and lung inflammation

Scurfy (Sf) mice bear a mutation in the Foxp3 transcription factor, lack regulatory T cells (Treg), develop multiorgan inflammation, and die prematurely. The major target organs affected are skin, lungs, and liver. “Sf mice lacking the Il2 gene (Sf.Il2–/–), despite being devoid of Treg, did not develop skin and lung inflammation, but the inflammation in liver remained [corrected]. Genome-wide microarray analysis revealed hundreds of genes that were differentially regulated among Sf, Sf.Il2(-/-), and B6 CD4(+) T cells, but the most significant changes were those encoding receptors for trafficking/chemotaxis/retention and cytokines. Our study suggests that IL-2 controls the skin and lung inflammation in Sf mice in an apparent "organ-specific" manner through two novel mechanisms: by regulating the expression of genes encoding a variety of receptors for T cell trafficking/chemotaxis/retention and by regulating Th2 cell expansion and cytokine production. Thus, IL-2 is potentially a master regulator for multiorgan inflammation and an underlying etiological factor for various diseases associated with skin and lung inflammation.