Publications by authors named "Charles Egwuagu"

61 Publications

Analysis of Regulatory B Cells in Experimental Autoimmune Uveitis.

Methods Mol Biol 2021 ;2270:437-450

Molecular Immunology Section, Laboratory of Immunology, National Eye Institute (NEI), National Institutes of Health, Bethesda, MD, USA.

Regulatory B cells (Bregs) that produce IL-35 and IL-10 (i35-Bregs) regulate central nervous system (CNS) autoimmune diseases including uveitis. In the mouse model of uveitis, i35-Breg cells suppress intraocular inflammation by inducing expansion of IL-10-producing B cells (B10), IL-10-producing T cells (Tregs), and IL-35-producing T cells (iT35), suggesting that i35-Bregs orchestrate an immune-suppressive milieu that regulates immunity during autoimmune diseases. In this chapter, we discuss uveitis and therapeutic challenges that necessitate the development of cell-based therapies for the treatment of these potentially blinding diseases that cause 10% visual handicap. We then describe the methods we set up for ex vivo generation of i35-Breg cells employed in i35-Breg immunotherapy in uveitis and in other CNS autoimmune diseases.
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http://dx.doi.org/10.1007/978-1-0716-1237-8_23DOI Listing
January 2021

Identifying Mouse Autoimmune Uveitis from Fundus Photographs Using Deep Learning.

Transl Vis Sci Technol 2020 12 2;9(2):59. Epub 2020 Dec 2.

University of Tennessee Health Science Center, Memphis, TN, USA.

Purpose: To develop a deep learning model for objective evaluation of experimental autoimmune uveitis (EAU), the animal model of posterior uveitis that reveals its essential pathological features via fundus photographs.

Methods: We developed a deep learning construct to identify uveitis using reference mouse fundus images and further categorized the severity levels of disease into mild and severe EAU. We evaluated the performance of the model using the area under the receiver operating characteristic curve (AUC) and confusion matrices. We further assessed the clinical relevance of the model by visualizing the principal components of features at different layers and through the use of gradient-weighted class activation maps, which presented retinal regions having the most significant influence on the model.

Results: Our model was trained, validated, and tested on 1500 fundus images (training, 1200; validation, 150; testing, 150) and achieved an average AUC of 0.98 for identifying the normal, trace (small and local lesions), and disease classes (large and spreading lesions). The AUCs of the model using an independent subset with 180 images were 1.00 (95% confidence interval [CI], 0.99-1.00), 0.97 (95% CI, 0.94-0.99), and 0.96 (95% CI, 0.90-1.00) for the normal, trace and disease classes, respectively.

Conclusions: The proposed deep learning model is able to identify three severity levels of EAU with high accuracy. The model also achieved high accuracy on independent validation subsets, reflecting a substantial degree of generalizability.

Translational Relevance: The proposed model represents an important new tool for use in animal medical research and provides a step toward clinical uveitis identification in clinical practice.
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http://dx.doi.org/10.1167/tvst.9.2.59DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7718814PMC
December 2020

STAT3 deficiency in B cells exacerbates uveitis by promoting expansion of pathogenic lymphocytes and suppressing regulatory B cells (Bregs) and Tregs.

Sci Rep 2020 10 1;10(1):16188. Epub 2020 Oct 1.

Molecular Immunology Section, Laboratory of Immunology, National Eye Institute (NEI), National Institutes of Health (NIH), Building 10, Room 10N248G, 10 Center Drive, Bethesda, MD, 20892-1857, USA.

STAT3 transcription factor induces differentiation of naïve T cells into Th17 cells and loss of STAT3 in T cell prevents development of CNS autoimmune diseases. However, function of STAT3 in the B lymphocyte subset is not well understood. In this study, we have generated mice lacking STAT3 in CD19 B cells (CD19-STAT3KO) and investigated intrinsic and extrinsic functions of STAT3 in B cells and its potential role in resistance or pathogenesis of organ-specific autoimmune diseases. We show that STAT3 regulates metabolic mechanisms in B cells with implications for bioenergetic and metabolic pathways that control cellular homeostasis in B cells. Thus, loss of STAT3 in CD19-STAT3KO cells perturbed growth and apoptosis by inducing rapid entry of B cells into the S-phase of the cell cycle, decreasing expression of cyclin-dependent kinase inhibitors and upregulating pro-apoptotic proteins. We further show that the CD19-STAT3KO mice develop severe experimental autoimmune uveitis (EAU), an animal model of human uveitis. Exacerbated uveitis in CD19-STAT3KO mice derived in part from enhanced expression of costimulatory molecules on B cells, marked increase of Th17 responses and increased recruitment of granulocytes into the neuroretina. The enhanced autoimmunity upon deletion of STAT3 in B cells is also recapitulated in experimental autoimmune encephalitis, a mouse model of multiple sclerosis and thus support our conclusion that STAT3 deletion in B cells enhanced inflammation and the effects observed are not model specific. Our data further indicate that STAT3 pathway modulates interactions between B and T cells during EAU resulting in alteration of lymphocyte repertoire by increasing levels of autoreactive pathogenic T cells while suppressing development and/or expansion of immune-suppressive lymphocytes (Bregs and Tregs). Taken together, STAT3 exerts diametrically opposite effects in lymphocytes, with loss of STAT3 in B cells exacerbating uveitis whereas Stat3 deletion in T cells confers protection.
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http://dx.doi.org/10.1038/s41598-020-73093-1DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7529787PMC
October 2020

Interleukin 35 Regulatory B Cells.

J Mol Biol 2021 Jan 2;433(1):166607. Epub 2020 Aug 2.

Molecular Immunology Section, Laboratory of Immunology, National Eye Institute (NEI), National Institutes of Health, Bethesda, MD 20892-1857, USA. Electronic address:

B lymphocytes play a central role in host immunity. They orchestrate humoral immune responses that modulate activities of other immune cells and produce neutralizing antibodies that confer lasting immunity to infectious diseases including smallpox, measles and poliomyelitis. In addition to these traditional functions is the recent recognition that B cells also play critical role in maintaining peripheral tolerance and suppressing the development or severity of autoimmune diseases. Their immune suppressive function is attributed to relatively rare populations of regulatory B cells (Bregs) that produce anti-inflammatory cytokines including interleukin 10 (IL-10), IL-35 and transforming growth factor-β. The IL-35-producing B cell (i35-Breg) is the newest Breg subset described. i35-Bregs suppress central nervous system autoimmune diseases by inducing infectious tolerance whereby conventional B cells acquire regulatory functions that suppress pathogenic Th17 responses. In this review, we discuss immunobiology of i35-Breg cell, i35-Breg therapies for autoimmune diseases and potential therapeutic strategies for depleting i35-Bregs that suppress immune responses against pathogens and tumor cells.
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http://dx.doi.org/10.1016/j.jmb.2020.07.019DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7779660PMC
January 2021

Interleukin 35-Producing Exosomes Suppress Neuroinflammation and Autoimmune Uveitis.

Front Immunol 2020 29;11:1051. Epub 2020 May 29.

Molecular Immunology Section, Laboratory of Immunology, National Eye Institute (NEI), National Institute of Health, Bethesda, MD, United States.

Corticosteroids are effective therapy for autoimmune diseases but serious adverse effects preclude their prolonged use. However, immune-suppressive biologics that inhibit lymphoid proliferation are now in use as corticosteroid sparing-agents but with variable success; thus, the need to develop alternative immune-suppressive approaches including cell-based therapies. Efficacy of -generated IL-35-producing regulatory B-cells (i35-Bregs) in suppressing/ameliorating encephalomyelitis or uveitis in mouse models of multiple sclerosis or uveitis, respectively, is therefore a promising therapeutic approach for CNS autoimmune diseases. However, i35-Breg therapy in human uveitis would require producing autologous Bregs from each patient to avoid immune-rejection. Because exosomes exhibit minimal toxicity and immunogenicity, we investigated whether i35-Bregs release exosomes that can be exploited therapeutically. Here, we demonstrate that i35-Bregs release exosomes that contain IL-35 (i35-Exosomes). In this proof-of-concept study, we induced experimental autoimmune uveitis (EAU), monitored EAU progression by fundoscopy, histology, optical coherence tomography and electroretinography, and investigated whether i35-Exosomes treatment would suppress uveitis. Mice treated with i35-Exosomes developed mild EAU with low EAU scores and disease protection correlated with expansion of IL-10 and IL-35 secreting Treg cells with concomitant suppression of Th17 responses. In contrast, significant increase of Th17 cells in vitreous and retina of control mouse eyes was accompanied by severe choroiditis, massive retinal-folds, and photoreceptor cell damage. These hallmark features of severe uveitis were absent in exosome-treated mice and visual impairment detected by ERG was modest compared to control mice. Absence of toxicity or alloreactivity associated with exosomes thus makes i35-Exosomes attractive therapeutic option for delivering IL-35 into CNS tissues.
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http://dx.doi.org/10.3389/fimmu.2020.01051DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7272665PMC
May 2020

Persistent Activation of STAT3 Pathway in the Retina Induced Vision Impairment and Retinal Degenerative Changes in Ageing Mice.

Adv Exp Med Biol 2019 ;1185:353-358

Molecular Immunology Section, National Eye Institute, National Institutes of Health, Bethesda, MD, USA.

Neurotrophic factors can promote the survival of degenerating retinal cells through the activation of STAT3 pathway. Thus, augmenting STAT3 activation in the retina has been proposed as potential therapy for retinal dystrophies. On the other hand, aberrant activation of STAT3 pathway is oncogenic and implicated in diverse human diseases. Furthermore, the STAT3/SOCS3 axis has been shown to induce the degradation of rhodopsin during retinal inflammation. In this study, we generated and used mice with constitutive activation of STAT3 pathway in the retina to evaluate the safety and consequences of enhancing STAT3 activities in the retina as a potential treatment for retinal degenerative diseases. We show that long-term activation of the STAT3 pathway can induce retinal degenerative changes and also exacerbate uveitis and other intraocular inflammatory diseases. Mechanisms underlying the development of vision impairment in the STAT3c-Tg mice derived in part from STAT3-mediated inhibition of rhodopsin and overexpression of SOCS3 in the retina. These results suggest that much caution should be exercised in the use of STAT3 augmentation therapy for retinal dystrophies.
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http://dx.doi.org/10.1007/978-3-030-27378-1_58DOI Listing
February 2020

Production of IL-35 by Bregs is mediated through binding of BATF-IRF-4-IRF-8 complex to il12a and ebi3 promoter elements.

J Leukoc Biol 2018 12 17;104(6):1147-1157. Epub 2018 Aug 17.

Molecular Immunology Section, Laboratory of Immunology, National Eye Institute, National Institutes of Health, Bethesda, Maryland, USA.

IL-10 and IL-35 suppress excessive immune responses and therapeutic strategies are being developed to increase their levels in autoimmune diseases. In this study, we sought to identify major cell types that produce both cytokines in-vivo and to characterize mechanisms that regulate their production. Experimental autoimmune uveitis (EAU) is a CNS autoimmune disease that serves as model of human uveitis. We induced EAU in C57BL/6J mice and investigated whether T cells, B lymphocytes, or myeloid cells are the major producers of IL-10 or IL-35 in blood, lymph nodes (LNs), spleen, and at the site of ocular inflammation, the neuroretina. Analysis of these tissues identified B cells as the major producers of IL-10 and IL-35 in-vivo. Compared to regulatory T cells (Tregs), IL-10- or IL-35-producing regulatory B cells (Bregs) are substantially expanded in blood, LNs, spleen, and retina of mice with EAU. We performed EMSA and chromatin immunoprecipitation (ChIP) assays on activated B cells stimulated with IL-35 or TLR agonists. We found that BATF, IFN regulatory factor (IRF)-4, and IRF-8 transcription factors were recruited and bound to AP1-IRF-composite elements (AICEs) of il12a, ebi3, and/or il10 loci, suggesting their involvement in regulating IL-10 and IL-35 transcriptional programs of B cells. Showing that B cells are major source of IL-10 and IL-35 in-vivo and identifying transcription factors that contribute to IL-10 and IL-35 expression in the activated B-cell, suggest that the BATF/IRF-4/IRF-8 axis can be exploited therapeutically to regulate physiological levels of IL-10/IL-35-Bregs and that adoptive transfer of autologous Bregs might be an effective therapy for autoimmune and neurodegenerative diseases.
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http://dx.doi.org/10.1002/JLB.3A0218-071RRRDOI Listing
December 2018

STAT-3-independent production of IL-17 by mouse innate-like αβ T cells controls ocular infection.

J Exp Med 2018 04 28;215(4):1079-1090. Epub 2018 Feb 28.

Laboratory of Immunology, National Eye Institute, National Institutes of Health, Bethesda, MD

Appropriate regulation of IL-17 production in the host can mean the difference between effective control of pathogens and uncontrolled inflammation that causes tissue damage. Investigation of conventional CD4 T cells (Th17 cells) has yielded invaluable insights into IL-17 function and its regulation. More recently, we and others reported production of IL-17 from innate αβ+ T cell populations, which was shown to occur primarily via IL-23R signaling through the transcription factor STAT-3. In our current study, we identify promyelocytic leukemia zinc finger (PLZF)-expressing iNKT, CD4/CD8, and CD4/CD8 (DN) αβ+T cells, which produce IL-17 in response to TCR and IL-1 receptor ligation independently of STAT-3 signaling. Notably, this noncanonical pathway of IL-17 production may be important in mucosal defense and is by itself sufficient to control pathogenic infection at the ocular surface.
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http://dx.doi.org/10.1084/jem.20170369DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5881461PMC
April 2018

IL-12p35 Inhibits Neuroinflammation and Ameliorates Autoimmune Encephalomyelitis.

Front Immunol 2017 5;8:1258. Epub 2017 Oct 5.

Molecular Immunology Section, Laboratory of Immunology, National Eye Institute (NEI), National Institutes of Health, Bethesda, MD, United States.

Multiple sclerosis (MS) is an inflammatory demyelinating disease in which cytokines produced by immune cells that infiltrate the brain and spinal cord play a central role. We show here that the IL-12p35, the alpha subunit of IL-12 or IL-35 cytokine, might be an effective biologic for suppressing neuroinflammatory responses and ameliorating the pathology of experimental autoimmune encephalomyelitis (EAE), the mouse model of human MS. We further show that IL-12p35 conferred protection from neuropathy by inhibiting the expansion of pathogenic Th17 and Th1 cells and inhibiting trafficking of inflammatory cells into the brain and spinal cord. In addition, exposure of encephalitogenic cells to IL-12p35 suppressed their capacity to induce EAE by adoptive transfer. Importantly, the IL-12p35-mediated expansion of Treg and Breg cells and its amelioration of EAE correlated with inhibition of cytokine-induced activation of STAT1/STAT3 pathways. Moreover, IL-12p35 inhibited lymphocyte proliferation by suppressing the expressions of cell-cycle regulatory proteins. Taken together, these results suggest that IL-12p35 can be exploited as a novel biologic for treating central nervous system autoimmune diseases and offers the promise of production of large amounts of Tregs and Bregs for immunotherapy.
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http://dx.doi.org/10.3389/fimmu.2017.01258DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5633738PMC
October 2017

IL-12p35 induces expansion of IL-10 and IL-35-expressing regulatory B cells and ameliorates autoimmune disease.

Nat Commun 2017 09 28;8(1):719. Epub 2017 Sep 28.

Molecular Immunology Section, Laboratory of Immunology, National Eye Institute (NEI), National Institutes of Health (NIH), Bethesda, MD, 20892, USA.

Interleukin 35 (IL-35) is a heterodimeric cytokine composed of IL-12p35 and Ebi3 subunits. IL-35 suppresses autoimmune diseases while preventing host defense to infection and promoting tumor growth and metastasis by converting resting B and T cells into IL-10-producing and IL-35-producing regulatory B (Breg) and T (Treg) cells. Despite sharing the IL-12p35 subunit, IL-12 (IL-12p35/IL-12p40) promotes inflammatory responses whereas IL-35 (IL-12p35/Ebi3) induces regulatory responses, suggesting that IL-12p35 may have unknown intrinsic immune-regulatory functions regulated by its heterodimeric partner. Here we show that the IL-12p35 subunit has immunoregulatory functions hitherto attributed to IL-35. IL-12p35 suppresses lymphocyte proliferation, induces expansion of IL-10-expressing and IL-35-expressing B cells and ameliorates autoimmune uveitis in mice by antagonizing pathogenic Th17 responses. Recapitulation of essential immunosuppressive activities of IL-35 indicates that IL-12p35 may be utilized for in vivo expansion of Breg cells and autologous Breg cell immunotherapy. Furthermore, our uveitis data suggest that intrinsic immunoregulatory activities of other single chain IL-12 subunits might be exploited to treat other autoimmune diseases.IL-12p35 is common to IL-35 and IL-12, which have opposing effects on inflammation. Here the authors show that the IL-12p35 subunit induces regulatory B cells and can be used therapeutically to limit autoimmune uveitis in mice.
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http://dx.doi.org/10.1038/s41467-017-00838-4DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5620058PMC
September 2017

SOCS1 Mimetic Peptide Suppresses Chronic Intraocular Inflammatory Disease (Uveitis).

Mediators Inflamm 2016 15;2016:2939370. Epub 2016 Sep 15.

Molecular Immunology Section, National Eye Institute, National Institutes of Health, Bethesda, MD 20892, USA.

Uveitis is a potentially sight-threatening disease characterized by repeated cycles of remission and recurrent inflammation. The JAK/STAT pathway regulates the differentiation of pathogenic Th1 and Th17 cells that mediate uveitis. A SOCS1 mimetic peptide (SOCS1-KIR) that inhibits JAK2/STAT1 pathways has recently been shown to suppress experimental autoimmune uveitis (EAU). However, it is not clear whether SOCS1-KIR ameliorated uveitis by targeting JAK/STAT pathways of pathogenic lymphocytes or via inhibition of macrophages and antigen-presenting cells that also enter the retina during EAU. To further investigate mechanisms that mediate SOCS1-KIR effects and evaluate the efficacy of SOCS1-KIR as an investigational drug for chronic uveitis, we induced EAU in rats by adoptive transfer of uveitogenic T-cells and monitored disease progression and severity by slit-lamp microscopy, histology, and optical coherence tomography. Topical administration of SOCS1-KIR ameliorated acute and chronic posterior uveitis by inhibiting Th17 cells and the recruitment of inflammatory cells into retina while promoting expansion of IL-10-producing Tregs. We further show that SOCS1-KIR conferred protection of resident retinal cells that play critical role in vision from cytotoxic effects of inflammatory cytokines by downregulating proapoptotic genes. Thus, SOCS1-KIR suppresses uveitis and confers neuroprotective effects and might be exploited as a noninvasive treatment for chronic uveitis.
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http://dx.doi.org/10.1155/2016/2939370DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5040805PMC
June 2017

Interferon Regulator Factor 8 (IRF8) Limits Ocular Pathology during HSV-1 Infection by Restraining the Activation and Expansion of CD8+ T Cells.

PLoS One 2016 12;11(5):e0155420. Epub 2016 May 12.

Molecular Immunology Section, National Eye Institute (NEI), National Institutes of Health (NIH), Bethesda, Maryland, United States of America.

Interferon Regulatory Factor-8 (IRF8) is constitutively expressed in monocytes and B cell lineages and plays important roles in immunity to pathogens and cancer. Although IRF8 expression is induced in activated T cells, the functional relevance of IRF8 in T cell-mediated immunity is not well understood. In this study, we used mice with targeted deletion of Irf8 in T-cells (IRF8KO) to investigate the role of IRF8 in T cell-mediated responses during herpes simplex virus 1 (HSV-1) infection of the eye. In contrast to wild type mice, HSV-1-infected IRF8KO mice mounted a more robust anti-HSV-1 immune response, which included marked expansion of HSV-1-specific CD8+ T cells, increased infiltration of inflammatory cells into the cornea and trigeminal ganglia (TG) and enhanced elimination of virus within the trigeminal ganglion. However, the consequence of the enhanced immunological response was the development of ocular inflammation, limbitis, and neutrophilic infiltration into the cornea of HSV-1-infected IRF8KO mice. Surprisingly, we observed a marked increase in virus-specific memory precursor effector cells (MPEC) in IRF8KO mice, suggesting that IRF8 might play a role in regulating the differentiation of effector CD8+ T cells to the memory phenotype. Together, our data suggest that IRF8 might play a role in restraining excess lymphocyte proliferation. Thus, modulating IRF8 levels in T cells can be exploited therapeutically to prevent immune-mediated ocular pathology during autoimmune and infectious diseases of the eye.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0155420PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4865128PMC
July 2017

A novel IL-23p19/Ebi3 (IL-39) cytokine mediates inflammation in Lupus-like mice.

Eur J Immunol 2016 06 13;46(6):1343-50. Epub 2016 Apr 13.

Laboratory of Immunology, Institute of Basic Medical Sciences, Beijing, China.

Interleukin-12 family cytokines have emerged as critical regulators of immunity with some members (IL-12, IL-23) associated with disease pathogenesis while others (IL-27, IL-35) mitigate autoimmune diseases. Each IL-12 family member is comprised of an α and a β chain, and chain-sharing is a key feature. Although four bona fide members have thus far been described, promiscuous chain-pairing between alpha (IL-23p19, IL-27p28, IL-12/IL-35p35) and beta (IL-12/IL-23p40, IL-27/IL-35Ebi3) subunits, predicts six possible heterodimeric IL-12 family cytokines. Here, we describe a new IL-12 member composed of IL-23p19 and Ebi3 heterodimer (IL-39) that is secreted by LPS-stimulated B cells and GL7(+) activated B cells of lupus-like mice. We further show that IL-39 mediates inflammatory responses through activation of STAT1/STAT3 in lupus-like mice. Taken together, our results show that IL-39 might contribute to immunopathogenic mechanisms of systemic lupus erythematosus, and could be used as a possible target for its treatment.
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http://dx.doi.org/10.1002/eji.201546095DOI Listing
June 2016

Pre-existing CD19-independent GL7(-) Breg cells are expanded during inflammation and in mice with lupus-like disease.

Mol Immunol 2016 Mar 4;71:54-63. Epub 2016 Feb 4.

Laboratory of Immunology, Institute of Basic Medical Sciences, Beijing 100850, China. Electronic address:

Interleukin 10 (IL-10)-producing regulatory B-cells (Bregs) suppress inflammatory responses that mediate autoimmune diseases. However, it is unknown whether Bregs derive from a pre-existing dedicated B-cell lineage or if any B-cell can differentiate into Bregs in response to BCR or TLR activation. GL7(+) B-cells are antigen-experienced differentiated B-cells while GL7(-/lo) are at an early stage of B-cell differentiation. While both GL7(-/lo) and GL7(+) B cells can produce IL-10, differentiation of GL7(-) B-cells into Bregs does not require CD19- or Bcl6-induced signals, suggesting that BCR-induced proliferation or Ig class-switching is not necessary for generation of Breg cells. Of particular importance, we show that GL7(-) Breg cells are dramatically expanded in lupus-like mice and GL7(-) Bregs suppressed inflammatory responses in lupus-like mice by inducing expansion of Foxp3(+)Treg cells. Taken together, these results suggest that pre-existing GL7(-)IL-10(+) cells are expanded during inflammation, differentiate into GL7(+) Bregs and contribute to immune-regulation in lupus-like mice.
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http://dx.doi.org/10.1016/j.molimm.2016.01.011DOI Listing
March 2016

Cutting Edge: IL-1 Receptor Signaling is Critical for the Development of Autoimmune Uveitis.

J Immunol 2016 Jan 7;196(2):543-6. Epub 2015 Dec 7.

Laboratory of Molecular Immunology and the Immunology Center, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD 20892; and

IL-1β is a proinflammatory cytokine important for local and systemic immunity. However, aberrant production of this cytokine is implicated in pathogenic mechanisms of a number of inflammatory diseases, including Behçet's disease and age-related macular degeneration. In this study, we report the increased secretion of IL-1β in the retina by neutrophils, macrophages, and dendritic cells during ocular inflammation and show that loss of IL-1R signaling confers protection from experimental autoimmune uveitis. Moreover, the amelioration of experimental autoimmune uveitis in Il1r-deficient mice was associated with reduced infiltration of inflammatory cells into the retina and decreased numbers of uveitogenic Th17 cells that mediate uveitis. These findings indicate the possible utility of IL-1R-blocking agents for the treatment of ocular inflammatory diseases.
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http://dx.doi.org/10.4049/jimmunol.1502080DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4707108PMC
January 2016

Interleukin 35: Critical regulator of immunity and lymphocyte-mediated diseases.

Cytokine Growth Factor Rev 2015 Oct 20;26(5):587-93. Epub 2015 Jul 20.

Laboratory of Immunology, Beijing Institute of Basic Medical Sciences, Beijing 100850, China.

Cytokines coordinate the activities of innate and adaptive immune systems and the Interleukin 12 (IL-12) family of cytokines has emerged as critical regulators of immunity in infectious and autoimmune diseases. While some members (IL-12 and IL-23) are associated with the pathogenesis of chronic inflammatory diseases, others (IL-27 and IL-35) mitigate autoimmune diseases. Unlike IL-12, IL-23 and IL-27 that are produced mainly by antigen presenting cells, IL-35 is predominantly secreted by regulatory B (i35-Bregs) and T (iTR35) cells. The discovery that IL-35 can induce the conversion or expansion of lymphocytes to regulatory B and T cells has considerable implications for therapeutic use of autologous regulatory B and T cells in human diseases. Although our current understanding of the immunobiology of IL-35 or its subunits (p35 and Ebi3) is still rudimentary, our goal in this review is to summarize what we know about this enigmatic cytokine and its potential clinical use, particularly in the treatment of CNS autoimmune diseases.
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http://dx.doi.org/10.1016/j.cytogfr.2015.07.013DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4581966PMC
October 2015

Dual Function of the IRF8 Transcription Factor in Autoimmune Uveitis: Loss of IRF8 in T Cells Exacerbates Uveitis, Whereas Irf8 Deletion in the Retina Confers Protection.

J Immunol 2015 Aug 10;195(4):1480-8. Epub 2015 Jul 10.

Molecular Immunology Section, National Eye Institute, National Institutes of Health, Bethesda, MD 20892; and

IFN regulatory factor 8 (IRF8) is constitutively expressed in monocytes and B cells and plays a critical role in the functional maturation of microglia cells. It is induced in T cells following Ag stimulation, but its functions are less well understood. However, recent studies in mice with T cell-specific Irf8 disruption under direction of the Lck promoter (LCK-IRF8KO) suggest that IRF8 directs a silencing program for Th17 differentiation, and IL-17 production is markedly increased in IRF8-deficient T cells. Paradoxically, loss of IRF8 in T cells has no effect on the development or severity of experimental autoimmune encephalomyelitis (EAE), although exacerbating colitis in a mouse colitis model. In contrast, mice with a macrophage/microglia-specific Irf8 disruption are resistant to EAE, further confounding our understanding of the roles of IRF8 in host immunity and autoimmunity. To clarify the role of IRF8 in autoimmune diseases, we have generated two mouse strains with targeted deletion of Irf8 in retinal cells, including microglial cells and a third mouse strain with targeted Irf8 deletion in T cells under direction of the nonpromiscuous, CD4 promoter (CD4-IRF8KO). In contrast to the report that IRF8 deletion in T cells has no effect on EAE, experimental autoimmune uveitis is exacerbated in CD4-IRF8KO mice and disease enhancement correlates with significant expansion of Th17 cells and a reduction in T regulatory cells. In contrast to CD4-IRF8KO mice, Irf8 deletion in retinal cells confers protection from uveitis, underscoring divergent and tissue-specific roles of IRF8 in host immunity. These results raise a cautionary note in the context of therapeutic targeting of IRF8.
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http://dx.doi.org/10.4049/jimmunol.1500653DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4530071PMC
August 2015

Topical administration of a suppressor of cytokine signaling-1 (SOCS1) mimetic peptide inhibits ocular inflammation and mitigates ocular pathology during mouse uveitis.

J Autoimmun 2015 Aug 19;62:31-8. Epub 2015 Jun 19.

Molecular Immunology Section, National Eye Institute, National Institutes of Health, USA. Electronic address:

Uveitis is a diverse group of potentially sight-threatening intraocular inflammatory diseases and pathology derives from sustained production of pro-inflammatory cytokines in the optical axis. Although topical or systemic steroids are effective therapies, their adverse effects preclude prolonged usage and are impetus for seeking alternative immunosuppressive agents, particularly for patients with refractory uveitis. In this study, we synthesized a 16 amino acid membrane-penetrating lipophilic suppressor of cytokine signaling 1 peptide (SOCS1-KIR) that inhibits JAK/STAT signaling pathways and show that it suppresses and ameliorates experimental autoimmune uveitis (EAU), the mouse model of human uveitis. Fundus images, histological and optical coherence tomography analysis of eyes showed significant suppression of clinical disease, with average clinical score of 0.5 compared to 2.0 observed in control mice treated with scrambled peptide. We further show that SOCS1-KIR conferred protection from ocular pathology by inhibiting the expansion of pathogenic Th17 cells and inhibiting trafficking of inflammatory cells into the neuroretina during EAU. Dark-adapted scotopic and photopic electroretinograms further reveal that SOCS1-KIR prevented decrement of retinal function, underscoring potential neuroprotective effects of SOCS1-KIR in uveitis. Importantly, SOCS1-KIR is non-toxic, suggesting that topical administration of SOCS1-Mimetics can be exploited as a non-invasive treatment for uveitis and for limiting cytokine-mediated pathology in other ocular inflammatory diseases including scleritis.
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http://dx.doi.org/10.1016/j.jaut.2015.05.011DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4529792PMC
August 2015

Interleukin 12 (IL-12) family cytokines: Role in immune pathogenesis and treatment of CNS autoimmune disease.

Cytokine 2015 Oct 18;75(2):249-55. Epub 2015 Mar 18.

Molecular Immunology Section, National Eye Institute, National Institutes of Health, USA. Electronic address:

Cytokines play crucial roles in coordinating the activities of innate and adaptive immune systems. In response to pathogen recognition, innate immune cells secrete cytokines that inform the adaptive immune system about the nature of the pathogen and instruct naïve T cells to differentiate into the appropriate T cell subtypes required to clear the infection. These include Interleukins, Interferons and other immune-regulatory cytokines that exhibit remarkable functional redundancy and pleiotropic effects. The focus of this review, however, is on the enigmatic Interleukin 12 (IL-12) family of cytokines. This family of cytokines plays crucial roles in shaping immune responses during antigen presentation and influence cell-fate decisions of differentiating naïve T cells. They also play essential roles in regulating functions of a variety of effector cells, making IL-12 family cytokines important therapeutic targets or agents in a number of inflammatory diseases, such as the CNS autoimmune diseases, uveitis and multiple sclerosis.
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http://dx.doi.org/10.1016/j.cyto.2015.01.030DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4553122PMC
October 2015

Interleukin 35-Producing B Cells (i35-Breg): A New Mediator of Regulatory B-Cell Functions in CNS Autoimmune Diseases.

Crit Rev Immunol 2015 ;35(1):49-57

Molecular Immunology Section, Laboratory of Immunology, National Eye Institute (NEI), National Institutes of Health (NIH), Bethesda, Maryland 20892.

Neuroinflammation contributes to neuronal deficits in neurodegenerative CNS (central nervous system) autoimmune diseases, such as multiple sclerosis and uveitis. The major goal of most treatment modalities for CNS autoimmune diseases is to limit inflammatory responses in the CNS; immune-suppressive drugs are the therapy of choice. However, lifelong immunosuppression increases the occurrence of infections, nephrotoxicity, malignancies, cataractogenesis, and glaucoma, which can greatly impair quality of life for the patient. Biologics that target pathogenic T cells is an alternative approach that is gaining wide acceptance as indicated by the popularity of a variety of Food and Drug Administration (FDA)-approved anti-inflammatory compounds and humanized antibodies such as Zenapax, Etanercept, Remicade, anti-ICAM, rapamycin, or tacrolimus. B cells are also potential therapeutic targets because they provide costimulatory signals that activate pathogenic T cells and secrete cytokines that promote autoimmune pathology. B cells also produce autoreactive antibodies implicated in several organ-specific and systemic autoimmune diseases including lupus erythematosus, Graves' disease, and Hashimoto's thyroiditis. On the other hand, recent studies have led to the discovery of several regulatory B-cell (Breg) populations that suppress immune responses and autoimmune diseases. In this review, we present a brief overview of Breg phenotypes and in particular, the newly discovered IL35-producing regulatory B cell (i35-Breg). We discuss the critical roles played by i35-Bregs in regulating autoimmune diseases and the potential use of adoptive Breg therapy in CNS autoimmune diseases.
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http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5433835PMC
http://dx.doi.org/10.1615/critrevimmunol.2015012558DOI Listing
February 2016

Suppressor of cytokine signaling 1 (SOCS1) mitigates anterior uveitis and confers protection against ocular HSV-1 infection.

Inflammation 2015 Apr;38(2):555-65

Molecular Immunology Section, Laboratory of Immunology, National Eye Institute, National Institutes of Health, Building 10, Room 10N109A, 10 Center Drive, Bethesda, MD, 20892-1857, USA.

Immunological responses to pathogens are stringently regulated in the eye to prevent excessive inflammation that damage ocular tissues and compromise vision. Suppressors of cytokine signaling (SOCS) regulate intensity/duration of inflammatory responses. We have used SOCS1-deficient mice and retina-specific SOCS1 transgenic rats to investigate roles of SOCS1 in ocular herpes simplex virus (HSV-1) infection and non-infectious uveitis. We also genetically engineered cell-penetrating SOCS proteins (membrane-translocating sequence (MTS)-SOCS1, MTS-SOCS3) and examined whether they can be used to inhibit inflammatory cytokines. Overexpression of SOCS1 in transgenic rat eyes attenuated ocular HSV-1 infection while SOCS1-deficient mice developed severe non-infectious anterior uveitis, suggesting that SOCS1 may contribute to mechanism of ocular immune privilege by regulating trafficking of inflammatory cells into ocular tissues. Furthermore, MTS-SOCS1 inhibited IFN-γ-induced signal transducers and activators of transcription 1 (STAT1) activation by macrophages while MTS-SOCS3 suppressed expansion of pathogenic Th17 cells that mediate uveitis, indicating that MTS-SOCS proteins maybe used to treat ocular inflammatory diseases of infectious or autoimmune etiology.
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http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4282977PMC
http://dx.doi.org/10.1007/s10753-014-9962-6DOI Listing
April 2015

Interleukin-35 induces regulatory B cells that suppress autoimmune disease.

Nat Med 2014 Jun 17;20(6):633-41. Epub 2014 Apr 17.

Molecular Immunology Section, Laboratory of Immunology, National Eye Institute (NEI), National Institutes of Health (NIH), Bethesda, Maryland, USA.

Interleukin-10 (IL-10)-producing regulatory B (Breg) cells suppress autoimmune disease, and increased numbers of Breg cells prevent host defense to infection and promote tumor growth and metastasis by converting resting CD4(+) T cells to regulatory T (Treg) cells. The mechanisms mediating the induction and development of Breg cells remain unclear. Here we show that IL-35 induces Breg cells and promotes their conversion to a Breg subset that produces IL-35 as well as IL-10. Treatment of mice with IL-35 conferred protection from experimental autoimmune uveitis (EAU), and mice lacking IL-35 (p35 knockout (KO) mice) or defective in IL-35 signaling (IL-12Rβ2 KO mice) produced less Breg cells endogenously or after treatment with IL-35 and developed severe uveitis. Adoptive transfer of Breg cells induced by recombinant IL-35 suppressed EAU when transferred to mice with established disease, inhibiting pathogenic T helper type 17 (TH17) and TH1 cells while promoting Treg cell expansion. In B cells, IL-35 activates STAT1 and STAT3 through the IL-35 receptor comprising the IL-12Rβ2 and IL-27Rα subunits. As IL-35 also induced the conversion of human B cells into Breg cells, these findings suggest that IL-35 may be used to induce autologous Breg and IL-35(+) Breg cells and treat autoimmune and inflammatory disease.
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http://dx.doi.org/10.1038/nm.3554DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4048323PMC
June 2014

Chronic intraocular inflammation and development of retinal degenerative disease.

Adv Exp Med Biol 2014 ;801:417-25

Molecular Immunology Section, Laboratory of Immunology, National Eye Institute, National Institutes of Health, Building 10, Room 10N116, 10 Center Drive, 20892-1857, Bethesda, MD, USA,

Elevated levels of inflammatory cytokines in the vitreous of patients with chronic intraocular inflammatory (uveitis) have long been suspected to contribute to the pathogenesis of retinal degenerative diseases. However, direct connection between chronic inflammation and development of retinal degenerative diseases has been difficult to establish because we lack an appropriate animal model of co-existing chronic intraocular inflammation and neurodegeneration. This report discusses new developments in immunological and diabetic research that suggest that persistent secretion of pro-inflammatory cytokines during uveitis might induce insulin resistance and retinal degenerative changes that contribute to the pathogenesis of Diabetic Retinopathy (DR), a retinal dystrophy of significant public health importance.
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http://dx.doi.org/10.1007/978-1-4614-3209-8_53DOI Listing
July 2014

STAT3 regulates proliferation and survival of CD8+ T cells: enhances effector responses to HSV-1 infection, and inhibits IL-10+ regulatory CD8+ T cells in autoimmune uveitis.

Mediators Inflamm 2013 24;2013:359674. Epub 2013 Sep 24.

Molecular Immunology Section, National Eye Institute, National Institutes of Allergy and Viral Diseases, National Institutes of Health, Building 10, Room 10N109A, 10 Center Drive, Bethesda, MD 20892-1857, USA.

STAT3 regulates CD4+ T cell survival and differentiation. However, its effects on CD8+ T cells are not well understood. Here, we show that in comparison to WT CD8+ T cells, STAT3-deficient CD8+ T cells exhibit a preactivated memory-like phenotype, produce more IL-2, proliferate faster, and are more sensitive to activation-induced cell death (AICD). The enhanced proliferation and sensitivity to AICD correlated with downregulation of class-O forkhead transcription factors (FoxO1, FoxO3A), p21(waf1), p27(KIP1), Bcl-2, OX-40, and upregulation of FasL, Bax, and Bad. We examined whether STAT3-deficient CD8+ T cells can mount effective response during herpes simplex virus (HSV-1) infection and experimental autoimmune uveitis (EAU). Compared to WT mice, HSV-1-infected STAT3-deficient mice (STAT3KO) produced less IFN-γ and virus-specific KLRG-1+ CD8+ T cells. STAT3KO mice are also resistant to EAU and produced less IL-17-producing Tc17 cells. Resistance of STAT3KO to EAU correlated with marked expansion of IL-10-producing regulatory CD8+ T cells (CD8-Treg) implicated in recovery from autoimmune encephalomyelitis. Thus, increases of IL-6-induced STAT3 activation observed during inflammation may inhibit expansion of CD8-Tregs, thereby impeding recovery from uveitis. These results suggest that STAT3 is a potential therapeutic target for upregulating CD8+ T cell-mediated responses to viruses and suggest the successful therapeutic targeting of STAT3 as treatment for uveitis, derived, in part, from promoting CD8-Treg expansion.
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http://dx.doi.org/10.1155/2013/359674DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3800609PMC
June 2014

SOCS3 deletion in T lymphocytes suppresses development of chronic ocular inflammation via upregulation of CTLA-4 and expansion of regulatory T cells.

J Immunol 2013 Nov 7;191(10):5036-43. Epub 2013 Oct 7.

Molecular Immunology Section, National Eye Institute, National Institutes of Health, Bethesda, MD 20892.

Suppressors of cytokine signaling (SOCS) proteins are negative-feedback regulators of the JAK/STAT pathway, and SOCS3 contributes to host immunity by regulating the intensity and duration of cytokine signals and inflammatory responses. Mice with Socs3 deletion in myeloid cells exhibit enhanced STAT3 signaling, expansion of Th1 and Th17 cells, and develop severe experimental autoimmune encephalomyelitis. Interestingly, development of the unique IL-17/IFN-γ double-producing (Th17/IFN-γ and Tc17/IFN-γ) subsets that exhibit strong cytotoxic activities and are associated with pathogenesis of several autoimmune diseases has recently been shown to depend on epigenetic suppression of SOCS3 expression, further suggesting involvement of SOCS3 in autoimmunity and tumor immunity. In this study, we generated mice with Socs3 deletion in the CD4 T cell compartment (CD4-SOCS3 knockout [KO]) to determine in vivo effects of the loss of Socs3 in the T cell-mediated autoimmune disease, experimental autoimmune uveitis (EAU). In contrast to the exacerbation of experimental autoimmune encephalomyelitis in myeloid-specific SOCS3-deleted mice, CD4-SOCS3KO mice were protected from acute and chronic uveitis. Protection from EAU correlated with enhanced expression of CTLA-4 and expansion of IL-10-producing regulatory T cells with augmented suppressive activities. We further show that SOCS3 interacts with CTLA-4 and negatively regulates CTLA-4 levels in T cells, providing a mechanistic explanation for the expansion of regulatory T cells in CD4-SOCS3 during EAU. Contrary to in vitro epigenetic studies, Th17/IFN-γ and Tc17/IFN-γ populations were markedly reduced in CD4-SOCS3KO, suggesting that SOCS3 promotes expansion of the Th17/IFN-γ subset associated with development of severe uveitis. Thus, SOCS3 is a potential therapeutic target in uveitis and other autoinflammatory diseases.
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http://dx.doi.org/10.4049/jimmunol.1301132DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4041279PMC
November 2013

Therapeutic targeting of STAT pathways in CNS autoimmune diseases.

JAKSTAT 2013 Jan;2(1):e24134

Molecular Immunology Section; National Eye Institute; National Institutes of Health; Bethesda, MD USA.

Signal transducers and activators of transcription (STATs) transduce extracellular signals that regulate the initiation, duration and intensity of immune responses. However, unbridled activation of STATs by pro-inflammatory cytokines or growth factors contributes to pathogenic autoimmunity. In this review, we briefly discuss STAT pathways that promote the development and expansion of T cells that mediate two CNS inflammatory diseases, multiple sclerosis (MS) and uveitis. Particular focus is on animal models of MS and uveitis and new approaches to the treatment of CNS autoimmune diseases based on therapeutic targeting of Th17 cells and STAT pathways.
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http://dx.doi.org/10.4161/jkst.24134DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3670276PMC
January 2013

STAT3 activates miR-155 in Th17 cells and acts in concert to promote experimental autoimmune uveitis.

Invest Ophthalmol Vis Sci 2013 Jun 10;54(6):4017-25. Epub 2013 Jun 10.

Laboratory of Immunology, National Institute of Allergy and Infectious Diseases (NIAID), National Institutes of Health, Bethesda, Maryland 20892, USA.

Purpose: MicroRNA-155 (miR-155) and STAT3 are implicated in uveitis and pathogenic mechanisms of CNS autoimmune diseases. In our study, we used miR-155(-/-) mice and mice with targeted STAT3 deletion in T cells (CD4-STAT3KO) to investigate roles of miR-155 and STAT3 in the development of experimental autoimmune uveitis (EAU), a mouse model of human uveitis.

Methods: We induced EAU in WT, miR-155(-/-), or CD4-STAT3KO mice by immunization with interphotoreceptor retinoid-binding protein/complete Freund's adjuvant (IRBP/CFA) or adoptive transfer of T cells. EAU was assessed by funduscopy and histology. RNA expression was analyzed by quantitative PCR (qPCR), while cytokine production was assessed by fluorescence-activated cell sorting (FACS).

Results: We used a combination of genomic and genetic tools to provide the first evidence that STAT3 binds directly to the miR-155 locus and that STAT3 is required for miR-155 expression. Furthermore, STAT3-dependent increase in miR-155 expression in vivo correlated temporally with onset of EAU, and miR-155(-/-) or CD4-STAT3KO mice did not suffer EAU. CD4(+) lymph node cells from IRBP-immunized WT mice transferred EAU to naïve wild-type (WT) and miR-155(-/-) mice, while miR-155(-/-) IRBP-specific T cells did not.

Conclusions: Although miR-155 and STAT3 have been implicated in the etiology of multiple sclerosis (MS), uveitis, or rheumatoid arthritis, their exact roles in these diseases are unclear. We show here for the first time to our knowledge that STAT3 regulates miR-155 expression in Th17 cells. We show further that STAT3 and miR-155 form an axis that promotes the expansion of pathogenic Th17 cells that mediate uveitis. Thus, STAT3 and miR-155 may be therapeutic targets for treating uveitis and other Th17-mediated inflammatory disorders.
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http://dx.doi.org/10.1167/iovs.13-11937DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3680004PMC
June 2013

Interleukin 27 induces the expression of complement factor H (CFH) in the retina.

PLoS One 2012 20;7(9):e45801. Epub 2012 Sep 20.

Molecular Immunology Section, National Eye Institute, National Institutes of Health, Bethesda, MD, USA.

Complement factor H (CFH) is a central regulator of the complement system and has been implicated in the etiology of age-related macular degeneration (AMD), a leading cause of blindness in the elderly. In view of previous studies showing that reduced expression of CFH in the retina is a risk factor for developing AMD, there is significant interest in understanding how CFH expression is regulated in the retina. In this study, we have shown that the anti-inflammatory cytokine, IL-27, induced CFH expression in mouse retinal cells and human retinal pigmented epithelial cells (RPE) through STAT1-mediated up-regulation of Interferon Regulatory Factor-1 (IRF-1) and IRF-8. We further show that cells in the ganglion and inner-nuclear layers of the retina constitutively express IRF-1 and IRF-8 and enhanced CFH expression in the retina during ocular inflammation correlated with significant increase in the expression of IRF-1, IRF-8 and IL-27 (IL-27p28 and Ebi3). Our data thus reveal a novel role of IL-27 in regulating complement activation through up-regulation of CFH and suggest that defects in IL-27 signaling or expression may contribute to the reduction of CFH expression in the retina of patients with AMD.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0045801PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3447806PMC
February 2013

Novel IL27p28/IL12p40 cytokine suppressed experimental autoimmune uveitis by inhibiting autoreactive Th1/Th17 cells and promoting expansion of regulatory T cells.

J Biol Chem 2012 Oct 30;287(43):36012-21. Epub 2012 Aug 30.

Molecular Immunology Section, Laboratory of Immunology, NEI, National Institutes of Health, Bethesda, Maryland 20892-1857, USA.

IL-12 family cytokines are important in host immunity. Whereas some members (IL-12, IL-23) play crucial roles in pathogenesis of organ-specific autoimmune diseases by inducing the differentiation of Th1 and Th17 lymphocytes, others (IL-27 and IL-35) suppress inflammatory responses and limit tissue injury induced by these T cell subsets. In this study, we have genetically engineered a novel IL27p28/IL12p40 heterodimeric cytokine (p28/p40) that antagonizes signaling downstream of the gp130 receptor. We investigated whether p28/p40 can be used to ameliorate uveitis, a CNS inflammatory disease. Experimental autoimmune uveitis (EAU) is the mouse model of human uveitis and is mediated by Th1 and Th17 cells. We show here that p28/p40 suppressed EAU by inhibiting the differentiation and inflammatory responses of Th1 and Th17 cells while promoting expansion of IL-10(+)- and Foxp3(+)-expressing regulatory T cells. Lymph node cells from mice treated with p28/p40 blocked adoptive transfer of EAU to naïve syngeneic mice by immunopathogenic T cells and suppressive effects of p28/p40 derived in part from antagonizing STAT1 and STAT3 pathways induced by IL-27 and IL-6. Interestingly, IL27p28 also suppressed EAU, but to a lesser extent than p28/p40. The inhibition of uveitogenic lymphocyte proliferation and suppression of EAU by p28/p40 and IL27p28 establish efficacy of single chain and heterodimeric IL-12 family cytokines in treatment of a CNS autoimmune disease. Creation of the biologically active p28/p40 heterodimeric cytokine represents an important proof-of-concept experiment, suggesting that cytokines comprising unique IL-12 α- and β-subunit pairing may exist in nature and may constitute a new class of therapeutic cytokines.
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http://dx.doi.org/10.1074/jbc.M112.390625DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3476269PMC
October 2012

STAT3 protein interacts with Class O Forkhead transcription factors in the cytoplasm and regulates nuclear/cytoplasmic localization of FoxO1 and FoxO3a proteins in CD4(+) T cells.

J Biol Chem 2012 Aug 2;287(36):30436-43. Epub 2012 Jul 2.

Molecular Immunology Section, NEI, National Institutes of Health, Bethesda, MD 20892, USA.

An important feature of the adaptive immune response is its remarkable capacity to regulate the duration of inflammatory responses, and effector T cells have been shown to limit excessive immune responses by producing anti-inflammatory cytokines such as IL-10 and IL-27. However, how anti-inflammatory cytokines mediate their suppressive activities is not well understood. In this study, we show that STAT3 contributes to mechanisms that control the duration of T cell proliferation by regulating the subcellular location of FoxO1 and FoxO3a, two Class O Forkhead transcription factors that mediate lymphocyte quiescence and inhibit T cell activation. We show that active FoxO1 and FoxO3a reside exclusively in the nucleus of naïve T cells whereas inactive pFoxO1 and pFoxO3a were most abundant in activated T cells and sequestered in their cytoplasm in association with unphosphorylated STAT3 (U-STAT3) and 14-3-3. We further show that FoxO1/FoxO3a rapidly relocalized into the nucleus in response to pSTAT3 activation by IL-6 or IL-10, and the accumulation of FoxO1/FoxO3a in their nuclei coincided with increased expression of p27(Kip1) and p21(WAF1). STAT3 inhibitors completely abrogated cytokine-induced translocation of FoxO1/FoxO3a into the nucleus. In naïve or resting STAT3-deficient T cells, expression of pFoxO1/pFoxO3a was predominantly in the cytoplasm and correlated with defects in p27(Kip1) and p21(WAF1) expression, suggesting requirement of STAT3 for importation or retention of FoxO in the nucleus and attenuation of lymphocyte proliferation. Taken together, these results suggest that U-STAT3 collaborates with 14-3-3 to sequester pFoxO1/pFoxO3a in cytoplasm and thus prolong T cell activation, whereas pSTAT3 activation by anti-inflammatory cytokines would curtail the duration of TCR activation and re-establish lymphocyte quiescence by inducing nuclear localization of FoxO1/FoxO3a and FoxO-mediated expression of growth-inhibitory proteins.
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http://dx.doi.org/10.1074/jbc.M112.359661DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3436293PMC
August 2012