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Purpose: It is speculated that retinal pigment epithelial (RPE) cells convert naïve T cells into regulatory T cells (Tregs) via soluble factors such as transforming growth factor beta (TGF-β). Yet presence or absence of similar membrane-bound mechanisms on RPE cells has yet to be addressed. Here the authors investigated the expression of surface TGF-β by RPE cells and its participation in the conversion of naive T cells into Tregs.Methods: They examined the phenotype of murine CD4(+) CD25(-) T cells activated in the presence of ethanol-fixed RPE cell layers as fixation preserves membrane structure while preventing the secretion of soluble factors.Results: Fixed RPE cells supported the development of a de novo foxp3(+) Th3-like suppressor phenotype in activated peripheral naïve T cells through an interaction that required both RPE-derived surface TGF-β, and T-cell derived TGF-β1.Conclusions: Aside from soluble factors, RPE-derived surface TGF-β can convert activated naïve T cells into Tregs. [ABSTRACT FROM AUTHOR]

Thrombospondin (TSP)-1 is a matricellular glycoprotein with immunoregulatory properties, which include inhibition of APC function. We show in transplantation that TSP-1 inhibits T cell allosensitization and consequently suppresses immune rejection. This was revealed by comparing wild-type (WT) versus TSP-1 null allografts in corneal transplantation, as the cornea is a rich source of TSP-1. Compared with only 50% of rejected WT allografts, nearly all TSP-1 null allografts succumbed to rejection. This effect was reflected by donor-derived APCs, which exhibited a distinctively greater capacity for allosensitization in transplanted hosts. Corroborated in MLRs, greater proliferation levels and robust IFN-γ (but not IL-10)–positive T cells resulted from stimulation by TSP-1 null APCs relative to WT ones. Moreover, enhanced expression of MHC class II and B7 maturation markers were detected on TSP-1 null APCs during inflammation. Increased expression of CCR7 was further matched by enhanced lymph node migration of TSP-1 null APCs posttransplantation. We therefore conclude that APC-derived TSP-1 suppresses their capacity to allosensitize T cells, and this regulation stems from their resistance to taking on a mature form. Future strategies targeting APCs for TSP-1 upregulation may thus be effective in promoting allograft survival.

Abstract Background The Gpnmb gene encodes a transmembrane protein whose function(s) remain largely unknown. Here, we assess if a mutant allele of Gpnmb confers susceptibility to glaucoma by altering immune functions. DBA/2J mice have a mutant Gpnmb gene and they develop a form of glaucoma preceded by a pigment dispersing iris disease and abnormalities of the immunosuppressive ocular microenvironment. Results We find that the Gpnmb genotype of bone-marrow derived cell lineages significantly influences the iris disease and the elevation of intraocular pressure. GPNMB localizes to multiple cell types, including pigment producing cells, bone marrow derived F4/80 positive antigen-presenting cells (APCs) of the iris and dendritic cells. We show that APCs of DBA/2J mice fail to induce antigen induced immune deviation (a form of tolerance) when treated with TGFβ2. This demonstrates that some of the immune abnormalities previously identified in DBA/2J mice result from intrinsic defects in APCs. However, the tested APC defects are not dependent on a mutant Gpnmb gene. Finally, we show that the Gpnmb mediated iris disease does not require elevated IL18 or mature B or T lymphocytes. Conclusion These results establish a role for Gpnmb in bone marrow derived lineages. They suggest that affects of Gpnmb on innate immunity influence susceptibility to glaucoma in DBA/2J mice.

Sjögren's disease (SjD) is a systemic autoimmune exocrinopathy with key features of dryness, pain, and fatigue. SjD can affect any organ system with a variety of presentations across individuals. This heterogeneity is one of the major barriers for developing effective disease modifying treatments. Defining core disease domains comprising both specific clinical features and incorporating the patient experience is a critical first step to define this complex disease. The OMERACT SjD Working Group held its first international collaborative hybrid meeting in 2023, applying the OMERACT 2.2 filter toward identification of core domains. We accomplished our first goal, a scoping literature review that was presented at the Special Interest Group held in May 2023. Building on the domains identified in the scoping review, we uniquely deployed multidisciplinary experts as part of our collaborative team to generate a provisional domain list that captures SjD heterogeneity., Competing Interests: Declaration of competing interest Valerie Devauchelle reports receinving funds for consulting to Novartis, Abbvie, Fresenius Kabi. Divi Cornec declares no personal financial competing interests and received research funding from Novartis and GSK. Benjamin A. Fisher has undertaken consultancy for Novartis, BMS, Servier, Galapagos, Roche, UCB, Sanofi and Janssen, and received grant/research support from Janssen, Celgene, Galapagos, Servier. Alberta Hoi reports receiving research funding from AstraZeneca, Bristol-Myers Squibb, Novartis, Janssen. Chiara Baldini reports receiving funds for consulting to GSK, Novartis and Horizon, honoraria for educational events from GSK and Sanofi, support for attending meetings from Abbvie and Bristol-Myers Squibb. WF Ng has consulted for Novartis, GlaxoSmithKline, Abbvie, BMS, Sanofi, MedImmune, Resolves Therapeutics, Janssen and UCB. Simon Bowman receiving funds for consulting from Bristol-Myers Squibb, Iqvia, Janssen, Kiniksa, Novartis, Otsuka-Visterra. His-salary is part funded by the Birmingham Biomedical Research Centre, Birmingham, UK. Karina Torralba reports receiving funds for consulting to Horizon, AstraZeneca, Janssen; for contracted research work with Bioclinica; for clinical trial funding from Novartis, AstraZeneca, GlaxoSmithKline, Amgen. Athena Papas declares grant funding from Novartis and Horizon; advisory board for Novartis. Ionut Pintilie reports receiving funds for consulting to Abbvie, Novartis, Pfizer, Sandoz, Ewopharma, KRKA, Stada, Boehringer Ingelheim, MagnaPharm, MSD. Xavier Mariette declares consulting fee from Astra Zeneca, BMS, Galapagos, GSK, Novartis, and Pfizer. Maria Antonietta D'Agostino, MD, PhD Speakers, or consultant fees from Amgen, Abbvie, BMS, Novartis, Galapagos, UCB, Pfizer, Lily, Janssen. Alan Baer reports receiving funds for consulting to Bristol-Myers Squibb and iCell Gene Therapeutics. Blake M. Warner declares research funding and material transfer agreements with Pfizer, Inc., and Mitobridge, Inc. Soumya D. Chakravarty is an employee of Janssen Scientific Affairs, LLC, and owns stock or stock options in Johnson & Johnson, of which Janssen Scientific Affairs, LLC is a wholly owned subsidiary. Nevsun Inanc reports claims to have received speakers fee from Novartis, Abbvie, Pfizer, UCB, Eli-Lilly and consultancy fee from Abbvie, UCB, Eli-Lilly. Vibeke Strand reports being a founding member of the executive committee of Outcome Measures in Rheumatology (OMERACT) [1992 – present], an international consensus organization that develops and validates outcome measures in rheumatology randomized controlled trials and longitudinal observational studies and has received arms-length funding from as many as 36 sponsors. Md Yuzaiful Md Yusof has received speaker fees from Roche and Novartis and consultancy fees from Aurinia Pharmaceuticals and UCB. Suzanne Arends declares consultancy fees from Argenx and Novartis. Anas Alexis Benyoussef is a consultant for Horus Pharma and Quantel Medical. Sharmila Masli is a consultant for Stellular Bio Inc. and Proteris Biotech. Maureen Rischmueller has undertaken consultancy/speaker engagements for AbbVie, Boehringer Ingelheim, Janssen Global Services, Novartis, Pfizer and Sandoz, and received grant/research support from AbbVie, Amgen, AstraZeneca, BMS, GSK, Janssen, Lilly, Novartis, Pfizer, Servier and UCB. Sara McCoy reports receiving funds for consulting to Bristol-Myers Squibb, Horizon, Novartis, Kiniksa, Targe RWE, Otsuka, Visterra, and iCell. Her time is supported by the Clinical and Translational Science Award (CTSA) program, through the NIH National Center for Advancing Translational Sciences (NCATS), grant 1KL2TR002374 and NIH/NIDCR R03DE031340. Raphaele Seror reports receiving funds for consulting to Bristol-Myers Squibb, Novartis, GSK, Janssen, Amgen. Hendrika Bootsma declares consultancy fees from Argenx, Novartis, BMS, AztraZeneca, Galapagos.Independent grants from AstraZeneca, Novartis, BMS., (Copyright © 2024. Published by Elsevier Inc.)

Differentiating patients with Sjögren's syndrome (SS)-associated dry eye from non-SS dry eye is critical for monitoring and appropriate management of possible sight- or life-threatening extraglandular complications associated with SS. We tested whether reduced tear levels of immunoregulatory thrombospondin (TSP)-1, which also inhibits matrix metalloproteinase (MMP)-9, would reflect SS pathogenesis aiding the identification of patients with SS-dry eye. Total of 61 participants, including healthy controls (n = 20), patients with non-SS dry eye (n = 20) and SS-dry eye (n = 21) were enrolled prospectively. Tear TSP-1 and MMP-9 levels were measured using a custom magnetic bead-based multi-plex assay in a masked manner. Analyte concentrations were assessed further according to ocular surface and tear film parameters. Relative to median tear TSP-1 (308 ng/ml) and MMP-9 (1.9 ng/ml) levels in the control group, significantly higher proportion of patients with SS-dry eye than non-SS had lower tear TSP-1 levels (55% vs. 29%, odds ratio [OR] = 3, 95% confidence interval [CI] = 1.64 to 5.35, p < 0.05) and higher tear MMP-9 levels (65% vs. 24%, OR = 5.8, 95% CI = 4.46 to 19.81, p < 0.05), respectively. The tear TSP-1/MMP-9 ratio was significantly reduced in patients with SS-dry eye compared to non-SS (B = -2.36, 95% CI = -3.94 to -0.0.79, p < 0.05), regardless of tear MMP-9 levels. Patients with a lower ratio were 2.3 times more likely to have SS (OR = 0.28, 95% CI = 0.1 to 0.75, p < 0.05). This ratio showed significant inverse correlations with clinical parameters (conjunctival and corneal staining scores). Our results denote that tear TSP-1/MMP-9 ratio can be useful in identifying patients with dry eye with underlying SS and used as a screening test., (© 2022 The Authors. Clinical and Translational Science published by Wiley Periodicals LLC on behalf of American Society for Clinical Pharmacology and Therapeutics.)

To address the conflicting role of thrombospondin (TSP)-1 reported in acute and chronic pathologies, this study investigated the role of TSP-1 in regulating leukocyte recruitment and regulation of VCAM-1 expression using mouse models of uveitis. The spontaneously increased VCAM-1 expression and leukocyte adhesion in retinas of TSP-1-deficient mice suggested a TSP-1-mediated regulation of VCAM-1 expression. In a chronic uveitis model, induced by immunizing wild-type mice with specific interphotoreceptor retinoid-binding protein (IRBP) peptide, topically applied TSP-1-derived CD47-binding peptide significantly reduced the clinical disease course and retinal leukocyte adhesion as compared to the control peptide-treated group. In contrast, in LPS-mediated acute uveitis, TSP-1 deficiency significantly reduced the retinal leukocyte adhesion. The results of our in vitro study, using vascular endothelial cell (EC) cultures, demonstrate that unlike TNF-α, VCAM-1 expression induced by IL-17 is associated with a reduced expression of endogenous TSP-1. Such reduced endogenous TSP-1 expression in IL-17-stimulated ECs helps limit the CD36-mediated increased VCAM-1 expression, while favoring CD47-mediated inhibition of VCAM-1 expression and leukocyte adhesion. Thus, our study identifies TSP-1:CD47 interaction as a molecular pathway that modulates IL-17-mediated VCAM-1 expression, contributing to its anti-inflammatory effect in chronic inflammatory conditions.

Conjunctival epithelium forms a barrier between the ocular surface microbial flora and the ocular mucosa. In addition to secreting gel-forming mucins, goblet cells, located in the conjunctival epithelium, help maintain local immune homeostasis by secreting active TGFβ2 and promoting tolerogenic phenotype of dendritic cells in the vicinity. Although dendritic cell subsets, characteristic of mucosal tissues, are found in the conjunctiva, previous studies provided limited information about their location within the tissue. In this study, we examine immunostained conjunctiva explants to determine the location of CD11c-positive dendritic cells in the context of MUC5AC-positive goblet cells. Considering that conjunctival goblet cells are responsive to signaling induced by pathogen recognition receptors, we also assess if their responses to microbial product, flagellin, can contribute to the disruption of ocular mucosal homeostasis that promotes activation of dendritic cells and results in chronic ocular surface inflammation. We find that dendritic cells in the conjunctiva with an increased microbial colonization are located adjacent to goblet cells. While their cell bodies in the stromal layer are immediately below the epithelial layer, several extensions of dendritic cells are projected across the epithelium towards the ocular surface. Such trans-epithelial dendrites are not detectable in healthy ocular mucosa. In response to topically applied flagellin, increased proportion of CD11c-positive cells in the conjunctiva strongly express MHC class II relative to the untreated conjunctiva. This change is accompanied by reduced immunoreactivity to TGFβ-activating Thrombospondin-1 in the conjunctival epithelium. These findings are supported by in vitro observations in primary cultures of goblet cells that respond to the TLR5 stimulation with an increased expression of IL-6 and reduced level of active TGFβ. The observed changes in the conjunctiva after flagellin application correspond with the development of clinical signs of chronic ocular mucosal inflammation including corneal epitheliopathy. Collectively, these findings demonstrate the ability of ocular mucosal dendritic cells to extend trans-epithelial dendrites in response to increased microbial colonization at the ocular surface. Moreover, this study provides key insight into how goblet cell responses to microbial stimuli may contribute to the disruption of ocular mucosal homeostasis and chronic ocular mucosal inflammation., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2021 Logeswaran, Contreras-Ruiz and Masli.)

Purpose: To assess the potential association of a thrombospondin 1 gene (THBS1) single-nucleotide polymorphism (rs1478604) with thrombospondin 1 (TSP-1) mRNA expression, as well as the risk of pterygium, in a pilot study., Methods: DNA and RNA were isolated from peripheral blood samples collected from normal volunteer subjects (n = 39). In addition, DNA was isolated from conjunctival tissue samples collected during pterygium excision surgeries (n = 42). Relative expression of TSP-1 mRNA was measured by quantitative RT-PCR, and rs1478604 genotype was determined using a TaqMan SNP genotyping assay. Genotype frequencies were compared with mRNA expression and between pterygium samples and normal controls., Results: Expression of TSP-1 mRNA was significantly lower in the peripheral blood of normal subjects who were homozygous for the C allele of rs1478604 (CC) compared to TT and CT genotypes (p = 0.004). When we compared rs1478604 genotypes between normal and pterygium patients, we found that the CC genotype was also associated with an increased risk of pterygium compared to TT (odds ratio (OR) = 5.39, 95% CI [1.26-22.99], p = 0.028), CT (OR = 7.86, 95% CI [1.92-32.17], p = 0.003), and combined CT and TT genotypes (OR = 6.67; 95% CI = [1.75-25.37]; p = 0.003)., Conclusions: We found that the C allele of rs1478604 was associated with both lower TSP-1 expression and higher risk of pterygium, possibly implicating TSP-1 in the pathogenesis of pterygium., (© 2021. The Author(s), under exclusive licence to Springer-Verlag GmbH, DE part of Springer Nature.)

Clear vision is dependent on features that protect the anatomical integrity of the eye (cornea and sclera) and those that contribute to internal ocular homeostasis by conferring hemangiogenic (avascular tissues and antiangiogenic factors), lymphangiogenic (lack of draining lymphatics), and immunologic (tight junctions that form blood-ocular barriers, immunosuppressive cells, and modulators) privileges. The later examples are necessary components that enable the eye to maintain an immunosuppressive environment that responds to foreign invaders in a deviated manner, minimizing destructive inflammation that would impair vision. These conditions allowed for the observations made by Medawar, in 1948, of delayed rejection of allogenic tissue grafts in the anterior chamber of mouse eye and permit the sequestration of foreign invaders (eg, Toxoplasma gondii) within the retina of healthy individuals. Yet successful development of intraocular drugs (biologics and delivery devices) has been stymied by adverse ocular pathology, much of which is driven by immune pathways. The eye can be intolerant of foreign protein irrespective of delivery route, and endogenous ocular cells have remarkable plasticity when recruited to preserve visual function. This article provides a review of current understanding of ocular immunology and the potential role of immune mechanisms in pathology observed with intraocular drug delivery.

Sjögren's syndrome (SS) is a systemic rheumatic disease that predominantly affects salivary and lacrimal glands resulting in oral and ocular dryness, respectively, referred to as sicca symptoms. The clinical presentation of ocular dryness includes keratoconjunctivitis sicca (KCS), resulting from the inflammatory damage to the ocular surface tissues of cornea and conjunctiva. The diagnostic evaluation of KCS is a critical component of the classification criteria used by clinicians worldwide to confirm SS diagnosis. Therapeutic management of SS requires both topical and systemic treatments. Several mouse models of SS have contributed to our current understanding of immunopathologic mechanisms underlying the disease. This information also helps develop novel therapeutic interventions. Although these models address glandular aspects of SS pathology, their impact on ocular surface tissues is addressed only in a few models such as thrombospondin (TSP)-1 deficient, C57BL/6.NOD. Aec1Aec2 , NOD.H2 b , NOD.Aire KO, and IL-2Rα (CD25) KO mice. While corneal and/or conjunctival damage is reported in most of these models, the characteristic SS specific autoantibodies are only reported in the TSP-1 deficient mouse model, which is also validated as a preclinical model. This review summarizes valuable insights provided by investigations on the ocular spectrum of the SS pathology in these models.

Purpose: Systemic implications necessitate the identification of dry eye patients with Sjögren syndrome (SS). This study aims to explore the utility of tear MUC5AC and inflammatory cytokine levels in the differential diagnosis of SS-related dry eye., Methods: A prospective, observational, case-control study was conducted on 62 patients (those with a definitive diagnosis of SS dry eye, non-SS dry eye, and age-matched healthy controls with no dry eye). Clinical evaluations included the following tests in the order listed here: noninvasive tear break-up time, osmolarity, tear sampling, Schirmer test without anesthesia, and ocular surface staining (lissamine green for conjunctiva and fluorescein for cornea). Tear MUC5AC levels were assessed with enzyme-linked immunosorbent assay, and cytokines [interferon-gamma, tumor necrosis factor alpha, interleukin (IL)-6, IL-17a, IL-1β, IL-8, IL-10, and IL-12p70] were measured using a Luminex assay in a masked fashion., Results: The Bulbar conjunctival lissamine green staining score was significantly greater in patients or controls with SS versus non-SS dry eye. This greater conjunctival staining was associated with a reduction in tear MUC5AC (B = -17.8 ng/mL, 95% confidence interval = -31.8 to -3.9, P = 0.01). Among the tear cytokines, a significant association was found between IL-8 levels (hazard ratio [HR] = 1.002, 95% confidence interval = 1.000-1.003, P = 0.03) and SS diagnosis. When patients were stratified based on tear MUC5AC levels, significantly increased tear IL-8 levels were detected in patients with SS dry eye but not with non-SS dry eye, in comparison with healthy controls., Conclusions: Tear levels of goblet cell-specific MUC5AC combined with IL-8 can potentially serve as a useful biomarker for differential diagnosis of SS dry eye from non-SS dry eye.

Thrombospondin 1 (TSP-1) is an extracellular matrix protein that interacts with a wide array of ligands including cell receptors, growth factors, cytokines and proteases to regulate various physiological and pathological processes. Constitutively expressed by certain ocular surface tissues (e.g. corneal and conjunctival epithelium), TSP-1 expression is modulated during ocular surface inflammation. TSP-1 is an important activator of latent TGF-β, serving to promote the immunomodulatory and wound healing functions of TGF-β. Mounting research has deepened our understanding of how TSP-1 expression (and lack thereof) contributes to ocular surface homeostasis and disease. Here, we review current knowledge of the function of TSP-1 in dry eye disease, ocular allergy, angiogenesis/lymphangiogenesis, corneal transplantation, corneal wound healing and infectious keratitis., (Copyright © 2019 Elsevier Inc. All rights reserved.)

Chronic inflammation of the ocular surface poses a risk of vision impairment. The understanding of the molecular mechanisms that are involved in the inflammatory response is critical to identify novel molecular targets. Recently, thrombospondin-1 (TSP-1) has emerged as a key player in ocular surface homeostasis that efficiently activates the TGF-β2 isoform that is predominantly expressed in the ocular mucosa. Here, the potential of the peptide derived from TSP-1 (KRFK), that can activate TGF-β, is proposed as a potentially applicable therapeutic for chronic ocular surface inflammatory disorders. Our in vitro results confirm that the chosen peptide activates TGF-β, reducing the expression of co-stimulatory molecules on dendritic cells, driving them towards a tolerogenic phenotype. For the in vivo studies, the TSP-1 -/- mouse is used as a pre-clinical model of chronic ocular inflammation. We observe that the topical application of KRFK alters the peripheral balance of effectors by reducing the proportion of pathogenic Th1 and Th17 cells while increasing Treg cell proportion in cervical lymph nodes. In line with these findings, the development of chronic ocular surface inflammation is significantly prevented in KRFK-treated TSP-1 -/- mice, as assessed by clinical parameters and inflammatory cytokine expression in conjunctival and lacrimal gland tissues. Together, our results identify the KRFK peptide as a novel therapeutic option to prevent the development of chronic inflammatory manifestations of the ocular surface.

Thrombospondin-1-deficient (TSP-1 -/- ) mice are used as an animal model of Sjögren's Syndrome because they exhibit many of the symptoms associated with the autoimmune type of dry eye found in primary Sjögren's Syndrome. This type of dry eye is linked to the inflammation of the lacrimal gland, conjunctiva, and cornea, and is thought to involve dysfunction of the complex neuronal reflex arc that mediates tear production in response to noxious stimuli on the ocular surface. This study characterizes the structural and functional changes to the corneal nerves that are the afferent arm of this arc in young and older TSP-1 -/- and wild type (WT) mice. The structure and subtype of nerves were characterized by immunohistochemistry, in vivo confocal microscopy, and confocal microscopy. Cytokine expression analysis was determined by Q-PCR and the number of monocytes was measured by immunohistochemistry. We found that only the pro-inflammatory cytokine MIP-2 increased in young corneas of TSP-1 -/- compared to WT mice, but tumor necrosis factor-α (TNF-α), monocyte chemoattractant protein-1 (MCP-1), and macrophage inflammatory protein-2 (MIP-2) all increased in older TSP-1 -/- mouse corneas. In contrast, CD11b+ pro-inflammatory monocytes did not increase even in older mouse corneas. Calcitonin gene-related peptide (CGRP)-, but not Substance P (SubP)-containing corneal nerves decreased in older, but not younger TSP-1 -/- compared to WT mouse corneas. We conclude that CGRP-containing corneal sensory nerves exhibit distinct structural deficiencies as disease progresses in TSP-1 -/- mice, suggesting that: (1) TSP-1 is needed for the development or repair of these nerves and (2) impaired afferent corneal nerve structure and hence function may contribute to ocular surface dysfunction that develops as TSP-1 -/- mice age.

The risk of developing lymphoma in patients with Sjögren's syndrome (SS) is 44 times higher than in the normal population with the most common lymphomas derived from marginal zone B (MZB) cells. Current understanding of the role of MZB cells in SS is primarily based on salivary gland pathology, while their contextual association with lacrimal glands and ocular manifestations largely remains unknown. We examined this possibility using a SS mouse model (thrombospondin-1 deficient (TSP1 -/- )) with well-characterized ocular disease. We determined the frequency, localization, and cytokine profiles of MZB cells and their association with an antibody response in TSP1 -/- mice treated with a TSP-derived peptide. A significantly increased frequency of MZB cells was detected in the spleens and lacrimal glands of TSP1 -/- mice in comparison to wild-type tissues as detected by immunostaining. An altered cytokine profile of TSP1 -/- MZB cells was supportive of T helper 17 (Th17)-related pathogenesis. A significantly reduced antibody response and the splenic MZB compartment against an eye-derived antigen were noted in TSP-derived peptide-treated mice. These changes correspond with the previously reported ability of the peptide to ameliorate SS-related ocular manifestations. Collectively, our results demonstrate dysregulation of MZB cells in TSP1 -/- mice and highlight their role in the context of SS-related chronic ocular surface disease.

The purpose of this study is to determine neural, vascular, protein secretion, and cellular signaling changes with disease progression in lacrimal glands of the thrombospondin-1 -/- (TSP-1 -/- ) mouse model of dry eye compared to C57BL/6 wild-type (WT) mice. Neural innervation was reduced in TSP-1 -/- lacrimal glands compared to WT controls, whereas the number of blood vessels was increased. Intracellular Ca 2+ stores and the amount of lysosomes, mitochondria, and secretory granules, but not the endoplasmic reticulum, were reduced in TSP-1 -/- compared to WT acini at 12 weeks of age. Ex vivo high KCl-evoked secretion was decreased in TSP-1 -/- compared to WT lacrimal gland tissue pieces. The α 1D -adrenergic agonist-stimulated response was increased in TSP-1 -/- at 4 and 24 weeks but decreased at 12 weeks, and the ATP and MeSATP-stimulated peak [Ca 2+ ] i responses were decreased at 24 weeks. These changes were observed prior to the appearance of mononuclear infiltrates. We conclude that in the lacrimal gland the absence of TSP-1: injures peripheral nerves; blocks efferent nerve activation; decreases protein secretion; and alters intracellular Ca 2+ stores. Through these effects the absence of TSP-1 leads to disruption of ocular surface homeostasis and development of dry eye.

Therapeutic breakthroughs in a number of retinal degenerative diseases have come about through the development of biotherapeutics administered directly into the eye. As a consequence of their use, we have gained more insight into the immune privileged status of the eye and the various considerations that development, manufacturing, and use of these drugs require. It has been observed that therapeutic proteins injected into the vitreous can elicit an immune response resulting in the production of anti-drug antibodies (ADAs) which can have clinical consequences. This review includes discussion of the anatomy, physiology, and specific area of the eye that are targeted for drug administration. The various immunologic mechanisms involved in the immune responses to intraocularly administered protein are discussed. This review entails discussion on chemistry, manufacturing, and control (CMC) and formulation-related issues that may influence the risk of immunogenicity. Based on the available immunogenicity profile of the marketed intraocular drugs and their reported adverse events, the animal models and the translational gap from animals to human are discussed. Thus, the objective of this review article is to assess the factors that influence immunogenicity in relation to intraocular administration and the steps taken for mitigating immunogenicity risks.

The purpose of this study was to investigate the changes that occur in the lacrimal glands (LGs) in female thrombospondin 1 knockout (TSP1 -/- ) mice, a mouse model of the autoimmune disease Sjogren's syndrome. The LGs of 4, 12, and 24 week-old female TSP1 -/- and C57BL/6J (wild type, WT) mice were used. qPCR was performed to measure cytokine expression. To study the architecture, LG sections were stained with hematoxylin and eosin. Cell proliferation was measured using bromo-deoxyuridine and immunohistochemistry. Amount of CD47 and stem cell markers was analyzed by western blot analysis and location by immunofluorescence microscopy. Expression of stem cell transcription factors was performed using Mouse Stem Cell Transcription Factors RT 2 Profiler PCR Array. Cytokine levels significantly increased in LGs of 24 week-old TSP1 -/- mice while morphological changes were detected at 12 weeks. Proliferation was decreased in 12 week-old TSP1 -/- mice. Three transcription factors were overexpressed and eleven underexpressed in TSP1 -/- compared to WT LGs. The amount of CD47, Musashi1, and Sox2 was decreased while the amount of ABCG2 was increased in 12 week-old TSP1 -/- mice. We conclude that TSP1 is necessary for maintaining normal LG homeostasis. Absence of TSP1 alters cytokine levels and stem cell transcription factors, LG cellular architecture, decreases cell proliferation, and alters amount of stem cell markers., (Copyright © 2016 Elsevier Ltd. All rights reserved.)

Sjögren's syndrome is an autoimmune disease associated with inflammation of exocrine glands with clinical manifestations of dry eye and dry mouth. Dry eye in this disease involves inflammation of the ocular surface tissues - cornea and conjunctiva. While systemic blockade of adhesion molecules has been used to treat autoimmune diseases, the purpose of this study was to determine the therapeutic efficacy of topical application of an integrin α4 adhesion molecule antagonist in a mouse model of dry eye associated with Sjögren's syndrome. To assess this spontaneously developed ocular surface inflammation related to Sjögren's syndrome in TSP-1null mice (12 wks) was evaluated. Mice were treated with topical formulations containing 0.1% dexamethasone or 30 mg/ml GW559090 or vehicle control. Corneal fluorescein staining and conjunctival goblet cell density were assessed. Real-time PCR analysis was performed to assess expression of the inflammatory marker IL-1β in the cornea and Tbet and RORγt in the draining lymph nodes. Ocular surface inflammation was detectable in TSP-1null mice (≥12 wk old), which resulted in increased corneal fluorescein staining indicative of corneal barrier disruption and reduced conjunctival goblet cell density. These changes were accompanied by increased corneal expression of IL-1β as compared to WT controls and an altered balance of Th1 (Tbet) and Th17 (RORγt) markers in the draining lymph nodes. Topically applied dexamethasone and GW559090 significantly reduced corneal fluorescein staining compared to vehicle treatment (p = 0.023 and p < 0.001, respectively). This improved corneal barrier integrity upon adhesion molecule blockade was consistent with significantly reduced corneal expression of pro-inflammatory IL-1β compared to vehicle treated groups (p < 0.05 for both treatments). Significant improvement in goblet cell density was also noted in mice treated with 0.1% dexamethasone and GW559090 (p < 0.05 for both). We conclude that similar to topical dexamethasone, topically administered GW559090 successfully improved corneal barrier integrity and inflammation in an established ocular surface disease associated with Sjögren's syndrome., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

An important role of transforming growth factor-β (TGF-β) in the development of regulatory T cells is well established. Although integrin-mediated activation of latent TGF-β1 is considered essential for the induction of regulatory T (Treg) cells by antigen-presenting cells (APCs), such an activation mechanism is not applicable to the TGF-β2 isoform, which lacks an integrin-binding RGD sequence in its latency-associated peptide. Mucosal and ocular tissues harbour TGF-β2-expressing APCs involved in Treg induction. The mechanisms that regulate TGF-β activation in such APCs remain unclear. In this study, we demonstrate that murine APCs exposed to TGF-β2 in the environment predominantly increase expression of TGF-β2. Such predominantly TGF-β2-expressing APCs use thrombospondin-1 (TSP-1) as an integrin-independent mechanism to activate their newly synthesized latent TGF-β2 to induce Foxp3(+) Treg cells both in vitro and in vivo. Expression of Treg induction by TGF-β2-expressing APCs is supported by a TSP-1 receptor, CD36, which facilitates activation of latent TGF-β during antigen presentation. Our results suggest that APC-derived TSP-1 is essential for the development of an adaptive regulatory immune response induced by TGF-β2-expressing APCs similar to those located at mucosal and ocular sites. These findings introduce the integrin-independent mechanism of TGF-β activation as an integral part of peripheral immune tolerance associated with TGF-β2-expressing tissues., (© 2015 John Wiley & Sons Ltd.)

Purpose: Increased expression of transforming growth factor-β2 (TGF-β2) is reported in the conjunctiva of dry eye patients with no increase of anti-inflammatory activity of TGF-β2. Our aim was to compare the expression of molecules involved in TGF-β2 activation, thrombospondin-1 (TSP-1) and CD36, during murine and human conjunctival inflammation., Methods: Human conjunctival tissue from cadaveric donors, human conjunctival epithelial primary cells and fibroblasts, and murine conjunctivas were immunostained for TSP-1, CD36, or TGF-β2. Inflamed conjunctival tissues were obtained from C57BL/6 wild-type (WT) mice induced to develop experimental dry eye (EDE) with 10 days of desiccating conditions and scopolamine injections and TSP-1-deficient (TSP1(-/-)) mice, which spontaneously develop Sjögren's syndrome-associated conjunctival inflammation with age. Immunostaining intensities were compared using ImageJ software. Cultures of human conjunctival fibroblasts were stimulated with IL-1β and both secreted protein and message levels of TSP-1, CD36, and TGF-β2 were analyzed., Results: TSP-1 and CD36 were detectable in human and murine conjunctival tissues as well as primary conjunctival epithelial cells and fibroblasts. Increased conjunctival immunostaining of TGF-β2 and reduced CD36 were detected in EDE mice compared with WT mice. Interestingly, increased TGF-β2 and CD36 conjunctival immunostaining was detected in TSP1(-/-) mice. The expression of TSP-1 and CD36 was downregulated in IL-1β-stimulated conjunctival fibroblasts at both the protein and message level, while active TGF-β2 was undetected., Conclusions: The absence or reduced expression of either of the molecules involved in TGF-β2 activation supports proinflammatory conditions in the conjunctiva. Changes in TSP-1 and CD36 may serve as potential biomarkers of conjunctival inflammation.

Purpose: The potential role of commensals as triggering factors that promote inflammation in dry eye disease has not been explored. The objective of this study was to evaluate whether ocular microbiota changes with the onset of dry eye disease in thrombospondin-1-deficient (TSP-1(-/-)) mice, a strain that develops Sjögren's syndrome-like disease., Methods: Conjunctival swabs were collected from TSP-1(-/-) and C57BL/6 mice and analyzed for bacterial presence. Opsonophagocytosis of the bacterial conjunctival isolates derived from the aged TSP-1(-/-) mice by neutrophils derived from either TSP-1(-/-) or C57BL/6 bone marrow was evaluated. The bactericidal activities of TSP-1-derived peptide were examined., Results: We found that in TSP-1(-/-) mice, the conjunctival colonization with Staphylococcus aureus and coagulase negative staphylococci sp (CNS) species was significantly increased with aging and preceded that of the wild-type C57BL/6 control mice. This correlated with increased neutrophil infiltration into the conjunctiva of the TSP-1(-/-) mice, suggesting that TSP-1 plays a significant role in regulating immunity to commensals. Accordingly, the TSP-1(-/-) PMNs opsonophagocytozed the ocular commensals less efficiently than the TSP-1-sufficient neutrophils. Furthermore, a TSP-1-derived peptide, 4N1K, exhibited significant antimicrobial activity when compared to a control peptide against commensal sp., Conclusion: These studies illustrate that alterations in the commensal frequency occur in the early stages of development of Sjögren's-like pathology and suggest that interventions that limit commensal outgrowth such as the use of TSP-1-derived peptides could be used for treatment during the early stages of the disease to reduce the commensal burden and ensuing inflammation.

Background: In the murine cornea, which is an established model for analyzing pathologic lymphatic vessel growth, phenotypic heterogeneity of the endogenous lymphatic vessels in the limbus of the cornea was previously described. In this study, the cornea of BALB/c, C57BL/6, and FVB mice with different limbal lymphangiogenic phenotypes was analyzed to identify novel candidates potentially influencing lymphatic vessel growth., Methods and Results: Pathway specific expression analysis of the cornea was performed to identify novel candidate genes. Corneal protein expression of the respective candidates was analyzed by fluorescent immunohistochemistry. The effect of the candidates on proliferation of human dermal lymphatic endothelial cells (HDLECs) was analyzed by BrdU proliferation ELISA. Thirteen genes were differentially regulated in corneas of mouse strains with more endogenous limbal lymphatic vessels (high-lymphangiogenic) (C57BL/6) compared to mouse strains with less endogenous limbal lymphatic vessels (low-lymphangiogenic) (BALB/c, FVB). Two candidates, Tumor necrosis factor (ligand) superfamily member 10 (Tnfsf10/Trail) and Plasminogen activator, tissue (Plat/tPA) were expressed in the cornea of BALB/c and C57BL/6 mice on the protein level. In vitro, Trail and recombinant tPA inhibited the proliferation of human dermal lymphatic endothelial cells., Conclusion: Molecular analysis of the naive cornea in mouse strains with different limbal lymphatic phenotypes is a valuable model to identify novel endogenous regulators of lymphangiogenesis.

Goblet cells are secretory epithelial cells of mucosal tissues that confer protection from environmental agents or pathogens via expression and secretion of soluble mucins. Loss of these cells is associated with several chronic inflammatory disorders of the mucosa. Although demonstrated to transfer antigens from the luminal surface to stromal cells in the intestinal mucosa, it is not known if goblet cells contribute to the regulation of an immune response. In this study we report that similar to intestinal and respiratory mucosal epithelia, mouse ocular surface epithelia predominantly express the TGF-ß2 isoform. Specifically, we demonstrate the ability of goblet cells to express TGF-ß2 and increase it in response to Toll-Like Receptor 4 mediated stimulus in cultures. Goblet cells not only express TGF-ß2, but are also able to activate it in a thrombospondin-1 (TSP-1) dependent manner via their cell surface receptor CD36. Furthermore, goblet cell derived soluble factors that possibly include TGF-ß2, alter dendritic cell (DC) phenotype to a tolerogenic type by downregulating DC expression of MHC class II and co-stimulatory molecules CD80, CD86 and CD40. Thus our study demonstrates goblet cells as a cellular source of active TGF-ß2 in ocular mucosa and implicates their immunomodulatory function in maintaining mucosal immune homeostasis.

Purpose of Review: Although conjunctival goblet cells are a major cell type in ocular mucosa, their responses during ocular allergy are largely unexplored. This review summarizes the recent findings that provide key insights into the mechanisms by which their function and survival are altered during chronic inflammatory responses, including ocular allergy., Recent Findings: Conjunctiva represents a major component of the ocular mucosa that harbors specialized lymphoid tissue. Exposure of mucin-secreting goblet cells to allergic and inflammatory mediators released by the local innate and adaptive immune cells modulates proliferation, secretory function, and cell survival. Allergic mediators like histamine, leukotrienes, and prostaglandins directly stimulate goblet cell mucin secretion and consistently increase goblet cell proliferation. Goblet cell mucin secretion is also detectable in a murine model of allergic conjunctivitis. Additionally, primary goblet cell cultures allow evaluation of various inflammatory cytokines with respect to changes in goblet cell mucin secretion, proliferation, and apoptosis. These findings in combination with the preclinical mouse models help understand the goblet cell responses and their modulation during chronic inflammatory diseases, including ocular allergy., Summary: Recent findings related to conjunctival goblet cells provide the basis for novel therapeutic approaches, involving modulation of goblet cell mucin production, to improve treatment of ocular allergies.

Thrombospondins are a family of large multi-domain glycoproteins described as matricelluar proteins based on their ability to interact with a broad range of receptors, matrix molecules, growth factors or proteases, and to modulate array of cellular functions including intracellular signaling, proliferation and migration. Two members of the thrombospondin family, thrombospondin 1 (TSP-1) and thrombospondin 2 (TSP-2) are studied extensively to determine their structure and function. While expressed at low levels in normal adult tissues, their increased expression is seen predominantly in response to cellular perturbations. Despite structural similarities, a notable functional difference between TSP-1 and TSP-2 includes the ability of former to activate of latent TGF-β and its competitive inhibition by the latter. Both these thrombospondins are reported to play important roles in TGF-β rich ocular environment with most reports related to TSP-1. They are expressed by many ocular cell types and detectable in the aqueous and vitreous humor. TSP-1 and TSP-2 influence many cellular interactions in the eye such as angiogenesis, cell migration, wound healing, TGF-β activation and regulation of inflammatory immune responses. Together, these processes are known to contribute to the immune privilege status of the eye. Emerging roles of TSP-1 and TSP-2 in ocular functions and pathology are reviewed here.

Purpose: To determine the association of single nucleotide polymorphisms (SNPs) of the thrombospondin 1 (THBS1) gene with development of chronic ocular surface inflammation (keratoconjunctivitis) after refractive surgery., Design: Retrospective cohort study., Participants: Active duty U.S. Army soldiers (n = 143) who opted for refractive surgery., Methods: Conjunctival impression cytology samples collected from participants before the surgery were used to harvest DNA for genotyping 5 THBS1 SNPs (rs1478604, rs2228262, rs2292305, rs2228262, and rs3743125) using the Sequenom iPLEX Gold platform (Sequenom, San Diego, CA). Samples collected after surgery were used to harvest RNA for gene expression analysis by real-time polymerase chain reaction (PCR). Participants were followed for 1 year after surgery to monitor the status of keratoconjunctivitis., Main Outcome Measures: Genetic basis of the development of chronic keratoconjunctivitis after refractive surgery., Results: Carriers of minor alleles of 3 SNPs each were found to be more susceptible to developing chronic keratoconjunctivitis (rs1478604: odds ratio [OR], 2.5; 95% confidence interval [CI], 1.41-4.47; P = 2.5 × 10(-3); rs2228262 and rs2292305: OR, 1.9; 95% CI, 1.05-3.51; P = 4.8 × 10(-2)). Carriers of the rs1478604 minor allele expressed significantly reduced levels of thrombospondin 1 (TSP1) (P = 0.042) and increased levels of an inflammatory cytokine associated with keratoconjunctivitis, interleukin-1β (P = 0.025), in their ocular surface epithelial cells compared with homozygous major allele controls., Conclusions: Genetic variation in the THBS1 gene that results in decreased expression of the encoded glycoprotein TSP1 in ocular surface epithelial cells significantly increases the susceptibility to develop chronic ocular surface inflammation after refractive surgery. Further investigation of THBS1 SNPs in a larger sample size is warranted., (Copyright © 2014 American Academy of Ophthalmology. Published by Elsevier Inc. All rights reserved.)

Background: The molecular mechanisms causing pigment dispersion syndrome (PDS) and the pathway(s) by which it progresses to pigmentary glaucoma are not known. Mutations in two melanosomal protein genes (Tyrp1(b) and Gpnmb(R150X)) are responsible for pigment dispersing iris disease, which progresses to intraocular pressure (IOP) elevation and subsequent glaucoma in DBA/2J mice. Melanosomal defects along with ocular immune abnormalities play a role in the propagation of pigment dispersion and progression to IOP elevation. Here, we tested the role of specific immune components in the progression of the iris disease and high IOP., Results: We tested the role of NK cells in disease etiology by genetically modifying the B6.D2-Gpnmb(R150X) Tyrp1(b) strain, which develops the same iris disease as DBA/2J mice. Our findings demonstrate that neither diminishing NK mediated cytotoxic activity (Prf1 mutation) nor NK cell depletion (Il2rg mutation) has any influence on the severity or timing of Gpnmb(R150X) Tyrp1(b) mediated iris disease. Since DBA/2J mice are deficient in CD94, an important immune modulator that often acts as an immune suppressor, we generated DBA/2J mice sufficient in CD94. Sufficiency of CD94 failed to alter either the iris disease or the subsequent IOP elevation. Additionally CD94 status had no detected effect on glaucomatous optic nerve damage., Conclusion: Our previous data implicate immune components in the manifestation of pigment dispersion and/or IOP elevation in DBA/2J mice. The current study eliminates important immune components, specifically NK cells and CD94 deficiency, as critical in the progression of iris disease and glaucoma. This narrows the field of possible immune components responsible for disease progression.

Lacrimal gland inflammation during autoimmune Sjögren's syndrome (SS) leads to ocular surface inflammation - Keratoconjunctivitis sicca (KCS). This condition afflicts both the cornea and conjunctiva that form the ocular surface. Thrombospondin-1 (TSP-1) deficiency in mice results in lacrimal gland and corneal inflammation that resembles the human disease. In this study we report conjunctival pathology in this mouse model of SS. We found that TSP-1 null mice develop inflammation in the conjunctiva and associated loss of goblet cell function similar to that seen in patients with SS. Increased expression of Th1 (IFN-γ, TNF-α) and Th17 (IL-6, IL-17A) inflammatory cytokines and related transcription factors (Tbet and RORγt) were detected in TSP-1 null conjunctiva as well as their draining lymph nodes (LNs). The conjunctival inflammation was also accompanied by an increase in local lymphatic vessels. Interestingly, migration of antigen-bearing dendritic cells (DCs) from the ocular surface to the LNs was dependent on the TSP-1 available in the tissue. These results not only reveal potential immunopathogenic mechanisms underlying KCS in SS but also highlight the therapeutic potential of TSP-1.

Lymphangiogenesis plays an important role in tumor metastasis and transplant outcome. Here, we show that thrombospondin-1 (TSP-1), a multifunctional extracellular matrix protein and naturally occurring inhibitor of angiogenesis inhibits lymphangiogenesis in mice. Compared with wild-type mice, 6-mo-old TSP-1-deficient mice develop increased spontaneous corneal lymphangiogenesis. Similarly, in a model of inflammation-induced corneal neovascularization, young TSP-1-deficient mice develop exacerbated lymphangiogenesis, which can be reversed by topical application of recombinant human TSP-1. Such increased corneal lymphangiogenesis is also detected in mice lacking CD36, a receptor for TSP-1. In these mice, repopulation of corneal macrophages with predominantly WT mice via bone marrow reconstitution ameliorates their prolymphangiogenic phenotype. In vitro, exposure of WT macrophages to TSP-1 suppresses expression of lymphangiogenic factors vascular endothelial growth factor (VEGF)-C and VEGF-D, but not of a primarily hemangiogenic factor VEGF-A. Inhibition of VEGF-C is not detected in the absence or blockade of CD36. These findings suggest that TSP-1, by ligating CD36 on monocytic cells, acts as an endogenous inhibitor of lymphangiogenesis.

Objectives: To analyze whether topical application of corticosteroids inhibits inflammatory corneal lymphangiogenesis and to study the potential underlying antilymphangiogenic mechanisms., Methods: Inflammatory corneal neovascularization was induced by suture placement, and the corneas were then treated with topical fluorometholone, prednisolone acetate, or dexamethasone sodium phosphate. After 1 week, the corneas were stained with lymphatic vessel endothelial hyaluronan receptor 1 for detection of pathological corneal lymphangiogenesis. The effect of these corticosteroids on macrophage recruitment was assessed via fluorescence-activated cell sorting analysis. The effect of these corticosteroids on proinflammatory cytokine expression by peritoneal exudate cells was tested via real-time polymerase chain reaction. Furthermore, the effect of steroid treatment on the proliferation of lymphatic endothelial cells was assessed via enzyme-linked immunosorbent assay., Results: Treatment with corticosteroids resulted in a significant reduction of inflammatory corneal lymphangiogenesis. The antilymphangiogenic effect of fluorometholone was significantly weaker than that of prednisolone and dexamethasone. Corneal macrophage recruitment was also significantly inhibited by the application of topical steroids. Treatment of peritoneal exudate cells with corticosteroids led to a significant downregulation of the RNA expression levels of tumor necrosis factor and interleukin 1β. Additionally, proliferation of lymphatic endothelial cells was also inhibited., Conclusions: Corticosteroids are strong inhibitors of inflammatory corneal lymphangiogenesis, with significant differences between various corticosteroids in terms of their antilymphangiogenic potency. The main mechanism of the antilymphangiogenic effect seems to be through the suppression of macrophage infiltration, proinflammatory cytokine expression, and direct inhibition of proliferation of lymphatic endothelial cells., Clinical Relevance: Steroids block corneal lymphangiogenesis, the main risk factor for immune rejections after corneal transplantation. The different antilymphangiogenic potency of these drugs should be taken into account when using steroids in clinical practice (eg, after keratoplasty).

The eye is one of the immune privilege sites of the body that is consequently protected from the detrimental and potentially blinding influences of immunologic inflammation. Within the eye, the anterior chamber has been recognized for its immune privilege property for many years now; however, a similar property detectable in the subretinal space has only recently been appreciated. These ocular sites are not only equipped with specialized mechanisms that barricade local inflammatory responses, but also induce systemic regulatory immune response. Numerous studies have characterized molecular and cellular mechanisms involved in conferring both these sites with an immune privilege status. Pigmented epithelial cells lining the anterior chamber in the iris and ciliary body area as well as those in the retina are endowed with immunomodulatory properties that contribute to ocular immune privilege. These cells, via expression of either soluble factors or membrane molecules, inhibit inflammatory T cell activation and promote the generation of regulatory T cells. In the anterior chamber resident antigen-presenting cells, influenced by the various immunosuppressive factors present in the aqueous humor, capture ocular antigens and present them in the spleen to T cells in association with NKT cells and marginal zone B cells. Immunomodulatory microenvironment created by these cells helps generate regulatory T cells, capable of interrupting the induction as well as expression of inflammatory responses. Furthermore, neural regulation of both intraocular and systemic regulatory mechanisms also contributes to ocular immune privilege.

The original evidence for the existence of immunologically privileged sites in the body was based on the prolonged survival of genetically disparate transplanted tissue in the anterior chamber of the eye. The failure of the immune system to elicit an immune response in this and other such sites constitutes the hallmark of the immune privilege status. The remarkably successful field of corneal transplantation in clinical practice is undoubtedly associated with corneal immune privilege. Several investigations have addressed the regulatory mechanisms governing this phenomenon, which involves a complex interplay between multiple molecular and cellular pathways. Furthermore, the use of various transgenic mouse models has facilitated the identification of critical pathways, which upon disruption can modify the immune privileged status of the eye. Understanding these pathways not only reveals the mechanisms underlying various ocular inflammatory disease conditions, but also has clinical implications for the transplantation field and for the treatment of autoimmunity.

Purpose: Thrombospondin (TSP)-1 has been demonstrated to play a vital role in immune privilege. The functional phenotype of ocular antigen-presenting cells that contributes to the immune privilege status of the eye is dependent on their expression of TSP-1. Microglia, the local antigen-presenting cells in the retina, undergo rapid activation in response to injury and have the ability to produce both proinflammatory and regenerative neurotrophic factors. In this study, the authors examined TSP-1 as a potential regulator of these phenotype of microglia activated in response to retinal injury., Methods: Expression of markers associated with activated microglia were examined by immunofluorescent staining and semiquantitative real-time PCR analysis of retina derived from WT or TSP-1 null mice at various time intervals after light- or laser-induced retinal injury., Results: In the absence of TSP-1, microglia in uninjured retina express major histocompatibility complex class II and migrate to the outer layers of the retina. Constitutively increased expression of activated microglia-derived inflammatory molecules such as TNF-alpha and iNOS is detectable in TSP-1 null retina compared with WT controls. After both light-induced and laser-induced retinal injury, enhanced migration of microglia is detected in TSP-1 null retina, and these microglia express markers associated with a proinflammatory phenotype. Compared with WT retina, TSP-1 null retina fails to recover from the laser-induced injury, resulting in irreversible damage., Conclusions: TSP-1 supports an anti-inflammatory phenotype of microglia in the retina and promotes recovery from injury.

Thrombospondin-1 (TSP-1) is a major activator of latent transforming growth factor-beta in vitro as well as in vivo. Mice deficient in TSP-1, despite appearing normal at birth, develop a chronic form of ocular surface disease that is marked by increased apoptosis and deterioration in the lacrimal gland, associated dysfunction, and development of inflammatory infiltrates that result in abnormal tears. The increase in CD4(+) T cells in the inflammatory infiltrates of the lacrimal gland, and the presence of anti-Sjögren's syndrome antigen A and anti-Sjögren's syndrome antigen B antibodies in the serum resemble autoimmune Sjögren's syndrome. These mice develop an ocular surface disorder dry eye that includes disruption of the corneal epithelial layer, corneal edema, and a significant decline in conjuctival goblet cells. Externally, several mice develop dry crusty eyes that eventually close. The inflammatory CD4(+) T cells detected in the lacrimal gland, as well as those in the periphery of older TSP-1 null mice, secrete interleukin-17A, a cytokine associated with chronic inflammatory diseases. Antigen-presenting cells, derived from TSP-1 null, but not from wild-type mice, activate T cells to promote the Th17 response. Together, these results indicate that TSP-1 deficiency results in a spontaneous form of chronic dry eye and aberrant histopathology associated with Sjögren's syndrome.

Mounting evidence points to a role for the sympathetic nervous system in suppressing inflammation. This role might be of specific relevance for immune privilege in the eye, where, sporadically, patients with denervated sympathetic fibers develop chronic inflammation. The present study used mice to investigate whether the robust innervation of intraocular structures by the sympathetic system plays a role in maintaining ocular immune privilege. We first performed surgical removal of the superior cervical ganglion, which supplies sympathetic fibers to the eye, and studied the immune response generated against soluble antigens or allogeneic tumor cells injected into the ocular anterior chamber under these conditions. Our results show that in the absence of functional sympathetic fibers, the eye loses its ability to prevent either the immune rejection of intraocular allogeneic tumor cells or the suppression of delayed type hypersensitivity responses against soluble antigens injected in the anterior chamber. This loss of immune privilege is accompanied by a decrease in the concentration of transforming growth factor-beta in the aqueous humor. These results suggest that immune privilege is lost in the absence of a functional sympathetic innervation of the eye, allowing intraocular immune responses to become exaggerated. We conclude that ocular sympathetic nerves are critical for the generation and maintenance of immune privilege in the eye through the facilitation of local transforming growth factor-beta production.

IkappaB alpha is an inhibitor of the transcriptional factor NF-kappaB, and it is an essential component of the signaling pathways that lead to expression of inflammatory molecules. These include cytokines and costimulatory molecules associated with antigen presentation in an inflammatory immune response. In this study, we report that antigen-presenting cells exposed to TGF-beta induce peripheral tolerance by increasing IkappaB alpha expression. Exposure of antigen presenting cells (APCs) to TGF-beta is known to impair their ability to secrete IL-12, and such impairment correlated with reduced NF-kappaB activity as indicated by significantly reduced nuclear levels of p50, an essential subunit of NF-kappaB for IL-12 transcription. Blockade of increased nuclear IkappaB alpha in APCs by expression of small interfering RNA molecules (siRNAs) targeting IkappaB alpha transcripts prevented IL-12 impairment and the decline in nuclear p50 levels. Furthermore, such IkappaB alpha blockade also interfered with the tolerogenic property of TGF-beta-exposed APCs. However, increased expression of IkappaB alpha in APCs, independent of TGF-beta exposure, reduced nuclear p50 levels and permitted tolerance induction by APCs. Thus, our findings attribute a direct and significant role to IkappaB alpha in the tolerogenic potential of APCs. Increased IkappaB alpha expression in APCs may therefore offer a therapeutic approach to achieve antigen-specific immunomodulation.

Exposure of macrophages to transforming growth factor (TGF)-beta is known to alter their functional phenotype such that antigen presentation by these cells leads to tolerance rather than an inflammatory immune response. Typically, eye-derived antigen-presenting cells (APCs) exposed to TGF-beta in the local environment are known to induce a form of peripheral tolerance and protect the eye from inflammatory immune effector-mediated damage. In response to TGF-beta, APCs increase their expression of tumour necrosis factor (TNF)-alpha and TNF receptor 2 (TNF-R2). Although TNF-alpha has been implicated in tolerance and the associated regulation of the inflammatory immune response, its source and the receptors involved remain unclear. In this report we determined the contribution of TNF-alpha and TNF-R2 expressed by TGF-beta-treated APCs to their anti-inflammatory tolerogenic effect. Our results indicate that APC-derived TNF-alpha is essential for the ability of APCs to regulate the immune response and their IL-12 secretion. Moreover, in the absence of TNF-R2, APCs exposed to TGF-beta failed to induce tolerance or regulatory cells known to participate in this tolerance. Also, blocking of TNF-R1 signalling enhanced the ability of the APCs to secrete increased TGF-beta in response to TGF-beta exposure. Together our results support an anti-inflammatory role of TNF-alpha in regulation of an immune response by TGF-beta-treated APCs and suggest that TNF-R2 contributes significantly to this role.

Transforming growth factor beta (TGF-beta) plays a role both in the induction of Treg and in the differentiation of the IL-17-secreting T cells (Th17) which drive inflammation in experimental autoimmune encephalomyelitis (EAE). We investigated the role that thrombospondin-1 (TSP-1) dependent activation of TGF-beta played in the generation of an encephalitic Th17 response in EAE. Upon immunization with myelin oligodendrocyte glycoprotein peptide (MOG(35-55)), TSP-1 deficient (TSP-1(null)) mice and MOG(35-55) TCR transgenic mice that lack of TSP-1 (2D2 x TSP-1(null)) exhibited an attenuated form of EAE, and secreted lower levels of IL-17. Adoptive transfer of in vitro-activated 2D2 x TSP-1(null) T cells induced a milder form of EAE, independent of TSP-1 expression in the recipient mice. Furthermore, in vitro studies demonstrated that anti-CD3/anti-CD28 pre-activated CD4+ T cells transiently upregulated latent TGF-beta in a TSP-1 dependent way, and such activation of latent TGF-beta was required for the differentiation of Th17 cells. These results demonstrate that TSP-1 participates in the differentiation of Th17 cells through its ability to activate latent TGF-beta, and enhances the inflammatory response in EAE.