Autoimmunity in dry eye is due to resistance of Th17 to Treg suppression

The immunoregulatory role of corneal epithelium-derived thrombospondin-1 in dry eye disease

PURPOSE

In this study, we examine the expression of corneal epithelium-derived thrombospondin-1 (TSP-1) and its immunomodulatory functions in a validated murine model of dry eye disease (DED).

METHODS

DED was induced in female C57BL/6 using a controlled environment chamber (CEC) for 14 days. mRNA and protein expression of TSP-1 by corneal epithelial cells was quantified using real-time PCR and flow cytometry. Corneal epithelial cells from either naïve or DED mice were cultured with bone marrow derived dendritic cells (BMDCs) in the presence of IFNγ for 48 h, and BMDC expression of MHC-II and CD86 was determined using flow cytometry. Next, either recombinant TSP-1 or anti-TSP-1 antibody was added to the co-culture, and BMDC expression of above activation markers was evaluated. Finally, either DED mice were topically treated with either recombinant TSP-1 or human serum albumin (HSA), and maturation of corneal DCs, expression of inflammatory cytokines, and DED severity were investigated.

RESULTS

mRNA expression of TSP-1 by the corneal epithelium was upregulated in DED. Corneal epithelial cells derived from mice with DED demonstrated an enhanced capacity in suppressing BMDC expression of MHC-II and CD86 relative to wild type mice, and this effect was abrogated by TSP-1 blockade and potentiated by recombinant TSP-1. Finally, topical application of recombinant TSP-1 significantly suppressed corneal DC maturation and mRNA expression of pro-inflammatory cytokines, and ameliorated disease severity in mice with DED.

CONCLUSIONS

Our study elucidates the function of epithelium-derived TSP-1 in inhibiting DC maturation and shows its translational potential to limit corneal epitheliopathy in DED.

TH17 cells mediate inflammation in a novel model of spontaneous experimental autoimmune lacrimal keratoconjunctivitis with neural damage

BACKGROUND

Dry eye disease (DED) affects one third of the population worldwide. In prior studies, experimental autoimmune lacrimal keratoconjunctivitis (EALK) induced by desiccating stress in mice has been used as a model of DED. This model is complicated by a requirement for exogenous epithelial cell injury and administration of anticholinergic agents with broad immunologic effects.

OBJECTIVE

We sought to develop a novel mouse model of EALK and to demonstrate the responsible pathogenic mechanisms.

METHODS

CD4+CD45RBhigh naive T cells with and without CD4+CD45RBlow regulatory T cells were adoptively transferred to C57BL/10 recombination-activating gene 2 (Rag2)-/- mice. The eyes, draining lymph nodes, lacrimal glands, and surrounding tissues of mice with and without spontaneous keratoconjunctivitis were evaluated for histopathologic changes, cellular infiltration, and cytokine production in tissues and isolated cells. Furthermore, the integrity of the corneal nerves was evaluated using whole-tissue immunofluorescence imaging. Gene-deficient naive T cells or RAG2-deficient hosts were evaluated to assess the roles of IFN-γ, IL-17A, and IL-23 in disease pathogenesis. Finally, cytokine levels were determined in the tears of patients with DED.

RESULTS

EALK developed spontaneously in C57BL/10 Rag2-/- mice after adoptive transfer of CD4+CD45RBhigh naive T cells and was characterized by infiltration of CD4+ T cells, macrophages, and neutrophils. In addition to lacrimal keratoconjunctivitis, mice had damage to the corneal nerve, which connects components of the lacrimal functional unit. Pathogenic T-cell differentiation was dependent on IL-23p40 and controlled by cotransferred CD4+CD45RBlow regulatory T cells. TH17 rather than TH1 CD4+ cells were primarily responsible for EALK, even though levels of both IL-17 and IFN-γ were increased in inflammatory tissues, likely because of their ability to drive expression of CXC chemokines within the cornea and the subsequent influx of myeloid cells. Consistent with the findings of this model, the tears of patients with DED had increased levels of inflammatory cytokines, including IL-17A and TNF-α.

CONCLUSION

We describe a novel model of spontaneous EALK that supports a role for TH17 cells in disease pathogenesis and that will contribute to our understanding of autoimmune lacrimal keratoconjunctivitis in many human eye diseases, including DED.

Suppression of Th1-Mediated Keratoconjunctivitis Sicca by Lifitegrast

PURPOSE

Increased interferon gamma (IFN-γ) expression in dry eye causes ocular surface epithelial disease termed keratoconjunctivitis sicca (KCS). The purpose of this study was to investigated the effects of the LFA-1 antagonist, lifitegrast, in a mouse desiccating stress (DS) dry eye model that develops KCS similar to Sjögren syndrome.

METHODS

Mice were treated with vehicle or lifitegrast twice daily for 5 days and expression of Th1 family genes (IFN-γ, CXCL9, and CXCL11) was evaluated by real-time polymerase chain reaction. Cornea barrier function was assessed by Oregon Green dextran staining and goblet cell number and area were measured.

RESULTS

Compared to the vehicle-treated group, the lifitegrast-treated group had significantly lower expression of Th1 family genes, less corneal barrier disruption, and greater conjunctival goblet cell density/area.

CONCLUSIONS

These findings indicate that lifitegrast inhibits DS-induced IFN-γ expression and KCS. This suggests that ICAM-LFA-1 signaling is involved with generation of Th1 inflammation in KCS.

Immune Privilege and Eye-Derived T-Regulatory Cells

Certain cellular components of the eye, such as neural retina, are unable to regenerate and replicate after destructive inflammation. Ocular immune privilege provides the eye with immune protection against intraocular inflammation in order to minimize the risk to vision integrity. The eye and immune system use strategies to maintain the ocular immune privilege by regulating the innate and adaptive immune response, which includes immunological ignorance, peripheral tolerance to eye-derived antigens, and intraocular immunosuppressive microenvironment. In this review, we summarize current knowledge regarding the molecular mechanism responsible for the development and maintenance of ocular immune privilege via regulatory T cells (Tregs), which are generated by the anterior chamber-associated immune deviation (ACAID), and ocular resident cells including corneal endothelial (CE) cells, ocular pigment epithelial (PE) cells, and aqueous humor. Furthermore, we examined the therapeutic potential of Tregs generated by RPE cells that express transforming growth factor beta (TGF-β), cytotoxic T lymphocyte-associated antigen-2 alpha (CTLA-2α), and retinoic acid for autoimmune uveoretinitis and evaluated a new strategy using human RPE-induced Tregs for clinical application in inflammatory ocular disease. We believe that a better understanding of the ocular immune privilege associated with Tregs might offer a new approach with regard to therapeutic interventions for ocular autoimmunity.

Controlled release of an HDAC inhibitor for reduction of inflammation in dry eye disease

Dry eye disease (DED), also known as keratoconjunctivitis sicca, is an ocular surface disease characterized by T-cell-mediated inflammation. Current therapeutics, such as immunosuppressive agents, act to suppress the clinical signs and inflammation. However, long-term usage of these treatments can cause severe side effects. In this study, we present an alternative therapeutic approach that utilizes a histone deacetylase inhibitor (HDACi) to regulate transcription of a variety of immunomodulatory genes. Specifically, HDACi have emerged as a potential anti-inflammatory agent, which can modulate the functions of a subset of suppressive T lymphocytes known as regulatory T cells (Tregs), enhancing FoxP3 acetylation and subsequently guarding the transcription factor from proteasomal degradation. Here, a specific HDACi known as SAHA (suberoylanilide hydroxamic acid) was formulated to controllably release in the lacrimal gland. Intralacrimal gland injection of PLGA-based SAHA microspheres prevented clinical signs of DED in mice with Concanavalin A-induced DED, reduced expression of pro-inflammatory cytokines, and increased expression of FoxP3 in the lacrimal glands. Murine T cell culture experiments also revealed that SAHA decreased effector T cell proliferation and enhanced suppressive function of Tregs in co-cultures of Tregs and effector T cells.

STATEMENT OF SIGNIFICANCE

In this study, we demonstrate a therapeutic approach that utilizes a histone deactylase inhibitor (HDACi) to regulate transcription of a variety of immunomodulatory genes. HDACi have emerged as a potential anti-inflammatory agent, which can modulate the functions of a subset of suppressive T lymphocytes known as regulatory T cells (Tregs). Here, HDACi microspheres composed of a biocompatible and biodegradable polymer (poly(lactic-co-glycolic acid) (PLGA)), were able to locally release the HDACi and prevent clinical signs of DED. This work is timely given the recent shift in treatments of DED towards immunological based therapies to reduce ocular inflammation. However, notably, many of these treatments require large amounts of drug, and non-specifically suppress the immune system, leading to several systemic side effects. Instead of merely suppressing or blocking inflammation, the formulation described herein intends to balance the microenvironment promoting immunological homeostasis. This particular drug delivery system may also have broad implications in the field of inflammatory mediated ocular disorders such as uveitis, Sjögren's syndrome, allergic conjunctivitis.

When Clarity Is Crucial: Regulating Ocular Surface Immunity

The ocular surface is a unique mucosal immune compartment in which anatomical, physiological, and immunological features act in concert to foster a particularly tolerant microenvironment. These mechanisms are vital to the functional competence of the eye, a fact underscored by the devastating toll of excessive inflammation at the cornea - blindness. Recent data have elucidated the contributions of specific anatomical components, immune cells, and soluble immunoregulatory factors in promoting homeostasis at the ocular surface. We highlight research trends at this distinctive mucosal barrier and identify crucial gaps in our current knowledge.

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

St. Leger et al. identify and examine innate-like αβ T cells that circumvent canonical STAT-3 phosphorylation to produce protective IL-17. These cells can exist in the ocular mucosa and protect the ocular surface from pathogenic Staphylococcus aureus infection.

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 Staphylococcus aureus infection at the ocular surface.

Interferon-gamma deficiency protects against aging-related goblet cell loss

Aging is a well-recognized risk factor for dry eye. Interferon-gamma (IFN-γ) has been implicated in conjunctival keratinization and goblet cell loss in dry eye. We investigated the role of IFN-γ in age-related dry eye by evaluating young (8 weeks) and aged (15 months; 15M) C57BL/6 (B6) and IFN-γKO mice. Age effects on the conjunctiva and cornea epithelium were assessed with PAS staining and corneal staining, respectively. Expression of T cell-related cytokines (IL-17A, IFN-γ), chemokines (CXCL10 and CCL20), in the ocular surface epithelium was evaluated by real time PCR. A significant decrease in filled goblet cells was noted in 15M B6 mice and this was significantly lower than age and sex-matched IFN-γKO mice. Aged male B6 had significantly higher IFN-γ, and CXCL10 mRNA in their conjunctiva than female B6 mice. Aged IFN-γKO females had significantly higher IL-17A mRNA in conjunctiva than IFN-γKO males and B6 mice. Corneal barrier dysfunction was observed in 15M female B6 and aged IFN-γKO mice of both sexes; however it was significantly higher in IFN-γKO compared to B6 mice. While there was a significant increase in IL 17A, and CCL20 in corneas of aged female B6 and IFN-γKO mice compared to males, these changes were more evident in aged female IFN-γKO group.

Partial resistance of IFN-γKO mice to aging-induced goblet cell loss indicates IFN-γ is involved in the age-related decline in conjunctival goblet cells. Increased corneal IL-17A expression paralleled corneal barrier disruption in aging female of both strains. IFN-γ appears to suppress IL-17A on the ocular surface.

Dry eye syndrome: developments and lifitegrast in perspective

Dry eye (DE) is a chronic ocular condition with high prevalence and morbidity. It has a complex pathophysiology and is multifactorial in nature. Chronic ocular surface inflammation has emerged as a key component of DE that is capable of perpetuating ocular surface damage and leading to symptoms of ocular pain, discomfort, and visual phenomena. It begins with stress to the ocular surface leading to the production of proinflammatory mediators that induce maturation of resident antigen-presenting cells which then migrate to the lymph nodes to activate CD4 T cells. The specific antigen(s) targeted by these pathogenic CD4⁺ T cells remains unknown. Two emerging theories include self-antigens by autoreactive CD4 T cells or harmless exogenous antigens in the setting of mucosal immunotolerance loss. These CD4 T cells migrate to the ocular surface causing additional inflammation and damage. Lifitegrast is the second topical anti-inflammatory agent to be approved by the US Food and Drug Administration for the treatment of DE and the first to show improvement in DE symptoms. Lifitegrast works by blocking the interaction between intercellular adhesion molecule-1 and lymphocyte functional associated antigen-1, which has been shown to be critical for the migration of antigen-presenting cells to the lymph nodes as well as CD4⁺ T cell activation and migration to the ocular surface. In four large multicenter, randomized controlled trials, lifitegrast has proven to be effective in controlling both the signs and symptoms of DE with minimal side effects. Further research should include comparative and combination studies with other anti-inflammatory therapies used for DE.

Novel everolimus-loaded nanocarriers for topical treatment of murine experimental autoimmune uveoretinitis (EAU)

In the present study, therapeutic effect of topically applied everolimus (EV)-loaded methoxy-poly(ethylene-glycol)-hexyl substituted poly (lactic acid) (mPEGhexPLA) nanocarriers on experimental autoimmune uveoretinitis (EAU) were investigated. EAU was induced in B10.RIII mice via immunization with human interphotoreceptor retinoid-binding protein peptide 161-180 (hIRBPp161-180) in complete Freund's adjuvant. Everolimus-loaded mPEGhexPLA (EV/mPEGhexPLA) nanocarriers were prepared by using a solvent evaporation method. On days 12-21 postimmunization (p.i.), the right eyes were treated five times daily either with 10 μl of 0.5% everolimus formulation or PBS (control). The EAU score of the eyes was determined histologically. On day 21 p.i., the peripheral immune responses were measured in serum, cervical lymph nodes (LN), and spleens via hIRBPp161-180-specific serum antibodies, cytokine secretion (ELISA), lymphocyte proliferation, and FoxP3+ regulatory T cells (Treg; flow cytometry). Compared to the PBS-treated mice, unilateral topical everolimus treatment significantly reduced EAU severity in both eyes (p < .05). The treatment reduced the antigen (Ag)-specific hIRBPp161-180-induced proliferation (p < .05), IL-2, IL-17, and IFN-γ secretion from cells isolated from the left and right cervical LN (p < .05). Under everolimus treatment, IL-10 secretion and CD4⁺CD25⁺FoxP3⁺ Treg frequency from cervical LN were enhanced. The proliferative response and cytokine secretion as well as the frequency of splenic Treg were almost unchanged. Topical administration of an everolimus formulation improved EAU in both eyes. The effect might also be related to systemic immunosuppressive effects, as several systemic cellular immune responses were influenced.

TRI Microspheres prevent key signs of dry eye disease in a murine, inflammatory model

Dry eye disease (DED) is a highly prevalent, ocular disorder characterized by an abnormal tear film and ocular surface. Recent experimental data has suggested that the underlying pathology of DED involves inflammation of the lacrimal functional unit (LFU), comprising the cornea, conjunctiva, lacrimal gland and interconnecting innervation. This inflammation of the LFU ultimately results in tissue deterioration and the symptoms of DED. Moreover, an increase of pathogenic lymphocyte infiltration and the secretion of pro-inflammatory cytokines are involved in the propagation of DED-associated inflammation. Studies have demonstrated that the adoptive transfer of regulatory T cells (Tregs) can mediate the inflammation caused by pathogenic lymphocytes. Thus, as an approach to treating the inflammation associated with DED, we hypothesized that it was possible to enrich the body's own endogenous Tregs by locally delivering a specific combination of Treg inducing factors through degradable polymer microspheres (TRI microspheres; TGF-β1, Rapamycin (Rapa), and IL-2). This local controlled release system is capable of shifting the balance of Treg/T effectors and, in turn, preventing key signs of dry eye disease such as aqueous tear secretion, conjunctival goblet cells, epithelial corneal integrity, and reduce the pro-inflammatory cytokine milieu in the tissue.

Modern Therapeutic Approaches for Noninfectious Ocular Diseases Involving Inflammation

Dry eye disease, age-related macular degeneration, and uveitis are ocular diseases that significantly affect the quality of life of millions of people each year. In these diseases, the action of chemokines, proinflammatory cytokines, and immune cells drives a local inflammatory response that results in ocular tissue damage. Multiple therapeutic strategies are developed to either address the symptoms or abate the underlying cause of these diseases. Herein, the challenges to deliver drugs to the relevant location in the eye for each of these diseases are reviewed along with current and innovative therapeutic approaches that attempt to restore homeostasis within the ocular microenvironment.

Analysis of Cytokine Levels in Tears and Clinical Correlations After Intense Pulsed Light Treating Meibomian Gland Dysfunction

PURPOSE

To investigate the change from baseline of inflammatory markers in tears of dry eye disease (DED) subjects owing to meibomian gland dysfunction (MGD) after intense pulsed light (IPL) treatment and meibomian gland expression (MGE) compared to sham treatment, and the correlations with ocular surface parameters.

DESIGN

Randomized, double-masked, controlled study.

METHODS

Those randomized into the active treatment arm received 3 consecutive treatments (14∼16 J/cm²) approximately 4 weeks apart in the periocular region. Control eyes received 3 treatments in the same intervals of 0 J/cm². Tear samples in all eyes were collected and analyzed at baseline, week 12, and/or week 4 for interleukin (IL)-17A, IL-6, and prostaglandin E2 (PGE2). The correlations between cytokines and ocular surface parameters were analyzed before and after IPL treatment.

RESULTS

All of the inflammatory markers declined in value compared to baselines. IL-17A and IL-6 showed statistically significant decreases compared to sham treatment at each measured time point. PGE2 showed statistically significant decreases compared to sham at week 12. Results showed that the expressions of IL-17A and IL-6 correlated well with ocular surface parameters of the lower eyelid before IPL. The changed values of IL-6 and PGE2 in tears correlated with the changed values of partial ocular surface parameters after IPL treatment in study eyes, respectively.

CONCLUSIONS

The study results suggest that IPL can significantly reduce inflammatory markers in tears of patients suffering with DED owing to MGD after IPL treatment. These findings indicate that IL-17A and IL-6 play roles in the pathogenesis of DED owing to MGD, and the reduction of the inflammatory factors is consistent with the improvement of partial clinical symptoms and signs.

The Pathophysiology of Dry Eye Disease: What We Know and Future Directions for Research

Clinical and laboratory studies performed over the past few decades have discovered that dry eye is a chronic inflammatory disease that can be initiated by numerous extrinsic or intrinsic factors that promote an unstable and hyperosmolar tear film. These changes in tear composition, in some cases combined with systemic factors, lead to an inflammatory cycle that causes ocular surface epithelial disease and neural stimulation. Acute desiccation activates stress signaling pathways in the ocular surface epithelium and resident immune cells. This triggers production of innate inflammatory mediators that stimulate the production of matrix metalloprotease, inflammatory cell recruitment, and dendritic cell maturation. These mediators, combined with exposure of autoantigens, can lead to an adaptive T cell-mediated response. Cornea barrier disruption develops by protease-mediated lysis of epithelial tight junctions, leading to accelerated cell death; desquamation; an irregular, poorly lubricated cornea surface; and exposure and sensitization of epithelial nociceptors. Conjunctival goblet cell dysfunction and death are promoted by the T helper 1 cytokine interferon gamma. These epithelial changes further destabilize the tear film, amplify inflammation, and create a vicious cycle. Cyclosporine and lifitegrast, the 2 US Food and Drug Administration-approved therapies, inhibit T-cell activation and cytokine production. Although these therapies represent a major advance in dry eye therapy, they are not effective in improving discomfort and corneal epithelial disease in all patients. Preclinical studies have identified other potential therapeutic targets, biomarkers, and strategies to bolster endogenous immunoregulatory pathways. These discoveries will, it is hoped, lead to further advances in diagnostic classification and treatment.

Inflammation in Dry Eye Disease: How Do We Break the Cycle?

This article reviews the literature and summarizes the role of inflammation in dry eye disease. A PubMed search was performed using the keywords inflammatory cycle and dry eye. All searches were limited to articles published in or translated into the English language, dating from 1973 through March 2017. There were no restrictions on the study design. Advances in understanding the pathogenesis of dry eye disease has revealed that inflammation is a core driver: the so-called "vicious circle" of inflammation. Researchers continue to analyze the precise mechanisms by which inflammation occurs. This has led to therapeutic options to break the cycle. Continued animal and human studies reveal other potential sites for treatment in this complex host of disorders.

Phosphoproteomics Reveals Regulatory T Cell-Mediated DEF6 Dephosphorylation That Affects Cytokine Expression in Human Conventional T Cells

Regulatory T cells (Tregs) control key events of immune tolerance, primarily by suppression of effector T cells. We previously revealed that Tregs rapidly suppress T cell receptor (TCR)-induced calcium store depletion in conventional CD4⁺CD25⁻ T cells (Tcons) independently of IP₃ levels, consequently inhibiting NFAT signaling and effector cytokine expression. Here, we study Treg suppression mechanisms through unbiased phosphoproteomics of primary human Tcons upon TCR stimulation and Treg-mediated suppression, respectively. Tregs induced a state of overall decreased phosphorylation as opposed to TCR stimulation. We discovered novel phosphosites (T595_S597) in the DEF6 (SLAT) protein that were phosphorylated upon TCR stimulation and conversely dephosphorylated upon coculture with Tregs. Mutation of these DEF6 phosphosites abrogated interaction of DEF6 with the IP₃ receptor and affected NFAT activation and cytokine transcription in primary Tcons. This novel mechanism and phosphoproteomics data resource may aid in modifying sensitivity of Tcons to Treg-mediated suppression in autoimmune disease or cancer.

Lacrimal gland-derived IL-22 regulates IL-17-mediated ocular mucosal inflammation

Inflammatory damage of mucosal surface of the eye is a hallmark of dry eye disease (DED) and, in severe cases, can lead to significant discomfort, visual impairment, and blindness. DED is a multifactorial autoimmune disorder with a largely unknown pathogenesis. Using a cross-sectional patient study and a well-characterized murine model of DED, herein we investigated the immunoregulatory function of interleukin-22 (IL-22) in the pathogenesis of DED. We found that IL-22 levels were elevated in lacrimal fluids of DED patients and inversely correlated with severity of disease. Acinar cells of the lacrimal glands (LGs), not inflammatory immune cells, are the primary source of IL-22, which suppresses inflammation in ocular surface epithelial cells upon desiccating stress. Moreover, loss of function analyses using IL-22 knockout mice demonstrated that IL-22 is essential for suppression of ocular surface infiltration of Th17 cells and inhibition of DED induction. Our novel findings elucidate immunoregulatory function of LG-derived IL-22 in inhibiting IL-17-mediated ocular surface epitheliopathy in DED thus making IL-22 a new relevant therapeutic target.

Treg-recruiting microspheres prevent inflammation in a murine model of dry eye disease

Dry eye disease (DED) is a common ocular disorder affecting millions of individuals worldwide. The pathology of DED involves the infiltration of CD4+ lymphocytes, leading to tear film instability and destructive inflammation. In the healthy steady state, a population of immunosuppressive T-cells called regulatory T-cells (Treg) regulates proliferation of immune cells that would otherwise lead to a disruption of immunological homeostasis. For this reason, it has been suggested that Tregs could restore the immunological imbalance in DED. To this end, one possible approach would be to recruit the body's own, endogenous Tregs in order to enrich them at the site of inflammation and tissue destruction. Previously, we have demonstrated a reduction of inflammation and disease symptoms in models of periodontitis corresponding to recruitment of endogenous Tregs, which was accomplished by local placement of controlled release systems that sustain a gradient of the chemokine CCL22, referred to here as Treg-recruiting microspheres. Given that DED is characterized by a pro-inflammatory environment resulting in local tissue destruction, we hypothesized that the controlled release of CCL22 could also recruit Tregs to the ocular surface potentially mediating inflammation and symptoms of DED. Indeed, data suggest that Treg-recruiting microspheres are capable of overcoming the immunological imbalance of Tregs and CD4+ IFN-γ+ cells in the lacrimal gland. Administration of Treg-recruiting microspheres effectively mitigated the symptoms of DED as measured through a number of outcomes such as tear clearance, goblet cells density and corneal epithelial integrity, suggesting that recruitment of endogenous Treg can mitigate inflammation associated with DED.

Alloimmunity and Tolerance in Corneal Transplantation

Corneal transplantation is one of the most prevalent and successful forms of solid tissue transplantation. Despite favorable outcomes, immune-mediated graft rejection remains the major cause of corneal allograft failure. Although low-risk graft recipients with uninflamed graft beds enjoy a success rate ∼90%, the rejection rates in inflamed graft beds or high-risk recipients often exceed 50%, despite maximal immune suppression. In this review, we discuss the critical facets of corneal alloimmunity, including immune and angiogenic privilege, mechanisms of allosensitization, cellular and molecular mediators of graft rejection, and allotolerance induction.

TFOS DEWS II pathophysiology report

The TFOS DEWS II Pathophysiology Subcommittee reviewed the mechanisms involved in the initiation and perpetuation of dry eye disease. Its central mechanism is evaporative water loss leading to hyperosmolar tissue damage. Research in human disease and in animal models has shown that this, either directly or by inducing inflammation, causes a loss of both epithelial and goblet cells. The consequent decrease in surface wettability leads to early tear film breakup and amplifies hyperosmolarity via a Vicious Circle. Pain in dry eye is caused by tear hyperosmolarity, loss of lubrication, inflammatory mediators and neurosensory factors, while visual symptoms arise from tear and ocular surface irregularity. Increased friction targets damage to the lids and ocular surface, resulting in characteristic punctate epithelial keratitis, superior limbic keratoconjunctivitis, filamentary keratitis, lid parallel conjunctival folds, and lid wiper epitheliopathy. Hybrid dry eye disease, with features of both aqueous deficiency and increased evaporation, is common and efforts should be made to determine the relative contribution of each form to the total picture. To this end, practical methods are needed to measure tear evaporation in the clinic, and similarly, methods are needed to measure osmolarity at the tissue level across the ocular surface, to better determine the severity of dry eye. Areas for future research include the role of genetic mechanisms in non-Sjögren syndrome dry eye, the targeting of the terminal duct in meibomian gland disease and the influence of gaze dynamics and the closed eye state on tear stability and ocular surface inflammation.

An Ocular Commensal Protects against Corneal Infection by Driving an Interleukin-17 Response from Mucosal γδ T Cells

Mucosal sites such as the intestine, oral cavity, nasopharynx, and vagina all have associated commensal flora. The surface of the eye is also a mucosal site, but proof of a living, resident ocular microbiome remains elusive. Here, we used a mouse model of ocular surface disease to reveal that commensals were present in the ocular mucosa and had functional immunological consequences. We isolated one such candidate commensal, Corynebacterium mastitidis, and showed that this organism elicited a commensal-specific interleukin-17 response from γδ T cells in the ocular mucosa that was central to local immunity. The commensal-specific response drove neutrophil recruitment and the release of antimicrobials into the tears and protected the eye from pathogenic Candida albicans or Pseudomonas aeruginosa infection. Our findings provide direct evidence that a resident commensal microbiome exists on the ocular surface and identify the cellular mechanisms underlying its effects on ocular immune homeostasis and host defense.

Kinetics of Corneal Antigen Presenting Cells in Experimental Dry Eye Disease

Objective

To evaluate dry eye disease (DED)-induced alterations in subsets of corneal antigen presenting cells (APCs) in a mouse model of experimental DED.

Methods and Analysis

Seven to 8-week-old female C57BL/6 mice were housed in a controlled environment chamber and were treated with subcutaneous scopolamine to induce DED. Normal mice were used as controls. The frequencies of different subsets of dendritic cells (DCs) and macrophages in the cornea were evaluated using immunohistochemistry and flow cytometry at days 2, 7 and 14 after DED induction. Real-time PCR was used to assess the functional phenotype of macrophages in the cornea of DED mice.

Results

Our results demonstrated significant corneal infiltration of CD11b⁺ and CD11c⁺ cells on days 7 and 14. Further analysis of different DC subsets revealed non-significant changes in the frequencies of total CD11b⁺CD11c⁺ cells at different time points. However, frequencies of CD11c⁺CD11b^- DCs, CD11c⁺ Langerin (CD207)⁺ DCs and macrophages were significantly increased on both days 7 and 14 after DED induction. Real-time PCR data demonstrated increased expression of M1 macrophage markers, iNOS and TNF-α, and reduced expression of M2 macrophage markers, Arg1 and IL-10, by corneal F4/80⁺ macrophages at day 7.

Conclusion

Although the frequencies of total CD11b⁺CD11c⁺ cells do not significantly change in the course of DED, CD11c⁺CD11b^- DCs and Langerin⁺ DCs do show a significant increase. Interestingly, macrophages exhibit a predominant inflammatory M1 phenotype and suppressed anti-inflammatory M2 phenotype early after induction of DED, which are restored to near baseline levels in later stages of the disease.

IFN-γ-Expressing Th17 Cells Are Required for Development of Severe Ocular Surface Autoimmunity

Th17 cells are critical effectors mediating the ocular surface autoimmunity in dry eye disease (DED). Increased IFN-γ has also been implicated in DED; however, it remains unclear to what extent Th1 cells contribute to DED pathogenesis. In this study, we investigated the cellular source of IFN-γ and assessed its contribution to corneal epitheliopathy in DED mice. We discovered a significant IL-17A⁺IFN-γ⁺ (Th17/1) population and determined that these cells are derived from Th17 precursors. Adoptive transfer of Th17/1, but not Th1, cells confers the disease to naive recipients as effectively as do Th17 cells alone. DED-induced IL-12 and IL-23 are required for in vivo transition of pathogenic Th17 cells to IFN-γ producers. Furthermore, using IFN-γ-deficient Th17 cells, we demonstrate the disease-amplifying role of Th17-derived IFN-γ in DED pathogenesis. These results clearly demonstrate that Th17 cells mediate ocular surface autoimmunity through both IL-17A and IFN-γ.

T Cell-Derived Granulocyte-Macrophage Colony-Stimulating Factor Contributes to Dry Eye Disease Pathogenesis by Promoting CD11b+ Myeloid Cell Maturation and Migration

Purpose

Growing evidence suggests that granulocyte-macrophage colony-stimulating factor (GM-CSF) contributes to T helper 17 (Th17) cell-associated immunoinflammatory diseases. The purpose of this study was to evaluate the effect of T cell-derived GM-CSF on CD11b+ myeloid cell function in dry eye disease (DED).

Methods

In a murine model of DED, quantitative real-time PCR and ELISA were used to measure GM-CSF expression at the ocular surface, and flow cytometry was used to enumerate GM-CSF producing Th17 cells. A granulocyte-macrophage colony-stimulating factor neutralizing antibody was used topically in vivo and in an in vitro culture system to evaluate the role of GM-CSF in recruiting and maturing CD11b+ cells. Clinical disease severity was evaluated after topical administration of GM-CSF neutralizing antibody.

Results

In dry eye disease, GM-CSF is significantly upregulated at the ocular surface and the frequency of GM-CSF producing Th17 cells is significantly increased in the draining lymph nodes. In vitro neutralization of GM-CSF from CD4+ T cells derived from DED mice suppresses major histocompatibility complex II expression by CD11b+ cells and CD11b+ cell migration. Topical neutralization of GM-CSF in a murine model of DED suppresses CD11b+ maturation and migration, as well as Th17 cell induction, yielding a reduction in clinical signs of disease.

Conclusions

T helper 17 cell-derived GM-CSF contributes to DED pathogenesis by promoting CD11b+ cell activation and migration to the ocular surface.

Review: The function of regulatory T cells at the ocular surface

Regulatory T cells (Tregs) are critical modulators of immune homeostasis. Tregs maintain peripheral tolerance to self-antigens, thereby preventing autoimmune disease. Furthermore, Tregs suppress excessive immune responses deleterious to the host. Recent research has deepened our understanding of how Tregs function at the ocular surface. This manuscript describes the classification, the immunosuppressive mechanisms, and the phenotypic plasticity of Tregs. We review the contribution of Tregs to ocular surface autoimmune disease, as well as the function of Tregs in allergy and infection at the ocular surface. Finally, we review the role of Tregs in promoting allotolerance in corneal transplantation.

Expression, Regulation, and Effects of Interleukin-17f in the Human Ocular Surface

PURPOSE

To evaluate the basal and possibly stimulated expression of interleukin (IL)-17 in the context of the ocular surface and potential downstream effects.

METHODS

Western blot and immunofluorescent staining were used to evaluate IL-17F expression in human cornea/conjunctival tissues and cornea epithelial cell line. Cytokines and matrix metalloproteinase (MMP) transcripts were quantified by qPCR. IL-17F effects on NF-κB were investigated by the secretary alkaline phosphatase assay.

RESULTS

IL-17F was expressed in the cytoplasm of human corneal and conjunctival epithelial tissues. In the corneal cell line, exogenous IL-17F did not increase the NF-κB activity, but Pam3CSK4 increased IL-17F transcripts. IL-17F stimulated MMP-9 activity, promoted IL-6, IL-8, tumor necrosis factor-α transcripts levels, and depressed monocyte chemoattractant protein-1 expression, but did not affect transforming growth factor beta-1 transcript levels.

CONCLUSIONS

Normal corneal/conjunctival epithelial cells express IL-17F. Microbial agents may stimulate IL-17F via the NF-κB pathway. Matrix dissolution stimulated by IL-17F may have a role in the melting and necrosis of cornea in severe inflammation.

Age-related spontaneous lacrimal keratoconjunctivitis is accompanied by dysfunctional T regulatory cells

In both humans and animal models, the development of Sjögren syndrome (SS) and non-SS keratoconjunctivitis sicca (KCS) increases with age. Here, we investigated the ocular surface and lacrimal gland (LG) phenotype of NOD.B10.H2^b mice at 7-14, 45-50, and 96-100 weeks. Aged mice develop increased corneal permeability, CD4⁺ T-cell infiltration, and conjunctival goblet cell loss. Aged mice have LG atrophy with increased lymphocyte infiltration and inflammatory cytokine levels. An increase in the frequency of CD4⁺Foxp3⁺ T regulatory cells (Tregs) was observed with age in the cervical lymph node (CLN), spleen, and LG. These CD4⁺CD25⁺ cells lose suppressive ability, while maintaining expression of Foxp3 (forkhead box P3) and producing interleukin-17 (IL-17) and interferon-γ (IFN-γ). An increase of Foxp3⁺IL-17⁺ or Foxp3⁺IFN-γ⁺ cells was observed in the LG and LG-draining CLN. In adoptive transfer experiments, recipients of either purified Tregs or purified T effector cells from aged donors developed lacrimal keratoconjunctivitis, whereas recipients of young Tregs or young T effector cells failed to develop disease. Overall, these results suggest inflammatory cytokine-producing CD4⁺Foxp3⁺ cells participate in the pathogenesis of age-related ocular surface disease.

Translational Immunoimaging and Neuroimaging Demonstrate Corneal Neuroimmune Crosstalk

Corneal immunoimaging and neuroimaging approaches facilitate in vivo analyses of the cornea, including high-resolution imaging of corneal immune cells and nerves. This approach facilitates the analyses of underlying immune and nerve alterations not detected by clinical slit-lamp examination alone. In this review, we describe recent work performed in our translational ocular immunology center with a focus on "bench-to-bedside" and "bedside-to-bench" research. The ability to visualize dendritiform immune cells (DCs) in patients with laser in vivo confocal microscopy (IVCM), recently discovered in the central murine cornea, has allowed us to demonstrate their utility as a potential surrogate biomarker for inflammatory ocular surface diseases. This biomarker for inflammation allows the measurement of therapeutic efficacy of anti-inflammatory drugs and its utility as an endpoint in clinical trials with high interobserver agreement. IVCM image analyses from our studies has demonstrated a significant increase in DC density and size in ocular disease, a positive correlation between DC density and clinical signs and symptoms of disease and pro-inflammatory tear cytokines, and a strong negative correlation between DC density and subbasal nerve density. In conjunction with preclinical research investigating the inflammatory state in a partial or fully denervated cornea, our results indicated that corneal nerves are directly involved in the regulation of homeostasis and immune privilege in the cornea.

Local ocular surface parameters in patients with systemic celiac disease

PurposeThis was a collaborative study from the Ophthalmology and Gastroenterology departments of a tertiary care hospital, designed to investigate the local ocular surface parameters in patients with celiac disease (CD).MethodsFifty-six eyes of 28 patients with CD and 58 eyes of 29 healthy adult subjects serving as controls were evaluated. The Schirmer test, tear-film break-up time, and conjunctival impression cytology were performed in addition to a complete ophthalmological examination. Impression cytology specimens of each group were graded and scored in the range 0-3.ResultsThe 28 patients with CD consisted of 24 females (86%) and 4 males (14%). The mean age was 34.4±11.3 years (22-55 years). Tear-film break-up time and Schirmer test results were significantly lower in the study group than in the controls (P<0.05). Also, there was a significant difference between the groups for impression cytology grading scores (P=0.001).ConclusionsThe CD group showed a marked preponderance of females with an F/M ratio of six females per male, as reported in the literature. Tear-film functions and conjunctival surface epithelial morphology were significantly altered in patients with CD.

Mucosal immune tolerance at the ocular surface in health and disease

The ocular surface is constantly exposed to environmental irritants, allergens and pathogens, against which it can mount a prompt immune response to preserve its integrity. But to avoid unnecessary inflammation, the ocular surface's mucosal immune system must also discriminate between harmless and potentially dangerous antigens, a seemingly complicated task. Despite its unique features, the ocular surface is a mucosal lining, and as such, it shares some homeostatic and pathophysiological mechanisms with other mucosal surfaces. The purpose of this review is to explore the mucosal homeostatic immune function of the ocular surface in both the healthy and diseased states, with a special focus on mucosal immunology concepts. The information discussed in this review has been retrieved by PubMed searches for literature published from January 1981 to October 2016.

Ageing and ocular surface immunity

The prevalence of ocular surface immunopathologies is enhanced in the elderly. This increased prevalence has been attributed to age-related dysregulation of innate and adaptive immune system responses. Age-related changes in ocular surface immunity have similar and distinct characteristics to those changes seen in other mucosal tissues. This mini review provides a brief outline of key findings in the field of ocular ageing, draws comparisons with other mucosal tissues and, finally, discusses age-related changes in the context of immunopathogenesis of infectious keratitis and dry eye disease, two of the most common inflammatory disorders of the ocular surface.

LFA-1/ICAM-1 Interaction as a Therapeutic Target in Dry Eye Disease

Dry eye disease (DED) is a common ocular disorder associated with inflammation of the lacrimal gland and ocular surface. The interaction of the integrin lymphocyte function-associated antigen-1 (LFA-1) with its cognate ligand intercellular adhesion molecule-1 (ICAM-1) is known to have important roles in the interaction of a variety of cells involved in immune responses and inflammation, including those prominent in ocular surface inflammation. Lifitegrast, an LFA-1 antagonist that blocks binding of ICAM-1 to LFA-1, has recently been approved in the United States for the treatment of signs and symptoms of DED. In this review, we evaluate research findings to explore the potential role of LFA-1/ICAM-1 interaction in the pathophysiology of DED, and the evidence supporting LFA-1/ICAM-1 interaction as a rational therapeutic target in DED. The results of our review suggest that LFA-1/ICAM-1 interaction may play important roles in the cell-mediated immune response and inflammation associated with DED, including facilitating the homing of dendritic cells to the lymph nodes, interaction of dendritic cells with T cells and subsequent T cell activation/differentiation, migration of activated CD4⁺ T cells from the lymph nodes to the ocular surface, reactivation of T cells by resident antigen-presenting cells at the ocular surface, and recruitment and retention of LFA-1-expressing T cells in the conjunctival epithelium. Based on the available evidence, inhibition of LFA-1/ICAM-1 interaction represents a rational targeted approach in treating DED. Notably, inhibition of LFA-1/ICAM-1 binding with lifitegrast offers a novel approach to reducing ocular surface inflammation in this condition.

Interleukin-7 and -15 maintain pathogenic memory Th17 cells in autoimmunity

Th17 cells are principal mediators of many autoimmune conditions. Recently, memory Th17 cells have been revealed as crucial in mediating the chronicity of various refractory autoimmune disorders; however, the underlying mechanisms maintaining memory Th17 cells have remained elusive. Here, using a preclinical model of ocular autoimmune disease we show that both IL-7 and IL-15 are critical for maintaining pathogenic memory Th17 cells. Neutralization of these cytokines leads to substantial reduction of memory Th17 cells; both IL-7 and IL-15 provide survival signals via activating STAT5, and IL-15 provides additional proliferation signals via activating both STAT5 and Akt. Topical neutralization of ocular IL-7 or IL-15 effectively reduces memory Th17 cells at the inflammatory site and draining lymphoid tissues, while topical neutralization of IL-17 alone, the major pathogenic cytokine secreted by Th17 cells, does not diminish memory Th17 cells at the draining lymphoid tissues. Our results suggest that the effective removal of pathogenic memory Th17 cells via abolishing environmental IL-7 or IL-15 is likely to be a novel strategy in the treatment of autoimmune diseases.

New Perspectives on Dry Eye Definition and Diagnosis: A Consensus Report by the Asia Dry Eye Society

For the last 20 years, a great amount of evidence has accumulated through epidemiological studies that most of the dry eye disease encountered in daily life, especially in video display terminal (VDT) workers, involves short tear film breakup time (TFBUT) type dry eye, a category characterized by severe symptoms but minimal clinical signs other than short TFBUT. An unstable tear film also affects the visual function, possibly due to the increase of higher order aberrations. Based on the change in the understanding of the types, symptoms, and signs of dry eye disease, the Asia Dry Eye Society agreed to the following definition of dry eye: "Dry eye is a multifactorial disease characterized by unstable tear film causing a variety of symptoms and/or visual impairment, potentially accompanied by ocular surface damage." The definition stresses instability of the tear film as well as the importance of visual impairment, highlighting an essential role for TFBUT assessment. This paper discusses the concept of Tear Film Oriented Therapy (TFOT), which evolved from the definition of dry eye, emphasizing the importance of a stable tear film.

Clinical evaluation of a nutraceutical diet as an adjuvant to pharmacological treatment in dogs affected by Keratoconjunctivitis sicca

Background

Canine keratoconjunctivitis sicca (cKCS) is an inflammatory eye condition related to a deficiency in the tear aqueous fraction. Etiopathogenesis of such disease is substantially multifactorial, combining the individual genetic background with environmental factors that contribute to the process of immunological tolerance disruption and, as a consequence, to the emergence of autoimmunity disease. In this occurrence, it is of relevance the role of the physiological immune-dysregulation that results in immune-mediated processes at the basis of cKCS. Current therapies for this ocular disease rely on immunosuppressive treatments. Clinical response to treatment frequently varies from poor to good, depending on the clinical-pathological status of eyes at diagnosis and on individual response to therapy. In the light of the variability of clinical response to therapies, we evaluated the use of an anti-inflammatory/antioxidant nutraceutical diet with potential immune-modulating activity as a therapeutical adjuvant in cKCS pharmacological treatment. Such combination was administered to a cohort of dogs affected by cKCS in which the only immunosuppressive treatment resulted poorly responsive or ineffective in controlling the ocular symptoms.

Results

Fifty dogs of different breeds affected by immune-mediated cKSC were equally distributed and randomly assigned to receive either a standard diet (control, n = 25) or the nutraceutical diet (treatment group, n = 25) both combined with standard immunosuppressive therapy over a 60 days period. An overall significant improvement of all clinical parameters (tear production, conjunctival inflammation, corneal keratinization, corneal pigment density and mucus discharge) and the lack of food-related adverse reactions were observed in the treatment group (p < 0.0001).

Conclusions

Our results showed that the association of traditional immune-suppressive therapy with the antioxidant/anti-inflammatory properties of the nutraceutical diet resulted in a significant amelioration of clinical signs and symptoms in cKSC. The beneficial effects, likely due to the presence of supplemented nutraceuticals in the diet, appeared to specifically reduce the immune-mediated ocular symptoms in those cKCS-affected dogs that were poorly responsive or unresponsive to classical immunosuppressive drugs. These data suggest that metabolic changes could affect the immune response orchestration in a model of immune-mediated ocular disease, as represented by cKSC.

IL-17 Augments B Cell Activation in Ocular Surface Autoimmunity

Accumulating evidence shows that IL-17 is critically involved in diverse autoimmune diseases. However, its effect on the induction and progression of the humoral immune response is not fully understood. Using a preclinical model of IL-17-mediated dry eye disease, we demonstrate that upon encountering both the BCR and a secondary T cell signal, IL-17 can enhance B cell proliferation and germinal center formation in dry eye disease mice, suggesting that a stable Ag-dependent T-B cell interaction is required. Additionally, IL-17 also promotes the differentiation of B cells into isotype-switched B cells and plasma cells. Furthermore, we show that Th17 cells are more effective than Th1 cells to provide B cell help. Reduced B cell response correlates with significant reduction in clinical disease after in vivo IL-17A neutralization. In conclusion, our findings demonstrate a new role of IL-17 in promoting autoimmunity in part through directly enhancing B cell proliferation, differentiation, and plasma cell generation.

FOXP3+ associated with the pro-inflammatory regulatory T and T helper 17 effector cells in asthma patients

Asthma is a chronic bronchial inflammation that results to reversible incidence of airway obstruction and shortness of breath. Under normal circumstances, the lung immune system is maintained in a state of controlled inflammation, where balance exists between protective immunity mediated by effector cells and tolerance mediated by cells with regulatory function. Therefore, the inflammation observed in asthma patients may be caused by an imbalance between regulatory T (Treg) cells (CD4-positive with high expression of CD25 surface markers) and forkhead box P3 (FOXP3)-positive pro-inflammatory T helper 17 (Th17) cells. The aim of the present study was to evaluate whether reduced Treg cells and increased Th17 cells could be observed in the peripheral blood samples of asthma patients. As important markers of Treg cells, the expression levels of FOXP3 and interleukin (IL)-17a were analyzed via reverse trancription-quantitative polymerase chain reaction. The results indicated that the levels of cytokines that promote Th17 cells, including IL-6, IL-23 and TGF-β, were found to increase in the bronchoalveolar lavage fluid sample of asthma patients. However, the IL-10 level in the corresponding sample was much lower compared with that in control individuals. In conclusion, these results suggest that asthma associated with a reduced proportion of Treg and Th17 cells in the blood is characterized by the expression of pro-inflammatory cytokines that may be beneficial for the continuous generation of Th17 cells.

Mucosal tolerance disruption favors disease progression in an extraorbital lacrimal gland excision model of murine dry eye

Dry eye is a highly prevalent immune disorder characterized by a dysfunctional tear film and a Th1/Th17 T cell response at the ocular surface. The specificity of these pathogenic effector T cells remains to be determined, but auto-reactivity is considered likely. However, we have previously shown that ocular mucosal tolerance to an exogenous antigen is disrupted in a scopolamine-induced murine dry eye model and that it is actually responsible for disease progression. Here we report comparable findings in an entirely different murine model of dry eye that involves resection of the extraorbital lacrimal glands but no systemic muscarinic receptor blockade. Upon ocular instillation of ovalbumin, a delayed breakdown in mucosal tolerance to this antigen was observed in excised but not in sham-operated mice, which was mediated by interferon γ- and interleukin 17-producing antigen-specific T cells. Consistently, antigen-specific regulatory T cells were detectable in sham-operated but not in excised mice. As for other models of ocular surface disorders, epithelial activation of the NF-κB pathway by desiccating stress was determinant in the mucosal immune outcome. Underscoring the role of mucosal tolerance disruption in dry eye pathogenesis, its prevention by a topical NF-κB inhibitor led to reduced corneal damage in excised mice. Altogether these results show that surgically originated desiccating stress also initiates an abnormal Th1/Th17 T cell response to harmless exogenous antigens that reach the ocular surface. This event might actually contribute to corneal damage and challenges the conception of dry eye as a strictly autoimmune disease.

Relationship Between Dynamic Changes in Expression of IL-17/IL-23 in Lacrimal Gland and Ocular Surface Lesions in Ovariectomized Mice

PURPOSE

An ovariectomized mouse model was constructed to observe the dynamic effects of hormone changes on the expression of interleukin (IL)-17A and IL-23 in the lacrimal glands.

METHODS

The ovariectomized mouse model was constructed by bilateral ovary removal. The concentrations of serum estradiol and testosterone in mouse cardiac blood were detected by radioimmunoassay. Mice in both groups underwent the phenol red cotton thread test and corneal fluorescein staining to assess the ocular surface, whereas Th17 cells in blood and spleen were detected by flow cytometry. IL-17A and IL-23 expression in the lacrimal glands was detected by immunohistochemistry, enzyme-linked immunosorbent assay, and real-time fluorescence quantitative polymerase chain reaction.

RESULTS

Serum estradiol and testosterone levels were significantly lower in the ovariectomized group compared with those in the control group. There was lymphocytic infiltration in the lacrimal gland of the ovariectomized group mice. At 6 months after the surgery, aqueous tear production was significantly lower, and statistically significant corneal fluorescein staining was found in the ovariectomized group, compared with that in the control group. In the ovariectomized group, IL-17A and the IL-23 expression in the lacrimal glands and the Th17 expression in the blood and spleen were significantly higher than in the control group.

CONCLUSION

The hormone levels are significantly reduced and lymphocytic infiltration in the lacrimal gland in ovariectomized mice, whereas the frequency of Th17 cells in the blood and spleen and IL-17A and IL-23 expression in the lacrimal glands are increased, leading to reduced tear production and positive fluorescein staining in the cornea.

Dry Eye Signs and Symptoms Persist During Systemic Neutralization of IL-1β by Canakinumab or IL-17A by Secukinumab

To evaluate whether inhibition of the proinflammatory cytokines IL-1β or IL-17A by canakinumab or secukinumab, respectively, influence the signs and symptoms of dry eye.

Age-related Defects in Ocular and Nasal Mucosal Immune System and the Immunopathology of Dry Eye Disease

Dry eye disease (DED) is a prevalent public health concern that affects up to 30% of adults and is particularly chronic and severe in the elderly. Two interconnected mechanisms cause DED: (1) an age-related dysfunction of lacrimal and meibomian glands, which leads to decreased tear production and/or an increase in tear evaporation; and (2) an age-related uncontrolled inflammation of the surface of the eye triggered by yet-to-be-determined internal immunopathological mechanisms, independent of tear deficiency and evaporation. In this review we summarize current knowledge on animal models that mimic both the severity and chronicity of inflammatory DED and that have been reliably used to provide insights into the immunopathological mechanisms of DED, and we provide an overview of the opportunities and limitations of the rabbit model in investigating the role of both ocular and nasal mucosal immune systems in the immunopathology of inflammatory DED and in testing novel immunotherapies aimed at delaying or reversing the uncontrolled age-related inflammatory DED.

The Prevalence of Dry Eye and Sjögren Syndrome in Patients with Migraine

PURPOSE

To evaluate the presence of dry eye and primary Sjögren syndrome (SS) in patients with migraine.

METHODS

In total, 46 eyes of 46 patients with migraine (group 1) and 50 eyes of 50 healthy subjects (group 2) were included in this study. Detailed ophthalmologic, neurologic and rheumatologic examination were performed on all participants. Ocular surface disease index questionnaire, tear function tests, visual analog scale for pain, serologic analysis were also performed.

RESULTS

Dry eye symptoms and findings were significantly higher and more severe in group 1 when compared with group 2. Primary SS was not found in any of the participants. The migraine lifetime duration was negatively correlated with the tear function tests while it was positively correlated with the ocular surface disease index scores.

CONCLUSIONS

Dry eye symptoms and findings are higher in migraine patients when compared with the healthy subjects without the presence of Sjögren syndrome.

Desiccating stress-induced disruption of ocular surface immune tolerance drives dry eye disease

Dry eye is an allegedly autoimmune disorder for which the initiating mechanisms and the targeted antigens in the ocular surface are not known, yet there is extensive evidence that a localized T helper type 1 (Th1)/Th17 effector T cell response is responsible for its pathogenesis. In this work, we explore the reconciling hypothesis that desiccating stress, which is usually considered an exacerbating factor, could actually be sufficient to skew the ocular surface's mucosal response to any antigen and therefore drive the disease. Using a mouse model of dry eye, we found that desiccating stress causes a nuclear factor kappa B (NF-κB)- and time-dependent disruption of the ocular surface's immune tolerance to exogenous ovalbumin. This pathogenic event is mediated by increased Th1 and Th17 T cells and reduced regulatory T cells in the draining lymph nodes. Conversely, topical NF-κB inhibitors reduced corneal epithelial damage and interleukin (IL)-1β and IL-6 levels in the ocular surface of mice under desiccating stress. The observed effect was mediated by an augmented regulatory T cell response, a finding that highlights the role of mucosal tolerance disruption in dry eye pathogenesis. Remarkably, the NF-κB pathway is also involved in mucosal tolerance disruption in other ocular surface disorders. Together, these results suggest that targeting of mucosal NF-κB activation could have therapeutic potential in dry eye.

Exogenous IL-2 controls the balance in Th1, Th17, and Treg cell distribution in patients with progressive rheumatoid arthritis treated with TNF-alpha inhibitors

Interleukin-2 (IL-2) has been suggested to control Treg/Th17 balance. Recently, we reported a relationship of rheumatoid arthritis (RA) activity/progression with irreversible systemic Treg and Th1 defects including serum IL-2 shortage. Herein, we explore the role of in vitro stimulation with rIL-2 in the observed immune alterations reversal. Patients with stable or progressive RA were assigned to methotrexate (MTX) group or to TNF-alpha inhibitors (iTNF) group, respectively. Flow cytometric analyses were performed before and after 6 months of treatment. Circulating Th1, Th17, and Treg cells were determined before and after 72-h culture with anti-CD3 + rIL-2. Before therapy, 72-h stimulation restored recently observed phenotypic Th cell alterations, except for the enriched Th17 subset normalized as late as after therapy in all patients. Under 6-month therapy, anti-CD3 stimulation changed the Th cell distribution only in progressive RA; despite Th1 enrichment, it revealed Treg population defects, which were completely reversed by exogenous IL-2 added to the stimulating culture. Our paper shows that in aggressive RA patients exhibiting serum IL-2 shortage despite iTNF therapy, exogenous rIL-2 is capable of promoting Treg differentiation affected by chronic activation, thus supporting its use in the combined strategy of biologic treatment of the progressive form of RA.

Changes of Ocular Surface and the Inflammatory Response in a Rabbit Model of Short-Term Exposure Keratopathy

Purpose

To evaluate the ocular surface change and the inflammatory response in a rabbit model of short-term exposure keratopathy.

Methods

Short term exposure keratopathy by continuous eyelid opening was induced in New Zealand white rabbits for up to 4 hours. Ultrasound pachymetry was used to detect central total corneal thickness. In vivo confocal microscopy and impression cytology were performed to evaluate the morphology of ocular surface epithelium and the infiltration of inflammatory cells. Immunohistochemistry for macrophage,neutrophil, CD4(+) T cells, and CD8(+) T cells were performed to classify the inflammatory cells. Scanning electron microscopy(SEM) was performed to detect ocular surface change.The concentrations of IL-8, IL-17, Line and TNF-αwere analyzed by multiplex immunobead assay. TUNEL staining was performed to detect cellular apoptosis.

Results

Significant decrease ofcentral total cornealthickness were found within the first 5 minutes and remained stable thereafter, while there were no changes of corneal epithelial thickness.No significant change of corneal, limbal and conjunctival epithelial morphology was found by in vivo confocal microscopy except the time dependent increase of superficial cellular defects in the central cornea. Impression cytology also demonstrated time dependent increase of sloughing superficial cells of the central cornea. Aggregations ofinflammatory cells were found at 1 hour in the limbal epithelium, 2 hours in the perilimbal conjunctival epithelium, and 3 hours in the peripheral corneal epithelium.In eyes receiving exposure for 4 hours, the infiltration of the inflammatory cells can still be detected at 8 hours after closing eyes.Immunohistochemical study demonstrated the cells to be macrophages, neutrophils, CD4-T cells and CD-8 T cells.SEM demonstrated time-depending increase of intercellular border and sloughing of superficial epithelial cells in corneal surface. Time dependent increase of IL-8, IL-17 and TNF-α in tear was found.TUNEL staining revealed some apoptotic cells in the corneal epithelium and superficial stroma at 3 hours after exposure.

Conclusions

Short term exposure keratopathy can cause significant changes to the ocular surface and inflammatory response. Decrease of central total corneal thickness, aggregation of inflammatory cells, and cornea epithelial cell and superficial keratocyte apoptosis were found no less than 4 hours following the insult.

Female-Specific Downregulation of Tissue Polymorphonuclear Neutrophils Drives Impaired Regulatory T Cell and Amplified Effector T Cell Responses in Autoimmune Dry Eye Disease

Immune-driven dry eye disease primarily affects women; the cause for this sex-specific prevalence is unknown. Polymorphonuclear neutrophils (PMN) have distinct phenotypes that drive inflammation but also regulate lymphocytes and are the rate-limiting cell for generating anti-inflammatory lipoxin A4 (LXA4). Estrogen regulates the LXA4 circuit to induce delayed female-specific wound healing in the cornea. However, the role of PMNs in dry eye disease remains unexplored. We discovered an LXA4-producing tissue PMN population in the corneal limbus, lacrimal glands, and cervical lymph nodes of healthy male and female mice. These tissue PMNs, unlike inflammatory PMNs, expressed a highly amplified LXA4 circuit and were sex-specifically regulated during immune-driven dry eye disease. Desiccating stress in females, unlike in males, triggered a remarkable decrease in lymph node PMN and LXA4 formation that remained depressed during dry eye disease. Depressed lymph node PMN and LXA4 in females correlated with an increase in effector T cells (Th1 and Th17), a decrease in regulatory T cells (Treg), and increased dry eye pathogenesis. Ab depletion of tissue PMN abrogated LXA4 formation in lymph nodes, as well as caused a marked increase in Th1 and Th17 cells and a decrease in Tregs. To establish an immune-regulatory role for PMN-derived LXA4 in dry eye, females were treated with LXA4. LXA4 treatment markedly inhibited Th1 and Th17 and amplified Treg in draining lymph nodes, while reducing dry eye pathogenesis. These results identify female-specific regulation of LXA4-producing tissue PMN as a potential key factor in aberrant effector T cell activation and initiation of immune-driven dry eye disease.

Thrombospondin-1 as a Regulator of Corneal Inflammation and Lymphangiogenesis: Effects on Dry Eye Disease and Corneal Graft Immunology

Thrombospondin-1 (TSP-1) is a matricellular glycoprotein that belongs to a family of evolutionary highly conserved calcium-binding proteins consisting of 5 members (TSP-1-TSP-5). In the eye, TSP-1 is expressed by several ocular cell types and is also detectable in the aqueous humor and the vitreous body. So far, TSP-1 is one of the major activators of TGFβ, suggesting a strong influence on various important cellular functions and interactions such as differentiation, migration, and wound healing. TSP-1 is also a key endogenous inhibitor of hem- and lymphangiogenesis. Several lines of evidence indicate a crucial role of TSP-1 in maintaining the ocular immune and angiogenic privilege, for example, by regulating T lymphocytes and the tolerance-promoting properties of ocular antigen-presenting cells. This review discusses the role of TSP-1 in dry eye disease and corneal graft rejection through its effects on hem- and lymphangiogenesis, as well as on the underlying immune responses. Recent work will be reviewed showing by which molecular mechanism TSP-1 modulates inflammatory processes during ocular diseases. This opens potential new treatment avenues in inflammatory and (lymph)angiogenic ocular diseases.

The core mechanism of dry eye disease is inflammation

PURPOSE

The purpose of this article is to review the evidence for the hypothesis that the core mechanism of dry eye disease (DED) is inflammation, including evidence from recent basic, clinical, and translational research involving human patients, animal models, and cell cultures.

METHODS

Using the key words "dry eye + inflammation," the authors conducted a comprehensive search of the PubMed and Web of Science databases for scientific articles published in English between January 1, 1900 and August 30, 2013 on the role of inflammation in DED in cell cultures, animal models, and humans. The resulting articles were then categorized and reviewed.

RESULTS

The literature search revealed a total of 458 publications, almost all published after 1992. The percentages of original studies and review articles are 77.29% (354) and 22.71% (104), respectively. Among the original studies, the number of reports on human DED is 200 (43.7%), on animal models is 115 (25.1%), and cell cultures is 39 (8.5%). A yearly distributing plot revealed that 76% were published from 2003 to 2011, 53% from 2008 to 2012, and 11% during the first 9 months of 2013. This distribution signifies a rapidly growing awareness of the importance of inflammation in DED pathogenesis.

CONCLUSIONS

Inflammation plays a key role in the pathogenesis of DED as evidenced by research using tissue culture, animal models, and subjects with DED. Developing biomarkers for inflammation of the ocular surface will provide improved understanding of the mechanisms leading to DED, classification of the severity of DED, and objective metrics for outcome measures of treatment. The chronicity of the disease suggests that dysregulation of immune mechanisms leads to a cycle of continued inflammation, accompanied by alterations in both innate and adaptive immune responses. Given the underlying mechanism for DED, developing effective and safe anti-inflammatory treatments is likely to be beneficial for patients with DED.