Person:

Chen, Yihe

Recent experimental and clinical data suggest that there is a link between dry eye disease (DED) and T cell-mediated immunity. However, whether these immune responses are a consequence or cause of ocular surface inflammation remains to be determined. Thus far, only models of acute DED have been used to derive experimental data. This is in contrast to clinical DED which usually presents as a chronic disease. In the present study, using a murine model of chronic DED, it was established that the chronic phase of the disease is accompanied by Th17 responses at the ocular surface, and that a significant memory T cell population can be recovered from chronic DED. This memory response is predominantly mediated by Th17 cells. Moreover, adoptive transfer of this memory T cell population was shown to induce more severe and rapidly progressing DED than did the adoptive transfer of its effector or naïve counterparts. Not only do these results clearly demonstrate that effector memory Th17 cells are primarily responsible for maintaining the chronic and relapsing course of DED, but they also highlight a potentially novel therapeutic strategy for targeting memory immune responses in patients with DED.

The tear film, lacrimal glands, corneal and conjunctival epithelia and Meibomian glands work together as a lacrimal functional unit (LFU) to preserve the integrity and function of the ocular surface. The integrity of this unit is necessary for the health and normal function of the eye and visual system. Nervous connections and systemic hormones are well known factors that maintain the homeostasis of the ocular surface. They control the response to internal and external stimuli. Our and others’ studies show that immunological mechanisms also play a pivotal role in regulating the ocular surface environment. Our studies demonstrate how anti-inflammatory factors such as the expression of vascular endothelial growth factor receptor-3 (VEGFR-3) in corneal cells, immature corneal resident antigen-presenting cells, and regulatory T cells play an active role in protecting the ocular surface.

Dry eye disease (DED) affects millions of people worldwide and negatively influences the quality of life for patients. In its most severe forms, DED may lead to blindness. The etiology and pathogenesis of DED remain largely unclear. Nonetheless, in this review we summarize the role of the disruption of afferent and efferent immunoregulatory mechanisms that are responsible for the chronicity of the disease, its symptoms, and its clinical signs. We illustrate current anti-inflammatory treatments for DED and propose that prevention of the disruption of immunoregulatory mechanisms may represent a promising therapeutic strategy towards controlling ocular surface inflammation.

Abstract To compare the surgical duration and clinical outcomes of nasolacrimal recanalization versus external dacryocystorhinostomy (DCR) in the treatment of failed nasolacrimal duct intubation. This is a retrospective, comparative, and interventional study. We evaluated the outcomes of 66 consecutive patients undergoing either nasolacrimal recanalization (n = 32) or DCR (n = 34) in a tertiary lacrimal disease referral center. Length of surgical duration, clinical outcomes, and rate of recurrence at 18 months postoperatively were compared. The mean surgical duration was 18.5 minutes (range, 15–25 minutes) for nasolacrimal recanalization and 48.2 minutes (range, 45–61 minutes) for DCR, respectively (P < 0.001). The rate of success was 84.4% in the recanalization group and 85.3% in the DCR group, respectively (P = 0.91). The time to recurrence was 2.6 ± 1.1 months in the recanalization group and 5.6 ± 2.1 months in the DCR group (P < 0.001). Five failed cases in each group received a secondary DCR surgery with the same resolution rate (40%). The absence of ocular discharge at baseline was a significant predictor for a successful outcome in the recanalization group (P = 0.04) but not in the DCR group (P = 0.63). Nasolacrimal recanalization is an effective, safe, and time-saving alternative to DCR for the treatment of failed nasolacrimal duct intubation. Clinicians should be cautious in patients with discharge.

Purpose.

To determine the effect of phosphodiesterase type-4 (PDE4) inhibition on IL-17–associated immunity in experimental dry eye disease (DED).

Methods.

Murine DED was induced, after which a PDE4 inhibitor (cilomilast), dexamethasone, cyclosporine, or a relevant vehicle was administered topically. Real-time PCR, immunohistochemical staining, and flow cytometry were employed to evaluate the immuno-inflammatory parameters of DED with a focus on IL-17–associated immunity. Corneal fluorescein staining (CFS) was performed to evaluate clinical disease progression.

Results.

DED induction increased proinflammatory cytokine expression, pathogenic immune cell infiltration, and CFS scores. Cilomilast significantly decreased the expression of TNF-α in the cornea (P ≤ 0.05) and IL-1α, IL-1β, and TNF-α in the conjunctiva (P ≤ 0.05) as compared with vehicle control. Cilomilast treatment markedly decreased the presence of CD11b+ antigen-presenting cells in the central and peripheral cornea (P ≤ 0.05), and led to decreased conjunctival expression of cytokines IL-6, IL-23, and IL-17 (P ≤ 0.05). Moreover, cilomilast decreased the expression of IL-17 and IL-23 in the draining lymph nodes (P ≤ 0.05). Topical cilomilast was significantly more effective than vehicle at reducing CFS scores (P ≤ 0.05). The therapeutic efficacy of cilomilast was comparable or superior to that of dexamethasone and cyclosporine in all tested measures.

Conclusions.

Topical cilomilast suppresses the generation of IL-17–associated immunity in experimental DED.

Purpose.

A majority of experimental data on dry eye disease (DED) immunopathogenesis have been derived from a murine model of DED that combines desiccating environmental stress with systemic muscarinic acetylcholine receptor (mAChR) inhibition. However, to our knowledge the effects of pharmacologic mAChR blockade on the pathogenesis of experimental DED have not been evaluated systemically. The purpose of our study was to investigate the differential effects of desiccating environmental stress and mAChR inhibition on the pathogenesis of DED.

Methods.

DED was induced in female C57BL/6 mice by exposure to a desiccating environment in the controlled-environment chamber or to systemic scopolamine, or by performing extraorbital lacrimal gland excision. Clinical disease was assessed using corneal fluorescein staining (CFS) and the cotton thread test (CTT). Corneal CD11b+ and conjunctival CD3+ T-cell infiltration were evaluated by flow cytometry. T-cells from draining cervical lymph nodes (CLN) and distant inguinal lymph nodes (ILN) were analyzed for Th1, Th2, Th17, and Treg responses by flow cytometry and ELISA.

Results.

Desiccating environmental stress and systemic mAChR blockade induced similar clinical signs of DED. However, desiccating environmental stress imparted higher conjunctival CD3+ T-cell infiltration, and greater Th17-cell activity and Treg dysfunction than mAChR blockade, while mAChR blockade decreased tear secretion to a greater extent than desiccating environmental stress. Systemic mAChR blockade attenuated Th17 activity and enhanced Th2 and Treg responses without affecting Th1 activity.

Conclusions.

In vivo inhibition of mAChRs variably affects CD4+ T-cell subsets, and desiccating environmental stress and systemic mAChR blockade induce DED through different primary pathogenic mechanisms.

Purpose.

Th17 cells are believed to be the primary effector cells in the pathogenesis of dry eye disease (DED). However, the mechanisms by which Th17 cells migrate from the lymphoid tissues to the ocular surface are unknown. The purpose of this study was to investigate the role of the C–C chemokine receptor 6/C–C chemokine ligand 20 (CCR6/CCL20) chemokine axis in mediating Th17 cell migration in DED.

Methods.

DED was induced by housing C57BL/6 mice in a low-humidity environment supplemented with scopolamine treatment. Th17 cell expression of CCR6 was evaluated using flow cytometry and ocular surface expression of CCL20 was measured using PCR and ELISA assays. CCL20 neutralizing antibody was administered subconjunctivally to DED mice and disease severity, including the frequency of conjunctival Th17 cells, was evaluated.

Results.

CCR6 is preferentially expressed by Th17 cells in both normal and DED mice and DED significantly upregulates ocular surface expression of CCL20. Disruption of CCR6/CCL20 binding with CCL20 neutralizing antibody decreases T-cell migration in vitro and reduces Th17 cell infiltration of the conjunctiva when administered in vivo, significantly improving clinical signs of DED. These changes were accompanied by a decrease in ocular surface inflammatory cytokine levels and corneal CD11b+ cell frequencies. Treatment also significantly reduced the generation of Th17 cells.

Conclusions.

Local neutralization of CCL20 decreases Th17 cell infiltration of the ocular surface in DED, leading to improvement in clinical signs of disease. This suggests that CCR6/CCL20 interactions direct Th17 cell migration in DED and that disruption of this axis may be a novel therapeutic approach to this condition.

Purpose.

We characterized antigen-presenting cell (APC)–relevant chemokine receptor expression in dry eye disease (DED), and investigated the effect of topical CC chemokine receptor (CCR)-7 blockade specifically on Th17 cell immunity and dry eye disease severity.

Methods.

We induced DED in female C57BL/6 mice. Chemokine receptor expression by corneal APCs was characterized using immunohistochemistry. To determine the functional role of CCR7 in DED, mice were treated topically with either anti-CCR7, a control isotype antibody, or left untreated, and clinical disease severity, Th17 responses, and molecular markers of DED were quantified.

Results.

Frequencies of CD11b+ cells and their chemokine expression were increased in the cornea of DED mice. Mice treated topically with anti-CCR7 antibody displayed a significant reduction in clinical disease severity and Th17 response compared to the isotype and untreated groups. Topical CCR7 blockade was effective in ameliorating DED in its acute and chronic stages.

Conclusions.

Our findings suggest that CCR7-mediated trafficking of APCs drives the induction and maintenance of Th17 immunity in DED and that CCR7 blockade is effective in suppressing the immunopathogenic mechanisms in DED.

Purpose.

To analyze the effect of a resolvin D1 (RvD1) analogue (RvD1a) on dendritic cell maturation, T-cell sensitization, and allograft rejection in corneal allotransplantation.

Methods.

The receptor expression of RvD1 (ALX/FPR2) on bone marrow–derived dendritic cells (BMDC) was measured using quantitative real-time PCR. We determined BMDC maturation after treatment with RvD1a using ELISA to measure interleukin (IL)-12 protein expression and flow cytometry to assess the expression of CD40, major histocompatibility complex (MHC) II, CD80, and CD86. After corneal transplantation in BALB/c mice, we analyzed T-cell infiltration in the cornea and the draining lymph nodes using flow cytometry. The enzyme-linked immunospot (ELISPOT) assay was used to measure T-cell sensitization via the direct and indirect pathway. Angiogenesis and lymphangiogenesis in the cornea after transplantation were measured using immunohistochemistry. Graft opacity and survival were evaluated by slit lamp biomicroscopy.

Results.

The receptor for RvD1, lipoxin A4/formyl peptide receptor 2 (ALX/FPR2), was expressed at a significantly lower level on immature than mature dendritic cells (DCs), and RvD1a reduced DC expression of MHC II, CD40, and IL-12 following lipopolysaccharide (LPS) stimulation. Using a murine model of corneal transplantation, RvD1a-treated hosts exhibited significantly reduced allosensitization as demonstrated by decreased frequencies of interferon-gamma–secreting T cells in the draining lymph nodes, and reduced T-cell infiltration into the grafts. Graft survival was significantly enhanced and angiogenesis at the graft site was suppressed in RvD1a-treated hosts compared with vehicle-treated hosts.

Conclusions.

These results suggest that RvD1 inhibits DC maturation and reduces alloimmune sensitization following transplantation, thereby establishing a novel connection between resolvin D1 and the regulation of DC-mediated, antigen-specific immunity.

Background

Corneal allograft survival dramatically decreases in hosts with inflamed or vascularized recipient beds. We have previously shown that in rejected corneal allografts regulatory T cells (Tregs) demonstrate diminished Foxp3 expression and immunoregulatory function. Treatment with low doses of IL-2 selectively expands Tregs and has been proposed for the treatment of autoimmune diseases. In this study we investigated the effect of low-dose IL-2 administration on Treg function and corneal allograft survival.

Methods

Allogeneic corneal transplantation was performed on inflamed host beds. Low-dose systemic IL-2 was administered starting three days before grafting until six weeks after transplantation. Frequencies of Tregs as well as their immunosuppressive function and antigen specificity were assessed using flow cytometry, in vitro proliferation assays and adoptive transfer experiments. Frequencies of effector T cells (Teff) and graft infiltrating immune cells were measured at 2 weeks post-transplantation. Long-term allograft survival was evaluated for up to 9 weeks using Kaplan-Meier survival analysis.

Results

Treatment with low-dose IL-2 significantly increased frequencies of CD4+CD25+Foxp3+ Tregs and their immunosuppressive function. It also suppressed alloimmune response as shown by the decreased CD4+IFNγ+T cell frequencies and graft infiltration of CD45+ and CD4+ cells. Clinical evaluation of the grafts showed significant improvement in long-term corneal allograft survival in the IL-2 treated group compared to controls.

Conclusions

Our study is the first to report that treatment with low-dose IL-2 increases survival of corneal allografts. We propose that IL-2-mediated Treg expansion can be an effective tool to prevent alloimmunity and to improve long-term allograft survival in transplantation.

CD4+CD25+Foxp3+ Regulatory T cells (Tregs) play a critical role in immune tolerance. The plasticity and functional adaptability of Tregs in an inflammatory microenvironment has been demonstrated in autoimmunity. Here, using a double transgenic mouse model that permits Foxp3 lineage tracing, we investigated the phenotypic plasticity of Foxp3+ Tregs in a well-characterized murine model of corneal transplantation. In order to subvert the normal immune privilege of the cornea and foster an inflammatory milieu, host mice were exposed to desiccating stress prior to transplantation. Treg frequencies and function were decreased following desiccating stress, and this corresponded to decreased graft survival. A fraction of Tregs converted to IL-17+ or IFNγ+ ‘exFoxp3’ T cells that were phenotypically indistinguishable from effector Th17 or Th1 cells, respectively. We investigated how Foxp3 expression is modulated in different Treg subsets, demonstrating that neuropilin-1− peripherally-derived Tregs are particularly susceptible to conversion to IL-17+/IFNγ+ exFoxp3 cells in response to cues from their microenvironment. Finally, we show that IL-6 and IL-23 are implicated in the conversion of Tregs to exFoxp3 cells. This report demonstrates that the pathological conversion of Tregs contributes to the loss of corneal immune privilege.