Tissue resident memory T cells in the human conjunctiva and immune signatures in human dry eye disease

Characterization of T cells in the progression of dry eye disease using single-cell RNA sequencing in mice

BACKGROUND

Increasing evidence indicated that T cells have significant effects in dry eye disease (DED). However, the regulatory role of T cells in DED remains unclear.

METHODS

In this study, we examined immune responses throughout the progression in murine DED model. Using cytometry by time-of-flight (CyTOF) and single-cell RNA sequencing (scRNA-seq), we observed dynamic alterations in the proportions of immune cell landscape. Pseudotime trajectory and cell-cell communication analyses further illustrated T-cell differentiation and interaction networks.

RESULTS

CD4+ and CD8+ T cells exhibited an initial decline on Day 3 (D3) and followed by a recovery on Day 7 (D7). Single-cell transcriptomics provided insights into 15 distinct subsets of T cells with heterogeneous functional states. Pseudotime trajectory analysis demonstrated coordinated differentiation patterns of CD4+ and CD8+ T cells, indicating their collaborative involvement in the inflammatory process.

CONCLUSIONS

Our results clarify the dynamics of the adaptive immune response in DED and indicate that targeting T cells may serve as a promising immune-modulatory approach in the treatment of DED model.

Blood integrin- and cytokine-producing T cells are associated with stage and genetic risk score in age-related macular degeneration

Age-related macular degeneration (AMD) remains a leading cause of vision loss in the geriatric population. There are age-related changes in peripheral blood leukocyte composition, but their significance for AMD remains unclear. We aimed to determine changes in immune cell populations in the blood of AMD patients. A standardized 31-parameter flow cytometry analysis was conducted on peripheral blood mononuclear cells from 59 patients with early and advanced AMD and 39 controls without AMD, all older than 65 years. Fundus photography and optical coherence tomography were used to classify disease stages and a custom genotype array was used to compute an AMD genetic risk score based on 52 AMD disease risk variants (GRS-52). A generalized linear regression model corrected for age, sex, and smoking status revealed that AMD patients showed decreased frequencies of CD4+ T helper cell population expressing Integrin Alpha E (CD103) (Padj = 0.019). We further noted that early AMD was characterized by increased interleukin-4 (IL-4)-producing CD4+ T helper cells (Padj = 0.013; <0.001), as well as IL-4-producing cytotoxic CD8+ T cells (Padj = 0.016; <0.001). Reclassification of samples based on the GRS-52 revealed that IL-17-producing T cells decreased incrementally across GRS-52 categories. In AMD, alterations in peripheral blood leukocyte populations are associated with genetic risk score and disease stage and include specifically IL-4 and IL-17A cytokine-producing and CD103 integrin-expressing T cell populations.

Redefining our vision: an updated guide to the ocular immune system

Balanced immune responses in the eyes are crucial to preserve vision. The ocular immune system has long been considered distinct, owing to the so-called 'immune privilege' of its component tissues. More recently, intravital imaging and transcriptomic techniques have reshaped scientific understanding of the ocular immune landscape, such as revealing the specialization of immune cell populations in the various tissues of the eye. As knowledge of the phenotypes of corneal and retinal immune cells has evolved, links to both the systemic immune system, and the central and peripheral nervous systems, have been identified. Using intravital imaging, T cells have recently been found to reside in, and actively patrol, the healthy human cornea. Disease-associated retinal microglia with links to retinal degeneration have also been identified. This Review provides an updated guide to the ocular immune system, highlighting current knowledge of the immune cells that are present in steady-state and specific diseased ocular tissues, as well as evidence for their relationship to systemic disease. In addition, we discuss emerging intravital imaging techniques that can be used to visualize immune cell morphology and dynamics in living human eyes and how these could be applied to advance understanding of the human immune system.

Evaluation of Dry Eye Severity and Ocular Surface Inflammation in Patients with Autoimmune Rheumatic Diseases

PURPOSE

To evaluate dry eye severity and ocular surface inflammation in autoimmune rheumatic diseases (ARDs).

METHODS

Seventy-nine patients with ARDs were enrolled, including 26 patients with rheumatoid arthritis (RA), 33 patients with systemic lupus erythematosus (SLE), and 20 patients with primary Sjögren's syndrome (pSS). All patients underwent ocular surface evaluations, including ocular surface symptoms, signs, conjunctival impression cytology, and tear multicytokine detection. Systemic conditions, including disease duration, disease activity, and serological parameters, were also noted.

RESULTS

SLE patients had the shortest disease duration, and nearly half of them had low disease activity, while RA patients and pSS patients had a relatively long disease duration, and approximately 90% of them had moderate or high disease activity. The incidence of dry eye and the levels of the proinflammatory tear cytokines in SLE were significantly lower than those in RA and pSS. However, ocular surface squamous metaplasia was more severe in SLE and pSS than in RA. Dry eye severity in all ARD patients was shown to be independent of disease activity, while Nelson's grades were positively correlated with disease duration in RA patients. Disease-related serological parameters were associated with tear proinflammatory cytokines in all ARD patients.

CONCLUSIONS

Variable degrees of dry eye and immune-mediated ocular surface inflammation persist in different ARD patients. In addition to a well-known association between dry eye and pSS, dry eye is also commonly observed in SLE and RA patients. Therefore, there is a definite need for regular ophthalmologic evaluations and topical medications in all patients with ARDs.

Changes in conjunctival mononuclear phagocytes and suppressive activity of regulatory macrophages in desiccation induced dry eye

PURPOSE

To evaluate the effects of dry eye on conjunctival immune cell number and transcriptional profiles with attention to mononuclear phagocytes.

METHODS

Expression profiling was performed by single-cell RNA sequencing on sorted conjunctival immune cells from non-stressed and C57BL/6 mice subjected to desiccating stress (DS). Monocle 3 modeled cell trajectory, scATAC-seq assessed chromatin accessibility and IPA identified canonical pathways. Inflammation and goblet cells were measured after depletion of MRC1+ MΦs with mannosylated clodronate liposomes.

RESULTS

Mononuclear phagocytes (monocytes, MΦs, DCs) comprised 72 % of immune cells and showed the greatest changes with DS. Distinct DS induced gene expression patterns were seen in phagocytes classified by expression of Ccr2 and [Timd4, Lyve1, Folr2 (TLR)]. Expression of phagocytosis/efferocytosis genes increased in TLF+CCR2- MΦs. Monocytes showed the highest expression of Ace, Cx3cr1, Vegfa, Ifngr1,2, and Stat1 and TLF-CCR2+ cells expressed higher levels of inflammatory mediators (Il1a, Il1b, Il1rn, Nfkb1, Ccl5, MHCII, Cd80, Cxcl10, Icam1). A trajectory from monocyte precursors branched to terminate in regulatory MΦs or in mDCs via transitional MΦ and cDC clusters. Activated pathways in TLF+ cells include phagocytosis, PPAR/RXRα activation, IL-10 signaling, alternate MΦ activation, while inflammatory pathways were suppressed. Depletion of MRC1+ MΦs increased IL-17 and IFN-γ expression and cytokine-expressing T cells, reduced IL-10 and worsened goblet loss.

CONCLUSIONS

Dryness stimulates distinct gene expression patterns in conjunctival phagocytes, increasing expression of regulatory genes in TLF+ cells regulated in part by RXRα, and inflammatory genes in CCR2+ cells. Regulatory MΦs depletion worsens DS induced inflammation and goblet cell loss.

Revolutionizing type 1 diabetes management: Exploring oral insulin and adjunctive treatments

Type 1 diabetes (T1D) is a chronic autoimmune condition that affects millions of people worldwide. Insulin pumps or injections are the standard treatment options for this condition. This article provides a comprehensive overview of the several type 1 diabetes treatment options, focusing on oral insulin. The article is divided into parts that include immune-focused treatments, antigen vaccination, cell-directed interventions, cytokine-directed interventions, and non-immunomodulatory adjuvant therapy. Under the section on non-immunomodulatory adjunctive treatment, the benefits and drawbacks of medications such as metformin, amylin, sodium-glucose cotransporter inhibitors, glucagon-like peptide-1 receptor agonists (GLP-1 Ras), and verapamil are discussed. The article also discusses the advantages of oral insulin, including increased patient compliance and more dependable and regular blood sugar control. However, several variables, including the enzymatic and physical barriers of the digestive system, impair the administration of insulin via the mouth. Researchers have looked at a few ways to get over these challenges, such as changing the structure of the insulin molecule, improving absorption with the use of absorption enhancers or nanoparticles, and taking oral insulin together with other medications. Even with great advancements in the use of these treatment strategies, T1D still needs improvement in the therapeutic difficulties. Future studies in these areas should focus on creating tailored immunological treatments, looking into combination medications, and refining oral insulin formulations in an attempt to better control Type 1 Diabetes. The ultimate objective is to create accurate, customized strategies that will enhance glycemic management and the quality of life for individuals with the condition.

Mass cytometry reveals the corneal immune cell changes at single cell level in diabetic mice

Introduction

Diabetic ocular complications include sight-threatening consequences and decreased corneal sensitivity, characterized by decreased tear production, corneal sensitivity and delayed corneal epithelial wound healing. The pathogenesis of diabetic corneal disorders remains largely unknown. Growing evidence implies the participation of immune cells in the development of diabetic corneal diseases. Nonetheless, the immunological changes that result in diabetic corneal problems are largely unknown.

Methods

Mass cytometry by time of flight (CyTOF) was used to investigate immune cell cluster alterations associated with diabetic corneal disorders. CyTOF test was performed on corneal cells at a single level from 21-week-old diabetic (db/db) and non-diabetic (db/m) mice. A panel of 41 immune-related markers monitored different immune cell types in diabetic corneas. To investigate the proportion of each immune cell subpopulation, an unsupervised clustering method was employed, and T-distributed stochastic neighbor embedding was used to visualize the distinctions between different immune cell subsets.

Results

Through CyTOF test, we identified 10 immune cell subsets in the corneal tissues. In a novel way, we discovered significant immune alterations in diabetic corneas, including pronounced alterations in T cells and myeloid cell subgroups in diabetic corneas linked to potential biomarkers, including CD103, CCR2, SiglecF, Ly6G, and CD172a. Comprehensive immunological profiling indicated remarkable changes in the immune microenvironment in diabetic corneas, characterized by a notable decrease in CD103+CD8+ tissue-resident memory T (TRM) cells and Tregs, as well as a dramatic increase of γδT cells and subsets of CD11b+Ly6G+ myeloid-derived suppressor cells (MDSCs).

Conclusion

CyTOF analysis revealed significant alterations in the immune microenvironment during the development of diabetic corneal complications. This study mapped the immune microenvironment landscape of type 2 diabetic corneas, providing a fundamental understanding of immune-driven diabetic corneal disorders.

Association of Ocular Surface Immune Cells With Dry Eye Signs and Symptoms in the Dry Eye Assessment and Management (DREAM) Study

Purpose

Dry eye disease (DED) is a multifactorial, heterogeneous disease of the ocular surface with one etiology being ocular surface inflammation. Studies using animal models demonstrate the role of ocular surface immune cells in the inflammatory pathway leading to DED, but few have evaluated humans. This study described the white blood cell population from the ocular surface of patients with DED and assessed its association with DED signs and symptoms in participants of the Dry Eye Assessment and Management (DREAM) study.

Methods

Participants were assessed for symptoms using the Ocular Surface Disease Index, signs via corneal staining, conjunctival staining, tear break-up time, and Schirmer test, and Sjögren's syndrome (SS) based on the 2012 American College of Rheumatology classification criteria. Impression cytology of conjunctival cells from each eye was evaluated using flow cytometry: T cells, helper T cells (Th), regulatory T cells (Tregs), cytotoxic T cells, and dendritic cells.

Results

We assessed 1049 eyes from 527 participants. White blood cell subtype percentages varied widely across participants. Significant positive associations were found for Th and conjunctival staining (mean score of 2.8 for 0% Th and 3.1 for >4.0% Th; P = 0.007), and corneal staining (mean score of 3.5 for 0% Th and 4.3 for >4.0% Th; P = 0.01). SS was associated with higher percent of Tregs (median 0.1 vs. 0.0; P = 0.01).

Conclusions

Th were associated with more severe conjunctival and corneal staining, possibly indicating their role in inflammation leading to damage of the ocular surface. There is no consistent conclusion about Tregs in SS, but these results support that Tregs are elevated in SS.

Conjunctival T Cell Profile in Allogeneic Hematopoietic Stem Cell Transplant Patients after Instilling Topical Cyclosporine-A 0.1% Cationic Emulsion

INTRODUCTION

To profile conjunctival T cell populations in allogeneic hematopoietic stem cell transplant (HSCT) patients after instillation of daily topical cyclosporine-A (CsA) 0.1% cationic emulsion (Ikervis), and to evaluate patients' tolerance to these eye drops.

METHODS

Nineteen participants were prescribed Ikervis prophylaxis once daily to both eyes from 3-5 weeks pre-HSCT to 12 months post-HSCT. The outcome measure was conjunctival T cell proportions from flow cytometry after impression cytology. Covariates included visual acuity, intraocular pressure, slit lamp and fundal examination, dry eye (SPEED) and quality of life questionnaires, non-invasive keratograph tear break-up time (NIKBUT), conjunctival redness, meibography, lipid thickness, Schirmer test, tear cytokines, fluorescein staining, tear osmolarity, and meibomian gland expressibility.

RESULTS

The conjunctival T cell analysis showed either stable or decreased proportions of conjunctival CD4 T cells at the last visit from baseline in compliant patients. CD4 proportions were increased in non-compliant patients and in the single patient who developed ocular graft-versus-host disease (GVHD). All patients were tolerant to Ikervis but 6/19 were not compliant. In the majority of patients, vision did not affect activities of daily living. Pre- and post-HSCT up to the last study visit, there was no statistically significant change in clinical covariates. Only one participant developed ocular GVHD at 9 months post-HSCT.

CONCLUSION

Superficial conjunctival T cell profile reflects compliance to daily topical Ikervis eye drops and clinical ocular surface parameters in allogenic HSCT patients. Tolerance is comparable to other formulations of topical CsA in the first 12 months.

CLINICALTRIALS

GOV IDENTIFIER

NCT04636918. URL: https://clinicaltrials.gov/ct2/show/NCT04636918?cond=ocular+Graft+Versus+Host+Disease&cntry=SG&draw=2&rank=2 .

Peripheral blood immune cell profiling of acute corneal transplant rejection

Acute rejection (AR) of corneal transplants (CT) has a profound effect on subsequent graft survival but detailed immunological studies in human CT recipients are lacking. In this multi-site, cross-sectional study, clinical details and blood samples were collected from adults with clinically diagnosed AR of full-thickness (FT)-CT (n = 35) and posterior lamellar (PL)-CT (n = 21) along with Stable CT recipients (n = 177) and adults with non-transplanted corneal disease (n = 40). For those with AR, additional samples were collected 3 months later. Immune cell analysis was performed by whole-genome microarrays (whole blood) and high-dimensional multi-color flow cytometry (peripheral blood mononuclear cells). For both, no activation signature was identified within the B cell and T cell repertoire at the time of AR diagnosis. Nonetheless, in FT- but not PL-CT recipients, AR was associated with differences in B cell maturity and regulatory CD4⁺ T cell frequency compared to stable allografts. These data suggest that circulating B cell and T cell subpopulations may provide insights into the regulation of anti-donor immune response in human CT recipients with differing AR risk. Our results suggest that, in contrast to solid organ transplants, genetic or cellular assays of peripheral blood are unlikely to be clinically exploitable for prediction or diagnosis of AR.

Ocular Surface Immune Cell Profiles in Contact Lens-Induced Discomfort

Purpose

Contact lens–induced discomfort (CLD) remains a primary factor in discontinuation or prevention of contact lens wear. Thus, we investigated the role of ocular surface immune cells in subjects with CLD.

Methods

Habitual contact lens (CL) wearers with CLD (n = 19; 38 eyes) and without CLD (n = 21; 42 eyes) as determined by the Contact Lens Dry Eye Questionnaire-8 was included in a trial. Enrolled subjects used either of the two types of CL (designated as CL-A or CL-D). Ocular surface cells from the bulbar conjunctiva were obtained by impression cytology. The collected cells were phenotyped using fluorochrome-conjugated antibodies specific for leukocytes (CD45⁺), neutrophils (CD66b^+,High,Low), macrophages (CD163⁺), T cells (CD3⁺CD4⁺, CD3⁺CD8⁺), natural killer (NK) cells (CD56^{+, High, Low}), natural killer T (NKT) cells (CD3⁺CD56⁺), and gamma delta T (γδT) cells (CD3⁺γδTCR⁺) by flow cytometry. Further, corneal dendritic cell density (cDCD) was also determined using in vivo confocal microscopy.

Results

Significantly higher proportions of CD45⁺ cells were observed in subjects with CLD compared to those without CLD. The percentages of CD66b^Total,Low, CD163⁺, pan T cells, CD4⁺T cells, CD8⁺T cells, CD56^{Total,High,Low} (NK) cells, and NKT cells, as well as the CD4/CD8 ratio, were significantly higher in CLD subjects. The proportion of T cells (CD4, CD8, CD4/CD8 ratio, NKT cells) and macrophages exhibited a direct association with discomfort score. The percentages of CD45⁺, CD66b^Total,Low, CD163⁺, CD3⁺, CD56^{Total,High,Low}, and NKT cells and cDCD were significantly higher in CLD subjects wearing CL-D. The percentages of CD66b^High, CD4⁺T cells, CD8⁺T cells, NKT cells, and CD4/CD8 ratio were significantly higher in CLD subjects wearing CL-A.

Conclusions

Increased proportions of ocular surface immune cells are observed in CLD, and the lens type could impact the immune cells associated with CLD.

Translational Relevance

The association between the proportion of altered ocular surface immune cell subsets and contact lens–induced discomfort underpins the importance of considering immune-related aspects during contact lens development and in the clinical management of ocular surface pain.

Corneal tissue-resident memory T cells form a unique immune compartment at the ocular surface

The eye is considered immune privileged such that immune responses are dampened to protect vision. As the most anterior compartment of the eye, the cornea is exposed to pathogens and can mount immune responses that recruit effector T cells. However, presence of immune memory in the cornea is not defined. Here, we use intravital 2-photon microscopy to examine T cell responses in the cornea in mice. We show that recruitment of CD8⁺ T cells in response to ocular virus infection results in the formation of tissue-resident memory T (T_RM) cells. Motile corneal T_RM cells patrol the cornea and rapidly respond in situ to antigen rechallenge. CD103⁺ T_RM cell generation requires antigen and transforming growth factor β. In vivo imaging in humans also reveals highly motile cells that patrol the healthy cornea. Our study finds that T_RM cells form in the cornea where they can provide local protective immunity.

Molecular Characteristics and Distribution of Adult Human Corneal Immune Cell Types

Background

The limbus is located at a 2-mm-wide area between the bulbar conjunctiva and the cornea and has been suggested to be the niche of corneal epithelial stem cells and immune cells. Like the skin and intestines, the cornea is also an important mucosal surface, and immune cells on the cornea play critical roles in immune surveillance to ensure barrier surface homeostasis and protection from various environmental damage and infections. Single-cell RNA sequencing (scRNA-seq) analysis of protein tyrosine phosphatase receptor type C positive (PTPRC⁺) hematopoietic cells from the corneal limbus could provide a single cell atlas of all the immune cell subsets.

Methods

We performed single-cell RNA sequencing to generate transcriptomic profile for 804 sort-purified hematopoietic cells from the corneal limbus of three healthy donors.

Results

Our analysis identified a primary transcriptomic pattern for multiple immune cell subtypes, including naive T cells, antiviral effector CD8⁺ T cells, and innate immune cells such as IDO1⁺ mature regulatory dendritic cells (mregDCs), macrophages, monocytes, and basophils in the human corneal limbus.

Conclusion

Overall, single-cell transcriptomic analysis of limbal immune cells suggested the possible contribution of these cells on the adaptive and innate immune response of the human cornea.

Tissue resident memory T cells inhabit the deep human conjunctiva

Mucosal linings of the body, including the conjunctiva, are enriched in tissue-resident memory T cells (T_RMs) whose defining feature is their continual tissue protection that does not rely on migration to lymphoid organs to elicit immune responses. Hitherto, conjunctival T_RMs have only been identified in the superficial epithelium. This work aims to develop a more complete understanding of the conjunctival immunological capacity by investigating the presence of T_RMs within the deeper, more stable layers of the healthy human conjunctiva. Using immunofluorescence microscopy and antibodies against CD3, CD4, CD69 and HLA-DR on bulbar conjunctival biopsies obtained from 7 healthy adults (age range = 32-77 years; females = 4), we identified CD69⁺T_RM subsets in all layers of the human conjunctiva: the superficial epithelium, the basal epithelium, the adenoid, and the fibrous layers. Interestingly, the adenoid layer showed significantly higher densities of both CD4 and CD8 T_RMs when compared to the fibrous layer and conjunctival epithelia. Additionally, CD4 T_RMs predominated significantly over CD8 T_RMs in the adenoid layer. The abundance of deep conjunctival CD69⁺T_RMs within the healthy human may suggest the presence of defence mechanisms capable of inducing long-term immunogenic memory. Understanding this spatial distribution of conjunctival CD69⁺T_RMs is essential to improving mucosal vaccine design.

Altered ocular surface immune cell profile in patients with dry eye disease

PURPOSE

Aberrant inflammation and immune dysregulation are known pathogenic contributors in dry eye disease (DED). Aim of the study was to determine the proportions of immune cell subsets on the ocular surface (OS) of DED patients.

METHODS

15 healthy controls (22 eyes) and 48 DED subjects (36 eyes with evaporative DED - EDED; 60 eyes with aqueous deficient DED - ADED) were included in the study. Tear break up time (TBUT), Schirmer's test 1 (ST1), corneal staining (CS) and ocular surface disease index (OSDI) scoring were recorded. OS wash was used to collect immune cells on the OS of study subjects. The cells immunophenotyped using flow cytometry include leukocytes, neutrophils, macrophages, natural killer-NK cells and T cell subsets (CD4; CD8; double positive-DP; gamma delta-γδ and NK T cells).

RESULTS

Significantly higher proportions of leukocytes, neutrophils, CD4 T cells, CD8 T cells, DP T cells and CD4/CD8 T cells ratio were observed in EDED and/or ADED patients. Significantly higher proportions of neutrophils and lower proportions of NK cells were observed in ADED subjects with corneal staining compared to those without and controls. Neutrophils/NK cells ratio was significantly higher in EDED and ADED subjects compared to controls. Correlation analysis revealed pathological relationships between proportions of leukocytes, neutrophils, CD4 T cells and Neutrophil/NK cells ratio with DED clinical parameters.

CONCLUSION

OS immune cell subset proportion changes in DED patients were associated with DED types and severity. The data suggests the potential for a new generation of therapies targeting immune cells on the ocular surface.

The ocular surface immune system through the eyes of aging

Since the last century, advances in healthcare, housing, and education have led to an increase in life expectancy. Longevity is accompanied by a higher prevalence of age-related diseases, such as cancer, autoimmunity, diabetes, and infection, and part of this increase in disease incidence relates to the significant changes that aging brings about in the immune system. The eye is not spared by aging either, presenting with age-related disorders of its own, and interestingly, many of these diseases have immune pathophysiology. Being delicate organs that must be exposed to the environment in order to capture light, the eyes are endowed with a mucosal environment that protects them, the so-called ocular surface. As in other mucosal sites, immune responses at the ocular surface need to be swift and potent to eliminate threats but are at the same time tightly controlled to prevent excessive inflammation and bystander damage. This review will detail how aging affects the mucosal immune response of the ocular surface as a whole and how this process relates to the higher incidence of ocular surface disease in the elderly.

Cluster Analysis of Dry Eye Disease Models Based on Immune Cell Parameters - New Insight Into Therapeutic Perspective

Dry eye disease (DED) can be represented as a display of disease in the mucosal part of the eye. It is quite distinct from the retinal side of the eye which connects with the neurons and thus represents the neuroimmunological disease. DED can occur either by the internal damage of the T cells inside the body or by microbial infections. Here we summarize the most common animal model systems used for DED relating to immune factors. We aimed to identify the most important immune cell/cytokine among the animal models of the disease. We also show the essential immune factors which are being tested for DED treatment. In our results, both the mechanism and the treatment of its animal models indicate the involvement of Th1 cells and the pro-inflammatory cytokine (IL-1β and TNF-α) related to the Th1-cells. The study is intended to increase the knowledge of the animal models in the field of the ocular surface along with the opening of a dimension of thoughts while designing a new animal model or treatment paradigm for ocular surface inflammatory disorders.

Short-Term Changes in Tear Lipid Layer Thickness After Instillation of Lipid Containing Eye Drops

Purpose

Lipid-containing eye drops is increasingly popular in eye clinics to treat dry eye. Tear lipid layer thickness (LLT) changes after instillation of lipid eye drops have not been characterized. We aim to evaluate these changes of LLT using a noninvasive interferometry-based method.

Methods

This prospective clinical study was conducted on staff and patients from Singapore National Eye Centre with ad hoc recruitment. Noninvasive tear break up time was measured using the Keratographer 5M. LLTs were measured using a tear interferometer machine before and at 1, 5, and 15 minutes after instillation of lipid-containing drops, either Cationorm unidose or Artelac Lipids. Fluorescein clearance (tear clearance rate) and Schirmer tests were conducted. The tear clearance rate of fluorescein dye was based on the visual examination of the color of a Schirmer strip after 5 minutes, compared against color standards.

Results

This study included a total of 84 participants aged ≥21 years. Many were female (92.8%) and Chinese (89.2%). A tear clearance rate of 1/16 was most common (35.7%), whereas 1/128 and 1/32 were uncommon (3.57% each). Schirmer results were 6.5 ± 8.1 mm, and noninvasive tear break up times were 8.12 ± 6.25 mm. Participants with baseline LLT <60 nm had greater changes in LLT after Cationorm instillation, compared with those with an LLT of >60 nm. LLT changes over 15 minutes were not associated with tear clearance rate. Similar results were obtained when using Artelac Lipids.

Conclusions

Our results showed that participants' initial LLT affected their responsiveness to lipid-containing eye drops more than other factors.

Translational Relevance

Doctors may choose to measure the baseline LLT of patients before deciding whether to prescribe lipid eye drops to patients.

Antigen-presenting cells in ocular surface diseases

PURPOSE

To review the role of antigen-presenting cells (APC) in the pathogenesis of ocular surface diseases (OSD).

METHODS

A thorough literature search was performed in PubMed database. An additional search was made in Google Scholar to complete the collected items.

RESULTS

APCs have the ability to initiate and direct immune responses and are found in most lymphoid and non-lymphoid tissues. APCs continuously sample their environment, present antigens to T cells and co-ordinate immune tolerance and responses. Many different types of APCs have been described and there is growing evidence that these cells are involved in the pathogenesis of OSD. OSD is a complex term for a myriad of disorders that are often characterized by ocular surface inflammation, tear film instability and impairment of vision.

CONCLUSIONS

This review summarizes the current knowledge concerning the immunotopographical distribution of APCs in the normal ocular surface. APCs appear to play a critical role in the pathology of a number of conditions associated with OSD including infectious keratitis, ocular allergy, dry eye disease and pterygium.

The Innate Immune Cell Profile of the Cornea Predicts the Onset of Ocular Surface Inflammatory Disorders

Ocular surface inflammatory disorder (OSID) is a spectrum of disorders that have features of several etiologies whilst displaying similar phenotypic signs of ocular inflammation. They are complicated disorders with underlying mechanisms related to several autoimmune disorders, such as rheumatoid arthritis (RA), Sjögren’s syndrome, and systemic lupus erythematosus (SLE). Current literature shows the involvement of both innate and adaptive arms of the immune system in ocular surface inflammation. The ocular surface contains distinct components of the immune system in the conjunctiva and the cornea. The normal conjunctiva epithelium and sub-epithelial stroma contains resident immune cells, such as T cells, B cells (adaptive), dendritic cells, and macrophages (innate). The relative sterile environment of the cornea is achieved by the tolerogenic properties of dendritic cells in the conjunctiva, the presence of regulatory lymphocytes, and the existence of soluble immunosuppressive factors, such as the transforming growth factor (TGF)-β and macrophage migration inhibitory factors. With the presence of both innate and adaptive immune system components, it is intriguing to investigate the most important leukocyte population in the ocular surface, which is involved in immune surveillance. Our meta-analysis investigates into this with a focus on both infectious (contact lens wear, corneal graft rejection, Cytomegalovirus, keratitis, scleritis, ocular surgery) and non-infectious (dry eye disease, glaucoma, graft-vs-host disease, Sjögren’s syndrome) situations. We have found the predominance of dendritic cells in ocular surface diseases, along with the Th-related cytokines. Our goal is to improve the knowledge of immune cells in OSID and to open new dimensions in the field. The purpose of this study is not to limit ourselves in the ocular system, but to investigate the importance of dendritic cells in the disorders of other mucosal organs (e.g., lungs, gut, uterus). Holistically, we want to investigate if this is a common trend in the initiation of any disease related to the mucosal organs and find a unified therapeutic approach. In addition, we want to show the power of computational approaches to foster a collaboration between computational and biological science.

Spatial Distribution of Noninvasive Break Up Times and Clinical Relevance in Healthy Participants and Mild Dry Eye

Purpose

Noninvasive keratograph break up times (NIKBUTs) are preferred to dye-based methods to evaluate tear stability in translational medicine. We analyzed the NIKBUTs in different regions of the precorneal tear by using a common imaging technology and explored potential correlations with clinical parameters.

Methods

We tested NIKBUTs of 120 participants (62.5% females, aged 61.0 ± 13.8 years) with the Keratograph 5M, with standardized symptoms, ocular surface evaluation, and tear lipid layer interferometry. NIKBUTs were obtained from color maps in up to 165 spatial zones corresponding to 7 concentric rings.

Results

The lowest NIKBUT of tested zones averaged 7.8 ± 7.4 seconds (median, 4.5; range, 1.5–24 seconds), with the lowest NIKBUT measuring <2 seconds in many inferior zones. A mean of 5 zones had broken up by 2 seconds compared to a mean of about 50 zones by 10 seconds. NIKBUTs in specific inferior peripheral zones were significantly directly correlated to tear lipid thicknesses. The receiver operating characteristics for detecting reduced tear lipid thickness were better than overall NIKBUTs for participants with readings in these zones. Weaker correlations of NIKBUTs with symptoms were observed in two other zones. Overall, the NIKBUT displayed by keratograph was not significantly associated with any clinical parameters.

Conclusions

Decreased NIKBUTs in specific peripheral locations may be associated with lower lipid thicknesses. Future measurements of NIKBUTs should ideally be determined in smaller defined zones than current maps.

Translational Relevance

An understanding of how to evaluate tear stability allows a more robust clinical evaluation of new drugs and medical devices for dry eye.

Update on the role of impression cytology in ocular surface disease

Understanding of the molecular pathology of ocular surface disease (OSD) is poor, and treatment is highly unsatisfactory. To facilitate treatment of OSD, a relatively noninvasive procedure, i.e. impression cytology (IC) has been shown to be useful. Recently, the technologies employed in research studies using IC in OSD have vastly improved, and standardized IC has even been used in clinical trials of dry eye. Here, this review aims to describe the advances of IC in the last 10 years, which serves as an update on the progress in this field since the last major review of IC. OSD that has been recently evaluated include meibomian gland dysfunction, Sjogren's syndrome, Steven–Johnson syndrome, and postmenopausal dry eye. The recent studies (4 longitudinal, 18 cross-sectional analyses) which utilized IC analyzed DNA, RNA, proteins, and ocular surface cells, including memory T-lymphocytes, dendritic cells (DCs), neutrophils, conjunctival epithelial cells, and goblet cells. These studies employed quantification of transcripts associated with inflammation, proteins involved in oxidative stress, enzymes such as matrix metalloproteinases, and cell surface proteins by flow cytometry, such as HLA-DR, cytokine and chemokine receptors, markers for T cell differentiation, and DC activation, in addition to the more traditional morphological evaluation of squamous metaplasia and staining for goblet cells. Some challenges in the clinical use of IC have also been described, including issues related to storage and normalization of data. In summary, advances in IC have permitted a more robust evaluation of the ocular surface and will facilitate progress in the understanding and treatment of OSD.

Role of immune cells in the ocular manifestations of pemphigoid diseases

Pemphigoid disease is classified according to the phenotypical location of the disease and the presence of different types of antibodies. The ocular distribution of pemphigoid mainly occurs in patients with bullous pemphigoid and mucous membrane pemphigoid. Several immune cells, including the cells of the innate immune system (neutrophils and γδ T cells) and the adaptive immune system (T and B cells), are involved in pemphigoid disease. The treatment of pemphigoid is still wide-ranging, and the most utilized treatment is the use of immunosuppressants and corticosteroids. In this scenario, it is absolutely important to screen the immune cells that are involved in this group of diseases and to determine if a targeted treatment approach is plausible. In conclusion, this review will identify some newer treatment possibilities for the whole spectrum of pemphigoid diseases.

Review of Biomarkers in Ocular Matrices: Challenges and Opportunities

Biomarkers provide a powerful and dynamic approach to improve our understanding of the mechanisms underlying ocular diseases with applications in diagnosis, disease modulation or for predicting and monitoring of clinical response to treatment. Defined as measurable indicator of normal or pathological processes, biomarker evaluation has been used extensively in drug development within clinical settings to better comprehend effectiveness of treatment in ocular diseases. Biomarkers in the eye have the advantage of access to multiple ocular matrices via minimally invasive methods. Repeat sampling for biomarker assessment has enabled reproducible objective measures of disease process or biological responses to a drug treatment. This review describes the usage of biomarkers with respect to four commonly sampled ocular matrices in clinic: tears, conjunctiva, aqueous humor and vitreous. Issues that affect the evaluation of biomarkers are discussed along with opportunities to leverage biomarkers such that ultimately, they can be used for customized targeted therapy.

Ion channels as therapeutic antibody targets

It is now well established that antibodies have numerous potential benefits when developed as therapeutics. Here, we evaluate the technical challenges of raising antibodies to membrane-spanning proteins together with enabling technologies that may facilitate the discovery of antibody therapeutics to ion channels. Additionally, we discuss the potential targeting opportunities in the anti-ion channel antibody landscape, along with a number of case studies where functional antibodies that target ion channels have been reported. Antibodies currently in development and progressing towards the clinic are highlighted.

Resident-Memory T Cells in Tissue-Restricted Immune Responses: For Better or Worse?

Tissue-resident-memory CD8+ T cells (T_RM) have been described as a non-circulating memory T cell subset that persists at sites of previous infection. While T_RM in all non-lymphoid organs probably share a core signature differentiation pathway, certain aspects of their maintenance and effector functions may vary. It is well-established that T_RM provide long-lived protective immunity through immediate effector function and accelerated recruitment of circulating immune cells. Besides immune defense against pathogens, other immunological roles of T_RM are less well-studied. Likewise, evidence of a putative detrimental role of T_RM for inflammatory diseases is only beginning to emerge. In this review, we discuss the protective and harmful role of T_RM in organ-specific immunity and immunopathology as well as prospective implications for immunomodulatory therapy.

Epidermal Fatty Acid-Binding Protein: A Novel Marker in the Diagnosis of Dry Eye Disease in Sjögren Syndrome

Purpose: Sjögren syndrome (SS) is a chronic inflammatory autoimmune disease of the lacrimal and salivary glands. This study compared the concentrations of epidermal fatty-acid binding protein (E-FABP) in the saliva, serum, and tears of SS patients with dry eye and dry mouth, with those of healthy adults to investigate the usefulness of E-FABP as a diagnostic marker for SS. Design: Prospective, observational case series. Participants: The subjects were 11 new patients with untreated Sjogren syndrome and 12 healthy control individuals. Methods: The diagnosis of SS was in accordance with the Ministry of Health, Labour and Welfare (Japan) Diagnostic Criteria (1999). Saliva, serum, and tear specimens were collected during internal medicine, dental, and ophthalmological examinations. The ophthalmological tests included the Dry Eye-related Quality of life Score (DEQS), tear break-up time (BUT), vital staining with fluorescein (FS) and lissamine green (LG), and the Schirmer test-1. The E-FABP concentration in the tears, saliva, and serum was measured by enzyme-linked immunosorbent assay (ELISA). Main outcome measure: The E-FABP concentrations were compared between patients and controls. Results: There were significant differences between the patient and healthy control groups in all ophthalmological test results. There were no significant differences between the groups in the E-FABP concentrations in the saliva (p = 0.1513) or the serum (p = 0.4799), but the E-FABP concentration in the tears significantly differed between groups. The E-FABP concentration in tears tended to be significantly lower in patients with SS (mean, 323.5 ± 325.6 pg/mL) than healthy control subjects (mean, 4076 pg/mL; p = 0.0136). The E-FABP concentration in tears significantly correlated with the results of dry eye parameters. Conclusion: The E-FABP concentration in tears appears to be related to ocular surface epithelial damage and tear stability and may be a promising novel biomarker in the diagnosis of SS.

Innate and Adaptive Cell Populations Driving Inflammation in Dry Eye Disease

Dry eye disease (DED) is the most common ocular disease and affects millions of individuals worldwide. DED encompasses a heterogeneous group of diseases that can be generally divided into two forms including aqueous-deficient and evaporative DED. Evidence suggests that these conditions arise from either failure of lacrimal gland secretion or low tear film quality. In its secondary form, DED is often associated with autoimmune diseases such as Sjögren's syndrome and rheumatoid arthritis. Current treatment strategies for DED are limited to anti-inflammatory medications that target the immune system as the source of deleterious inflammation and tissue injury. However, there is a lack of understanding of the underlying pathogenesis of DED, and subsequently, there are very few effective treatment strategies. The gap in our knowledge of the etiology of primary DED is in part because the majority of research in DED focused on secondary autoimmune causes. This review focuses on what is currently understood about the contribution of innate and adaptive immune cell populations in the pathogenesis of DED and highlights the need to continue investigating the central role of immunity driving DED.

Leukocyte Distribution in the Open Eye Tears of Normal and Dry Eye Subjects

PURPOSE

Leukocytes accumulate in the eye with sleep, but little is known about the presence or absence of leukocytes in awake, open eye tears. This study sought to compare normal and dry eye subjects for daily variation in open eye leukocyte composition.

MATERIALS AND METHODS

Ten normal subjects and nine dry eye subjects were enrolled. Subjects were trained for self-collection of tear samples using an ocular surface wash with 5 mL of phosphate buffered saline per eye. Subjects performed washes at awakening, between 8 and 9 am, between 11 am and 12 pm, and between 4 pm and 5 pm on four separate days. Leukocytes were isolated from the wash and were counted with a cell counter before staining with an anti-CD45 antibody and viability stain. Stained leukocytes were then analyzed via flow cytometry. Side scatter characteristics were used to distinguish granulocytes from lymphocytes. Results were interpreted both by time of wash as well as time from awakening.

RESULTS

At awakening, dry eye subjects had approximately twice as many recovered leukocytes and had a statistically significantly higher granulocyte-to-lymphocyte ratio as compared to normals. Leukocytes were rapidly cleared from the eye with a significant decrease in leukocyte counts at the 8 am time point as compared to awakening. Leukocyte counts across all open eye time points appeared to be consistent, with no differences between normal and dry eye subjects.

CONCLUSIONS

There is a low level, constitutively expressed population of leukocytes in the open eye tears of normal and dry eye subjects. Higher levels of granulocytes in dry eye disease subjects warrants further investigation into this population of cells, and their role in homeostasis and dysregulation.

Altered expression level of inflammation-related genes and long-term changes in ocular surface after trabeculectomy, a prospective cohort study

PURPOSE

We aim to evaluate changes in the ocular surface in a cohort of post-trabeculectomy patients and whether these were associated with conjunctival inflammatory gene expression.

METHODS

This is a single-arm interventional cohort performed in a tertiary referral center. These were assessed: dry eye symptom questionnaire, tear osmolarity, Schirmer's test, non-invasive tear break up time (BUT), conjunctival redness and corneal fluorescein staining evaluation. Conjunctival impressions were performed using Eyeprim, and after RNA extraction, transcripts of 255 inflammatory genes were analysed using the Nanostring nCounter assay.

RESULTS

Thirty three patients were recruited with age 66.88 ± 9.76 at baseline, with a predominance of men. There was a significant decrease in inferior corneal staining at 6 months (p < 0.05) (n = 22) and significant decrease in tear osmolarity at 12 months (p < 0.01) (n = 27). No patient required glaucoma eyedrops post-surgery up to 3 years. At baseline 31/33 transcript profiles passed the quality control, and after normalization, 249 transcripts were subsequently analysed. Increased discomfort was associated with higher Protein Tyrosine Kinase-2 at the cross-sectional analysis at baseline. Lower baseline complement factor-D and higher levels of Mitogen associated kinase-8, MAP3K1 and MyD88, were associated with presence of corneal staining at 6 months. Nine genes, including the proinflammatory lipo-oxygenase (ALOX5) showed a significantly reduced level at 3 years (n = 5).

CONCLUSIONS

Glaucoma surgery may confer long term beneficial effect on the ocular surface, if anti-glaucoma eyedrops are no longer necessary. This may be due to reduced expression of conjunctival proinflammatory genes and immune-related genes.

Review of Literature on Measurements of Non-invasive Break Up Times, Lipid Morphology and Tear Meniscal Height Using Commercially Available Hand-held Instruments

Purpose/aims: Dry eye is a common multi-factorial disease characterized by tearfilm dysfunction. Diagnosis of dry eye requires documentation of tear status with non-invasive tear break up times (NIBUT), tear meniscal height (TMH), and tearfilm lipid layer. These parameters objectively assess tear stability and indirectly, the functional impact of meibomian gland dysfunction. While it is obvious that portable instrumentation gives broader access than fixed instrumentation, its value would be limited if it is unreliable and its precision and accuracy substantially worse than fixed instruments.

MATERIALS/METHODS

Because of the lack of systematic reviews concerning the Tearscope, we performed a scoping review of the literature to determine 1. the ranges of the tear parameters as measured by the device, 2. relationship between these measurements and other clinical variables, 3. Information about intra or inter-observer agreement, and comparison with another technique, where available.

RESULTS

We found 22 reports related to NIBUT, 18 reports concerning tearfilm lipid morphology (LM) based on classification of interference patterns, and 8 reports on TMH. While publication of these reports indicates an acceptance of the reliability of portable instruments, we interrogated these studies further to evaluate the results obtained from portable devices and found that there was no equivalent measurements in fixed devices (LM) or measurements differ considerably from fixed devices (NIBUT). In the case of TMH, portable measurements were similar to those by traditional slit-lamp microscopy. There were relatively few studies on TMH measured using handheld devices, but it was found to be correlated to NIBUT but not the Schirmer test values.

CONCLUSIONS

Imaging algorithms in portable tearfilm instruments should be further standardized to facilitate wider adoption and evaluation. In the next few years, new emerging technologies will employ a strategy of non-invasive tear testing that is portable and relatively inexpensive, and these will enhance adoption of such tools in the clinic.

Venom-derived peptide inhibitors of voltage-gated potassium channels

Voltage-gated potassium channels play a key role in human physiology and pathology. Reflecting their importance, numerous channelopathies have been characterised that arise from mutations in these channels or from autoimmune attack on the channels. Voltage-gated potassium channels are also the target of a broad range of peptide toxins from venomous organisms, including sea anemones, scorpions, spiders, snakes and cone snails; many of these peptides bind to the channels with high potency and selectivity. In this review we describe the various classes of peptide toxins that block these channels and illustrate the broad range of three-dimensional structures that support channel blockade. The therapeutic opportunities afforded by these peptides are also highlighted. This article is part of the Special Issue entitled 'Venom-derived Peptides as Pharmacological Tools.'

A Non-invasive Way to Isolate and Phenotype Cells from the Conjunctiva

Traditionally, ocular surface cytology is studied with techniques such as spatula technology and brush technology. The problem with these techniques is that they may induce traumatic lesions on the surface of the eye, which can progress to scarring, eyelid deformity, limbal stem cell deficiency and in some cases, cause great discomfort to the subject. To avoid these clinical problems, impression cytology (IC) was developed to diagnose dry eye disease and later neoplasia, atopic disease, vernal keratoconjunctivitis and keratoconjunctivitis sicca. Typically, clinicians manually cut filter papers into required shapes and apply these to the ocular surface. Here, we describe how to perform IC using a commercially available medical device. This technique is explained here followed by immunophenotyping by flow cytometry. This technique requires less manual handling and causes less injury to the ocular surface.

The link between morphology and complement in ocular disease

The complement system is a vital component of the immune-priveliged human eye that is always active at a low-grade level, preventing harmful intraocular injuries caused by accumulation of turnover products and controlling pathogens to preserve eye homeostasis and vision. The complement system is a double-edged sword that is essential for protection but may also become harmful and contribute to eye pathology. Here, we review the evidence for the involvement of complement system dysregulation in age-related macular degeneration, glaucoma, uveitis, and neuromyelitis optica, highlighting the relationship between morphogical changes and complement system protein expression and regulation in these diseases. The potential benefits of complement inhibition in age-related macular degeneration, glaucoma, uveitis, and neuromyelitis optica are abundant, as are those of further research to improve our understanding of complement-mediated injury in these diseases.