Expression of T lymphocyte chemoattractants and activation markers in vernal keratoconjunctivitis

[Predictive significance of genetic analysis of the development of dry eye disease of different origin]

One of the etiological causes of dry eye disease (DED) is systemic autoimmune diseases (AID): primary Sjögren's syndrome (PSS), rheumatoid arthritis (RA); their manifestation may begin with ophthalmic symptoms. The relationship of PSS and RA with genetic factors is proven. The contribution of polymorphic markers of the genes THBS1, MUC1, TRIM21, STAT4, PTPN22 in the development of these diseases is established, as well as their connection with the development of DED. A panel of genetic markers for evaluating the risk of developing DED in PSS and RA is developed, and its sensitivity and specificity is determined.

PURPOSE

The aim of the study was to determine the prognostic significance of a panel of polymorphic gene markers in the development of dry eye syndrome in patients with primary Sjögren's syndrome and rheumatoid arthritis over a five-year follow-up period.

MATERIAL AND METHODS

Patients with a verified diagnosis of PSS and RA without signs of DED were examined (n=35 and n=42, respectively). The control group included 82 volunteers without AID and DED. The observation period was 5 years. Every year all study subjects underwent an ophthalmological clinical and functional examination.

RESULTS

Dry eye disease had developed in groups of patients with AID with predisposing genotypes of polymorphic markers of the genes THBS1, MUC1, TRIM21, STAT4, PTPN22. The peak of DED development in these patients was in the third year of the follow-up. As a result of ROC analysis, it was found that the sensitivity and specificity of determining the predisposing genotypes of polymorphic markers of the THBS1, MUC1, TRIM21, STAT4, PTPN22 genes was 68 and 87%, respectively (p<0.0001).

CONCLUSION

Genetic research methods are essential for minimally invasive early diagnosis of dry eye disease, and can subsequently become the basis for a personalized approach to its treatment.

Chemokines in allergic conjunctivitis

PURPOSE OF REVIEW

Chemokines are a large group of low molecular weight cytokines that attract and activate leukocytes throughout the body and therefore have a key role in the framework of late-phase allergic responses. The purpose of this article is to provide an overview of the main chemokines involved in allergic conjunctivitis, their primary functions and their physiological roles, and therapies targeted at chemokines and their receptors for ocular allergic diseases.

RECENT FINDINGS

In recent years, there have been considerable advances in the understanding of ocular pathophysiology of ocular surface inflammatory diseases including both allergic eye diseases and dry eye syndrome. Several therapies being developed for dry eye inflammation are recognized as possible therapies for ocular allergic diseases as there are often common chemokines involved in both disease spectra.

SUMMARY

Chemokines represent an integral part of the late-phase cascade of ocular allergic inflammation. A deep understanding of specific chemokines and their interactions will help in targeting therapies to effectively manage ocular clinical findings and symptoms of allergic eye disease.

The ocular surface, coronaviruses and COVID-19

The ocular surface has been suggested as a site of infection with Coronavirus-2 (SARS-CoV-2) responsible for the coronavirus disease-19 (COVID-19). This review examines the evidence for this hypothesis, and its implications for clinical practice. Severe Acute Respiratory Syndrome Coronavirus-2 (SARS-CoV-2), responsible for the COVID-19 pandemic, is transmitted by person-to-person contact, via airborne droplets, or through contact with contaminated surfaces. SARS-CoV-2 binds to angiotensin converting enzyme-2 (ACE2) to facilitate infection in humans. This review sets out to evaluate evidence for the ocular surface as a route of infection. A literature search in this area was conducted on 15 April 2020 using the Scopus database. In total, 287 results were returned and reviewed. There is preliminary evidence for ACE2 expression on corneal and conjunctival cells, but most of the other receptors to which coronaviruses bind appear to be found under epithelia of the ocular surface. Evidence from animal studies is limited, with a single study suggesting viral particles on the eye can travel to the lung, resulting in very mild infection. Coronavirus infection is rarely associated with conjunctivitis, with occasional cases reported in patients with confirmed COVID-19, along with isolated cases of conjunctivitis as a presenting sign. Coronaviruses have been rarely isolated from tears or conjunctival swabs. The evidence suggests coronaviruses are unlikely to bind to ocular surface cells to initiate infection. Additionally, hypotheses that the virus could travel from the nasopharynx or through the conjunctival capillaries to the ocular surface during infection are probably incorrect. Conjunctivitis and isolation of the virus from the ocular surface occur only rarely, and overwhelmingly in patients with confirmed COVID-19. Necessary precautions to prevent person-to-person transmission should be employed in clinical practice throughout the pandemic, and patients should be reminded to maintain good hygiene practices.

Inhibition of LPS-stimulated ecto-adenosine deaminase attenuates endothelial cell activation

Vascular inflammation is an important factor in the pathophysiology of cardiovascular diseases, such as atherosclerosis. Changes in the extracellular nucleotide and in particular adenosine catabolism may alter a chronic inflammation and endothelial activation. This study aimed to evaluate the relation between vascular ecto-adenosine deaminase (eADA) activity and endothelial activation in humans and to analyze the effects of LPS-mediated inflammation on this activity as well as mechanisms of its increase. Moreover, we investigated a therapeutic potential of ADA inhibition by deoxycofromycin (dCF) for endothelial activation. We demonstrated a positive correlation of vascular eADA activity and ADA1 mRNA expression with endothelial activation parameters in humans with atherosclerosis. The activation of vascular eADA was also observed under LPS stimulation in vivo along with endothelial activation, an increase in markers of inflammation and alterations in the lipid profile of a rat model. Ex vivo and in vitro studies on human specimen demonstrated that at an early stage of vascular pathology, eADA activity originated from activated endothelial cells, while at later stages also from an inflammatory infiltrate. We proposed that LPS-stimulated increase in endothelial adenosine deaminase activity could be a result of IL-6/JAK/STAT pathway activation, since the lack of IL-6 in mice was associated with lower vascular and plasma eADA activities. Furthermore, the inhibitors of JAK/STAT pathway decreased LPS-stimulated adenosine deaminase activity in endothelial cells. We demonstrated that cell surface eADA activity could be additionally regulated by transcytosis pathways, as exocytosis inhibitors including lipid raft inhibitor, methyl-β-cyclodextrin decreased LPS-induced eADA activity. This suggests that cholesterol-dependent protein externalization mediated by lipid rafts could be an important factor in the eADA increase. Moreover, endocytosis inhibitors and exocytosis activators increased this activity on the cell surface. Furthermore, the inhibition of adenosine deaminase in endothelial cells in vitro attenuated LPS-mediated IL-6 release and soluble ICAM-1 and VCAM-1 concentration in the incubation medium through the restoration of the extracellular adenosine pool and adenosine receptor-dependent pathways. This study demonstrated that the vascular endothelial eADA activity remains under control of inflammatory mediators acting through JAK/STAT pathway that could be further modified by dyslipidemic-dependent exocytosis and transcytosis pathways. Inhibition of eADA blocked endothelial activation suggesting a crucial role of this enzyme in the control of vascular inflammation. This supports the concept of eADA targeted vascular protection therapy.

Intracellular IL-4, IL-5, and IFN-γ as the main characteristic of CD4+CD30+ T cells after allergen stimulation in patients with vernal keratoconjunctivitis

BACKGROUND

Vernal keratoconjunctivitis (VKC) is a severe form of allergic conjunctivitis, in which inflammatory infiltrates of the conjunctiva are characterized by CD3+ and CD30+ cells. Until today, the functional involvement of CD30+ T cells in VKC was unclear. Our aim was to evaluate the functional characteristics of CD30+ T cells after allergen stimulation in peripheral blood mononuclear cells obtained from patients with VKC.

METHODS

Seventeen consecutive patients at the Institute of Ophthalmology with active forms of VKC were included.

RESULTS

After allergen stimulation, we observed the frequency of CD30+ T cells increased compared with non-stimulated cells (p<0.0001). The CD30+ T cells responded to the specific allergen-inducing expression of intracellular interleukin-4 (IL-4), IL-5, and interferon-gamma (IFN-γ) compared with the CD30- T cells (p<0.0001). Increased early secretion of soluble CD30 was observed in the supernatant of the cultured cells from patients with keratoconjunctivitis, compared with healthy controls (p=0.03). Blockage with IL-4 significantly diminished CD30 frequency in the allergen-stimulated cells.

CONCLUSIONS

Our results suggest that after allergenic stimulation, CD4+CD30+ cells are the most important source of IL-4, IL-5, and IFN-γ. IL-4 acts as an activation loop that increases CD30 expression on T cells after specific stimulation. These findings suggest that CD4+CD30+ T cells are effector cells and play a significant role in the immune pathogenic response in patients with vernal keratoconjunctivitis.

Detection of Antigen-Specific T Cells in Experimental Immune-Mediated Blepharoconjunctivitis in DO11.10 T Cell Receptor Transgenic Mice

Antigen (Ag)-specific T cells are thought to play a key role in pathogenesis of chronic allergic conjunctivitis (AC) such as atopic keratoconjunctivitis (AKC) and vernal keratoconjunctivitis (VKC). In order to investigate the trafficking of Ag-specific T cells in experimental immune-mediated blepharoconjunctivitis (EC), we established a novel AC model in DO11.10 T cell receptor (TcR) transgenic (Tg) mice. DO11.10 TcR-Tg mice were challenged with eye drops of whole OVA protein, OVA peptide 1-15, 321-335, or 323-339. Their eyes were histologically examined. Conventional proliferation assay was performed against each Ag. Phenotypes of infiltrating cells and kinetics of Ag-specific T cells were investigated by immunohistochemistry. Adoptive transfer of CD4(+) Ag-specific T cells from DO11.10 TcR-Tg to WT mice was performed. The distribution of KJ1-26(+) cells was investigated in recipient mice. The challenge of OVA peptide 323-339 induced infiltration of inflammatory cells in conjunctivae in a dose dependent manner, accompanied by the proliferative responses of splenocytes. Immunohistochemical analysis revealed Agspecific/ non-Ag-specific T cells, macrophages, and eosinophils in conjunctivae. Infiltration of Ag-specific T cells increased 24 hr later. Transfer of CD4(+) cells from DO11.10 TcR-Tg to WT mice induced EC depending on the number of transferred cells. Ag-specific T cells were detected in the conjunctivae and spleens of recipient mice, though its numbers were significantly smaller compared to DO11.10 TcR-Tg mice. The challenge of OVA peptide 323-339 induced EC in DO11.10 TcR-Tg mice without prior sensitization. The response was mediated by CD4(+) Ag-specific T cells. The trafficking of Ag-specific T cells in EC was clearly visualized.

Orally administered dipeptidyl peptidase-4 inhibitor (alogliptin) prevents abdominal aortic aneurysm formation through an antioxidant effect in rats

OBJECTIVE

Dipeptidyl peptidase-4 (DPP-4) inhibitor, a novel antidiabetic drug, has a cardioprotective effect on ischemia-reperfusion injury through an antioxidant effect. However, the effect of DPP-4 inhibitor on aneurysm formation has not been investigated. We aimed to test the hypothesis that the DPP-4 inhibitor, alogliptin, attenuates vascular oxidative stress and thus inhibits abdominal aortic aneurysm (AAA) formation.

METHODS

AAAs were created with intraluminal elastase and extraluminal calcium chloride in 36 male rats. Rats were divided into three groups: a low dose of alogliptin group (group LD; 1 mg/kg/d), a high-dose group (group HD; 3 mg/kg/d), and a control group (group C, water). Alogliptin was administered by gastric gavage once daily beginning 3 days before surgery. On day 7 after aneurysm preparation, reactive oxygen species (ROS) expression was semiquantified by dihydroethidium staining, and the oxidation product of DNA produced by ROS, 8-hydroxydeoxyguanosine (8-OHdG), was measured by immunohistochemical staining. Blood glucose concentrations were measured. Hematoxylin and eosin and elastica Van Gieson stainings were performed on day 28, and the AAA dilatation ratio was calculated.

RESULTS

On day 7 (six in each group), dihydroethidium staining of the aneurysm wall showed a reduced level of ROS expression (4.6 ± 0.6 in group C, 2.7 ± 0.3 in group LD, and 1.7 ± 0.5 in group HD; P < .0001) and showed fewer 8-OHdG-positive cells in alogliptin-treated samples (138.1 ± 7.4 cells in group C, 102.5 ± 4.5 cells in group LD, and 66.1 ± 4.5 cells in group HD; P < .0001) The treatment significantly reduced messenger RNA expression of matrix metalloproteinases (MMPs) in aneurysm walls (relative expression: MMP-2: 2.1 ± 0.4 in group C, 1.3 ± 0.3 in group LD, and 0.9 ± 0.2 in group HD; P < .001; MMP-9: 2.0 ± 0.5 in group C, 0.3 ± 0.3 in group LD, and 0.3 ± 0.2 in group HD; P < .001). On day 28 (six in each group), the aortic wall in groups LD and HD was less dilated (dilatation ratio: 199.2% ± 11.8% in group C, 159.6% ± 2.8% in group LD, and 147.1% ± 1.9% in group HD; P < .02 group C vs HD) and had higher elastin content than in group C. The difference in blood glucose levels among the three groups was not significant.

CONCLUSIONS

The DPP-4 inhibitor, alogliptin, attenuates aneurysm formation and expansion dose-dependently in a rat AAA model via an antioxidative action.

Pulmonary CCL18 recruits human regulatory T cells

CCL18 is both a constitutively expressed and an inducible chemokine, whose role in the inflammatory reaction is poorly known. The aim of this study was to evaluate whether CCL18 has the capacity to attract human T cells with a regulatory function (regulatory T cells [Treg]). Results from chemotaxis assays performed on different types of Treg showed that CD4(+)CD25(+)CD127(low) cells, but neither T regulatory type 1 clones nor Treg differentiated in vitro with anti-CD3/CD46 mAbs, were recruited by CCL18 in a dose-dependent manner. CCL18-recruited memory CD4(+) T cells were enriched in CD25(high), CD25(+)CD127(low), latency-associated peptide/TGF-β1, and CCR4-expressing T cells, whereas there was no enrichment in Foxp3(+) cells as compared with controls. Stimulated CCL18-recruited memory T cells produced significantly increased amounts of the regulatory cytokines IL-10 and TGF-β1, as well as IL-4, but not IFN-γ and IL-17. Cell surface CCL18 binding was found predominantly on IL-10(+) (26.3 ± 5.8%) and on a few latency-associated peptide/TGF-β1(+) (18.1 ± 1.9%) and IL-4(+) (14.5 ± 2.9%) memory T cells. In an in vivo model of SCID mice grafted with human skin and reconstituted with autologous PBMCs, the intradermal injection of CCL18 led to the cutaneous recruitment of CD4(+), CD25(+), and IL-10(+) cells, but not Foxp3(+) cells. Furthermore, CCL18-recruited memory T cells inhibited the proliferation of CD4(+)CD25(-) effector T cells through an IL-10-dependent mechanism. These data suggest that CCL18 may contribute to maintaining tolerance and/or suppressing deleterious inflammation by attracting memory Tregs into tissues, particularly in the lung, where it is highly and constitutively expressed.

Up-regulation of the chemokine CCL18 by macrophages is a potential immunomodulatory pathway in cutaneous T-cell lymphoma

Mycosis fungoides (MF) is the most frequent form of cutaneous T-cell lymphoma (CTCL), which can deteriorate from patch stage to dermal-based tumors and systemic involvement in years. The interaction of chemokines in the skin with CTCL cells might have implications for the pathogenesis of the disease. In this study, we show by PCR analysis and immunofluorescence staining that the chemokine CCL18 is present in skin biopsy specimens of patients with MF and its precursor form parapsoriasis en plaque but not in healthy tissue. In addition, the serum levels of CCL18 were increased threefold in MF patients compared with those in healthy controls. In skin, CCL18 was specifically expressed by CD163(+) CD209(+) macrophages at the invasive margin of the tumor and not expressed by mature CD208(+) dendritic cells in the center of the tumor. The chemokine CCL17 was, by contrast, ubiquitously expressed. Furthermore, CCL18 promoted the chemotaxis but not the proliferation of CTCL cells. CCL18 inhibited proliferation of tumor cells and abolished the CXCL12-induced growth of a CTCL cell line. These data link the increased expression of CCL18 with CTCL and suggest an immunomodulatory effect of the chemokine in the pathogenesis of CTCL.

Allergic conjunctivitis and nasal allergy

Allergic conjunctivitis (AC) can be divided into the primary form (caused by an allergic reaction occurring primarily in the conjunctivae) and the secondary form (induced by allergic reaction originating primarily in the nasal mucosa, where the released mediators can reach conjunctiva through the lacrimal system, the blood, the lymphatic network, or the neurogenic network). Patients with primary AC develop an immediate, late, or delayed conjunctival response (CR) during conjunctival provocation tests. Patients with secondary AC develop an immediate, late, or delayed type of secondary CR, induced by the nasal allergic reaction, due to the nasal allergen challenge. Various hypersensitivity mechanisms may be involved in the particular CR types. The secondarily induced AC and CRs can only be confirmed by nasal provocations tests, performed by rhinomanometry combined with recording of conjunctival signs. The existence of the primary and secondarily induced AC has an impact on treatment of this disorder.

Involvement of CCL18 in allergic asthma

Allergic asthma is associated with a pulmonary recruitment of Th type 2 cells, basophils, and eosinophils, mainly linked to chemokine production. CCL18 is a chemokine preferentially expressed in the lung, secreted by APCs, induced by Th2-type cytokines, and only present in humans. Therefore, CCL18 may be involved in allergic asthma. PBMC from asthmatics allergic to house dust mite cultured in the presence of Dermatophagoides pteronyssinus 1 (Der p 1) allergen secreted CCL18, 48 and 72 h after stimulation, whereas those from healthy donors did not. Part of CCL18 was directly derived from Der p 1-stimulated plasmacytoid dendritic cells, whereas the other part was linked to monocyte activation by IL-4 and IL-13 produced by Der p 1-stimulated T cells. In bronchoalveolar lavages from untreated asthmatic allergic patients, CCL18 was highly increased compared with controls. Functionally, CCL18 preferentially attracted in vitro-polarized Th2 cells and basophils, but not eosinophils and Th1 cells, and induced basophil histamine and intracellular calcium release. These data show a new function for CCL18, i.e., the recruitment of Th2 cells and basophils, and suggest that CCL18 may play a predominant role in allergic asthma.

Primary Cutaneous CD30+ Large Cell B-Cell Lymphoma

BACKGROUND

White CD30 expression is described in extracutaneous diffuse large B-cell lymphomas, a primary cutaneous B-cell lymphoma (PCBCL) equivalent is not well defined.

METHODS

Between June 1999 and July 2002 the authors encountered 10 patients with CD30+ PCBCLs of the large cell type.

RESULTS

The patients comprised seven women and three men; five patients were over 80 years of age, all except one presenting with solitary plaques. With the exception of one death from myocardial infarction and one recurrence, all patients are well at a mean follow-up of 23.4 months. Skin biopsies showed a background of T-cell-rich reactive lymphoid hyperplasia in 7 of 10 patients, with variable granulomatous inflammation in 5 cases. The neoplastic large cells were immunoblastic in appearance. In four patients the infiltrate was dominated by large cells. In the remaining patients the reactive infiltrate defined the dominant cell population. The neoplastic cells expressed CD20, CD30, CD43, and BCL-2. In two cases associated with methotrexate therapy, Epstein-Barr virus expression was observed amid the neoplastic cell populace.

CONCLUSIONS

CD30+ PCBCL is a distinctive form of B-cell lymphoma presenting in elderly patients and can be associated with a very good prognosis. In some patients the intensity of reactive inflammation obscures the diagnosis. In the authors' experience almost a third of the cases were associated with Epstein-Barr virus infection and methotrexate therapy, suggesting a distinctive association.

Involvement of CC chemokine ligand 18 (CCL18) in normal and pathological processes

CC chemokine ligand 18 (CCL18) was originally discovered as pulmonary and activation-regulated chemokine (PARC), dendritic cell (DC)-chemokine 1 (DC-CK1), alternative macrophage activation-associated CC chemokine-1 (AMAC-1), and macrophage inflammatory protein-4 (MIP-4). CCL18 primarily targets lymphocytes and immature DC, although its agonistic receptor remains unknown so far. CCL18 is mainly expressed by a broad range of monocytes/macrophages and DC. A more profound understanding of the various activation programs and functional phenotypes of these producer cells might give a better insight in the proinflammatory versus anti-inflammatory role of this CC chemokine. It is interesting that CCL18 is constitutively present at high levels in human plasma and likely contributes to the physiological homing of lymphocytes and DC and to the generation of primary immune responses. Furthermore, enhanced CCL18 production has been demonstrated in several diseases, including various malignancies and inflammatory joint, lung, and skin diseases. The lack of a rodent counterpart for human CCL18 sets all hope on primate animal models to further elucidate the importance of CCL18 in vivo. This review will address these different aspects in more detail.

Tear cytokines in acute and chronic ocular allergic inflammation

PURPOSE OF REVIEW

Elevated levels of inflammatory cytokines have been reported in tears from ocular allergic disease states. The purpose of this review is to assimilate recent research contrasting tear cytokine concentrations in non-allergic subjects versus subjects with acute (seasonal allergic conjunctivitis) and chronic (giant papillary conjunctivitis, vernal keratoconjunctivitis, atopic keratoconjunctivitis) ocular allergic inflammation to discover whether the cytokine profiles could provide useful insight into disease mechanisms and therapeutic targets.

RECENT FINDINGS

Recent studies have revealed distinct differences in the cytokine/chemokine concentrations in tears between the various manifestations of ocular allergy. The acute (seasonal allergic conjunctivitis) and iatrogenic (giant papillary conjunctivitis) forms of ocular allergic inflammation are characterized by an overall lack of significant cytokine changes in tears compared with chronic disease (vernal keratoconjunctivitis, atopic keratoconjunctivitis). Chronic ocular allergic inflammation produces increased concentrations of T helper 1 and 2, and proinflammatory cytokines as well as chemokines. However, vernal and atopic keratoconjunctivitis portray distinct differences in the patterns of tear cytokines/chemokines expressed.

SUMMARY

The plethora of increased cytokines and chemokines in vernal and atopic keratoconjunctivitis compared with non-allergic, seasonal allergic conjunctivitis and giant papillary conjunctivitis provides a new perspective into the complex inflammatory processes occurring on the ocular surface in chronic disease. The ability to measure multiple cytokines in tears, combined with knowledge obtained from in-vitro analysis of the individual and combined effects of these cytokines on various conjunctival cells (i.e. mast cells, epithelial cells, fibroblasts) has facilitated further understanding of specific processes contributing to maintenance of inflammation and progression of vision-threatening disease and paved the way toward new therapeutic targets.

CCL18 Is Expressed in Atopic Dermatitis and Mediates Skin Homing of Human Memory T Cells

CCL18 is a human chemokine secreted by monocytes and dendritic cells. The receptor for CCL18 is not yet known and the functions of this chemokine on immune cells are not fully elucidated. In this study, we describe that CCL18 is present in skin biopsies of atopic dermatitis (AD) patients but not in normal or psoriatic skin. CCL18 was specifically expressed by APCs in the dermis and by Langerhans and inflammatory dendritic epidermal cells in the epidermis. In addition, the serum levels of CCL18 and the percentages of CCL18-producing monocyte/macrophages and dendritic cells were significantly increased in AD patients compared with healthy controls. Furthermore, we demonstrate that CCL18 binds to CLA(+) T cells in peripheral blood of AD patients and healthy individuals and induces migration of AD-derived memory T cells in vitro and in human skin-transplanted SCID mice. These findings highlight a unique role of CCL18 in AD and reveal a novel function of this chemokine mediating skin homing of a subpopulation of human memory T cells.

Roles of Chemokines in Ocular Allergy and Possible Therapeutic Strategies

The mechanism of ocular surface allergy in the forms of atopic conjunctivitis and vernal keratoconjunctivitis has been highlighted by specific functions of chemokines. In the context of late-phase allergic responses, these molecules have key roles in recruitment and activation of leukocytes. Their interaction with ligands is redundantly regulated; however, results from strategies to block subsets of chemokines have revealed unexpected or highly organized roles of these mediators. Exemplified by analyses of CCL11 function, current concepts of ocular allergy support CCL11 as central mediator. We emphasize the functions as modulator of mast cell activation/differentiation. With the prospect of understanding these functions, new modalities of drugs specifically developed to target CCL11/CCR3 interaction have been discussed.

The role of chemokines and their receptors in ocular disease

The migration and infiltration of cells into the eye whether blood-borne leucocytes, endothelial or epithelial cells occurs in many ocular diseases. Dysregulation of this process is apparent in chronic inflammation, corneal graft rejection, allergic eye disease and other sight-threatening conditions. Under normal and inflammatory conditions, chemokines and their receptors are important contributors to cell migration. To date, 47 chemokines and 19 chemokine receptors have been identified and characterised. In recent years, investigations into the role of chemokines and their receptors in ocular disease have generated an increasing number of publications. In the eye, the best understood action of these molecules has arisen from the study of their ability to control the infiltration of leucocytes in uveitis. However, the involvement of chemokines in angiogenesis in several ocular conditions and in the survival of corneal transplants demonstrates the multifaceted nature of their effects. Interestingly, the constitutive expression of chemokines and their receptors in ocular tissues suggests that certain chemokines have a homeostatic function. In this review, we discuss the nature and function of chemokines in health and disease, and describe the role of chemokines in the pathogenesis of different ocular conditions.

The role of the lacrimal functional unit in the pathophysiology of dry eye

The majority of dry eye symptoms are due to a chronic inflammation of the lacrimal functional unit resulting in a loss of tear film integrity and normal function. This leads to a reduction in the ability of the ocular surface to respond to environmental challenges. The underlying cause of tear film dysfunction is the alteration of tear aqueous, mucin, and lipid components. This may result from a systemic autoimmune disease or a local autoimmune event. A lack of systemic androgen support to the lacrimal gland has been shown to be a facilitative factor in the initiation of this type of pathophysiology. Tear secretion is controlled by the lacrimal functional unit consisting of the ocular surface (cornea, conjunctiva, accessory lacrimal glands, and meibomian glands), the main lacrimal gland and the interconnecting innervation. If any portion of this functional unit is compromised, lacrimal gland support to the ocular surface is impeded. Factors such as neurogenic inflammation and T cell involvement in the disease pathogenesis as well as newly developed animal models of ocular surface inflammation are discussed.

The T-lymphocyte chemoattractant Mig is highly expressed in vernal keratoconjunctivitis

PURPOSE

To examine the expression of the three interferon-gamma-inducible CXCR3-binding chemokines, CXCL10/IP-10 (interferon-gamma-inducible protein of 10 KDa), CXCL9/Mig (monokine induced by interferon-gamma), and CXCL11/I-TAC (interferon-inducible T-cell alpha chemoattractant) in the conjunctiva of patients with vernal keratoconjunctivitis (VKC). These chemokines exhibit potent T-lymphocyte chemoattractant activity.

DESIGN

Immunohistochemical study.

METHODS

Conjunctival biopsy specimens from 16 patients with active VKC and nine control subjects were studied by immunohistochemical techniques using monoclonal antibodies directed against IP-10, Mig, and I-TAC. The phenotype of inflammatory cells expressing chemokines was examined by double immunohistochemistry.

RESULTS

In the normal conjunctiva, very weak Mig immunoreactivity was observed on basal epithelial cells and on vascular endothelial cells in the upper substantia propria. There was no immunoreactivity for the other chemokines. In all VKC specimens, strong immunoreactivity for Mig was expressed by epithelial cells, vascular endothelial cells, and inflammatory mononuclear cells. Inflammatory mononuclear cells expressing IP-10 and I-TAC were noted in 10 and nine specimens, respectively. The numbers of Mig(+) inflammatory cells were significantly higher than the numbers of IP-10(+) and I-TAC(+) inflammatory cells (P <.001). Inflammatory cells expressing Mig were CD4(+) T-helper/inducer cells (71.6 +/- 3.2%), CD8(+) T-cytotoxic/suppressor cells (19.5 +/- 1.5%), and CD68(+) monocytes/macrophages (5.3 +/- 5%). All inflammatory cells expressing IP-10 and I-TAC were CD68(+) monocytes/macrophages.

CONCLUSIONS

The CXC chemokine Mig is selectively and highly expressed in VKC suggesting a pathogenic role of the chemokine receptor CXCR3 and the ligand Mig in the recruitment of activated T lymphocytes.

Allergic chronic inflammation of the ocular surface in vernal keratoconjunctivitis

PURPOSE OF REVIEW

The purpose of this review is to describe the new immunopathologic features of vernal keratoconjunctivitis: the involvement of cytokines, growth factors, cells, mediators and neurotransmitters, as well as the mechanism leading to tissue remodelling.

RECENT FINDINGS

Vernal keratoconjunctivitis is an allergic eye disease affecting young boys living in a warm climate. It is characterized by conjunctival giant papillae, hyperemia and frequent involvement of the cornea. Approximately 50% of the patients with vernal keratoconjunctivitis do not have a family or medical history of atopic diseases, and do not show IgE sensitization, suggesting that this disease is not solely IgE mediated. Vernal keratoconjunctivitis is a Th2 lymphocyte driven disease with a Th2 cytokine derived pattern, increased levels of mRNA for IL-3, IL-4, IL-5 and IL-13. Th2 lymphocytes induce IgE hyperproduction, activation of mast cells, eosinophils, neutrophils and their toxic products. An overexpression of adhesion molecules, RANTES, eotaxin and metalloproteinases contribute to chronic inflammation. A role for substance P and nerve growth factor has been postulated, as well as for other growth factors (epidermal growth factor, fibroblast growth factor and transforming growth factor beta 1) that induce fibroblast growth and new collagen production. Recent studies have also pointed out the role of resident conjunctival cells, such as epithelial cells and fibroblasts, in the inflammatory and remodelling process of vernal keratoconjunctivitis. The pathogenesis of the condition is probably multifactorial, with the interaction of the immune, nervous and endocrine systems.

SUMMARY

Vernal keratoconjunctivitis is a chronic inflammatory and potentially blinding disease. Understanding of the complex interactions and cross talk between cells, cytokines and other mediators is relevant for new therapeutic approaches.

T-cell characterization in chronic allergic eye disease

Chronic allergic eye disease encompasses several disorders, but it is vernal keratoconjunctivitis (VKC) and atopic keratoconjunctivitis (AKC) that have sight-threatening sequelae. T cells, eosinophils, and mast cells are all found in the conjunctiva, and are thought to play a role in disease pathogenesis. Recently, the conjunctival epithelium has also been considered to play a key role. New and effective therapeutic strategies for the future for these patients depend on achieving a greater understanding of the roles and interactions of the cell populations in these sight-threatening disorders.