Expression of CD23/CD21 and CD40/CD40 ligand in vernal keratoconjunctivitis

Understanding Vernal Keratoconjunctivitis: Beyond Allergic Mechanisms

Vernal keratoconjunctivitis (VKC) is a chronic, recurrent, inflammatory disease of the cornea and conjunctiva mostly affecting boys in prepubertal age. VKC recurrence is characterized by intense symptoms of itching, redness, and photophobia associated with corneal damage, impairment of visual function, and quality of life. The pathogenesis of VKC has not yet been completely understood, and it is still controversial. In fact, VKC is considered an ocular allergic disease due to the involvement of immunoglobulin E, eosinophils, and mast cells, and of a lymphocyte T-helper type 2 reaction. However, approximately half of VKC patients have negative allergological history and testing, suggesting that other pathogenic mechanisms participate in VKC development and severity. Specifically, evidence suggests that genetic, endocrine, neuronal factors and an imbalance of innate immunity are involved in the pathogenesis of VKC. The purpose of this review is to summarize evidence on the pathogenic role of innate immunity, neuroimmune reaction, and hormonal changes in VKC. Increasing understanding of the pathogenic mechanisms behind VKC may lead to the identification of novel biomarkers for diagnosis and/or potential therapeutic targets in order to improve the management of this challenging condition.

Ocular diseases: immunological and molecular mechanisms

Many factors, such as environmental, microbial and endogenous stress, antigen localization, can trigger the immunological events that affect the ending of the diverse spectrum of ocular disorders. Significant advances in understanding of immunological and molecular mechanisms have been researched to improve the diagnosis and therapy for patients with ocular inflammatory diseases. Some kinds of ocular diseases are inadequately responsive to current medications; therefore, immunotherapy may be a potential choice as an alternative or adjunctive treatment, even in the prophylactic setting. This article first provides an overview of the immunological and molecular mechanisms concerning several typical and common ocular diseases; second, the functions of immunological roles in some of systemic autoimmunity will be discussed; third, we will provide a summary of the mechanisms that dictate immune cell trafficking to ocular local microenvironment in response to inflammation.

Microarray-based IgE detection in tears of patients with vernal keratoconjunctivitis

BACKGROUND

A specific allergen sensitization can be demonstrated in approximately half of the vernal keratoconjunctivitis (VKC) patients by conventional allergic tests. The measurement of specific IgE in tears using a multiplex allergen microarray may offer advantages to identify local sensitization to a specific allergen.

METHODS

In spring-summer 2011, serum and tears samples were collected from 10 active VKC patients (three females, seven males) and 10 age-matched normal subjects. Skin prick test, symptoms score and full ophthalmological examination were performed. Specific serum and tear IgE were assayed using ImmunoCAP ISAC, a microarray containing 103 components derived from 47 allergens.

RESULTS

Normal subjects resulted negative for the presence of specific IgE both in serum and in tears. Of the 10 VKC patients, six resulted positive to specific IgE in serum and/or tears. In three of these six patients, specific IgE was found positive only in tears. Cross-reactivity between specific markers was found in three patients. Grass, tree, mites, animal but also food allergen-specific IgE were found in tears. Conjunctival provocation test performed out of season confirmed the specific local conjunctival reactivity.

CONCLUSIONS

Multiple specific IgE measurements with single protein allergens using a microarray technique in tear samples are a useful, simple and non-invasive diagnostic tool. ImmunoCAP ISAC detects allergen sensitization at component level and adds important information by defining both cross- and co-sensitization to a large variety of allergen molecules. The presence of specific IgE only in tears of VKC patients reinforces the concept of possible local sensitization.

Ocular allergy: recognizing and diagnosing hypersensitivity disorders of the ocular surface

Ocular allergy includes several clinically different conditions that can be considered as hypersensitivity disorders of the ocular surface. The classification of these conditions is complex, and their epidemiology has not been adequately studied because of the lack of unequivocal nomenclature. Ocular allergy symptoms are often, but not always, associated with other allergic manifestations, mostly rhinitis. However, specific ocular allergic diseases need to be recognized and managed by a team that includes both an ophthalmologist and an allergist. The diagnosis of ocular allergy is usually based on clinical history and signs and symptoms, with the support of in vivo and in vitro tests when the identification of the specific allergic sensitization is required for patient management. The aims of this Task Force Report are (i) to unify the nomenclature and classification of ocular allergy, by combining the ophthalmology and allergy Allergic Rhinitis and its Impact on Asthma criteria; (ii) to describe current methods of diagnosis; (iii) to summarize the therapeutic options for the management of ocular allergic inflammation.

Vernal keratoconjunctivitis: a major review

Vernal keratoconjunctivitis (VKC) is a chronic, bilateral, at times asymmetrical, seasonally exacerbated, allergic inflammation of the ocular surface, involving tarsal and/or bulbar conjunctiva. Though the allergic nature of this entity has been accepted for a long time, the accumulation of a large amount of immunological data has proved that the pathogenesis of VKC is much more complex than a mere type 1 hypersensitivity reaction. In the past several years, many clinical and experimental studies about the cells and mediators involved in initiating and perpetuating the ocular allergic inflammation have shown that T helper type 2 cells and their cytokines, corneal fibroblasts and epithelium along with various growth factors play an important role in the pathogenesis of VKC. Based on this information about the pathogenesis of VKC newer, more selective drugs like anti-chemokine receptor antibodies and leukotriene receptor antagonists are under evaluation. Cyclosporine has been shown to be effective in the treatment of VKC but further randomized control trials are required to establish the minimum effective concentration.

Immunopathogenesis of ocular allergy: a schematic approach to different clinical entities

PURPOSE OF REVIEW

The immunopathogenesis of ocular allergic disorders is generally related to the specific immunoglobulin E-mediated mast cell activation and the following cascade of inflammatory mediators. Seasonal and perennial allergic conjunctivitis, however, are the only ocular diseases to involve solely type I hypersensitivity. The other main forms, vernal and atopic keratoconjunctivitis, have a more complex immunological basis and a chronic inflammatory component. Involvement of inflammatory cells, particularly eosinophils and T cells, cytokines and proteases can lead to more serious corneal damage with vision-threatening potential.

RECENT FINDINGS

Experimental allergic conjunctival models and clinical research studies have shown that T helper type 2-related mechanisms are definitely involved in the sensitization phase of ocular allergy, however, both T helper type 1 and type 2 cytokines are overexpressed in the active disease, contributing to the development of ocular inflammation.

SUMMARY

A review of the recent literature allows us to better understand the mechanisms involved in the development of ocular allergy and to guide us toward a more schematic approach, which could possibly be useful in forming a new classification, standardizing clinical phases and individuating new treatment targets.

Case series of 406 vernal keratoconjunctivitis patients: a demographic and epidemiological study

PURPOSE

To evaluate the specific allergic sensitization and epidemiological characteristics of vernal keratoconjunctivitis (VKC).

METHODS

This retrospective non-comparative case series included 406 VKC patients. Data included patient and family histories, and results of allergic tests. Annual incidence and prevalence rates were calculated for a cohort of 128 VKC patients from the greater Padua area.

RESULTS

The great majority of VKC patients were male (76%), with a male : female ratio of 3.3 : 1. A skin prick test, specific serum IgE or conjunctival challenge was positive in 43%, 56% and 58% of patients, respectively. In the cohort of patients from the Padua area, the prevalence of the disease was 7.8/100,000, with a higher rate in young males (57/100,000) compared with young females (22/100,000), and lower rates in people over 16 years of age (3.8/100,000 in males, 1/100,000 in females). The incidence of VKC was 1/100,000, with a higher rate in males under 16 years of age (10/100,000) compared with females (4.2/100,000). In people over 16 years of age, the incidence of the disease was 0.06/100,000, with no difference between males and females.

CONCLUSION

An IgE-mediated sensitization was found in only half of the VKC patients. Vernal keratoconjunctivitis is not a rare event in the paediatric population but is an extremely rare new disease in adults.

Immuno-histochemical evaluation of conjunctival remodelling in vernal keratoconjunctivitis

PURPOSE

To study the expression of the extracellular matrix (ECM) proteins, tenascin, laminin, and fibronectin in the conjunctiva of patients with active vernal keratoconjunctivitis (VKC).

METHODS

Conjunctival biopsy specimens were obtained from nine patients with active VKC and 6 normal control subjects. The presence and distribution of tenascin, laminin, and fibronectin were assessed microscopically with immunohistochemical techniques and a panel of monoclonal and polyclonal antibodies directed against tenascin, laminin, and fibronectin.

RESULTS

In normal conjunctiva, weak immunoreactivity for tenascin was localized to the walls of blood vessels in the upper substantia propria. Weak immunoreactivity for laminin was located at the epithelial-stromal junction and in the walls of blood vessels. Staining for fibronectin was absent. In VKC specimens, intense immunoreactivity for tenascin was noted in the substantia propria associated with the inflammatory infiltrate and in the perivascular stroma. Intense immunoreactivity for laminin around all stromal vessels and fibrillar immunoreactivity among basal epithelial cells were noted. There was no immunoreactivity for fibronectin.

CONCLUSION

Our data indicate increased deposition of tenascin and laminin in the conjunctiva from patients with active VKC. Our findings suggest that tenascin and laminin might play distinct roles in chronic inflammation seen in VKC.

Spectrum of ocular allergy

PURPOSE OF REVIEW

To elaborate and review the immunologic spectrum of the five basic types of ocular allergy.

RECENT FINDINGS

Perennial allergic conjunctivitis (PAC) appears to be an extension of seasonal allergic conjunctivitis (SAC) based on the similarity of clinical symptoms and the immune mechanism involved. T helper type 2 (TH2)-type cytokines, increased ratio of TH1/TH2 cytokines and increased statement of adhesion molecules all appear to play an integral role in the inflammatory process of SAC and PAC. Vernal keratoconjunctivitis (VKC), which is a pediatric disease, differs from SAC and PAC by its more severe and chronic nature. Increased numbers of T cells, eosinophils (along with the products of degranulation), chemokines and their receptors may contribute to the more serious symptoms of VKC. Atopic keratoconjunctivitis (AKC) is similar to VKC by the increased concentration of cytokines involved (i.e. interleukin-4 and -5). Despite clinical similarities with VKC, the presence of atopic dermatitis, along with some differences in clinical signs, make AKC a separate entity, which is sometimes referred to as an adult variant of VKC. Giant papillary conjunctivitis has similar cell involvement as VKC and AKC. However, giant papillary conjunctivitis differs from VKC and AKC by the clinical signs present (i.e. the presence of giant papillae) and the necessary concurrent contact lens wear.

SUMMARY

The important differences and similarities observed in these five types of allergic diseases might help to better treat the patients affected with these disorders.

Vernal keratoconjunctivitis: pathogenesis and treatment

Vernal keratoconjunctivitis (VKC) is a recurrent or chronic ocular allergic disease that affects mostly children and young adults living in warm climates worldwide. Understanding and treating VKC has been a challenge for ophthalmologists since the pathogenesis is unclear and anti-allergic therapy often unsuccessful. In this paper, the culmination of 11 years of research into the immunological characteristics of this disease in a group of 221 VKC patients will be presented. Cytological, biohumoral, immunohistological and molecular biological studies indicate that VKC is a Th2 lymphocyte-mediated disease. Mast cells, eosinophils and their mediators play major roles in the clinical manifestation of VKC. In addition to typical Th2-derived cytokines, IL-4, IL-5 and IL-13, other cytokines, chemokines, growth factors and enzymes are over-expressed in the conjunctiva of VKC patients. Furthermore, structural cells, such as epithelial cells and fibroblasts, are involved both in the inflammatory process and in the tissue remodeling phase, ultimately resulting in the formation of giant papillae. Interactions between specific (IgE- and Th2-mediated) and non-specific triggers and mechanisms may account for treatment failure. New insights into the pathogenesis of VKC should generate the means to better design the strategies for this complex disease.