The role of IL-12 in the induction of late-phase cellular infiltration in a murine model of allergic conjunctivitis

Selected cytokine expression in dogs with alergic conjunctivitis: Correlation with disease activity

INTRODUCTION

Canine allergic conjunctivitis (cAC) is described as the most frequent ocular manifestation associated with canine atopic dermatitis (cAD).

OBJECTIVES

Clinical and immunological characterization of cAD through IL-6, TNF-α and IL-12 mRNA expression quantification in canine conjunctivae.

PROCEDURES

Twenty client-owned dogs with both cAC and cAD and twenty-one healthy controls were enrolled and clinician assessed CADESI-04 and grade of ocular signs were calculated. Conjunctival biopsies were performed on all animals and relative quantification of the interleukins mRNA expression performed by qRT-PCR. The correlation between cytokine gene expression and cAC score was evaluated, as well as CADESI-04 values.

RESULTS

The qRT-PCR showed a significant gene upregulation of respectively 291.48 (p = 1.306e-09) and 4.85 (p = .00033) folds on IL-6 and IL-12 in dogs with allergic conjunctivitis compared to the control group. Regarding the average expression of TNF-α there were no statistical significant differences between both groups (p = .18). Higher cAC scores were associated with enhanced gene expression of TNF-α and IL-12. No correlation was found between the cytokine gene expression levels and the CADESI-04 values.

CONCLUSION

An increase of IL6 and IL12 in cAC was found in the studied population. These two cytokines may be potential immunotherapy targets cAC classification.

Allergy and Infections: Long-Term Improvement of Vernal Keratoconjunctivitis following Viral Conjunctivitis

PURPOSE

Vernal keratoconjunctivitis (VKC) is a severe, chronic allergic inflammatory disease of the ocular surface poorly responsive to antiallergic treatments and possibly leading to permanent visual impairment. VKC, because of mast cell, eosinophil, and Th2-type inflammation, polyclonal IgE activation, and tissue remodeling, is considered to be a typical Th2- driven disease. Viral infection stimulates a Th1 type immune response, potentially attenuating allergen-induced inflammation. The purpose of this report is to describe the effect of viral keratoconjunctivitis in a patient with VKC.

METHODS

The authors report on a patient with a severe form of VKC, poorly responsive to antiallergic treatments, who developed a viral keratoconjunctivitis. Signs, symptoms, and cytologic findings were recorded during the 5-year follow-up period.

RESULTS

The authors observed a prompt and permanent improvement of signs and symptoms of the allergic condition after the viral infection. Conjunctival scraping confirms that the inhibition of the eosinophilic inflammation lasts at least for 5 years.

CONCLUSIONS

In this case, the viral infection seemed to induce a clinical recovery of allergic disease, suggesting that an immune deviation induced by Th1-polarizing agents may revert an ongoing Th2 inflammation.

Secondary allergic T cell responses are regulated by dendritic cell-derived thrombospondin-1 in the setting of allergic eye disease

Allergic eye disease, as in most forms of atopy, ranges in severity among individuals from immediate hypersensitivity to a severe and debilitating chronic disease. Dendritic cells play a key role in stimulating pathogenic T cells in allergen re-exposure, or secondary responses. However, molecular cues by dendritic cells underpinning allergic T cell response levels and the impact that this control has on consequent severity of allergic disease are poorly understood. Here, we show that a deficiency in thrombospondin-1, a matricellular protein known to affect immune function, has subsequent effects on downstream T cell responses during allergy, as revealed in an established mouse model of allergic eye disease. More specifically, we demonstrate that a thrombospondin-1 deficiency specific to dendritic cells leads to heightened secondary T cell responses and consequent clinical disease. Interestingly, whereas thrombospondin-1-deficient dendritic cells augmented activity of allergen-primed T cells, this increase was not recapitulated with naïve T cells in vitro. The role of dendritic cell-derived thrombospondin-1 in regulating secondary allergic T cell responses was confirmed in vivo, as local transfer of thrombospondin-1-sufficient dendritic cells to the ocular mucosa of thrombospondin-1 null hosts prevented the development of augmented secondary T cell responses and heightened allergic eye disease clinical responses. Finally, we demonstrate that topical instillation of thrombospondin-1-derived peptide reduces T cell activity and clinical progression of allergic eye disease. Taken together, this study reveals an important modulatory role of dendritic cell-derived thrombospondin-1 on secondary allergic T cell responses and suggests the possible dysregulation of dendritic cell-derived thrombospondin-1 expression as a factor in allergic eye disease severity.

T helper subsets in allergic eye disease

PURPOSE OF REVIEW

Ocular allergy is an IgE-mediated disease that results in inflammation of the conjunctiva and, in more severe cases, the cornea. This is driven by an immediate hypersensitivity response via mast cells, followed by a late phase response mediated by eosinophils both of which are indeed dependent on T helper (Th) lymphocyte activity. Here, we provide an update on Th subsets [Th1, Th2, Th17, and T regulatory (Treg)] and their relevance in ocular allergy.

RECENT FINDINGS

Recent evidence in ocular allergy points to an involvement of other Th subsets, in addition to Th2. However, how these subsets are activated and their role in mediating the different clinical forms is poorly understood. Novel mouse models may facilitate addressing such unknowns, and future challenges will involve how to translate such findings into more effective and 'patho-specific' treatments.

SUMMARY

Ocular allergy, especially in severe forms, involves subsets other than Th2. Th1 cells have been detected in mild and severe forms, and recent evidence points to a possible role for IL-17 in severe disease. Tregs, on the other hand, dampen pathogenic Th cell function and allergy immunotherapy is associated with Treg augmentation in disease management. Further understanding of Th biology is warranted and may lead to better therapies.

Risk of cervical cancer associated with allergies and polymorphisms in genes in the chromosome 5 cytokine cluster

BACKGROUND

Human papillomavirus is the acknowledged cause of cervical cancer. We hypothesized that allergies, characterized by hyperimmune reaction to common allergens and which have been associated with various cancers, may be related to cervical cancer, and that genetic variation in cytokine genes related to allergies might impact cervical cancer risk.

METHODS

We investigated the risk of invasive squamous cell cervical cancer (SCC) associated with self-reported allergies and with variation in allergy-related cytokine genes using data from a case-control study (561 cases, 1,258 controls) conducted in Washington State. Logistic regression models yielded odds ratios (OR) and 95% CI.

RESULTS

Pollen allergy, the most commonly reported allergy, was associated with reduced SCC risk (OR: 0.6; 95% CI: 0.5-0.8). Of 60 tagging single-nucleotide polymorphisms covering eight genes (CSF2, IL3, IL4, IL13, CSF2RB, IL4R, IL13RA1, IL13RA2), several were related to pollen allergies among controls: IL4R rs3024647 (dominant OR: 1.5; 95% CI: 1.0-2.3; P = 0.04), CSF2RB rs16997517 (dominant OR: 2.2; 95% CI: 1.0-4.7; P = 0.04), and IL13 rs1800925 (per-allele OR: 1.7; 95% CI: 1.3-2.4; P = 0.0007). Two variants were inversely associated with SCC risk: IL4R rs3024656 (per-allele OR: 0.8; 95% CI: 0.6-1.0; P = 0.03) and CSF2RB rs16997517 (dominant OR: 0.4; 95% CI: 0.2-0.9; P = 0.04).

CONCLUSIONS

Pollen allergies were related to reduced SCC risk. CSF2RB rs16997517 was directly related to pollen allergies in controls and to reduced SCC risk.

IMPACT

If other studies confirm these results, the mechanism behind allergy-associated immune response associated with SCC risk may be worth exploring in the context of therapeutic or prophylactic vaccines.

Seasonal and perennial allergic conjunctivitis: the possible role of nasal allergy

BACKGROUND

There is a link between conjunctiva and nose. Nasal allergy is suspected to be involved in some cases of conjunctivitis. This work aims to investigate the possible role of nasal allergy in seasonal (SAC) and perennial (PAC) allergic conjunctivitis and the value of nasal challenges with allergens (nasal provocation tests [NPTs]) for the diagnostic procedures of the conjunctivitis.

METHODS

In 61 adults suffering from SAC or PAC with a positive history and skin tests, but responding insufficiently to the local treatment, 122 NPTs and 61 control nasal challenges with phosphate-buffered saline (PBS) were performed using rhinomanometry combined with recording of ocular response. In 16 control subjects suffering only from allergic rhinitis without a history of conjunctivitis, 16 positive NPTs were repeated and supplemented with registration of ocular features.

RESULTS

Of the 61 patients, 55 developed 103 positive nasal responses of various types (P < 0.01), 82 of which were accompanied by significant conjunctival response (P < 0.01) without any corneal involvement. No significant ocular responses were recorded during 61 control PBS challenges (P > 0.05) as well as during 16 challenges in control subjects (P > 0.1).

CONCLUSIONS

These results illustrate a possible involvement of nasal allergy in some patients with allergic conjunctivitis (SAC and PAC) and the value of the nasal challenges with allergen combined with registration of the ocular features in the diagnostic approach to these disorders.

Interleukin-4–Mediated Infiltration of Eosinophils into the Conjunctiva and Its Suppression by Interferon-γ

PURPOSE

Interleukin (IL)-4 is a T helper (Th)2 cytokine that plays an important role in the development of allergic reactions. It has been suggested that IL-4 is responsible for the infiltration of eosinophils into the conjunctiva during the development of allergic conjunctivitis. However, it is still unclear whether IL-4 is able to induce this eosinophilic infiltration on its own. We investigated whether subconjunctival injection of IL-4 can induce eosinophils to infiltrate into the conjunctiva.

METHODS

Brown Norway rats were subconjunctivally injected with IL-4, eotaxin, or phosphate buffered saline (PBS), and the conjunctivas were harvested for histologic analysis (including immunohistochemistry) 6, 12, 18, and 24 hr later. The harvested conjunctivas were also subjected to reverse transcription-polymerase chain reaction (RT-PCR) analysis to examine chemokine expression. In a separate experiment, the effect of coadministering interferon-gamma (IFN-gamma) along with IL-4 was examined.

RESULTS

The subconjunctival injection of IL-4 induced eosinophil infiltration into the conjunctiva in a dose-dependent manner. IL-4 was as potent as eotaxin. The eosinophilic infiltration started 6 hr after the injection and persisted for up to 24 hr after the injection. Other infiltrating cell phenotypes were noted but were also observed in conjunctivas injected with PBS alone. RT-PCR analysis demonstrated that IL-4 injection did not upregulate chemokine RNA expression in the conjunctiva. Coinjection of IFN-gamma suppressed the infiltration of eosinophils into the conjunctiva induced by IL-4 injection.

CONCLUSIONS

The subconjunctival injection of IL-4 specifically induces eosinophils to infiltrate into the conjunctiva. In addition, IFN-gamma in the conjunctiva can counteract this effect of IL-4.

Late-phase reaction in ocular allergy

PURPOSE OF REVIEW

To determine if the late-phase reaction, which commonly occurs in allergic rhinitis and asthma, is also found in ocular allergy.

RECENT FINDINGS

Using PubMed, 542 articles were found; 18 articles in the allergy and ophthalmology literature were specifically related to late-phase reaction. Ocular late-phase reaction is clinically seen in 50-100% of allergic rhinoconjunctivitis patients, is associated with progression to systemic atopic disorders that is allergic rhinoconjunctivitis and occurs in several forms including biphasic, multiphasic and a prolonged response.

SUMMARY

The existing literature demonstrates that an ocular late-phase reaction also exists and has implications in the development severity of disease, change of reactivity and progression of the atopic disease state from a localized target organ, such as the nose or eye, to a more systemic atopic disorder. The existence of the clinically relevant allergic late-phase response is not only limited to the nose, skin and lungs but also includes the eyes. The appreciation that the late-phase response may be clinically very important as there is a continuum of ocular mast-cell activation during the waking hours of the day, a better understanding of its clinical impact may be a more appropriate focus in the development of future treatments.

Endogenous IL-17 does not play a significant role in the development of experimental murine allergic conjunctivitis

BACKGROUND

Endogenous IL-17 is needed for the Ag sensitization that results in murine allergic asthma, a Th2-mediated disease. Here, we aimed to investigate the role IL-17 plays in the development of murine experimental allergic conjunctivitis (EC) which is also a Th2-mediated disease.

METHODS

To induce EC, wild-type (WT) and IL-17-deficient (IL-17 KO) mice on the BALB/c and C57BL/6 backgrounds were immunized with ragweed (RW) in alum and challenged with RW in eye drops. Alternatively, EC was induced by adoptively transferring RW-primed splenocytes followed by challenge with RW-containing eye drops. Twenty-four hours after the RW challenge, the conjunctivas and spleens were harvested for histological analyses and cytokine assays, respectively.

RESULTS

The WT and IL-17 KO mice on both backgrounds did not differ in terms of the severity of actively induced EC, as evaluated by the conjunctival eosinophil infiltration. They also did not differ with regard to the phenotypes of the inflammatory cells infiltrating the conjunctivas, although primed IL-17 KO splenocytes stimulated in vitro with RW extract did produce significantly higher amounts of IL-4, IL-13 and IFN-gamma than WT splenocytes. Reciprocal adoptive transfer experiments also demonstrated that the IL-17 from both the donor splenocytes and the recipient mice is not involved in the development of EC.

CONCLUSIONS

Endogenous IL-17 does not appear to play a significant role in the development of EC.

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.

Role of suppressor of cytokine signaling in ocular allergy

PURPOSE OF REVIEW

The goal of this article is to evaluate developments in the knowledge of suppressor of cytokine signaling (SOCS) protein ocular allergy and the potential of SOCS proteins as targets for therapeutic strategies.

RECENT FINDINGS

The family of proteins designated SOCS proteins plays an important role in Th2-mediated allergic responses through the control of the balance between Th1 and Th2 cells. SOCS3 and SOCS5 are predominantly expressed in Th2 and Th1 cells, respectively, and they reciprocally inhibit the Th1 and Th2 differentiation processes. SOCS3 is highly expressed at the disease site of allergic conjunctivitis, and T-cell-specific expression of SOCS3 deteriorates clinical and pathological features of allergic conjunctivitis. Reduction of the expression level or inhibition of function clearly reduces the severity of allergic conjunctivitis. On the other hand, constitutive expression of SOCS5, a specific inhibitor of IL-4 signaling, results in reduced eosinophil infiltration. Moreover, negative regulation of the Th2-mediated response by dominant-negative SOCS3 and SOCS5 reduced the incidence of allergic conjunctivitis in a mouse model.

SUMMARY

The present article summarizes recent findings in terms of a role of SOCS protein as a negative regulator in ocular allergy and its clinical application.

Antibodies to T-cell Ig and mucin domain-containing proteins (Tim)-1 and -3 suppress the induction and progression of murine allergic conjunctivitis

The T cell Ig and mucin domain-containing proteins (Tim) regulate Th1- and Th2-mediated immune responses. We investigated the ability of Abs blocking Tim-1 or Tim-3 ligand-binding activity to prevent and treat murine experimental allergic conjunctivitis (EC), a Th2-mediated disease. Treatment with either Ab during the induction phase of EC in actively immunized wild-type mice suppressed EC and upregulated Th1 and Th2 immune responses. In contrast, both Abs exacerbated EC in actively immunized IFN-gamma-knockout mice. Thus, both anti-Tim Abs suppress the pathogenic immune responses generated in the induction phase by upregulating systemic IFN-gamma production. Treatment of actively immunized mice and passively immunized mice with either anti-Tim Ab just prior to RW challenge also suppressed EC. Thus, treatment with anti-Tim-1 or anti-Tim-3 Ab can suppress both the induction and progression of EC, which could indicate potential preventive and/or therapeutic approaches for allergic diseases such as allergic conjunctivitis.

Analysis of the interaction between IFN-gamma and IFN-gammaR in the effector phase of experimental murine allergic conjunctivitis

IFN-gamma acts to promote the severity of experimental allergic conjunctivitis (EC) during the effector phase. To identify the cell source and cell target of this cytokine in the effector phase of EC, we established mice lacking both IFN-gamma and the IFN-gamma receptor (Dbl-KO). Reciprocal adoptive transfer experiments involving wild-type, Dbl-KO, IFN-gamma-lacking and IFN-gammaR-lacking mice were performed. EC was then induced by RW challenge in eye drops. Analysis of the resulting eosinophil infiltration in the six donor/recipient combinations revealed that IFN-gamma produced by both donor and recipient cells plays an important role in the EC effector phase, and that the targets for this cytokine are also both donor and recipient cells. That EC was attenuated when any of the IFN-gamma-IFN-gammaR interactions were disturbed confirms that IFN-gamma promotes the severity of EC during the effector phase. These observations indicate that Dbl-KO mice will be useful for investigating the role(s) IFN-gamma play in inflammatory diseases.

Roles of CD4+CD25+ T cells in the development of experimental murine allergic conjunctivitis

BACKGROUND

CD25+ regulatory T (T reg) cells play a suppressive role in experimental autoimmune uveoretinitis as well as experimental airway inflammation but their involvement in the development of allergic conjunctivitis (AC) remains unclear. We therefore investigated whether T reg cells play a role in the development of experimental AC (EC).

METHODS

BALB/c and C57BL/6 mice were actively immunized with ragweed (RW). The mice were treated with an anti-CD25 Ab (PC61) or control normal rat IgG (nrIgG) either 2 days prior to active immunization or during the induction phase (days 0, 2, 4, 6 and 8). Ten days after active immunization, the mice were challenged with RW-containing drops. Twenty-four hours after the challenge, the conjunctivas were harvested for histological analysis of eosinophil infiltration, and the spleens were harvested for cell culture for splenocyte transfer. Cultured splenocytes were transferred into syngeneic mice, and 4 days after the transfer, the recipient mice were challenged with RW. Twenty-four hours after the challenge, conjunctivas were collected for histological analysis.

RESULTS

Pretreatment with PC61 did not affect EC in either strain of mice; however, treatment with PC61 during the induction phase significantly suppressed EC in C57BL/6 mice. In contrast, transfer of RW-primed splenocytes from mice treated with PC61 induced EC that was significantly more severe regardless of strain and treatment protocol.

CONCLUSIONS

The finding that T reg cells play a suppressive role in the development of EC in splenocyte transfer experiments suggests that modulation of T reg cells may be a possible therapy for AC.

Ascaris suum-derived products suppress mucosal allergic inflammation in an interleukin-10-independent manner via interference with dendritic cell function

We have previously demonstrated that protection from allergic inflammation by Ascaris suum infection was characterized by a global increase in interleukin-10 (IL-10) and the development of protective CD4(+)/CD25(+) T cells (L. Schopf, S. Luccioli, V. Bundoc, P. Justice, C. C. Chan, B. J. Wetzel, H. H. Norris, J. F. Urban, Jr., and A. Keane-Myers, Investig. Ophthalmol. Vis. Sci. 46:2772-2780, 2005). Here, we used A. suum pseudocoelomic fluid (PCF) in lieu of infection to define molecular mechanisms of allergic protection in a mouse model of allergic inflammation. Mice were sensitized with ragweed (RW) and PCF (RW/PCF), PCF alone, or RW alone and then challenged intratracheally, intranasally, and supraocularly with RW. Histological examination of the eyes and lungs, analysis of the bronchoalveolar lavage fluid (BALF), and characterization of ex vivo cytokine responses were performed to determine allergic inflammatory responses. RW/PCF-treated mice had suppressed allergic immune responses compared to mice given RW alone. To investigate whether IL-10 was involved in PCF-mediated allergic protection, similar experiments were performed using mice genetically deficient for IL-10. Persistent protection from allergic disease was observed in the absence of IL-10, indicating the primary mechanism of PCF protection is IL-10 independent. Ex vivo and in vitro analysis of PCF-treated dendritic cells (DC) demonstrated reduced activation receptor expression and cytokine production in response to either RW or lipopolysaccharide stimulation. These findings extend previous studies that showed infection with A. suum alters expression of allergic disease and suggest that PCF can contribute to this effect by interference with DC function.

Modulation of murine experimental allergic conjunctivitis by treatment with α-galactosylceramide

When mice are treated with alpha-galactosylceramide (alpha-GalCer), NKT cells are activated and suppress the development of experimental airway inflammation. This suppressive effect is believed to be mediated by the upregulation of IFN-gamma. Here, we investigated whether alpha-GalCer treatment can also modulate the development of experimental allergic conjunctivitis (EC). EC was induced in wild-type and IFN-gamma-deficient Balb/c mice by active immunization with ragweed (RW) followed by challenge with RW in eye drops. The mice were intraperitoneally injected with alpha-GalCer or vehicle at the time of immunization or before RW challenge. Twenty-four hours after RW challenge, conjunctivas, spleens and sera were harvested for histological analysis, flow cytometric, proliferation and cytokine assays, and measurement of immunoglobulin levels, respectively. Treatment with alpha-GalCer at the time of the EC-priming immunization significantly increased Th2 responses and markedly upregulated the severity of the EC. However, treatment with alpha-GalCer just before the Ag challenge that triggers EC in primed animals significantly suppressed the disease. This was associated with an increased frequency of CD4(+)CD25(+) cells, which express Foxp3, in the spleen. alpha-GalCer treatment just prior to Ag challenge also suppressed the development of EC in IFN-gamma-deficient mice, and we found apoptosis and anergy are unlikely to play a major role in the mechanism by which pre-challenge alpha-GalCer treatment suppresses EC. These data suggest that NKT cells can play a downregulatory role in the development of EC and that alpha-GalCer may be useful for treating allergic conjunctivitis.

Th1- and Th2-type cytokines in chronic ocular allergy

BACKGROUND

Previous reports have suggested that Th2-type cytokines are important in the pathogenesis of ocular allergic diseases. The purpose of this study is to measure levels and mRNA expression of Th1- and Th2-type cytokines in patients with active vernal keratoconjunctivitis (VKC) and atopic keratoconjunctivitis (AKC).

METHODS

Tear samples and tear-isolated cells were obtained from 9 healthy participants (CT--controls), 28 VKC, and 6 AKC patients. IL-4, IL-13, and interferon gamma (IFNgamma) tear levels were determined by ELISA, and IL-4 and IFNgamma tear cell mRNA expression by RT-PCR. Effects of these cytokines on IL-6 and IL-8 secretion, and on ICAM-1 expression by conjunctival fibroblasts, were evaluated by ELISA and flow cytometry respectively.

RESULTS

Interleukin-4 tear levels were increased in VKC and AKC compared with CT, but only IFNgamma significantly correlated with corneal involvement. An IL-4/13-dominant profile was found in 50% of VKC and in 17% of AKC patients, while a IFNgamma-dominant profile was found in 18% of VKC and in 17% of AKC patients. IL-4 and IFNgamma transcripts were detected in tear cells from 11 out of 12 VKC patients. IFNgamma upregulated expression of ICAM-1 on conjunctival fibroblasts and the secretion of IL-6 and IL-8.

CONCLUSIONS

Although both IL-4 and IFNgamma are detected in tears, only IFNgamma levels correlated with disease severity and upregulated ICAM-1 on conjunctival fibroblasts, suggesting the role of IFNgamma in the inflammatory phase of chronic allergic eye diseases.

Genetic background determines susceptibility to experimental immune-mediated blepharoconjunctivitis: Comparison of Balb/c and C57BL/6 mice

Balb/c and C57BL/6 mice have been reported to be biased towards Th2 and Th1 immune responses, respectively. We investigated which strain is more susceptible to the development of experimental immune-mediated blepharoconjunctivitis (EC), which is predominantly mediated by Th2 immune responses. EC was induced by three different methods in Balb/c and C57BL/6 mice using ragweed (RW) as the antigen. The mice were thus either actively immunized with RW, passively immunized by transfer of RW-primed T cells, or passively immunized by transfer of RW-specific IgE, followed by RW challenge in eye drops. Twenty-four hours after the challenge, conjunctivas, sera and spleens were harvested for histological analysis, measurement of serum IgE and assessment of cellular immune responses, respectively. The responses of the Balb/c and C57BL/6 mice were compared. In addition, to assess the involvement of IFN-gamma in the development of EC in the two strains, IFN-gamma knockout (GKO) mice of the two strains were actively immunized and evaluated as above. Regardless of the method of induction, EC, as determined by the degree of eosinophil infiltration into the conjunctiva, was more severe in Balb/c mice than in C57BL/6 mice. Moreover, more IgE was produced by actively immunized Balb/c mice than C57BL/6 mice and RW-primed splenocytes from Balb/c mice produced more IL-4 but less IFN-gamma than those from C57BL/6 mice. EC could be induced in the GKO mice of both strains. However, when their EC was compared to that in WT mice, significantly less infiltration of eosinophils was noted in the Balb/c GKO mice. Taken together, Balb/c mice are more susceptible to EC than C57BL/6 mice and this higher susceptibility might be related to the Th2 immune response bias of Balb/c mice. Furthermore, the involvement of endogenous IFN-gamma in the development of EC in these two strains differs.

The control of allergic conjunctivitis by suppressor of cytokine signaling (SOCS)3 and SOCS5 in a murine model

Allergic conjunctivitis (AC) is a common allergic eye disease characterized by clinical symptoms such as itchiness, conjunctival congestion, elevated Ag-specific IgE, mast cell activation, and local eosinophil infiltration. In this study we established a murine model for Ag-induced AC to understand the pathogenesis of the disease. Cell transfer experiments indicated that AC can be divided into early and late phase responses (EPR and LPR). EPR was associated with IgE responses, leading to itchiness, whereas LPR was characterized by local eosinophil infiltration. Both EPR and LPR were significantly inhibited in STAT6-deficient mice, and adoptive transfer of Th2 cells reconstituted LPR. Furthermore, SOCS3 was highly expressed at the disease site, and T cell-specific expression of SOCS3 deteriorated clinical and pathological features of AC, indicating that Th2-mediated SOCS3 expression controls the development and persistence of AC. Reduction of the expression level in SOCS3 heterozygous mice or inhibition of function in dominant-negative SOCS3 transgenic mice clearly reduced the severity of AC. In contrast, constitutive expression of SOCS5, a specific inhibitor of IL-4 signaling, resulted in reduced eosinophil infiltration. These results suggest that negative regulation of the Th2-mediated response by dominant-negative SOCS3 and SOCS5 could be a target for therapeutic intervention in allergic disease.

Engagement of 4-1BB inhibits the development of experimental allergic conjunctivitis in mice

The 4-1BB receptor acts as a costimulator in CD8(+) T cell activation. Agonistic stimulation through this molecule by treatment with anti-4-1BB Abs has been demonstrated to inhibit various experimentally induced diseases in animals. However, the effect of anti-4-1BB Abs on experimental allergic diseases has not been reported. We investigated the effect of anti-4-1BB Abs on the development and progression of experimental allergic conjunctivitis in mice. To examine the effects of Abs during the induction or effector phase, actively immunized mice or passively immunized mice by splenocyte transfer were treated with agonistic anti-4-1BB Abs, blocking anti-4-1BB ligand Abs, or normal rat IgG. Eosinophil infiltration into the conjunctiva was significantly reduced in wild-type mice by the anti-4-1BB Ab treatment during either induction or effector phase. Th2 cytokine production by splenocytes and total serum IgE were significantly reduced by the anti-4-1BB Ab treatment, while IFN-gamma production was increased. The anti-4-1BB Ab treatment induced a relative increase of CD8-positive cell numbers in the spleens. Moreover, inhibition of eosinophil infiltration by the treatment with anti-4-1BB Abs was also noted in actively immunized IFN-gamma knockout mice. Taken altogether, in vivo treatment with agonistic anti-4-1BB Abs in either induction or effector phase inhibits the development of experimental allergic conjunctivitis, and this inhibition is likely to be mediated by suppression of Th2 immune responses rather than up-regulation of IFN-gamma.

The immunization protocol determines whether endogenous interferon-γ suppresses the infiltration of eosinophils into the conjunctiva

BACKGROUND

Studies with interferon-gamma knockout (GKO) mice showed that endogenous IFN-gamma suppresses the infiltration of inflammatory cells into the conjunctiva. To examine whether this phenomenon is universally true, we induced conjunctival inflammation by four different immunization protocols.

METHODS

Both wild type (WT) and GKO mice (C57BL/6 background) were immunized with ragweed (RW) in aluminum hydroxide (alum). Two different immunization protocols were used: either the emulsion was injected into only the left hind footpad or it was also injected into the tail base (50 microg RW in 2mg alum per injection site). In addition, to compare the effects of the immunization dose of RW and the immunization site, 100 microg RW in 2mg alum was injected into only the left hind footpad and 25 microg RW in 2mg alum per injection site was injected into both the left hind footpad and the tail base. Ten days later, the mice were challenged with 2mg RW in 10 microl PBS. Twenty-four hours later, the conjunctivas were analyzed histologically, and the cellular and humoral immune responses in the spleens and sera were determined, respectively.

RESULTS

Similar to a previous report, GKO mice showed significant eosinophilic infiltration into the conjunctiva after the footpad only injection of 50 microg RW. However, injection of 50 microg RW per injection site into the footpad plus the tail base resulted in comparable levels of eosinophilic infiltration in WT and GKO mice. On the contrary, either immunization of 100 microg RW in 2mg alum into only the left hind footpad or that of 25 microg RW in 2mg alum into both the left hind footpad and the tail base induced significant infiltration of eosinophils into the conjunctiva of GKO mice, compared to WT mice.

CONCLUSIONS

These results show that the immunization protocol employed has a marked effect on the severity of eosinophilic infiltration. These observations indicate that in interpreting experimental results in the study of EC, the immunization protocol employed must be considered.

Systemic interferon-gamma suppresses the development of endotoxin-induced uveitis in mice

PURPOSE

It has been shown that interferon (IFN)-gamma is involved in the development of endotoxin-induced uveitis (EIU), but its exact role is unclear. We aimed to elucidate the role that endogenous systemic IFN-gamma plays in EIU pathogenesis.

METHODS

EIU was induced in wild-type (WT) or IFN-gamma knockout (GKO) mice on the C57BL/6 background by injecting Salmonella typhimurium endotoxin into a hind footpad. Twenty-four hours later, the eyes were harvested for histological analysis, and the serum was collected for cytokine ELISAs. WT and GKO mice were also intraperitoneally injected with 1 microg of recombinant murine IFN-gamma (rmIFN-gamma) just after and 6 h after EIU induction, and their eyes and sera were evaluated 24 h after EIU induction, as above.

RESULTS

The GKO mice had significantly more severe EIU as determined by the number of ocular infiltrating cells and lower serum IL-6 levels after EIU induction compared to WT mice. The injection of rmIFN-gamma suppressed the severity of EIU and increased the serum IL-6 levels in both the WT and GKO mice.

CONCLUSIONS

Endogenous IFN-gamma suppresses EIU pathogenesis. In addition, the systemic administration of IFN-gamma suppresses EIU. The suppressive mechanism involved is unclear but may relate to the production of IL-6.

Animal models of allergic and inflammatory conjunctivitis

Allergic eye diseases are complex inflammatory conditions of the conjunctiva with an increasing prevalence and incidence. The diseases are often concomitant with other allergic diseases such as allergic rhinitis, atopic dermatitis and allergic asthma. Despite the disabling and prominent symptoms of ocular allergies, they are less well studied and further insights into the molecular basics are still required. To establish new therapeutic approaches and assess immunological mechanisms, animal models of ocular allergies have been developed in the past years. The major forms of allergic ocular diseases, seasonal and perennial allergic conjunctivitis, vernal and atopic keratoconjunctivitis and giant papillary conjunctivitis, each have different pathophysiological and immunological components. In contrast to these distinct entities, the current animal models are based on the sensitization against a small number of allergens such as ovalbumin, ragweed pollen or major cat allergens and consecutive challenge. Different animal species have been used so far. Starting with guinea-pig models of allergic conjunctivitis to assess pharmacological aspects, new models including rats and mice have been developed which mimic major features of ocular allergy. The presently preferred species for the investigation of the immunological basis of the disease is represented by murine models of allergic conjunctivitis. In the future, combined ocular, nasal and aerosolic challenges with allergens may provide a model of allergy that encompasses simultaneously the target organs eye, nose and airways with conjunctivitis, rhinitis and asthma.

Animal models of ocular allergy and their clinical correlations

Ocular allergic diseases represent a wide spectrum of disorders, from the acute self-limited, mild form of seasonal allergic conjunctivitis to the chronic, severe, sight-threatening atopic keratoconjunctivitis. The least problematic forms are the most prevalent, and several animal models have contributed to elucidate their etiopathogenetic mechanisms and have served to test numerous anti-allergic compounds. The most severe and chronic, although less prevalent, ocular allergic problems have not benefited from a similar advance, with the subsequent lack of full understanding and a limited therapeutic armamentarium. Research in this field is currently concentrating efforts in developing more protracted models of ocular allergic inflammation involving the cornea and mimicking more closely the human disease caused by chronic ocular allergy. Most recent experimental models are demonstrating that inhibiting Th2 cells and their secreted cytokines might be one important therapeutic target for inhibiting chronic allergic inflammation in the ocular surface.

Effect of GM-CSF on immune, inflammatory, and clinical responses to ragweed in a novel mouse model of mucosal sensitization

BACKGROUND

Conventional models of allergic airway inflammation involve intraperitoneal administration of ovalbumin in conjunction with a chemical adjuvant (generally aluminum hydroxide) to generate allergic airways inflammation. Here we have investigated the effect of respiratory mucosal exposure to a ragweed extract in the absence of chemical adjuvant on the generation of allergic responses.

OBJECTIVES

We sought to develop a mouse model of ragweed-induced allergic airway inflammation through mucosal sensitization and to investigate the role of GM-CSF in this process.

METHODS

Ragweed was delivered intranasally to an airway microenvironment enriched with GM-CSF, which was achieved by means of either multiple coadministrations of recombinant GM-CSF or a single delivery of an adenoviral vector carrying the GM-CSF transgene.

RESULTS

Administration of a purified ragweed extract leads to T(H)2 sensitization (and not inhalation tolerance) accompanied by mild airway inflammation, modest clinical symptoms, and moderate production of T(H)2 cytokines by splenocytes on ragweed restimulation. The administration of anti-GM-CSF antibodies in conjunction with ragweed diminished T(H)2-associated cytokine production. These responses were amplified by enriching the airway microenvironment with GM-CSF. Under these conditions, all T(H)2-associated immune-inflammatory responses, as well as the clinical responses, were considerably enhanced. To investigate the mechanism underlying these effects, we examined lung mononuclear cells by means of flow cytometry and detected a substantial expansion of antigen-presenting cells, particularly dendritic cells, as well as a substantially increased activation of these antigen-presenting cells, as demonstrated by the expression of B7 molecules, particularly B7.2.

CONCLUSION

GM-CSF plays an important role in the generation of allergic immune-inflammatory responses to ragweed.

STAT4 signal pathways regulate inflammation and airway physiology changes in allergic airway inflammation locally via alteration of chemokines

Mice homozygous for the STAT4-null mutation were sensitized to cockroach Ag, challenged intratracheally 21 days later, and compared with STAT4-competent allergic mice. The STAT4(-/-) mice showed significant decreases in airway hyperreactivity (AHR) and peribronchial eosinophils compared with wild-type controls. In addition, pulmonary levels of chemokines were decreased in the STAT4(-/-) mice, including CC chemokine ligand (CCL)5, CCL6, CCL11, and CCL17. However, levels of Th2-type cytokines, such as IL-4 and IL-13, as well as serum IgE levels were similar in the two groups. Transfer of splenic lymphocytes from sensitized wild-type mice into sensitized STAT4(-/-) mice did not restore AHR in the mutant mice. Furthermore, chemokine production and peribronchial eosinophilia were not restored during the cellular transfer experiments. Thus, it appears that STAT4 expression contributes to a type 2 process such as allergen-induced chemokine production and AHR. In additional studies, competent allergic mice were treated with anti-IL-12 locally in the airways at the time of allergen rechallenge. These latter studies also demonstrated a decrease in AHR. Altogether, these data suggest that STAT4-mediated pathways play a role locally within the airway for the exacerbation of the allergen-induced responses.

Differential expression and signaling of IFN-gamma in the conjunctiva between Lewis and Brown Norway rats

Genetic background determines the histological features of experimental immune-mediated blepharoconjunctivitis (EC) in rats, which is a model for human allergic conjunctivitis (AC). A great number of lymphocytes predominate in EC of Lewis rats, while less lymphocytes and more eosinophils are present in that of Brown Norway (BN) rats. Although this difference could be attributed to their systemic Th1/Th2 dominancy, it remains unclear whether some regulatory mechanisms may exist in the inflammatory site in the conjunctiva. Here, we aim to investigate this hypothesis by comparing the expression levels of inflammatory mediators in the conjunctiva between the two strains. EC was induced in Lewis and BN rats by transfer of ovalbumin (OVA)-specific CD4(+) T-cell lines followed by eye drops of OVA as antigen challenge, and then was clinically and histologically evaluated. Reverse-transcription (RT)-PCR was performed to compare the expressions of cytokines and cytokine receptors (Rs) in conjunctivas of both strains of rats either with or without EC. To confirm the biological significance of interferon (IFN)-gamma R expression, phosphorylation of signal transducers and activators of transcription (STAT)-1 was examined in the conjunctivas, followed by subconjunctival injection of IFN-gamma. BN T cells contained interleukin (IL)-4 and IFN-gamma, while Lewis T cells expressed no IL-4. Transfer of those cells induced more severe EC in Lewis rats. RTPCR using naive conjunctivas detected more IL-4, IFN-gamma, and IFN-gamma R beta-chain RNA expression in BN rats. After the EC induction, BN rats expressed significantly higher amounts of IFN-gamma R beta-chain, and upregulation of interferon regulatory factor (IRF)-1 was observed. Phosphorylation of STAT-1 was more remarkable in BN rats. The findings demonstrate differential expression of IFN-gamma R and signaling through IFN-gamma in the conjunctiva between the two strains. This may be due to differences in histopathological character between the two strains.

Exertion of the suppressive effects of IFN-gamma on experimental immune mediated blepharoconjunctivitis in Brown Norway rats during the induction phase but not the effector phase

BACKGROUND/AIMS

Interferon gamma (IFN-gamma) knockout mice exhibit severe allergic conjunctivitis (AC), indicating that IFN-gamma regulates the development of AC. The authors examined whether this inhibitory effect of IFN-gamma is exerted during the induction or effector phase of experimental AC.

METHODS

Experimental immune mediated blepharoconjunctivitis (EC) was induced in Brown Norway (BN) rats, using ovalbumin (OVA) as the antigen. To investigate the role of IFN-gamma in the induction phase, EC was induced by active immunisation and IFN-gamma (10 micro g/time, total 70 micro g), or phosphate buffered saline (PBS) as a control, was injected intraperitoneally every other day from the day of immunisation. The rats were challenged with OVA eye drops 13 days after immunisation, and 24 hours later, the eyes were harvested for histology. To examine the effects of IFN-gamma in the effector phase, OVA specific T cells were transferred into syngeneic rats and IFN-gamma (10 micro g/time, total 50 micro g) or PBS was injected each day after the transfer until induction of EC 4 days later with an OVA challenge. To investigate the role of endogenous IFN-gamma during the effector phase, an anti-IFN-gamma monoclonal antibody (3 mg/time) was injected on days 3 and 4.

RESULTS

Injection of IFN-gamma into actively immunised rats suppressed eosinophilic infiltration but not infiltration of mononuclear cells. In contrast, neither IFN-gamma nor anti-IFN-gamma affected EC in passively immunised rats.

CONCLUSION

IFN-gamma is a suppressive cytokine for the development of EC and exerts this suppressive effect during the induction phase.

Advances in ocular allergy: basic mechanisms, clinical patterns and new therapies

Ocular allergy presents unsolved mysteries in molecular and cellular mechanisms, and at the same time continues to challenge ophthalmologists daily in a wide array of disease forms. The recent understanding of the key role of the T helper type 2 cytokines, adhesion molecules and chemokines may provide future avenues for pharmacological targeting of releasable inflammatory mediators. More potent topical mast cell stabilizers and H1 receptor antagonists have become commercially available for the management of the prevalent and benign forms of allergic conjunctivitis. Immunostimulatory DNA sequences present an innovative and promising route for the treatment of ocular allergy, but clinical studies are needed to demonstrate their efficacy in humans. Surgical methods are suggested to reconstruct the ocular surface in the sight-threatening diseases vernal keratoconjunctivitis and atopic keratoconjunctivitis. This review presents an update of the major advances in both the basic mechanisms and clinical and therapeutic aspects of ocular allergic diseases that were reported during the past year.

The increase in allergic respiratory diseases: survival of the fittest?

The prevalence of allergic respiratory diseases, asthma and allergic rhinoconjunctivitis, has increased since the advent of industrialization. The inverse relationship between the number of infections early in life and atopy has been interpreted as the "hygiene hypothesis." That is, many infections early in life promote the development of T helper type 1 cytokines, while fewer infections early in life favor the development of T helper type 2 (Th2) cytokines and atopy. An alternate interpretation of the same data, that atopy is protective against infections early in life, is rarely considered. With epidemiologic, historical, and immunologic data, I suggest that human evolution has favored individuals with an atopic predisposition. Th2 immune responses promote parity, and ensure successful pregnancy and term birth; provide the infant protection against infections and the inflammation induced by common pathogens in the first years of life until the immune system matures; and protect young adults exposed to viral respiratory pathogens. These traits are of particular value with the advent of industrialization, especially so in the era prior to the development of antibiotics. This theory contradicts the assumption that there is no biological or evolutionary advantage for allergic disease to exist in humans and has significant implications for our current and future treatments of allergic diseases.

Comparison of the clinical efficacy and comfort of olopatadine hydrochloride 0.1% ophthalmic solution and nedocromil sodium 2% ophthalmic solution in the human conjunctival allergen challenge model

BACKGROUND

Mast cell stabilizers, such as the ocular antiallergic agent nedocromil sodium 2% ophthalmic solution, are not rapid acting and often require a loading period of > or =2 weeks for maximal efficacy. Olopatadine hydrochloride 0.1% ophthalmic solution is a member of a new class of topical antiallergic agents that have combined antihistaminic and mast cell-stabilizing properties.

OBJECTIVE

The purpose of this study was to compare the clinical efficacy and comfort of olopatadine with those of nedocromil in the conjunctival allergen challenge model.

METHODS

This was a single-center, 3-visit, randomized, double-masked, contralaterally controlled study. Seventy-five subjects with a history of allergic conjunctivitis were screened, and the 52 who responded to conjunctival allergen challenge at visits I and 2 were randomized by eye to receive olopatadine, nedocromil, or placebo (a "natural tears" lubricant eye drop). Because nedocromil may require a 2-week loading period for maximal efficacy, the eyes assigned to that agent received nedocromil for 14 days (between visits 2 and 3), whereas the eyes assigned to olopatadine or placebo received placebo during this period. Throughout the loading phase, subjects instilled 1 drop of the assigned masked medication in each eye twice daily. At the assessment visit (visit 3), subjects received I drop of masked olopatadine, nedocromil, or placebo in each eye and were asked to rate the comfort of each drop on a scale from 0 to 8. Fifteen minutes after instillation of medication, subjects were challenged with the allergen concentration that had elicited a positive conjunctival allergic response at the previous visits. Subjects then scored their itching on a scale from 0 to 4 at 3, 5, and 10 minutes after challenge. Mean itching scores for all eyes were compared by treatment. Paired t tests were performed on the mean itching and ocular comfort scores at each time point. At the end of the study, subjects were asked which treatment they preferred in terms of comfort and efficacy.

RESULTS

Forty-nine subjects completed the study. Forty eyes received olopatadine, 36 received nedocromil, and 22 received placebo. Olopatadine was clinically and statistically superior to nedocromil at reducing itching in the conjunctival allergen challenge model (mean unit difference: -1.60 at 3 minutes, -1.68 at 5 minutes, -1.19 at 10 minutes; P < 0.001). One drop of olopatadine was more efficacious than 29 drops of nedocromil. Olopatadine-treated eyes were rated as being significantly more comfortable than nedocromil-treated eyes (0.73 vs 1.55; P = 0.034). Of the 14 subjects treated with olopatadine and nedocromil who stated a preference, 10 (71%) were more satisfied with olopatadine than with nedocromil.

CONCLUSION

In the conjunctival allergen challenge model, olopatadine was more efficacious and comfortable than nedocromil in reducing the itching associated with allergic conjunctivitis.

Allergic and immunologic disorders of the eye. Part II: ocular allergy

Allergy affects more than 15% of the world population, and some studies have shown that up 30% of the US population has some form of allergy. Most of these patients have various target organs for their allergies, and most have ocular involvement. The ocular component may be the most prominent and sometimes disabling feature of their allergy. Some are affected for only a few weeks to months, whereas others have symptoms that last throughout the year. The seasonal forms may present to clinical allergists, whereas the more chronic forms may present to ophthalmologists. Thus, in the second of this 2-part review series (Part I: Ocular Immunology appeared in the November issue of the Journal), an overview is provided of the spectrum of ocular allergy that ranges from acute seasonal allergic conjunctivitis to chronic variants of atopic keratoconjunctivitis. With a better understanding of the immunologic mechanisms, we now can develop better treatment approaches and design further research in intervention of allergic eye diseases.

Effects of IL-4 and IL-12 on experimental immune-mediated blepharoconjunctivitis in Brown Norway rats

IL-12 and IL-4 are critical cytokines for Th1 and Th2 differentiation, respectively. To assess the roles of these cytokines in the development of experimental immune-mediated blepharoconjunctivitis (EC) in Brown Norway (BN) rats, their effects were tested either in vitro or in vivo. Draining lymph node cells from rats immunized with ragweed pollen (RW) in Al(OH)3 were collected and cultured for 3 days with RW in the presence of IL-4, IL-12, or PBS as a control. After harvesting the culture supernatants for cytokine ELISA and the cells for cytokine reverse transcriptase-polymerase chain reaction, 10 million cells were injected intravenously into syngeneic recipient rats (n = 12 per group). The rats were challenged with RW by eye drops 4 days after transfer. Eyes were harvested for histology 24 h later. Furthermore, IL-12 (500 ng per injection) or PBS was injected intraperitoneally every other day seven times from the day of active immunization (n = 6 per group). One day after the last injection, rats were challenged and EC was evaluated as above. Transfer of cells with IL-4 in vitro augmented eosinophilic infiltration in the conjunctiva compared with the other two groups, whereas IL-12 in vitro suppressed eosinophilic infiltration and increased lymphocytic infiltration. Interferon-gamma production was augmented by IL-12. IL-4 RNA expression was augmented by IL-4. IL-12 administration in vivo augmented lymphocytic infiltration in the conjunctiva without affecting infiltration of eosinophils. In conclusion, IL-4 and IL-12 either in vitro or in vivo augmented Th2 and Th1 immunity, respectively, thus leading to distinct histological features of EC.