Dissection of Antigen-Specific Humoral and Cellular Immune Responses for the Development of Experimental Immune-Mediated Blepharoconjunctivitis in C57BL/6 Mice

A nerve-goblet cell association promotes allergic conjunctivitis through rapid antigen passage

The penetration of allergens through the epithelial layer is the initial step in the development of allergic conjunctivitis. Although pollinosis patients manifest symptoms within minutes after pollen exposure, the mechanisms of the rapid transport of the allergens remain unclear. In the present study, we found that the instillation of pollen shells rapidly induces a large number of goblet cell-associated antigen passages (GAPs) in the conjunctiva. Antigen acquisition by stromal cells, including macrophages and CD11b+ dendritic cells, correlated with surface GAP formation. Furthermore, a substantial amount of antigen was transported to the stroma during the first 10 minutes of pollen exposure, which was sufficient for the full induction of an allergic conjunctivitis mouse model. This inducible, rapid GAP formation and antigen acquisition were suppressed by topical lidocaine or trigeminal nerve ablation, indicating that the sensory nervous system plays an essential role. Interestingly, pollen shell-stimulated GAP formation was not suppressed by topical atropine, suggesting that the conjunctival GAPs and intestinal GAPs are differentially regulated. These results identify pollen shell-induced GAP as a therapeutic target for allergic conjunctivitis.

Pollen shells and soluble factors play non-redundant roles in the development of allergic conjunctivitis in mice

PURPOSE

We aimed to clarify the role of particulate allergen exposure to the conjunctiva in the development of allergic conjunctivitis.

METHODS

We administered ragweed pollen suspension, pollen extract, pollen shell, particulate air pollutants, and their combinations to the mouse conjunctiva five days a week without prior sensitization. Clinical signs were scored. Histological changes, cellular infiltrations, mRNA expressions, lymph node cell recall responses, and serum immunoglobulin levels were assessed. Immune cell-depleting antibodies and ST2 knockout mice were used to investigate the cellular and molecular requirements.

RESULTS

Pollen suspension, but not the extract or shell alone, induced robust eosinophilic conjunctivitis, accompanied by a proliferative response of epithelial cells. A combination of pollen extract and shell completely restored eosinophil accumulation. In addition, eosinophilic conjunctivitis was induced by a mixture of particulate air pollutants and pollen extract. Mechanistically, eosinophil accumulation was ameliorated by deficiency of the IL-33 receptor ST2 and abolished by depleting CD4⁺ T cells. Pollen shells, but not the extract, induced IL-33 release from conjunctival epithelial cells in vivo.

CONCLUSIONS

Our results indicate the non-redundant roles for the allergens' particulate properties and soluble factors in the development of allergic conjunctivitis.

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.

CD8+ T Cells Play Disparate Roles in the Induction and the Effector Phases of Murine Experimental Allergic Conjunctivitis

Although CD4+ Th2 cells clearly play an essential role in the development of experimental allergic diseases, the functions CD8+ T cells may have in these diseases have been investigated less extensively and remain controversial. Here, we investigated the roles of CD8+ T cells in the development of experimental allergic conjunctivitis (EC). EC was induced in CD8alpha-deficient (CD8KO) mice and wild-type (WT) mice by active immunization with short ragweed pollen (RW) followed by challenge with RW-containing eye drops. Alternatively, EC was induced by transferring RW-primed splenocytes followed by RW challenge. With regard to actively immunized mice, CD8KO mice showed significantly less severe eosinophil infiltration of the conjunctiva and lower total IgE levels, although the levels of the other Igs were equivalent between the two strains. Cytokine production by cultured splenocytes also did not differ, but the WT conjunctivas showed upregulated IL-5 and IL-6 expression and greater upregulation of IL-4 expression than the conjunctivas of CD8KO mice. Thus, CD8+ T cells may play a significant role during the induction phase by aiding IgE production and the generation of Th2 cytokines in the conjunctiva, thus promoting the development of EC. In contrast, splenocytes from CD8KO mice induced significantly more severe EC in WT mice than cells from WT mice. In addition, transfer of RW-primed splenocytes induced significantly more severe eosinophil infiltration in CD8KO recipient mice. Thus, CD8+ T cells promote the development of EC during the induction phase, but suppress it during the effector phase.

γδ T cells are required for maximal expression of allergic conjunctivitis

PURPOSE

To determine the function of γδ T cells in early- and late-phase responses in allergic conjunctivitis.

METHODS

Wild-type (WT) C57BL/6 and γδ T cell-deficient (TCR-δ(-/-)) mice were immunized intraperitoneally and challenged topically for 7 consecutive days with short ragweed pollen. Natural killer T (NKT) and γδ T cell-double-deficient mice were generated by treating TCR-δ(-/-) mice with anti-CD1d antibody. Allergic conjunctivitis was evaluated clinically, and the late-phase response was assessed by histopathology. Cytokine profiles were evaluated by ELISA. The afferent and efferent arms of allergic conjunctivitis were assessed by adoptive transfer of CD4(+) T cells from WT or TCR-δ(-/-) mice into naive TCR-δ(-/-) or WT mice.

RESULTS

TCR-δ(-/-) mice had decreased clinical manifestations of allergic conjunctivitis compared with WT mice. TCR-δ(-/-) mice had decreased eosinophilic infiltration compared with WT mice. TCR-δ(-/-) mice produced less Th2-associated cytokines interleukin (IL)-4, -5, and -13 compared with WT mice. Clinical manifestations of allergic conjunctivitis were lowest in NKT cell-depleted TCR-δ(-/-) mice. However, late-phase allergic conjunctivitis in NKT cell-depleted, TCR-δ(-/-) mice was the same as TCR-δ(-/-) mice. Adoptive transfer of CD4(+) T cells revealed that γδ T cells are needed for the afferent and efferent arms of allergic conjunctivitis.

CONCLUSIONS

γδ T cells are needed for full expression of both the clinical manifestations and the late phase of allergic conjunctivitis. Thus, γδ T cells have an important impact in the expression of allergic conjunctivitis and are a potential therapeutic target in the management of allergic diseases of the ocular surface.

T cell-related costimulatory molecules in the conjunctiva of patients with severe allergic conjunctivitis

BACKGROUNDS

We showed previously that costimulatory molecules such as OX40 and 4-1BB participate in the development of murine allergic conjunctivitis (AC). We investigated whether these molecules are expressed in the conjunctiva of patients with severe AC.

METHODS

Giant papillae were collected from 4 patients with severe AC. As a control, bulbar conjunctivas from 4 normal volunteers were used. Frozen sections of the conjunctivas were stained with anti-CD4, anti-CD8, anti-OX40, anti-4-1BB, or control antibodies (Abs) and then incubated with the biotinylated secondary Ab. Alternatively, staining was performed with a biotinylated anti inducible costimulator (ICOS) Ab. After using an avidin-biotin complex kit, the staining levels were graded from 0 to 3. For immunofluorescence analysis, conjunctival sections were stained with primary Abs that had been fluorescently labeled.

RESULTS

The conjunctival stroma of all 4 patients with severe AC were infiltrated with CD4+ and CD8+ cells, whereas only 1 control sample contained stromal CD4+ and CD8+ cells. Conjunctivas from patients but none of the control conjunctivas expressed OX40, 4-1BB, and ICOS. The expression levels of these molecules were significantly higher in patients than the control volunteers. Immunofluorescence analysis demonstrated that the OX40 and 4-1BB, but not the ICOS, molecules were expressed by the infiltrating CD4+ and/or CD8+ cells.

CONCLUSIONS

Together with the data in murine AC, OX40 and 4-1BB are expressed in the conjunctiva of patients with severe AC but not in the control conjunctivas, which suggests that OX40 and 4-1BB participate, at least in part, in the development of severe AC.

NKT cells are necessary for maximal expression of allergic conjunctivitis

Allergic conjunctivitis (AC) is elicited by immediate hypersensitivity responses to environmental agents. It is initiated by a T(h)2-dominated immune response that is characterized by production of IgE antibodies and eosinophilic infiltration. By using an experimental mouse model of AC induced by short ragweed (SRW) pollen, we show that sensitized Jalpha18(-/-) mice, which lack type I NKT cells, and CD1d(-/-) mice, which lack type I and type II NKT cells, exhibited a decrease in tearing, lid edema, conjunctival edema and vasodilatation and eosinophil infiltration into the conjunctiva when compared with wild-type (WT) mice in both T(h)1- and T(h)2-prone hosts (C57BL/6 and BALB/c mice, respectively). This demonstrates that NKT cells are needed for both the early and late phases of AC. Adoptive transfer of SRW-primed CD4(+) T cells from Jalpha18(-/-) mice into naive WT BALB/c mice revealed that NKT cells were needed for the maximal induction of allergen-specific T(h)2 cells. Results from adoptive transfer of SRW-primed CD4(+) T cells from WT BALB/c mice to naive Jalpha18(-/-) mice indicated that NKT cells were also needed for the expression of AC produced by allergen-primed CD4(+) T cells. The decreased expression of AC in NKT cell-deficient mice was correlated with significant reduction in the production of T(h)2 cytokines in SRW pollen-sensitized mice compared with WT mice and in the capacity of SRW pollen-sensitized CD4(+) T cells to mediate ocular inflammation when the hosts were confronted with SRW pollen at the ocular surface.

Mouse models of allergic diseases

The increasing prevalence of allergic diseases worldwide is posing significant socio-economic challenges. The pathogenesis of these diseases reflects a complex interaction of genetic and environmental factors. The heterogeneity of disease phenotypes challenges the concept of single mechanisms of disease. As human experimentation is limited, animal models have been developed to provide insights into pathogenesis and potential for discovery of novel therapeutics. Mice have served in models of many of the allergic diseases including asthma, allergic rhinitis, food allergy, atopic dermatitis (AD), and allergic conjunctivitis. Although much has been learned from these investigations, there are limitations when these models are translated to the human diseases.

Notch ligand Delta-like4 inhibits the development of murine experimental allergic conjunctivitis

BACKGROUND

To investigate the involvement of Notch ligands in the development of experimental allergic conjunctivitis (EC) in mice.

METHODS

To induce EC, wild-type (WT) or IFN-gamma-deficient (GKO) BALB/c mice were immunized with ragweed (RW) in alum followed by RW challenge in eye drops. Twenty-four hours after RW challenge, the conjunctivas, spleens and blood were harvested to evaluate conjunctival eosinophil infiltration, RW-specific cytokine production and serum Ig levels, respectively. Abs against Notch ligands (anti-Jagged1, anti-Jagged2, anti-Delta-like (Dll)1 and anti-Dll4) were injected intraperitoneally into EC-developing mice during the induction or effector phase. As a control, normal hamster IgG (nhIgG) was injected.

RESULTS

Treatment with anti-Dll4 Ab but not the other Abs during the induction phase significantly augmented the severity of EC, as measured by the conjunctival eosinophil infiltration. Anti-Dll4 Ab treatment also significantly upregulated RW-recall IL-4 production and suppressed serum IgE and IgG1 levels. However, anti-Dll4 Ab treatment during the induction phase did not significantly affect the severity of EC in GKO mice. None of the Abs significantly affected the severity of EC, splenocyte cytokine production, or serum Ig levels when administered during the effector phase.

CONCLUSIONS

These observations suggest that Dll4, a Notch ligand, plays a role in suppressing the development of EC, possibly by providing a negative signal for Th2 development during the induction phase. In addition, IFN-gamma may participate in the augmentation of EC by anti-Dll4 Ab treatment.

Immune regulatory mechanisms in allergic conjunctivitis: insights from mouse models

PURPOSE OF REVIEW

This review highlights recent findings regarding the immune regulation of allergic conjunctivitis. Mouse models have facilitated prospective studies that have not been possible in patients. The availability of gene knockout mice and the wealth of monoclonal antibodies have permitted exquisite dissection of the pathophysiology and immune regulation of allergic conjunctivitis.

RECENT FINDINGS

New insights have emerged in three areas: role of costimulatory molecules in the induction of Th2 immune responses; crucial role of IFN-gamma in the expression of allergic conjunctivitis; and the function of T regulatory cells in shaping conjunctival inflammation once the immune response has been initiated.

SUMMARY

Allergic conjunctivitis involves early phase and late phase reactions. The early phase reaction is IgE antibody-dependent, whereas the late phase reaction is IgE-independent and is mediated by inflammatory cells, especially eosinophils. Recent studies on mouse models of allergic conjunctivitis have provided important insights into the immune regulation of both the early phase reaction and late phase reaction of allergic conjunctivitis. Mounting evidence suggests that IFN-gamma is crucial for optimum expression of allergic conjunctivitis. Costimulatory molecules influence the induction of Th2 immune responses and the early phase reaction, whereas regulatory T cells shape the expression of the late phase reaction of allergic conjunctivitis.

Depletion of thymus-derived CD4+CD25+ T cells abrogates the suppressive effects of alpha-galactosylceramide treatment on experimental allergic conjunctivitis

BACKGROUND

We showed previously that alpha-galactosylceramide (alpha-GalCer) treatment elevated splenic CD4+CD25+Foxp3+ T-cell numbers and suppressed the development of experimental allergic conjunctivitis (EC). Here, we investigated whether CD4+CD25+Foxp3+ T cells mediate the suppressive effects of alpha-GalCer treatment on EC.

METHODS

To deplete CD4+CD25+Foxp3+ T cells, neonatal mice were thymectomized and intraperitoneally injected with anti-CD25 Ab. At 6 weeks of age, these mice were immunized with ragweed (RW) in aluminum hydroxide. Ten days later, the mice were challenged with RW in eye drops and 24 hours later, the conjunctivas and spleens were harvested for histological and flow cytometric analyses, respectively. alpha-GalCer or vehicle was injected 2 hours prior to RW challenge. In addition, alpha-GalCer was injected into thymus-intact EC-developing mice that had not been treated with anti-CD25 Ab.

RESULTS

alpha-GalCer treatment significantly suppressed EC in the thymus-intact mice that had not been treated with anti-CD25 Ab. In contrast, alpha-GalCer treatment of thymectomized and anti-CD25 Ab-treated mice did not affect the severity of EC or splenic CD4+CD25+Foxp3+ T-cell numbers. However, alpha-GalCer treatment did significantly increase splenic CD4+CD25+Foxp3+ T-cell numbers in thymectomized mice that had not received anti-CD25 Ab.

CONCLUSIONS

alpha-GalCer treatment during the effector phase of EC increased CD4+CD25+Foxp3+ T-cell numbers, which in turn suppressed the development of EC.

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.

Roles of galectin-9 in the development of experimental allergic conjunctivitis in mice

BACKGROUND

Galectin-9 was recently identified as a ligand for Tim-3, which negatively regulates Th1 cells. Here, we investigated whether administration of anti-galectin-9 antibodies (Abs) affects the development of murine experimental allergic conjunctivitis (EC), a Th2-mediated disease.

METHODS

EC was induced in BALB/c mice by active immunization with ragweed (RW) followed by RW challenge in eye drops. Normal rat IgG (nrIgG) or anti-galectin-9 Ab was injected intraperitoneally into the mice either during the induction phase treatment or effector phase treatment. Alternatively, Abs were injected into the subconjunctival space during the effector phase. To evaluate in vitro effects of anti-galectin-9 Abs, splenocytes from RW-sensitized mice were cultured in vitro with RW in the presence of nrIgG or anti-galectin-9 Abs. To induce EC, these splenocytes were transferred into naïve BALB/c mice followed by RW challenge.

RESULTS

Treatment with anti-galectin-9 Abs in vivo during either the induction or effector phase did not significantly affect the severity of EC. However, when the splenocytes from RW-primed mice treated with anti-galectin-9 Abs during the induction phase were stimulated in vitro and adoptively transferred into naïve recipients, they induced significantly severer EC. In contrast, when RW-primed splenocytes were restimulated in vitro with RW in the presence of anti-galectin-9 Abs and then adoptively transferred, they induced less severe EC and produced significantly less IL-5 and IL-13 and more IFN-gamma compared to nrIgG-treated control splenocytes.

CONCLUSIONS

These observations may reflect the fact that galectin-9 not only regulates T-cell function, it is also involved in many other biological functions.

Roles of T-Cells in the Development of Allergic Conjunctival Diseases

Massive infiltration of eosinophils is the typical histopathologic feature of severe forms of allergic conjunctival diseases (ACDs) such as vernal keratoconjunctivitis. Although ACD is an antigen (Ag)-specific disease, eosinophils lack Ag-specific receptors. Therefore, my group studied the likely roles of immunocompetent cells bearing Ag-specific receptors in inducing conjunctival eosinophil infiltration in ACDs. To induce experimental conjunctivitis (EC), Brown Norway rats and C57BL/6 and Balb/c mice were passively immunized by the transfer of Ag-specific or primed IgE, splenocytes, or purified T-cells and then challenged with Ag in eyedrops. The transfer of Ag-primed splenocytes or T-cells, but not of Ag-specific IgE, induced conjunctival eosinophil infiltration. We also showed that soon after EC induction by T-cell transfer, activated Ag-specific T-cells infiltrated the conjunctiva. Moreover, when EC-developing animals were topically treated with the T-cell-specific immunosuppressants cyclosporin A and FK506, conjunctival eosinophil infiltration was abrogated. In addition, only the transfer of Ag-specific type 2 helper T-cells (TH2 cells), but not of type 1 helper T-cells or CD8 T-cells, could induce conjunctival eosinophil infiltration. Our data show that Ag-specific TH2 cells play a crucial role in inducing conjunctival eosinophil infiltration during the development of EC. It is necessary to elucidate the roles that conjunctival residential cells and immunocompetent cells other than T-cells play in the conjunctival eosinophil infiltration of EC.

B7-H3 regulates the development of experimental allergic conjunctivitis in mice

B7-H3 negatively regulates Th1-mediated immune responses. Here, we aimed to investigate whether B7-H3 is involved in the development of murine experimental allergic conjunctivitis (EC), which is predominantly mediated by Th2 cells. Intraperitoneal injection of anti-B7-H3 Ab during the induction phase of EC significantly augmented the severity of EC evaluated as conjunctival eosinophil numbers and Ag-induced IL-5 production by splenocytes. Injection of anti-B7-H3 Ab during the effector phase of EC did not significantly affect the severity of EC. In addition, transfer of Ag-primed splenocytes treated with anti-B7-H3 Ab in vitro did not significantly affect the severity of EC, compared to the splenocytes treated with the control Ab. Thus, regulation of EC by blocking of B7-H3 was observed during the induction phase but not the effector phase. Moreover, this study provides a new notion that B7-H3 regulates not only Th1-mediated but also Th2-mediated immune reactions.

Endogenous interleukin-10 produced by antigen-irrelevant cells promotes the development of experimental murine allergic conjunctivitis

Interleukin (IL)-10 is known to act as an immunoregulatory cytokine in both T helper cell 1 (Th1)- and Th2-mediated immune responses. Here, we ask whether IL-10 regulates the development of experimental allergic conjunctivitis (EC), a Th2-mediated inflammatory disease. Wild-type (WT) and IL-10 knockout (IL-10 KO) mice were immunized with ragweed (RW) and then repeatedly challenged with RW in eye drops. Twenty-four hours after the final challenge, conjunctivas were harvested for histological analysis, while the blood and spleens were used to determine the RW-specific immunoglobulin levels in serum and proliferation or cytokine responses and splenocyte transfer, respectively. The IL-10 KO mice had significantly less severe EC (as determined by conjunctival eosinophil infiltration) than the WT mice and evinced greater RW-specific splenocyte proliferation and cytokine production. However, the RW-specific immunoglobulin levels of the two strains did not differ. When the splenocytes from RW-primed WT mice were transferred into IL-10 KO or WT mice, the IL-10 KO mice showed significantly less conjunctival eosinophil infiltration. In contrast, when the splenocytes from RW-primed IL-10 KO or WT mice were transferred into WT mice, both splenocyte populations generated equivalent severe EC. These data indicate that IL-10 does not serve as an immunoregulatory cytokine in the development of EC. Instead, it appears that IL-10 produced by antigen-irrelevant cells acts in the effector phase to promote the development of EC.

Thymus-Derived CD4+ CD25+ T Cells Suppress the Development of Murine Allergic Conjunctivitis

CD4+ CD25+ T cells regulate various kinds of immune-mediated diseases. Here, we sought to clarify whether CD4+ CD25+ T cells also regulate the development of experimental allergic conjunctivitis (EC). Thymectomized BALB/c mice, treated with anti-CD25 antibody (PC61), normal rat immunoglobulin G (nrIgG) or left untreated were immunized with short ragweed pollen (RW). Ten days later, the mice were challenged with RW in eye drops, and 24 h later, the conjunctivas, blood and spleens were harvested. The severity of EC, as evaluated by conjunctival eosinophil numbers, was significantly higher in the PC61-treated group as compared with the other two groups. The PC61-treated group also had significantly higher RW-specific IgE and IgG1 levels and displayed RW-specific splenocyte proliferation and RW-induced splenocyte T helper cell 2 cytokine production. However, PC61 treatment of unthymectomized mice did not affect the severity of EC. Thus, thymus-derived CD25+ T cells regulate the development of EC. Furthermore, transfer of Foxp3-expressing CD4+ CD25+ T cells from naïve mice into RW-sensitized mice suppressed the development of EC in these mice after RW challenge. Taken together, these results suggest that CD4+ CD25+ T cells regulate the development of EC.

Cryptomeria japonica-Induced Allergic Conjunctivitis in Mice

Japanese cedar pollen (Cryptomeria japonica, Cry j) is the most common allergen causing pollinosis in Japan. However, short ragweed pollen is used commonly as the antigen for experimentally-induced allergic conjunctivitis (EC) and Cry j-induced EC in mice has not been published. We actively immunized BALB/c mice with Cry j, and then performed a challenge with eye drops containing Cry j. We evaluated the early phase and late phase reactions in the conjunctiva, using Evans blue dye leakage and eosinophil infiltration, respectively. Significant inhibition of the early phase reaction was observed following pre-challenge with eye drops that block histamine H1 receptor in the conjunctiva. Thus, Cry j-induced EC appears to represent a suitable model for the study of pollinosis in Japan.

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.

Differential contributions of B7-1 and B7-2 to the development of murine experimental allergic conjunctivitis

B7-1 and B7-2 are the co-stimulatory molecules that are involved in activation of T cells. We investigated whether B7-1 and B7-2 play a role in the development of T cell-mediated experimental allergic conjunctivitis (EC). EC was induced in Balb/c mice by active immunization with ragweed (RW) followed by RW challenge in eye drops. These mice were treated with neutralizing anti-B7-1 Ab, anti-B7-2 Ab, both Abs, anti-cytotoxic T lymphocyte-associated Ag-4 (CTLA-4) Ab or normal IgGs as controls either during the induction phase or the effector phase. With regard to the induction phase treatment, EC was significantly attenuated when both anti-B7-1 and anti-B7-2 Abs were injected. In contrast, anti-CTLA-4 Ab treatment significantly exacerbated EC. With regard to the effector phase treatment, anti-B7-2 Ab alone significantly attenuated EC, while anti-CTLA-4 Ab tended to exacerbate EC. Collectively, B7-1 and B7-2 differently contribute to the development of EC during the induction and effector phases.

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.

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.

Interleukin 10 and transforming growth factor beta contribute to the development of experimentally induced allergic conjunctivitis in mice during the effector phase

AIM

To investigate the involvement of interleukin (IL)10 and transforming growth factor (TGF) beta in the development of experimentally induced allergic conjunctivitis in mice.

METHODS

Balb/c mice were actively sensitised with ragweed in alum, and then challenged with ragweed in eye drops after 10 days. 24 h later, the conjunctivas, spleens and blood were collected for histological and cytokine expression analyses, proliferation and cytokine production assays and measurement of immunoglobulin (Ig) levels. Mice developing experimentally induced allergic conjunctivitis were injected intraperitoneally with 200 microg of anti-IL10 or anti-TGF beta antibodies at 0, 2, 4, 6 and 8 days (induction phase treatment) or 500 microg of antibodies 2 h before ragweed challenge (effector phase treatment). Normal rat IgG was used for control injections.

RESULTS

Treatment with either anti-IL10 or anti-TGF beta antibodies during the induction phase did not affect eosinophil infiltration into the conjunctiva. By contrast, treatment with either antibody during the effector phase suppressed infiltration. During the effector phase, treatment with anti-TGF beta antibody, but not the anti-IL10 antibody, markedly up regulated proliferation and Th2 cytokine production by splenocytes. IL1alpha levels in the conjunctiva were reduced after treatment with either antibody; in addition, eotaxin and tumour necrosis factor alpha levels were reduced after treatment with antibody to TGF beta.

CONCLUSIONS

IL10 and TGF beta do not have immunosuppressive roles in the development of experimentally induced allergic conjunctivitis. Rather, they augment the infiltration of eosinophils into the conjunctiva during the effector phase of experimentally induced allergic conjunctivitis.

Cyclosporin A inhibits eosinophilic infiltration into the conjunctiva mediated by type IV allergic reactions

BACKGROUND

Eosinophils are important effector cells in severe allergic conjunctivitis such as vernal keratoconjunctivitis. Infiltration of eosinophils into the conjunctiva is mediated by type I and type IV allergic reactions. Cyclosporin A (CsA) eye drops are administered therapeutically for severe allergic conjunctivitis, but the mechanism by which CsA acts, that is, by inhibiting type I, type IV or both types of allergic reactions, is not known. We investigated whether CsA eye drops inhibit type I, type IV or both types of allergic reactions in the conjunctiva.

METHODS

Experimental immune-mediated blepharoconjunctivitis (EC) was induced in BALB/c mice by either active immunization or passive immunization by transfer of ragweed (RW)-primed splenocytes and RW-specific IgE, followed by RW challenge to the conjunctiva. These mice were treated in eye drops with vehicle, 0.1% CsA, 0.5% CsA or 0.1% betamethasone five times (1 and 2 h before RW challenge and 1, 2 and 3 h after RW challenge). Twenty-four hours after the challenge, the conjunctivas were harvested for histological analysis to evaluate eosinophilic infiltration. To evaluate effects of CsA eye drops on systemic immune responses, sera and spleens were collected from actively immunized mice at the time of sacrifice to examine serum IgE levels and cellular immune responses, respectively.

RESULTS

CsA eye drops significantly inhibited eosinophilic infiltration into the conjunctiva in actively immunized EC-developing mice compared with vehicle-treated mice. The CsA-induced inhibition was similar to inhibition induced by 0.1% betamethasone. Serum IgE levels and splenocyte responses in CsA-treated mice were equivalent to those in vehicle-treated mice. Betamethasone treatment inhibited eosinophilic infiltration into the conjunctiva induced by both splenocyte transfer and IgE transfer, while CsA treatment inhibited infiltration induced by splenocyte transfer.

CONCLUSIONS

CsA eye drops inhibited eosinophilic infiltration into the conjunctiva without affecting systemic immune responses. CsA predominantly inhibits eosinophilic infiltration by interfering with the type IV allergic reaction in the conjunctiva.

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 interaction between ICOS and B7RP-1 is not required for the development of experimental murine allergic conjunctivitis

It is still unclear whether the interaction between inducible costimulator (ICOS) and its ligand, B7 related protein (B7RP)-1, is important for the development of allergic diseases. We investigated whether blocking the ICOS/B7RP-1 interaction affects the development of murine experimental allergic conjunctivitis (EC). EC was induced in Balb/c mice either by active immunization of ragweed (RW) or by transferring RW-primed splenocytes, followed by challenge with RW-containing eye drops. The mice were treated with anti-B7RP-1 antibody (Ab) or normal rat immunoglobulin G (IgG) during either the induction or effector phase. Regardless of the induction method or when the animals were treated, eosinophil infiltration into the conjunctiva was not affected by the anti-B7RP-1 Ab treatment. Splenocyte responses were not largely affected by this treatment. However, serum Ig levels were significantly reduced. These data suggest that blocking the ICOS/B7RP-1 in allergic diseases may not always be therapeutic.

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.