Comparison of clinical and experimental uveitis

Comprehensive Grading System for Experimental Autoimmune Uveitis in Mice

Experimental autoimmune uveitis (EAU) is the most commonly used animal model to study the progression of chronic uveitis and to test various therapies to treat the disease. However, to accurately evaluate the effectiveness of such treatments, a grading system that combines the latest imaging techniques with definitive quantitative grading thresholds is required. This study aimed to develop a comprehensive grading system that objectively evaluates EAU progression in C57BL/6J mice. EAU was induced following immunisation with interphotoreceptor retinoid-binding protein (IRBP) and pertussis toxin. Weekly fundus and optical coherence tomography (OCT) images were acquired over 12 weeks using a Micron IV imaging system. Each mouse was graded (between 0 to 4) based on changes seen on both the fundus (optic disc, retinal blood vessels and retinal tissue) and OCT (vitreous and retinal layers) images. A total EAU response (with a maximum score of 48) was calculated for each mouse based on the sum of the individual scores each week. Analysis of the clinical scores depicted a gradual increase in inflammatory signs including optic disc and vascular swelling, leukocyte infiltration in the vitreous, lesions in the retina and formation of granulomas and hyper-reflective foci in the retinal layers in EAU mice, with most signs reaching a plateau towards the end of the study period. Development of these signs into sight-threatening complications such as optic disc atrophy, structural damage to the retina and subretinal oedema were noted in 80-90% of mice suggesting consistent disease induction. Overall, a comprehensive and objective grading system encompassing all pathologies occurring in EAU mice was developed to enhance the preclinical evaluation of novel uveitis treatments.

microRNA 146a ameliorates retinal damage in experimental autoimmune uveitis

Introduction

Uveitis and related intraocular inflammations are a major cause of blindness due to retinal damage caused by degeneration and loss of the photoreceptor cells. In mouse experimental autoimmune uveitis (EAU) previously we have shown mitochondrial oxidative stress with marked upregulation of αA crystallin in the inner segments of the photoreceptors. Furthermore, αA crystallin treatment prevented photoreceptor mitochondrial oxidative stress by suppressing innate and adaptive immunity in EAU.

Methods

Since these immune processes are modulated by microRNAs, in this study we investigated (a) modulation of microRNAs during development of EAU by αA crystallin administration and (b) microRNA therapeutic intervention.

Results

Few microRNAs were significantly upregulated in EAU mice with intravenous injection of αA crystallin and among these, computational bioinformatic analysis revealed that the upregulated microRNA 146a targets the innate and adaptive immune responses. In EAU, intravenous as well as intravitreal administration of this microRNA prevented inflammatory cell infiltration in uvea and retina and preserved photoreceptor cells.

Discussion

This protective function suggests that microRNA146a can be a novel therapeutic agent in preventing retinal damage in uveitis.

Use of optical coherence tomography angiography in the uveitis clinic

As optical coherence tomography angiography is revolutionizing the ophthalmology world, the uveitis community is learning to understand where and how this new powerful imaging tool fits into the management of the panorama of ocular inflammations and infections. A non-invasive method of studying the retinal and choroidal vasculature, OCTA allows for the assessment of vessel density changes during active and inactive uveitis making it the natural imaging application of choice in uveitis clinical trials. However, these data and results are of limited utility to the ophthalmologists who are looking to apply OCTA in their everyday uveitis clinic. If employed strategically, OCTA can be a powerful tool for the uveitis specialist to evaluate iris involvement in viral uveitis; to assess the integrity of the vascular layers in the settings of white dot syndromes; to distinguish inflammatory choroidal neovascularization from outer retinal avascular inflammatory material; and to diagnose and follow infectious choroidal granulomas and satellite foci of chorioretinal inflammation without the need to administer dyes. The present review will analyze all the recent publications that apply OCTA in uveitis to offer the reader a guide on how to maximize the utility of this imaging modality in a clinical practice.

Intravitreal Antivascular Endothelial Growth Factor Treatment for Inflammatory Choroidal Neovascularization in Noninfectious Uveitis

PURPOSE

To compare visual outcome and recurrence rates of eyes with noninfectious inflammatory choroidal neovascularization (CNV) treated with or without anti-vascular endothelial growth factor (VEGF) injections and immunosuppression.

DESIGN

Retrospective, nonrandomized clinical study.

METHODS

Participants: Patients with CNV secondary to noninfectious inflammatory causes who attended uveitis clinics at Moorfields Eye Hospital between January 2000 and April 2016. Data were gathered from the clinical notes of all subjects examined in clinic.

MAIN OUTCOME MEASURES

change in best-corrected visual acuity (BCVA), mean time to CNV recurrence, moderate vision loss (≤20/50), and severe vision loss (≤20/200).

RESULTS

A total of 166 patients (204 eyes) with noninfectious inflammatory CNV were included in this study with a median follow-up of 6.9 years (interquartile range: 2.9-11.7; 1652 eye-years). The mean BCVA at the time of CNV diagnosis was 0.38 ± 0.05 logarithm of the minimum angle of resolution (logMAR) (Snellen equivalent 20/47) in the eyes that received the first-line anti-VEGF treatment and 0.44 ± 0.03 logMAR (Snellen equivalent 20/55) in the eyes on other treatment modalities (P = .39). Eyes treated first with anti-VEGF (n = 55) received the mean of 4.35 ± 0.53 injections and showed a statistically significant improvement in vision at all time points (P < .001) except for a 5-year visit (P = .25). The rest of the eyes demonstrated no significant change in vision throughout follow-up (all P > .05). At the final visit, the mean BCVA was 0.26 ± 0.11 logMAR (Snellen equivalent 20/36) in the former and 0.35 ± 0.06 logMAR (Snellen equivalent 20/44) in the latter. The mean time to CNV recurrence was 186 ± 15.1 months, and the risk was significantly reduced by treatment with oral corticosteroids (adjusted hazard ratio = 0.32, confidence interval: 0.17-0.59, P < .001) or anti-VEGF injections (adjusted hazard ratio = 0.31, confidence interval: 0.18-0.52, P < .001).

CONCLUSIONS

Eyes that developed inflammatory CNV were at risk of vision loss. Those receiving early anti-VEGF injections achieved a better visual outcome and had a reduced risk of CNV recurrence. Oral corticosteroids also had an effect that reduces the risk of recurrence in eyes previously treated.

Cytotoxic effect of specific T cells from mice with experimental autoimmune uveitis on murine photoreceptor cells

AIM

To investigate the cytotoxic effect of specific T cells from mice with experimental autoimmune uveitis (EAU) as well as their secreted interferon (IFN)-γ and interleukin (IL)-17A on murine photoreceptor (661W) cells.

METHODS

An EAU model was established in female mice by injection of interphotoreceptor retinoid binding protein (IRBP) emulsion supplemented with complete Freund's adjuvant (CFA) and Mycobacterium tuberculosis (TB). On day 12 after induction of EAU, specific T cells from spleen and lymph node tissues were isolated and cultured for 4d and the levels of IFN-γ and IL-17A in the supernatants were determined by enzyme-linked immunosorbent assays (ELISAs). T cells and their supernatants were added to 661W cells to observe the alteration of cell morphology; IFN-γ and IL-17A were separately added to 661W cells to observe the effect of IFN-γ and IL-17A on cell proliferation.

RESULTS

The levels of IFN-γ and IL-17A in the T cell supernatants were 1568.64±38.79 pg/mL and 1456.57±46.98 pg/mL, respectively. The supernatants apparently inhibited 661W cell proliferation (P<0.05). T cells could also attach to the surface of 661W cells, and IFN-γ showed a more serious cytotoxic effect on 661W cells than IL-17A, inhibiting cell proliferation (P<0.01).

CONCLUSION

IFN-γ and IL-17A from T cells of EAU mice model can exert cytotoxic effects on murine photoreceptor cell proliferation, and IFN-γ shows more serious cytotoxic effects on murine photoreceptor cells than IL-17A.

Systemic Immunosuppression Is Highly Effective in the Long-term Control of Inflammatory non-infectious Uveitic Choroidal Neovascularization: A Comparative Study

Purpose: To compare immediate versus delayed introduction of immunosuppressives for naive noninfectious inflammatory choroidal neovascularization (iCNV).Methods: a retrospective, consecutive, comparative, interventional case series of patients with a diagnosis of inflammatory CNV and a minimum follow of 36 months. Patients were divided into two groups: Group A received Immunosuppressives if needed, while Group B since baseline. Both groups received systemic steroids and intravitreal ranibizumab since baseline. Primary end point was to compare the BCVA outcome till 36-month follow-up.Results: Twenty-nine eyes with iCNV were enrolled. In the long term, best-corrected visual acuity (BCVA) was significantly better in group B. At 3-month follow-up, Group B reduced steroids <10 mg/day significantly (p = .0001, Fisher's Exact Test). At 36 months of follow up, injections given were 2.9 (0.9 SD) in group A and 1.25 (0.4 SD) in group B.Conclusion: early immunosuppressive therapy exerts a positive action on the long-term control of uveitic CNV.

Partial retinal photoreceptor loss in a transgenic mouse model associated with reduced levels of interphotoreceptor retinol binding protein (IRBP, RBP3)

Organ-specific transgenic membrane expression of hen egg lysozyme (HEL) as a "neo-self antigen" has been used in several models to study immunological tolerance. In this study we report the changes which occur in the B10.BR mouse retina when membrane-bound HEL is expressed in photoreceptors under the control of the promoter for interphotoreceptor retinoid binding protein (IRBP, RBP3). On direct clinical examination of the single transgenic (sTg-IRBP:HEL) mouse fundus, a low-level increase in retinal degeneration compared to non-transgenic controls was observed, presenting as drusenoid deposits and occasional small patches of atrophy. On histological examination, there was an overall shortening of outer segments and loss of photoreceptor nuclei in sTg-IRBP:HEL mice, which was more pronounced in the retinal periphery, particularly inferiorly. The fundoscopically observed lesions did not correlate with the photoreceptor shortening/loss but appeared to be located at the level of the retinal pigment epithelium/choriocapillaris layer and were an exaggeration in size and number of similar age-related changes found in wild type (WT) mice. In addition, neither the atrophic lesions nor the photoreceptor shortening were associated with common retinal degeneration genes, nor were they caused by exposure to light damage since mice housed at both high and low ambient light levels had similar degrees of retinal degeneration. Instead, sTg-IRBP:HEL mice expressed reduced levels of soluble retinal IRBP compared to WT mice which were present from postnatal day16 (P16) and preceded development of photoreceptor shortening (onset P21). We propose that insertion of the HEL transgene in the photoreceptor membrane disrupted normal photoreceptor function and led to reduced levels of soluble IRBP and retinal thinning. A similar phenotype has been observed in IRBP deficient mice. Despite the retinal thinning, the amount of HEL expressed in the retina was sufficient to act as an autoantigenic target when the mice were crossed to the HEL T cell receptor Tg mouse, since double transgenic (dTg-IRBP:HEL) mice spontaneously developed a severe uveoretinitis with onset at weaning. We suggest that, although membrane expression of foreign transgene products is likely to modify the structure and function of tissues and cells, the technology provides useful models to investigate mechanisms of antigen-specific immunological tolerance.

Macrophages and Uveitis in Experimental Animal Models

Resident and infiltrated macrophages play relevant roles in uveitis as effectors of innate immunity and inductors of acquired immunity. They are major effectors of tissue damage in uveitis and are also considered to be potent antigen-presenting cells. In the last few years, experimental animal models of uveitis have enabled us to enhance our understanding of the leading role of macrophages in eye inflammation processes, including macrophage polarization in experimental autoimmune uveoretinitis and the major role of Toll-like receptor 4 in endotoxin-induced uveitis. This improved knowledge should guide advantageous iterative research to establish mechanisms and possible therapeutic targets for human uveitis resolution.

Effects of Japanese herbal medicine Sairei-to on murine experimental autoimmune uveitis

PURPOSE

It has been suggested thatSairei-to (TJ114), a traditional Japanese herbal medicine, has immunomodulatory activities. To evaluate the effects of TJ114 on uveitis, we examined the effectiveness of oral administration in a murine model of experimental autoimmune uveitis (EAU).

METHODS

Murine EAU was induced by subcutaneous injection of human inter-photoreceptor retinoid-binding protein (IRBP) peptide mixed with complete Freund's adjuvant. In the TJ114-treated group, 2 g/kg was administrated orally from 0 to 20 days after immunization. Clinical scoring, histopathological scoring of EAU, cell proliferation, cytokine assessment, and adoptive transfer experiment of splenic T cells into naïve mice were performed.

RESULTS

EAU development occurred in 32 of 38 mice (86 %) in the untreated group and 12 of 33 (36 %) in the TJ114-treated group. The clinical scores for EAU in the vehicle-treated and TJ114-treated groups were 1.56 ± 1.65 and 0.59 ± 0.63 respectively, at 14 days after immunization (p < 0.01, Mann-Whitney U-test), and 2.26 ± 1.56 and 0.75 ± 1.31 respectively at 21 days (p < 0.001, Mann-Whitney U-test), while the histopathological scores at 21 days were 1.47 ± 1.42 and 0.54 ± 0.84 respectively (p < 0.01, Mann-Whitney U-test). Interferon (IFN)-γ and tumor necrosis factor (TNF)-α production by cervical lymph node cells obtained from the TJ114-treated group were significantly reduced as compared with those from the vehicle-treated group (p < 0.01, Student's unpaired t-test). Moreover, the levels of C-C motif chemokine 2 (CCL2) and IFN-γ were significantly reduced in splenocytes of TJ114-treated mice as compared with the vehicle-treated group (p < 0.01, Student's unpaired t-test). Mice that received adoptive transfer of splenic T cells from TJ114-treated EAU mice caused significantly lower severity of EAU compared to those that received from vehicle-treated EAU mice.

CONCLUSION

Oral administration of TJ114 has an inhibitory effect on a murine model of EAU, possibly via reduction in cytokine production by helper type-1 T cells.

Comparative analysis of induced vs. spontaneous models of autoimmune uveitis targeting the interphotoreceptor retinoid binding protein

Animal models of autoimmunity to the retina mimic specific features of human uveitis, but no model by itself reproduces the full spectrum of human disease. We compared three mouse models of uveitis that target the interphotoreceptor retinoid binding protein (IRBP): (i) the "classical" model of experimental autoimmune uveitis (EAU) induced by immunization with IRBP; (ii) spontaneous uveitis in IRBP T cell receptor transgenic mice (R161H) and (iii) spontaneous uveitis in Autoimmune Regulator (AIRE)(-/-) mice. Disease course and severity, pathology and changes in visual function were studied using fundus imaging and histological examinations, optical coherence tomography and electroretinography. All models were on the B10.RIII background. Unlike previously reported, IRBP-induced EAU in B10.RIII mice exhibited two distinct patterns of disease depending on clinical scores developed after onset: severe monophasic with extensive destruction of the retina and rapid loss of visual signal, or lower grade with a prolonged chronic phase culminating after several months in retinal degeneration and loss of vision. R161H and AIRE(-/-) mice spontaneously developed chronic progressive inflammation; visual function declined gradually as retinal degeneration developed. Spontaneous uveitis in R161H mice was characterized by persistent cellular infiltrates and lymphoid aggregation, whereas AIRE(-/-) mice characteristically developed multi-focal infiltrates and severe choroidal inflammation. These data demonstrate variability and unique distinguishing features in the different models of uveitis, suggesting that each one can represent distinct aspects of uveitis in humans.

Use of optical coherence tomography and electroretinography to evaluate retinal pathology in a mouse model of autoimmune uveitis

Experimental autoimmune uveoretinitis (EAU) in mice is a model for human autoimmune uveitis. Longitudinal follow-up is only possible by non-invasive techniques, but the information obtained by visual fundus examination can be limited. We therefore evaluated the efficacy of optical coherence tomography (OCT) and electroretinography (ERG) to monitor pathological and functional changes of the retina in vivo. OCT imaging and ERG recording as a measure of visual function were compared with visual fundoscopic imaging and histology findings in the same mouse. Our results showed that OCT imaging of the retina was well correlated with clinical and histological observations in mice during EAU. However, OCT imaging was more sensitive than fundoscopic imaging in detecting the cell infiltrates at the early phase of disease onset. Furthermore, by allowing multi-layer cross- and horizontal-sectional visualizations of retinal lesions longitudinally in a noninvasive fashion, OCT added information that could not be obtained by fundoscopic and histological examinations. Lastly, retinal thickness obtained by OCT imaging provided a key indicator reflecting disease activity, which showed a close association with visual dysfunction as measured by ERG recordings in EAU mice. Thus, our findings demonstrate that OCT is a highly sensitive and reliable technique, and a valuable method for the semi-quantitative evaluation of retinal inflammation in vivo in the mouse.

Cell-based therapies for ocular inflammation

Since the plasticity and the potential for re-programming cells has become widely accepted, there has been great interest in cell-based therapies. These are being applied to a range of diseases, not least ocular diseases, where it is assumed that there is a reduced risk of immune rejection although this may be more perceived than real. There are two broad classes of cell-based therapies: those aimed at restoring structure and function of specific tissues and cells; and those directed towards restoring immunological homeostasis by controlling the damaging effects of inflammatory disease. Stem cells of all types represent the first group and prototypically have been used with the aim of regenerating failing cells. In contrast, immune cells have been suggested as potential modulators of inflammation. However, there is functional overlap in these two applications, with some types of stem cells, such as mesenchymal stem cells, demonstrating a potent immunomodulatory effect. This review summarises recent information on cell based therapies for ocular disease, with special emphasis on ocular inflammatory disease, and explores current uses, potential and limitations.

Functional macrophage heterogeneity in a mouse model of autoimmune central nervous system pathology

Functional macrophage heterogeneity is well appreciated outside the CNS in wound healing and cancer, and was recently also demonstrated in several CNS compartments after "sterile" insults. Yet, such heterogeneity was largely overlooked in the context of inflammatory autoimmune pathology, in which macrophages were mainly associated with disease induction and propagation. In this article, we show the diversity of monocyte-derived macrophages along the course of experimental autoimmune uveitis, an inflammatory condition affecting the ocular system, serving as a model for CNS autoimmune pathology. Disease induction resulted in the appearance of a distinct myeloid population in the retina, and in the infiltration of monocyte-derived macrophages that were absent from control eyes. During the disease course, the frequency of CX3CR1(high) infiltrating macrophages that express markers associated with inflammation-resolving activity was increased, along with a decrease in the frequency of inflammation-associated Ly6C(+) macrophages. Inhibition of monocyte infiltration at the induction phase of experimental autoimmune uveitis prevented disease onset, whereas monocyte depletion at the resolution phase resulted in a decrease in Foxp3(+) regulatory T cells and in exacerbated disease. Thus, monocyte-derived macrophages display distinct phenotypes throughout the disease course, even in an immune-induced pathology, reflecting their differential roles in disease induction and resolution.

Therapeutic dosing of fingolimod (FTY720) prevents cell infiltration, rapidly suppresses ocular inflammation, and maintains the blood-ocular barrier

Fingolimod (FTY720) is an FDA-approved therapeutic drug with efficacy demonstrated in experimental models of multiple sclerosis and in phase III human multiple sclerosis trials. Fingolimod prevents T-cell migration to inflammatory sites by decreasing expression of the sphingosine-1 phosphate receptor normally required for egress from secondary lymphoid tissue. As a preclinical model of human uveitis, experimental autoimmune uveoretinitis permits assessment of immunotherapeutic efficacy. Murine experimental autoimmune uveoretinitis is induced by activation of retinal antigen-specific CD4(+) T cells that infiltrate the eye. High-dose fingolimod treatment administered before disease onset reduces ocular infiltration within hours of administration and suppresses clinicopathologic expression of experimental autoimmune uveoretinitis. In the present investigation of the efficacy of fingolimod treatment for established disease, single-dose treatment was effective and immunosuppressive ability was maintained through a dose range, demonstrating significant and rapid reduction in CD4(+) cell infiltration at clinically relevant therapeutic doses of fingolimod. A repeated-treatment regimen using a dose similar to that in current multiple sclerosis patient protocols significantly reduced infiltration within 24 hours of administration; importantly, repeated doses did not compromise the vascular integrity of the blood-ocular barrier. On withdrawal of fingolimod, drug-induced remission was lost and recrudescence of clinical disease was observed. These results support a strong therapeutic potential for fingolimod as an acute rescue therapy for the treatment of ocular immune-mediated inflammation.

Persistent inflammation subverts thrombospondin-1-induced regulation of retinal angiogenesis and is driven by CCR2 ligation

Neovascular retinal disease is a leading cause of blindness orchestrated by inflammatory responses. Although noninfectious uveoretinitis is mediated by CD4(+) T cells, in the persistent phase of disease, angiogenic responses are observed, along with degeneration of the retina. Full clinical manifestation relies on myeloid-derived cells, which are phenotypically distinct from, but potentially sharing common effector responses to age-related macular degeneration. To interrogate inflammation-mediated angiogenesis, we investigated experimental autoimmune uveoretinitis, an animal model for human uveitis. After the initial acute phase of severe inflammation, the retina sustains a persistent low-grade inflammation with tissue-infiltrating leukocytes for over 4 months. During this persistent phase, angiogenesis is observed as retinal neovascular membranes that arise from inflamed venules and postcapillary venules, increase in size as the disease progresses, and are associated with infiltrating arginase-1(+) macrophages. In the absence of thrombospondin-1, retinal neovascular membranes are markedly increased and are associated with arginase-1(-) CD68(+) macrophages, whereas deletion of the chemokine receptor CCR2 resulted in reduced retinal neovascular membranes in association with a predominant neutrophil infiltrate. CCR2 is important for macrophage recruitment to the retina in experimental autoimmune uveoretinitis and promotes chronicity in the form of a persistent angiogenesis response, which in turn is regulated by constitutive expression of angiogenic inhibitors like thrombospondin-1. This model offers a new platform to dissect the molecular and cellular pathology of inflammation-induced ocular angiogenesis.

Inflammatory choroidal neovascularization

Purpose and Methods:

Choroidal neovascularization (CNV) can be a severe sight-threatening sequela, which can be secondary to both infectious and noninfectious uveitis. This review summarizes the different diseases associated with CNV, highlighting new treatment modalities and the possible strategies, which could be applied for the therapy of this occurrence.

Results:

Since CNV can often originate from posterior pole lesions and can be hard to identify, an accurate examination is mandatory in order to identify the correct diagnosis. In the majority of cases, fluorescein angiography (FA), indocyanine green angiography (ICGA) and optical coherence tomography (OCT) enable the determination of the clinical characteristics of the CNV. An infectious disease should be looked for to include a suitable therapy when available. The treatment strategy for CNV secondary to noninfectious uveal inflammations should be directed at controlling the inflammatory process. Systemic corticosteroids with or without immunosuppressive agents are indicated even when the CNV occurs with apparently inactive uveitis: Chronic subclinical inflammation can be the basis for the pathogenesis of CNV. Additional therapies aimed directly at the neovascular process, such as the intravitreal anti-Vascular Endothelial Growth Factor (VEGF) agents, are recommended particularly when the therapy shows an insufficient response.

Conclusion:

CNV secondary to uveitis is a severe sequela leading to significant visual impairment. ICGA is mandatory in order to obtain relevant information about the choroidal status. Several therapeutic options have been considered, but no guidelines are provided at the moment. Moreover, the current data are still only based on case reports or small series. For such reasons, further trials are mandatory to validate the preliminary available results.

Anti-inflammatory treatment of uveitis with biologicals: new treatment options that reflect pathogenetic knowledge of the disease

BACKGROUND

Endogenous uveitis is a sight-threatening disease. In addition to corticosteroids, immunosuppressive agents are commonly used to treat patients with severe course. Immunosuppressive drugs act nonspecifically, rather than providing a specific interaction with the critical pathogenetic pathways of uveitis. Better knowledge of the basic mechanisms underlying uveitis and of the molecules that are important for regulating inflammation has helped to create new and more specific treatment approaches. Biological therapy for inflammatory diseases employs substances that interfere with specific molecules or pathways induced in the body during the inflammatory process.

METHODS

This review gives an overview on molecules that play a critical role in the pathogenetic process of uveitis, as has been observed in patients or the respective animal models, and summarizes the current experience with biologicals for the treatment of uveitis refractive to conventional immunosuppressives.

The role of TLR4 in photoreceptor {alpha}a crystallin upregulation during early experimental autoimmune uveitis

Purpose. Previous studies indicate that the upregulation of alphaA crystallin prevents photoreceptor mitochondrial oxidative stress-mediated apoptosis in experimental autoimmune uveitis (EAU). In this study, the role of TLR4 was investigated in the upregulation of alphaA crystallin in the retinas of animals with EAU. Methods. TLR4(-/-), iNOS(-/-), TNF-alpha(-/-), MyD88(-/-), wild-type (WT) control (C57BL/6), and nude mice (B6.Cg-Foxn1(nu)) were immunized with IRBP mixed with complete Freund's adjuvant; eyes were enucleated on day 7 after immunization. Real-time polymerase chain reaction was first used to detect upregulated inflammatory cytokines and alphaA crystallin in retinas with EAU; confirmed with Western blot analysis, and the site of upregulation was localized by immunohistochemistry. Oxidative stress was localized using 8-OHdG, and TUNEL staining was used to detect apoptosis. Results. In early EAU, increased expression of TNF-alpha, iNOS, and alphaA crystallin genes were detected in the retinas of WT mice, whereas such upregulation was absent in TLR4-deficient mice (P < 0.001). alphaA Crystallin was not elevated in MyD88(-/-), TNF-alpha(-/-), and iNOS(-/-) mice with EAU. Immunostaining revealed TNF-alpha, iNOS, and alphaA crystallin localization in the photoreceptor inner segments and outer plexiform layer in the WT controls with EAU; but such staining was absent in TLR4-deficient mice with EAU. 8-OHdG staining showed oxidative stress in the photoreceptors in WT mice with EAU and there was no apoptosis. Conclusions. TLR4 plays an important role in the upregulation of alphaA crystallin through the interaction of MyD88 and the subsequent generation of TNF-alpha and iNOS in the EAU retina. Such crystallin upregulation may prevent oxidative stress-mediated apoptosis of photoreceptors in uveitis.

Systemic and local anti-C5 therapy reduces the disease severity in experimental autoimmune uveoretinitis

Activation of complement occurs during autoimmune retinal and intraocular inflammatory disease as well as neuroretinal degenerative disorders. The cleavage of C5 into fragments C5a and C5b is a critical event during the complement cascade. C5a is a potent proinflammatory anaphylatoxin capable of inducing cell migration, adhesion and cytokine release, while membrane attack complex C5b-9 causes cell lysis. Therapeutic approaches to prevent complement-induced inflammation include the use of blocking monoclonal antibodies (mAb) to prevent C5 cleavage. In these current experiments, the rat anti-mouse C5 mAb (BB5.1) was utilized to investigate the effects of inhibition of C5 cleavage on disease progression and severity in experimental autoimmune uveoretinitis (EAU), a model of organ-specific autoimmunity in the eye characterized by structural retinal damage mediated by infiltrating macrophages. Systemic treatment with BB5.1 results in significantly reduced disease scores compared with control groups, while local administration results in an earlier resolution of disease. In vitro, contemporaneous C5a and interferon-gamma signalling enhanced nitric oxide production, accompanied by down-regulation of the inhibitory myeloid CD200 receptor, contributing to cell activation. These experiments demonstrate that C5 cleavage contributes to the full expression of EAU, and that selective C5 blockade via systemic and local routes of administration can suppress disease. This presents great therapeutic potential to protect against tissue damage during autoimmune responses in the retina or inflammation-induced degenerative disease.

Inhibition of experimental autoimmune uveitis by amino acid copolymers

Glatiramer acetate (GA), a synthetic random amino acid copolymer, poly(Y, E, A, K)n, is widely used for treatment of multiple sclerosis. It inhibits experimental autoimmune encephalomyelitis (EAE) in mice by competition with the antigen and by induction of regulatory T cells. A novel copolymer, poly (F, Y, A, K)n , designated FYAK, was more effective than GA in its immunomodulatory activity in EAE. Here, FYAK and GA were compared in the amelioration of another disease model in mice, experimental autoimmune uveoretinitis (EAU). When tested by co-immunization with an uveitogenic antigen, FYAK was superior to GA in its capacity to inhibit EAU induction, as well as immune processes related to this condition. Further, regulatory T-cell lines specific to FYAK were more immunosuppressive than GA-specific lines in the EAU model. The superiority of FYAK-specific lines was accompanied by higher production of Th2 cytokines. These data thus demonstrate that FYAK, a novel copolymer, is superior to GA in its capacity to inhibit immunopathogenic processes in a non-central nervous system tissue.

The Efficacy of Hyperbaric Oxygen for the Treatment of Experimental Uveitis Induced in Rabbits

OBJECTIVE

The aim of the present study was to examine the efficacy of hyperbaric oxygen (HBO) therapy in the treatment of experimental uveitis induced in rabbits. It was hypothesized that HBO therapy improves the regression of experimental uveitis induced in rabbits.

RESEARCH DESIGN AND METHODS

An experimental animal study was conducted on 48 rabbits (48 right eyes of these rabbits) to evaluate the effects of HBO therapy on endotoxin-induced acute anterior uveitis in rabbits. To induce acute anterior uveitis, Salmonella typhimurium lipopolysaccharide endotoxin (LPS) was intravitreally injected into the right eyes of the rabbits. The animals were randomly assigned to five groups. No treatment was given to the rabbits in Group A. Prednisolone acetate was topically administered to the rabbits in Group B. Methylprednisolone acetate was administered by anterior subtenon injection to the rabbits in Group C four hours after LPS application. HBO therapy was administered to the rabbits in Group D. Both HBO therapy and anterior subtenon injection of methylprednisolone therapy were administered to the rabbits in Group E. To compare the effects of the different therapies on the progression of endotoxin-induced uveitis, examinations including clinical scoring of anterior uveitis, microscopic examination of aspirated aqueous humor for inflammatory responses, and aqueous protein level assessment were performed once a day after LPS injection.

RESULTS

There was a statistically significant difference between the control group (Group A) and other groups (Groups B-E) with respect to the number of inflammatory cells and protein levels in the aqueous one and three days after LPS injection (p < 0.05), indicating that the treatments resulted in less inflammation in Groups B-E compared to Group A. Moreover, there was no statistically significant difference between Groups B and C, Groups B and D, Groups B and E, Groups C and D, and Groups C and E with regard to the number of inflammatory cells in the aqueous at Day 1 after LPS injection (p > 0.05). In addition, Groups B and C and Groups B and D were comparable with regard to cell counts at Day 3 (p > 0.05), showing that HBO was comparable to corticosteroids in reducing inflammation. The differences between Groups B and E and Groups C and E were significant with regard to aqueous cell counts at Day 3 (p < 0.05), showing that HBO plus steroid was more effective than steroids alone.

CONCLUSION

The intensity of ocular inflammation in the group receiving HBO therapy combined with anterior subtenon injection of methylprednisolone therapy was lower than in the other groups. We also demonstrated that HBO therapy was an effective therapeutic modality for the treatment of experimental uveitis induced in rabbits with an efficacy comparable to that of corticosteroids. Moreover, HBO plus steroid was superior to steroids alone in reducing inflammation.

Down-regulation of inducible co-stimulator (ICOS) by intravitreal injection of small interfering RNA (siRNA) plasmid suppresses ongoing experimental autoimmune uveoretinitis in rats

BACKGROUND

RNA interference (RNAi) is now being exploited as a powerful tool for gene knockdown. Recently, we had shown that inducible co-stimulator (ICOS) was up-regulated in experimental autoimmune uveoretinitis (EAU). The aim of this study was to investigate whether intravitreal injection of small interfering RNA (siRNA) plasmid, targeting ICOS, suppresses the ongoing experimental autoimmune uveoretinitis (EAU) in rats.

METHODS

Oligonucleotide targeting ICOS was cloned into linearized pRNAT-U6.1/Neo eukaryotic expression vector to construct the recombinant plasmid (pRNAT-U6.1/Neo-ICOS). After transfecting activated rat T cells with the recombinant plasmid, ICOS mRNA and protein expression levels were determined by real-time RT-PCR and Western blot analysis respectively. Rats were immunized with IRBP R16 peptide emulsified in complete Freund's adjuvant (CFA) and given an intravitreal injection of pRNAT-U6.1/Neo-ICOS on day 6 after immunization. After 13days of immunization, the ICOS protein expression and CD4(+) ICOS (+) T cells were identified in retinae through Western blot analysis and flow cytometry respectively. Intraocular inflammation was assessed by the scores of the clinical and histological appearances. Delayed-type hypersensitivity (DTH) and lymphocyte proliferation were detected to evaluate the systemic effect of intravitreal injection of pRNAT-U6.1/Neo-ICOS.

RESULT

The recombinant plasmid (pRNAT-U6.1/Neo-ICOS) for the ICOS siRNA was successfully constructed. In vitro studies using the recombinant plasmid has showed the down-regulation of ICOS gene expression both at the mRNA and protein levels. Clinical and pathological scores showed that ocular inflammation of pRNAT-U6.1/Neo-ICOS-treated eyes was markedly less than that of vehicle-treated eyes. The expression of ICOS protein and the amount of CD4(+) ICOS(+) T cells in retinae significantly decreased by intravitreal injection of the recombinant plasmid, whereas delayed-type hypersensitivity response and lymphocyte proliferation were not impaired in rats treated with the recombinant plasmid.

CONCLUSION

Intravitreal injection of siRNA plasmid targeting ICOS effectively down-regulated the expression of ICOS, and was highly effective in suppressing the ongoing process of EAU without any side-effects on systemic cellular immunity.

A clinical grading system for retinal inflammation in the chronic model of experimental autoimmune uveoretinitis using digital fundus images

Experimental autoimmune uveoretinitis (EAU), a widely used animal model of human posterior/pan-uveitis, is extremely valuable in allowing understanding of the pathogenesis of uveitis as well as in developing new treatments. Depending on the animal strain and immunization protocol used, the clinical course of EAU can be acute, severe and involving the anterior and posterior part of the eye, or chronic, mild and involving only the posterior part of the eye. Clinical signs of EAU can be examined by bio-microscopy. Using appropriate criteria EAU can be quantitatively evaluated clinically in living animals. However, correlation of research within different laboratories is difficult since clinical grading systems are subjective and susceptible to considerable variability. In this study, we have developed a recordable, image-based clinical grading system for the chronic models of EAU. Fundus images were taken from EAU mice using an endoscopic imaging system. Fundus changes were classified as (1) inflammatory changes (including optic disc inflammation, vasculitis and retinal tissue inflammation) and (2) retinal structural damage. Each element was scored separately based on the severity of the lesions, and the average score of the three inflammatory elements was used as the overall EAU clinical inflammation grade of the eye. The validity and reproducibility of the grading system was tested using a set of images scored independently in a masked manner by 5 individuals. The grading system proved robust, easy to use and reliable. We offer this image-based EAU clinical grading system as a useful quantitative evaluation method for clinical grading of the severity of inflammation in the chronic EAU model, in which the inflammation can be mild and mainly involves posterior part of the eye.

Limited peripheral T cell anergy predisposes to retinal autoimmunity

Autoimmune uveoretinitis accounts for at least 10% of worldwide blindness, yet it is unclear why tolerance to retinal Ags is so fragile and, particularly, to what extent this might be due to defects in peripheral tolerance. To address this issue, we generated double-transgenic mice expressing hen egg lysozyme, under the retinal interphotoreceptor retinoid-binding promoter, and a hen egg lysozyme-specific CD4(+) TCR transgene. In this manner, we have tracked autoreactive CD4(+) T cells from their development in the thymus to their involvement in uveoretinitis and compared tolerogenic mechanisms induced in a variety of organs to the same self-Ag. Our findings show that central tolerance to retinal and pancreatic Ags is qualitatively similar and equally dependent on the transcriptional regulator protein AIRE. However, the lack of Ag presentation in the eye-draining lymph nodes results in a failure to induce high levels of T cell anergy. Under these circumstances, despite considerable central deletion, low levels of retinal-specific autoreactive CD4(+) T cells can induce severe autoimmune disease. The relative lack of anergy induction by retinal Ags, in contrast to the same Ag in other organs, helps to explain the unique susceptibility of the eye to spontaneous and experimentally induced autoimmune disease.

Photodynamic treatment versus photodynamic treatment associated with systemic steroids for idiopathic choroidal neovascularisation

AIM

To compare photodynamic therapy (PDT) with PDT associated with systemic steroids (SS) for the control of juxta/subfoveal idiopathic choroidal neovascularisation (ICNV).

METHODS

Patients with juxta/subfoveal ICNV were randomised and then treated. Visual gain and loss were defined as improvement in or worsening for two or more lines of best-corrected visual acuity (BCVA), respectively. Choroidal neovascularisation size after treatment was classified as "increased" and "reduced" if it was increased or reduced by >200 microm(2), respectively.

RESULTS

10 patients were treated with PDT, 10 with SS followed by PDT. The median follow-up time was 22 and 21 months for the "steroid+PDT group" and the "PDT group", respectively. At 1 year, in the PDT group, five patients had stable/improved BCVA, and five became worse; the mean number of PDT was 2.3; in the steroid+PDT group, all patients were stable/improved and the mean number of PDT was 1.2. The difference between the two groups was significant (p<0.05). At 1 year, the ICNV size after treatment was better in the steroid+PDT group than in the PDT group (p<0.05).

CONCLUSION

The use of SS before PDT has shown better BCVA outcome than PDT alone (p<0.05), reducing the mean number of PDT applications (1.2 vs 2.3, respectively), with smaller scar size.

Photoreceptor mitochondrial oxidative stress in early experimental autoimmune uveoretinitis

AIMS

In early S-antigen induced experimental uveitis (EAU), photoreceptor mitochondrial proteins are nitrated prior to macrophage infiltration of the retina, suggesting that oxidative stress is an initial event in the development of EAU. We attempted to detect the oxidative stress and localise it in the EAU retina.

METHODS

Lewis rats were immunised with S-antigen in complete Freund's adjuvant (CFA). Animals were injected with CFA alone and non-immunised animals served as controls. Immunised and non-immunised animals were killed on day 5 and subsequent days. Isolated retinas were processed for inducible nitric oxide synthase (iNOS), tumour necrosis factor (TNF)alpha, interferon (IFN)gamma, interleukin (IL)Ialpha and CD28 expression by real time polymerase chain reaction. In addition, iNOS was colocalised with cytochrome c oxidase on day 5 of EAU. Oxidative stress was detected by 2', 7'-dichlorodihydrofluorescein diacetate and localised by a mitochondrial specific marker. Leucocyte and T cell infiltration in the retina/choroid was evaluated by immunohistochemistry.

RESULTS

The iNOS, TNFalpha, IFNgamma, IL1alpha and CD28 transcripts were significantly upregulated on day 5 in EAU, and iNOS was colocalised with cytochrome c oxidase in the photoreceptor mitochondria. Oxidative stress was seen primarily in the photoreceptor mitochondria. Occasional T cells were present in the retina at this stage.

CONCLUSIONS

During early EAU, mitochondrial oxidative stress is selectively noted in the photoreceptor inner segments. The oxidative stress appears to result from iNOS upregulation in the photoreceptor mitochondria and cytokine generation in the retina by a few antigen specific infiltrating T cells.

Intravitreal injection of Tacrolimus (FK506) suppresses ongoing experimental autoimmune uveoretinitis in Rats

AIM

To determine whether intravitreal injection of tacrolimus suppresses ongoing experimental autoimmune uveoretinitis (EAU) in rats.

METHODS

Rats were immunised with interphotoreceptor retinoid-binding protein peptide (R14) and given an intravitreal injection of tacrolimus on day 12 after immunisation. Intraocular inflammation was assessed by slit-lamp biomicroscopy and histopathological examination. Interferon gamma and tumour necrosis factor alpha protein levels in the ocular tissues were measured. Gene expression of chemokines was determined in ocular tissues by reverse transcription-polymerase chain reaction. To evaluate the systemic effect of intravitreal injection of tacrolimus, delayed-type hypersensitivity was measured by ear swelling.

RESULTS

Clinical and pathological scores showed that ocular inflammation of tacrolimus-treated eyes was markedly less than that of vehicle-treated eyes. The amount of interferon gamma and tumour necrosis factor alpha was considerably inhibited in tacrolimus-treated eyes. The gene expression of monocyte chemattractant protein-1 (MCP-1) and regulated upon activation, normal T cell expressed and secreted (RANTES) was markedly reduced in tacrolimus-treated eyes. Delayed-type hypersensitivity responses were not impaired in tacrolimus-treated rats.

CONCLUSIONS

Intravitreal injection of tacrolimus was highly effective in suppressing the ongoing process of EAU without any side effects on systemic cellular immunity. This treatment may be useful in the management of patients with severe uveitis.

Mechanisms for inducing nasal mucosal tolerance in experimental autoimmune uveoretinitis

Delivering soluble (auto) antigenic peptides via the naso-respiratory route induces tolerance to that peptide and suppression of experimental models of autoimmune disease. In the normal lung, respiratory tract dendritic cells (RTDCs) efficiently endocytose soluble antigens, migrate to regional lymph nodes and present peptide to T cells that subsequently become tolerant. This article describes protocols for inducing tolerance via the naso-respiratory tract in experimental autoimmune uveoretinitis (EAU); for the isolation of RTDCs to facilitate definition of, and conditions for, maturation and activation of cells; and to test RTDC ability to induce tolerance in murine EAU when adoptively transferred.

Evaluation of MRI for in vivo monitoring of retinal damage and detachment in experimental ocular inflammation

Two quantitative methods were developed for investigation of the potential of MRI for in vivo monitoring of retinal damage and detachment in experimental autoimmune uveitis (EAU). Measurements of retinal thickness and detachment area were performed on matched MR and histologic (HIST) images of rat eyes at different stages of EAU. In vivo MR images of rat eyes were acquired at 4.7 T using a figure-of-eight surface coil and a spin echo pulse sequence. Ex vivo measurements were performed on HIST images acquired using a digital camera attached to a microscope. MR images mirrored the HIST appearance of inflamed eyes at each stage of disease. Retinal detachments as small as 0.1 mm(2) were measured in vivo by MRI and confirmed in the same eye ex vivo by histology. Measurements performed on corresponding MR and HIST images demonstrated a good agreement between the two techniques. The potential of MRI for in vivo visualization and for monitoring changes in the eye during development of EAU was demonstrated in this study.

Immunological effects of allopurinol in the treatment of experimental autoimmune uveitis (EAU) after onset of the disease

PURPOSE

Allopurinol reduces oxidative tissue damage and exerts immunomodulating effects in the treatment of experimental autoimmune uveitis (EAU). However, the mechanism of the immunologic pathway remains unclear. In previous studies, treatment was started at the time of immunization. Therefore, whether allopurinol prevents the onset of the disease (i.e., acts in a protective manner) is not known.

METHODS

Sixteen male Lewis rats were used: 6 EAU without therapy [control]; 4 EAU with allopurinol treatment starting 7 days after immunization [AL7]; and 6 EAU with allopurinol treatment starting 11 days after immunization [AL11]. Their sera were tested against Western blots of sodium dodecyl sulfate-polyacrylamide gel electrophoresis of retinal proteins. Based on digital image analysis, analysis of discriminance was done.

RESULTS

There were significant immunomodulating effects in both therapy groups (Wilks' lambda 0.001, P < 0.008) compared to controls. However, the effects were more pronounced in the AL7 group, where peak intensities and the number of peaks were markedly more reduced.

CONCLUSIONS

Immunomodulating effects of allopurinol can be detected even if the therapy starts after the onset of the disease. Thus allopurinol strongly influences the immunologic mechanism in this model of autoimmune disease. In view of its minimal side effects, the drug could be a promising alternative for the therapy and prophylaxis of uveitis and other autoimmune diseases.

Role of oxygen and nitrogen species in experimental uveitis: anti-inflammatory activity of the synthetic antioxidant ebselen

This study was aimed at examining the role of oxygen and nitrogen reactive species in a model of experimental uveitis upon intravitreal injection of bacterial endotoxin to albino New Zealand rabbits. The inflammatory response was evaluated in terms of: (i) the integrity of the blood aqueous barrier (protein and cell content in samples of aqueous humor), (ii) histopathological changes of the eyes, (iii) clinical evaluation (with a score index based on clinical symptoms), and (iv) the concentration of malondialdehyde (MDA), in aqueous humor, as a marker of oxidative stress. Betamethasone was used as reference treatment, superoxide dismutase as quencher of superoxide anion, L-N(G)-nitro-L-arginine-methyl-esther (L-NAME) and chlorpromazine as nitric oxide synthase inhibitors, and ebselen, a glutathione peroxidase mimic, as peroxynitrite reductant. All the substances were injected subconjunctivally to the rabbits immediately after the intravitreal endotoxin injection. Ebselen was the only treatment able to decrease MDA concentration to control values, exerting an effect similar to that elicited by L-NAME on the rest of the parameters tested. The data presented render ebselen a notable choice for the treatment of uveitis, with implications for clinical trials.

Cytokines in immunotherapy of experimental uveitis

A better understanding of the basic mechanisms of uveitis and of the role of cytokines in experimental ocular inflammation autoimmune diseases should allow us to define new approaches for therapy. Modulation of the cytokine network by either blocking cytokine activity or administration of regulatory Th2 cytokines has shown its efficacy in several experimental autoimmune diseases including uveitis. However, cytokines present pleiotropic activities and thus may exert different effects depending on the autoimmune diseases, making interventions on their production complex. Anti-cytokine therapy or a combination of anti-cytokine drugs, antibodies, and cytokine gene therapy to synergize the therapeutical effects of other treatments appear to be of interest. Improvements in drug delivery and in biotechnology will also allow us to elaborate new and safe immunomodulatory strategies.

Single dose intranasal administration of retinal autoantigen generates a rapid accumulation and cell activation in draining lymph node and spleen: implications for tolerance therapy

BACKGROUND/AIMS

A single intranasal delivery of retinal autoantigen suppresses effectively experimental autoimmune uveoretinitis (EAU). To further unravel underlying mechanisms the authors wished to determine, firstly, the kinetics of antigen delivery and, secondly, the early cellular responses involved in the initial stages of nasal mucosal tolerance induction.

METHODS

Flow cytometry, cell proliferation assays, and microscopy were used to track antigen following a single, intranasal dose of Alexa-488 labelled retinal antigen.

RESULTS

A rapid accumulation of antigen within both superficial cervical lymph nodes (SCLN) and spleen was observed after 30 minutes. Significant proliferative responses to IRBP were elicited by 48 hours indicating that systemic priming of naive T cells to retinal antigen had occurred. Cell activation was further confirmed by immunoprecipitation studies, which demonstrated phosphorylation of STAT4 but not STAT6 in both lymph nodes and spleen. However, at 24 hours, STAT4 heterodimerisation with STAT 3 was only observed in spleen.

CONCLUSIONS

The results provide novel evidence that following a single intranasal application rapid transfer of antigen occurs. Resulting T cell proliferation develops consequent to differential cell signalling in SCLN and spleen. Further understanding of these underlying cellular mechanisms, in particular as is inferred by the results the contribution of local versus systemic tolerance induction, may assist in strategies to clinically apply mucosal tolerance therapy successfully.

Total dose and frequency of administration critically affect success of nasal mucosal tolerance induction

AIMS

Nasal tolerance induction with autoantigens can effectively protect against a variety of experimental models of autoimmune disease. The aims of this study were to characterise the dosage and kinetics of inhibition of experimental autoimmune uveoretinitis (EAU) via intranasal administration of the uveitogenic antigen interphotoreceptor retinal binding protein (IRBP) in the murine model of IRBP induced EAU.

METHODS

B10RIII mice were tolerised by intranasal administration of IRBP either with a long term multiple low dose or a short term/high dosing regimen before subcutaneous immunisation with IRBP in complete Freund's adjuvant (CFA). On day 15 post-immunisation, mice were killed and eyes were removed for histological examination and quantification of inflammatory cell infiltration and degree of target organ (rod outer segment, ROS) destruction.

RESULTS

Nasal administration of multiple low doses of IRBP (1 microg or 3 microg IRBP per mouse per day for 10 days) significantly protected mice from IRBP induced EAU. Short term/high dose regimens were only effective when given either as a single or, at most, as two consecutive doses (40 microg per dose). Multiple doses in the range of 45-120 microg over 3 days afforded no protection.

CONCLUSIONS

These results indicate that both dose and frequency of intranasal antigen administration are pivotal to tolerance induction and subsequent suppression of T cell mediated autoimmune disease.

Allopurinol has immunomodulating activity following topical and systemic application in experimental autoimmune uveitis

PURPOSE

Allopurinol has beneficial effects in the systemic treatment of lens-induced uveitis and experimental autoimmune uveitis (EAU). This is believed to be due to a reduction of oxidative tissue damage through its dose-dependent free radical scavenging ability, and to an immunomodulating effect. The purpose of this study was to demonstrate the immunological effects on the IgG-antibody repertoire in EAU after topical and systemic allopurinol and steroids.

METHODS

We assigned 43 male Lewis rats to 6 different groups: healthy rats (BASE, n=3)

Immunological and aetiological aspects of macular degeneration

Aetiological and immunological aspects of AMD, a leading cause of blindness in Western countries, have been reviewed. Developmental studies suggest that anatomical features unique to the fovea result in a critical relationship between metabolic demand and blood supply at the macula, which is maintained throughout life. Recent studies show a sufficient degree of consistency in the link between smoking and both dry and wet AMD to regard it as causative. Dry AMD is considered to be the natural endstage of the disease; epidemiological and morphological studies point to choroidal vascular atrophy as the causative event and it is suggested that signals associated with acute vascular compromise lead to the development of subretinal neovascularisation. The relationship between sub-pigment epithelial deposits, including basal laminar deposit, and the pathogenesis of AMD is examined. Much of the literature is consistent with a choroidal origin for the constituents of drusen. The blood-retinal barrier preserves the physiological environment of the neural retina and limits inflammatory responses. The factors, including cytokines, adhesion molecules and the presence of resident immunocompetent cells (microglia), which determine the immune status of the retina are considered. Historical descriptions of the involvement of inflammatory cells are provided, evidence implicating inflammation in the pathogenesis of AMD involving macrophages, giant cells and microglia has been derived from observations of human and animal subretinal neovascular lesions. The role of humoral factors such as anti-retinal autoantibodies and acute phase proteins together with clinical observations has been surveyed. Taken together these data demonstrate the involvement of both cellular and humoral immunity in the pathogenesis of AMD. It remains to be determined to what degree the influence of immunity is causative or contributory in both wet and dry AMD, however, the use of anti-inflammatory agents to ameliorate the condition further indicates the existence of an inflammatory component.

Delayed onset and decreased severity of experimental autoimmune uveoretinitis in mice lacking nitric oxide synthase type 2

To investigate the role of nitric oxide (NO), produced by the inducible form of NO synthase (NOS-2) in the development of experimental autoimmune uveoretinitis (EAU), we immunized C57BL/6x129Sv (H-2(b)) mice carrying a targeted disruption of the gene encoding NOS-2 (NOS-2[-/-]), and wild-type (WT) C57BL/6x129Sv controls with interphotoreceptor retinoid binding protein (IRBP). NOS-2[-/-] mice developed a clinical EAU with delayed onset and decreased severity compared to WT controls. The ocular tissues from WT mice contained activated F4/80 macrophages with NOS-2 expression and retinal destruction whereas less intense EAU was detected in NOS-2[-/-] mice. The expression of NOS-2 mRNA was detected in the retina at the peak of EAU in WT. Analysis of cytokine production in the spleen from NOS-2[-/-] mice by RT-PCR showed high levels of IL-10 mRNA. Our results demonstrate that NO is clearly involved in EAU and may be important for the regulation of immune responses through the regulation of IL-10.