Uveitis induced in primates by interphotoreceptor retinoid-binding protein

International Harmonization of Nomenclature and Diagnostic Criteria (INHAND): Non-proliferative and Proliferative Lesions of the Non-human Primate (M. fascicularis)

The INHAND (International Harmonization of Nomenclature and Diagnostic Criteria for Lesions Project (www.toxpath.org/inhand.asp) is a joint initiative of the Societies of Toxicologic Pathology from Europe (ESTP), Great Britain (BSTP), Japan (JSTP) and North America (STP) to develop an internationally accepted nomenclature for proliferative and nonproliferative lesions in laboratory animals. The purpose of this publication is to provide a standardized nomenclature for classifying microscopic lesions observed in most tissues and organs from the nonhuman primate used in nonclinical safety studies. Some of the lesions are illustrated by color photomicrographs. The standardized nomenclature presented in this document is also available electronically on the internet (http://www.goreni.org/). Sources of material included histopathology databases from government, academia, and industrial laboratories throughout the world. Content includes spontaneous lesions as well as lesions induced by exposure to test materials. Relevant infectious and parasitic lesions are included as well. A widely accepted and utilized international harmonization of nomenclature for lesions in laboratory animals will provide a common language among regulatory and scientific research organizations in different countries and increase and enrich international exchanges of information among toxicologists and pathologists.

Tolerance Induction in Relation to the Eye

Inflammatory intraocular eye diseases, grouped under the term uveitis are blinding conditions, believed to be mediated by pathogenic autoimmune processes that overcome the protective mechanisms of the immune privilege status of the eye. An animal model for these diseases, named experimental autoimmune uveitis (EAU), is induced by initiation of immunity against ocular-specific antigens, or it develops spontaneously in mice with T-cells that transgenically express TCR specific to the target eye antigen(s). T-Cells specific to ocular antigens are generated in the thymus and their majority are eliminated by exposure to their target antigen expressed in this organ. T-cells that escape this negative selection acquire pathogenicity by their activation with the target antigen. In spontaneous EAU, the microbiota play crucial roles in the acquisition of pathogenicity by providing both antigenic stimulation, by molecules that mimic the target ocular antigen, and an additional stimulation that allows invasion of tissues that harbor the target antigen. The pathogenic process is physiologically inhibited by the peripheral tolerance, composed of antigen-specific T-regulatory (Treg) lymphocytes. Deleting the Tregs enhances the ocular inflammation, whereas adoptively transferring them suppresses the pathogenic response. Potential usage of Treg cells for suppression of autoimmune diseases in humans is under intensive investigation.

Autoantibody profiling in intraocular fluid of patients with uveitis

A high prevalence of serum antiretinal antibodies (ARAs) in patients with uveitis has been previously described, though their clinical role remains elusive. Assessment of intraocular ARAs may provide further insight into the pathogenesis of diverse uveitis entities. In this study we investigate the prevalence of multiple specific anti-ocular antibodies (AOcAs), including ARAs, in intraocular fluid of patients with uveitis. Autoantibody profiling with 188 different ocular antigens was performed by a multiplex immunoassay with intraocular fluid samples of 76 patients with uveitis. Clinical data from uveitis patients were collected and statistical analyses were executed to evaluate associations between intraocular AOcAs and clinical characteristics. Controls consisted of 19 intraocular fluid samples from cataract patients. A spectrum of 22 different AOcAs was present in higher levels in patients with uveitis than in controls (p < 0.05), but in moderately elevated titers (<2x). High elevations of intraocular AOcAs in uveitis (>5x compared to cataract) were observed in varicella zoster virus-induced uveitis, multiple sclerosis-associated uveitis and patients with unexplained uveitis but positive quantiferon test. Presence of macular edema was associated with increased intraocular levels of tyrosinase antibodies. Our results show that patients with uveitis are characterized by the presence of a broad spectrum of moderately elevated levels of intraocular AOcAs, and high intraocular AOcA levels were found in several specific uveitis entities. This study favors secondary production of AOcAs and not their inciting role.

Inhibition of T cell-mediated inflammation in uveitis by a novel anti-CD3 antibody

Background

A novel anti-mouse CD3ε antibody, Dow2, recognizes mouse CD3ε without activating T cells and suppresses T-cell activation. The purpose of this study was to determine whether Dow2 can inhibit T cells in uveitis.

Methods

Experimental autoimmune uveitis (EAU) was induced in mice by immunization with retinal peptides, followed by administration of Dow2. Inflammation was evaluated by color fundus photography, optical coherence tomography, fluorescein angiography, and histology. Intraocular cells from EAU mice were used to examine the effect of Dow2 on retinal antigen-specific T cells. The effects of Dow2, conventional CD3ε antibodies, and isotype control immunoglobulin G (IgG) on splenic T cells were compared by assessing cell proliferation by the mixed lymphocyte reaction assay, inflammatory cytokine production by enzyme-linked immunosorbent assay (ELISA) and immunohistochemistry, and gene expression by quantitative reverse-transcription polymerase chain reaction (RT-PCR). T-cell subpopulations were characterized by flow cytometry to evaluate the expression of CD4, CD8, CD44, CD62L, and Foxp3.

Results

Dow2 significantly reduced T-cell activation and counteracted activation associated with anti-CD3ε antibodies. Unlike conventional CD3ε antibodies, Dow2 treatment did not upregulate T helper (Th)1-/Th17-associated gene expression and cytokine production in splenic T cells. Interferon (IFN)-γ production by retinal antigen-specific T cells was also significantly reduced. Ocular inflammation was significantly reduced in Dow2-treated EAU mice compared to control EAU mice, with fewer T cells infiltrating into the retinas of Dow2-treated EAU mice. In immunohistochemistry, Th1 and Th17 cells invaded the retina in control EAU mice but not Dow2-treated EAU mice. No effects on peripheral T-cell numbers were observed following systemic administration of Dow2.

Conclusion

The novel anti-CD3 antibody Dow2 can inhibit T cell-mediated inflammation in uveitis models. Thus, inhibition of T-cell activation by anti-CD3 therapy with this new antibody may protect uveitis patients from severe ocular inflammation.

Evisceration in the modern age

Evisceration is an ophthalmic surgery that removes the internal contents of the eye followed usually by placement of an orbital implant to replace the lost ocular volume. Unlike enucleation, which involves removal of the entire eye, evisceration potentially causes exposure of uveal antigens; therefore, historically there has been a concern about sympathetic ophthalmic (SO) associated with evisceration. However, critical review of the literature shows that SO occurs very rarely, if ever, as a consequence of evisceration. Its clinical applications overlap with those of enucleation in cases of penetrating ocular trauma and blind painful eyes, but it is absolutely contraindicated in the setting of suspected intraocular malignancy and may be preferred for treatment of end-stage endophthalmitis. From a technical standpoint, traditional evisceration has a limitation in the orbital implant size. Innovations with scleral modification have overcome this limitation, and accordingly, due to its simplicity, efficiency, and good cosmetic results, evisceration has once again been gaining popularity.

Animal Models in Behçet's Disease

Behçet's disease is a chronic, recurrent, multisystemic, inflammatory disorder affecting mainly the oral and urogenital mucosa and the uveal tract. Although the etiology and pathogenesis of Behçet's disease are unknown, numerous etiologies have been proposed, including environmental, infectious, and immunological factors; an autoimmune basis, characterized by circulating immune complexes and complement activation, has gained increasing acceptance. To test and understand immunopathogenesis of Behçet's disease, animal models were developed based on enviromental pollutants, bacterial and human heat shock protein derived peptides, and virus injections. Using these animal models separately and/or concurrently allows for a more effective investigation into Behçet's disease. Animal models developed in the last 10 years aim at the development of efficient and safe treatment options.

A suppressive oligodeoxynucleotide inhibits ocular inflammation

Synthetic oligodeoxynucleotides (ODN) expressing 'suppressive' TTAGGG motifs down-regulate a variety of proinflammatory and T helper type 1 (Th1)-mediated pathological immune responses. The ability of the archetypal suppressive ODN A151 to inhibit ocular inflammation was examined in two murine models: experimental autoimmune uveitis, induced by immunization with a retinal antigen, interphotoreceptor retinoid-binding protein (IRBP) and adoptively transferred ocular inflammation, induced by transferring Th1 cells specific to hen egg lysozyme (HEL) into recipient mice that express HEL in their eyes. A151 treatment suppressed the inflammation in both models. In addition, A151 inhibited IRBP-specific cytokine production and lymphocyte proliferation in mice immunized with IRBP. These findings suggest that suppressive ODN affects both afferent and efferent limbs of the immunopathogenic process and may be of use in the treatment of autoimmune ocular inflammation.

Cytokines and chemokines in uveitis: is there a correlation with clinical phenotype?

Uveitis is a general term for intraocular inflammation and includes a large number of clinical phenotypes. As a group of disorders, it is responsible for 10% of all registered blind patients under the age of 65 years. Immune-mediated uveitis may be associated with a systemic disease or may be localized to the eye. The pro-inflammatory cytokines interleukin (IL)-1beta, IL-2, IL-6, interferon-gamma and tumor necrosis factor-alpha have all been detected within the ocular fluids or tissues in the inflamed eye together with others, such as IL-4, IL-5, IL-10 and transforming growth factor-beta. The chemokines IL-8, monocyte chemoattractant protein-1, macrophage inflammatory protein (MIP)-1alpha, MIP-1beta and fractalkine are also thought to be involved in the associated inflammatory response. There have been a number of studies in recent years investigating cytokine profiles in different forms of uveitis with a view to determining what cytokines are important in the inflamed eye. This review attempts to present the current state of knowledge from in vitro and in vivo research on the inflammatory cytokines in intraocular inflammatory diseases.

Immunopathology of recurrent uveitis in spontaneously diseased horses

Equine recurrent uveitis (ERU) is the most serious eye disease in horses worldwide. Despite the fact that ERU is generally considered to be immune mediated, a detailed description of the histopathology of the posterior part of ERU eyes is lacking. Here, we examined sections of paraffin-embedded eyes using histological and immunhistological methods. Twenty seven eyes of 20 horses with ERU and 30 eyes of 15 healthy control horses were included in this study. We could consistently demonstrate an involvement of the retina and the choroid in all examined eyes of horses with spontaneous ERU. In eyes with minimal histopathological changes, the infiltrates consisted almost exclusively of T-cells. Histopathological changes start with the destruction of the photoreceptor outer segments, which often leads to focal retinal detachment. In more severely affected eyes, there is additional disintegration of the ganglion cell layer and the inner nuclear layer. In almost all examined eyes, lymphoid follicle formation could be demonstrated. Typical localizations of these follicles were the iris stroma and the choroid underneath the transition zone of the retina without photoreceptor cells to the region containing photoreceptor cells. These follicles consist of a T-cell rich periphery with a small center of CD3-negative lymphocytes. In cases with extreme histopathological changes, the retinal architecture is widely disintegrated with massive infiltration of the retina, the choroid, and the ciliary body by several types of inflammatory cells. Necrotic remnants of the retina are end-stage findings and there is only a minor inflammatory infiltration left. This study provides clear evidence that the retina is involved in all stages of ERU. Inflammation is mainly driven by T-cells as T-cells were demonstrated in mild stages of the disease and are also the predominating cell type in all other stages of ERU.

Chemokine gene expression in iris-ciliary body during experimental autoimmune uveoretinitis

PURPOSE

To evaluate, through differential gene expression of chemokines in iris-ciliary body (I/CB), the extent to which leukocyte recruitment to the ocular anterior segment participates in the pathogenesis of experimental autoimmune uveoretinitis (EAU) in mice.

METHODS

B10.A mice were immunized with 50 microg of interphotoreceptor retinoid binding protein (IRBP) mixed with complete Freund's adjuvant. Aqueous humor (AqH) was collected at 0, 11, 17, and 28 days and assayed for leukocyte content and protein levels. Enucleated eyes were subjected to histologic analysis. Chemokine gene expression in I/CB was determined at these same time points by a multiprobe ribonuclease protection assay (RPA) system.

RESULTS

Inflammation was detected in the anterior chamber (AC) at 11 days and leukocyte recruitment continued thereafter. Polymorphonuclear neutrophils (PMN) were the predominant cell type in the AC, whereas macrophages/monocytes and lymphocytes were predominant in the retina/subretinal space at 17 days. Peak gene expression of macrophage inflammatory protein (MIP)-1alpha, MIP-1beta, and MIP-2 and interferon-gamma-inducible protein of 10 kd (IP-10) was detected in I/CB on day 11, whereas peak expression of RANTES and eotaxin was observed at 17 days.

CONCLUSIONS

Early I/CB peak expression of mRNA for MIP-2 followed by PMN recruitment into the AC, suggests that PMN may play an important role in EAU pathogenesis.

IFN-γ Increases the Severity and Accelerates the Onset of Experimental Autoimmune Uveitis in Transgenic Rats

Experimental autoimmune uveitis (EAU) is a predominantly Th1-mediated intraocular inflammatory disease that serves as a model for studying the immunopathogenic mechanisms of uveitis and organ-specific autoimmune diseases. Despite the well-documented role of IFN-γ in the activation of inflammatory cells that mediate autoimmune pathology, recent studies in IFN-γ-deficient mice paradoxically show that IFN-γ confers protection from EAU. Because of the implications of these findings for therapeutic use of IFN-γ, we sought to reexamine these results in the rat, another species that shares essential immunopathologic features with human uveitis and is the commonly used animal model of uveitis. We generated transgenic rats (TR) with targeted expression of IFN-γ in the eye and examined whether constitutive ocular expression of IFN-γ would influence the course of EAU. We show here that the onset of rat EAU is markedly accelerated and is severely exacerbated by IFN-γ. In both wild-type and TR rats, we found that the disease onset is preceded by induction of ICAM-1 gene expression and is characterized by selective recruitment of T cells expressing a restricted TCR repertoire in the retina. In addition, these events occur 2 days earlier in TR rats. Thus, in contrast to the protective effects of IFN-γ in mouse EAU, our data clearly show that intraocular secretion of IFN-γ does not confer protection against EAU in the rat and suggest that IFN-γ may activate distinct immunomodulatory pathways in mice and rats during uveitis.

Progressive subretinal fibrosis and blindness in patients with multifocal granulomatous chorioretinitis

PURPOSE

To describe the clinical and histopathologic findings in four eyes of three patients who became blind because of multifocal choroiditis and massive subretinal fibrosis.

METHODS

Clinicopathologic correlative study.

RESULTS

During a period of several years, three healthy elderly patients developed severe visual loss only partly explained by multifocal chorioretinitis and massive subretinal fibrosis. Histopathologic examination of four eyes from these patients disclosed widespread destruction of the outer retina and retinal pigment epithelium, massive areas of subretinal fibrous tissue proliferation, granulomatous inflammation centered around degenerated and fragmented Bruch's membrane, and chronic uveitis. No infectious organisms were identified by special stains or electron microscopy in one eye.

CONCLUSIONS

Clinical and histopathologic findings in these three patients were consistent with an autoimmune disease process directed at the retina, retinal pigment epithelium, inner choroid, or all three. Cellular injury in this location can result in massive subretinal fibrosis. Subretinal fibroplasia, however, is probably a nonspecific reparative response to injury. The pathogenesis of this blinding disorder in elderly patients may be similar to the less severe disease usually occurring in younger patients with multifocal choroiditis, panuveitis, and punctate inner choroiditis.

S-antigen specific T cell clones from a patient with Behçet's disease

The isolation and characterisation of T cell clones or lines specific to retinal antigens are valuable tools to clarify the underlying mechanisms of autoimmunity to retinal antigens as a contributing factor in ocular inflammation. Patients with Behçet's disease have been reported to be sensitised to S-antigen (S-Ag). In the present study, four T cell clones established from the peripheral blood of a patient with Behçet's disease were analysed. A CD4+ T cell clone (clone 2) and a CD8+ T cell clone (clone 10) proliferated specifically to bovine S-Ag. Although these S-Ag specific T cell clones proliferated vigorously to the intact antigen, their responses to S-Ag derived synthetic peptides M and G were weak, suggesting that the sites of human T cell recognition of S-Ag may be different from those established in the experimental model. The proliferative responses of both clones (2 and 10) were inhibited by anti-HLA-DR monoclonal antibody but not by anti-HLA-class 1 monoclonal antibody. The other two clones studied, clones 6 and 30, were CD3+, CD4-, CD8-, and they did not proliferate specifically to S-Ag. Clone 6 expressed gamma delta T cell receptors (TCR) and showed non-specific cytotoxic activity toward K562 and Daudi cell lines. Clone 30 expressed alpha beta TCR, and was devoid of cytotoxic activity. Human T cell lines and clones specific to retinal antigens will provide the framework necessary to examine the events that lead to ocular inflammation.

Analysis of the uveitogenic determinant in repeat structure of retinal interphotoreceptor retinoid-binding protein (IRBP)

IRBP is a glycolipoprotein with a four-fold partially homologous repeat structure approximately 300 residues in length, and is one of the retinal antigens capable of inducing experimental autoimmune uveoretinitis (EAU) in susceptible animals by their active immunization. The most immunopathogenic peptide of bovine IRBP for EAU in Lewis rats is reported to be the sequence 1169-1191 (PTARSVGAADGSSWEGVGVVPDV) with two immunogenic motifs common to T cell epitopes (underlined). The uveitogenic site of peptide 1169-1191 was localized at the carboxyl terminus (peptide 1182-1191) and not at the amino acid terminus (peptide 1169-1182). Repeat peptides of sequence 1179-1191 containing the four homologous residues (1182W, 1186G, 1187V and 1189P), that is the peptides 271-283, 579-591 and 880-892, all elicited EAU. Peptide 579-591 could not stimulate proliferation of lymphocytes from rats immunized with IRBP, but had the capacity to adoptively transfer EAU. The role of the homologous residues was examined using analogues of the uveitogenic peptide 1182-1194, in which each homologous residue was substituted by glycine (G) or leucine (L) (1182W-->G, 1186G-->L, 1187V-->G, and 1189P-->G). One analogue (1186G-->L) strongly diminished the ability to induce EAU, while the other three analogues completely abolished the ability, indicating that these homologous residues were essential for the induction of EAU. In addition, the uveitogenic peptides tested in this study were found not to contain the major epitope for antibody production.

Treatment of autoimmune uveitis

The number of effective drugs for the treatment of autoimmune uveitis has greatly increased over the past 40 years. Many patients previously condemned to blindness can now be successfully treated with new immunosuppressive agents. New targets of the immune system, such as cell adhesion molecules, may offer novel therapeutic approaches for the treatment of inflammatory disease. However, since the catholicon for uveitis is not yet available, the search for new antiinflammatory therapy continues.

Cellular autoimmunity to retinal specific antigens in patients with Behçet's disease

The notion that autoimmune mechanisms play a role in the pathogenesis of certain uveitic conditions in humans is supported by the observation that lymphocytes from such patients respond in culture against retinal specific antigens which are uveitogenic in animals. A large proportion of uveitis patients with Behçet's disease are reported to respond well to S antigen, to interphotoreceptor retinoid binding protein (IRBP) and to several of their uveitogenic peptides, in particular, the S antigen derived peptide M. Patients with Behçet's disease without ocular involvement were reported not to differ in their responses to S antigen from the responses in the control group, yet 35% of them responded to IRBP and approximately two thirds of them responded to the peptides (peptide M, peptide N, R-4, or R-14). The responses were inhibited by monoclonal antibodies to CD4 and to class II MHC HLA-DR molecules. The presence of lymphocyte responses to retinal antigens in patients with Behçet's disease without uveitis might indicate a preclinical stage of ocular involvement. Thus, these data support the idea that autoimmunity to retinal specific antigens may play a role in the ocular inflammation in Behçet's disease.

The expression of class I major histocompatibility antigens by human retinal pigment epithelium in vitro

Since the expression of class I major histocompatibility antigens by the retinal pigment epithelium (RPE) may be important with regard to ocular immune responses, we investigated this using flow cytometry and compared the RPE cells with the colon carcinoma cell line SW742. Six cultured RPE cell lines were examined. All showed strong basal expression of class I antigen. However, this expression was not maximal, and all the RPE lines tested showed a marked capacity for up-regulation of expression by culture in the presence of interferon-alpha, interferon-gamma, or tumour necrosis factor alpha, cytokines involved in immunological responses.

The existence of two completely distinct antigenic sites within a decapeptide

A decapeptide (1182-1191) derived from the bovine interphotoreceptor retinoid-binding protein (IRBP) was found to contain two completely distinct antigenic sites when tested in Lewis rats. One site, localized in sequence 1182-1191, is the core of the immunodominant and highly uveitogenic determinant of IRBP. The second site localizes within sequence 1183-1191 and becomes detectable only when tryptophan at position 1182 is deleted. Lymphocytes sensitized against the first, larger site recognized all longer peptides within sequence 1169-1191, as well as whole IRBP. In contrast, lymphocytes sensitized against the second, short epitope recognized only two peptides, 1184-1191 and (to a lesser degree) 1183-1191. The responses to both sites were restricted by the same major histocompatibility complex (MHC) product (I-A), as shown by monoclonal antibody blocking and by the finding that the lymphocyte response to 1184-1191 was competitively inhibited by peptide 1181-1191. The unique finding of two completely distinct antigenic sites within a decapeptide could be explained by the hypothesis that peptides of the two sites combine with the MHC molecule on antigen-presenting cells by different configurations, thus forming two distinct antigenicities.

Cellular immune responses to retinal antigens in retinitis pigmentosa

Patients with retinitis pigmentosa and a group of controls were tested for their cellular immune response toward two retinal proteins, S-antigen and interphotoreceptor retinoid-binding protein (IRBP), as well as their reaction against two synthetic peptides ("M" and "N") derived from the sequence of S-antigen and peptide "R14", derived from IRBP. Positive responses to the retinal antigens were found in larger proportions and with higher levels in the patient group than in the controls. The difference between the two groups was statistically significant in their response to S-antigen, but the patients reacted better than the controls against the other antigens as well. Of particular interest was the finding that several patients responded to both retinal proteins and/or to their peptides. These patients suffered from severe retinal changes and the data are thus interpreted as suggesting that the responses to the retinal antigens are secondary to these changes and to nonphysiological release of retinal antigens.

Inhibition of experimental autoimmune uveitis by retinal photoreceptor antigens coupled to spleen cells

Experimental autoimmune uveitis (EAU) and experimental autoimmune pinealitis (EAP) are CD4+ T cell-mediated inflammatory diseases of the uveal tract and retina of the eye and of the pineal gland. EAU and EAP can be induced by several retinal autoantigens including S-antigen (S-Ag) and interphotoreceptor retinoid binding protein (IRBP). In this study we investigated the effect of intravenous administration of S-Ag and IRBP coupled to syngeneic spleen cells on the development of EAU and EAP. Injection of S-Ag or IRBP coupled to spleen cells 5 days prior to immunization with native S-Ag or IRBP, respectively, was effective in preventing the induction of EAU and EAP in LEW rats. Conversely, LEW rats receiving S-Ag-coupled spleen cells and challenged with IRBP or LEW rats receiving IRBP-coupled spleen cells and challenged with S-Ag developed a severe EAU within 10 days to 2 weeks following immunization, as did all control animals receiving sham-coupled spleen cells and challenged with the two retinal antigens. The results show that the administration of retinal autoantigens coupled to spleen cells effectively protects against the development of EAU when animals are subsequently challenged with the tolerizing antigen but not when challenged with another unrelated pathogenic retinal autoantigen.

Immunopathology of experimental autoimmune uveoretinitis in primates

The eyes and pineal glands from 10 monkeys immunized with S-antigen were studied using routine histopathological and immunohistochemical techniques. Seven out of 10 animals developed uveitis between 19 and 33 days after the initial immunization. Histopathology of the eyes harvested 70 days after immunization showed moderate to marked uveoretinitis, subretinal fibrosis, retinal necrosis and gliosis. The pineal glands demonstrated chronic pinealitis. The infiltrating cells were both CD3 and CD19/CD22 lymphocytes with a ratio of 1.4 in the eye and 2.2 in the pineal gland. The ratio of CD4 to CD8 lymphocytes was 1.5:1. MHC Class II antigens and adhesion molecule (ICAM-1) were observed on resident cells. The influx of B lymphocytes and the formation of subretinal fibrosis differentiate the disease in the monkey from that in the rat and mouse. These findings are similar to Vogt-Koyanagi-Harada syndrome and subretinal fibrosis with uveitis syndrome in human.

Suppression of experimental autoimmune uveitis in rats by the oral administration of the uveitopathogenic S-antigen fragment or a cross-reactive homologous peptide

The oral administration of S-antigen fragment (a synthetic peptide designated as peptide M and known to be uveitopathogenic for rat, guinea pig, and monkey) to Lewis rats prior to challenge with an emulsion of peptide M and CFA resulted in either a total or partial suppression of experimental autoimmune uveitis (EAU), a T cell-mediated autoimmune disease studied as a model for human uveitis and experimental autoimmune pinealitis (EPA). Both the clinical and histopathologic manifestations of the disease were suppressed in a dose-dependent manner. Pinealitis associated with EAU was also suppressed by the oral administration of peptide M. Additionally, ingestion of a fragment of baker's yeast (Saccharomyces cerevisiae) histone H3, which has five consecutive amino acids identical to peptide M and which has been found to be uveitopathogenic in Lewis rats, induced tolerance to either peptide M or synthetic histone H3 peptide. In addition, the proliferative response to peptide M was inhibited in peptide M-fed rats. The suppression of EAU and in vitro lymphocyte proliferative responses to peptide M were observed to be antigen specific, since oral feeding of a control protein (BSA) exerted no suppressive effect. Furthermore, the T cells isolated from the spleen and lymph nodes of animals rendered tolerant by oral administration of peptide M can transfer protection against EAU adoptively. These results demonstrate that the oral administration of an autoantigen or its homologous peptide initiates an antigen-specific cellular mechanism which may ameliorate EAU.

Production of interleukin-6 by human retinal pigment epithelium in vitro and its regulation by other cytokines

Interleukin-6 (IL-6) is a pleiotropic cytokine which produces uveitis if administered intraocularly. It has been demonstrated in the aqueous of patients with various uveitis entities. We have investigated the ability of human retinal pigment epithelium (RPE) to produce IL-6 in vitro, both unstimulated, and in the presence of interleukin-1 (IL-1), tumor necrosis factor alpha (TNF), interferon (IFN) gamma, and lipopolysaccharide (LPS). Five human RPE cell lines were cultured over a 6-day period, both unstimulated and in the presence of these cyokines. IL-6 in the supernatants was measured using an ELISA assay. Unstimulated RPE produced small amounts of IL-6. IL-1 at 100 or 10 U/ml markedly upregulated IL-6 production, and TNF at 1000, 100 or 10 U/ml did so to a lesser extent. Neither IFN gamma or LPS alone increased IL-6 expression, but together gave significant upregulation. Thus human RPE can produce IL-6 and may be the source of this cytokine in ocular inflammatory states.

Specificity of T and B cell responses to bovine rhodopsin in Lewis rats

Rhodopsin, an integral membrane protein of rod photoreceptor cells, induces an experimental autoimmune uveitis (EAU) when injected into Lewis rats. This disease is characterized by a mononuclear and polymorphonuclear cellular infiltrate of the retina resulting in destruction of the photoreceptor cells. In this study the B and T cell specificities of the response to bovine rhodopsin by Lewis rats were determined. Antibodies induced by injection of rhodopsin were directed almost exclusively to the IV-V loop (residues 174-202). Later in the response, antibody to the N-terminus was also detected. At the T cell level, most activity was directed to the C-terminus as measured by in vitro lymphocyte proliferation. Other minor T cell epitopes were found in the II-III (96-114) and IV-V (174-202) loops. Further dissection of the amino acid sequence responsible for the activity isolated to the C-terminus indicated that a 12-amino acid-long sequence (331-342) elicited the strongest proliferative response.

Spontaneous development of autoimmune uveoretinitis in nude mice following reconstitution with embryonic rat thymus

This paper describes the spontaneous occurrence of an autoimmune uveoretinitis in nude (nu/nu) mice reconstituted when 4 weeks old by the grafting of rat embryonic thymus. The uveoretinitis was characterized histologically by progressive loss of the photoreceptor layer, observed in 4.0, 17.6, 42.9% and 71.4% of such mice at 3, 5, 7 and 12 months of age, respectively. Mice with uveoretinitis were shown to have serum IgG antibody reactive by indirect immunofluorescence with retinal photoreceptors, and with interphotoreceptor retinoid-binding protein (IRBP), but not retinal S-antigen, by immunoblotting and ELISA. A uveoretinitis could be adoptively transferred to syngeneic ungrafted nude mice by splenic CD4+ T cells from diseased animals. This is the first experimental model of a (T cell mediated) autoimmune uveoretinitis which develops spontaneously and which is not dependent upon deliberate sensitization with retinal antigens and adjuvants.

Interphotoreceptor retinoid-binding protein (IRBP) in progressive rod-cone degeneration (prcd)--biochemical, immunocytochemical and immunologic studies

Interphotoreceptor retinoid-binding protein (IRBP) is synthesized and secreted by photoreceptor cells and is thought to facilitate the transport of retinoids during the visual cycle as well as fatty acids essential to the maintenance of normal outer segment membranes. Proteins such as IRBP, which are unique to the photoreceptor cells in the retina, are prime candidates in the consideration of biochemical defects which could contribute to photoreceptor cell degeneration in man and animals. In this study, the association between IRBP and retinal degeneration was examined using the progressive rod-cone degeneration (prcd) mutant retina in dogs as an animal model. This study shows that loss of IRBP is not an early occurrence in prcd. IRBP is present in relatively normal amounts and distribution even at 1.7 years of age, a time when there is extensive visual cell disease and degeneration. By 2.7-3.0 years of age, IRBP loss correlates with the severity of the disease and concomitant loss of photoreceptor cells. IRBP immunoreactivity was present in the interphotoreceptor matrix (IPM) as long as inner segments were present to a significant degree. The late loss of IRBP immunoreactivity seems to be, therefore, the result of advanced degeneration and end-stage atrophy of the retina. In addition, immunological studies were carried out in order to examine the possible role of an autoimmune response against IRBP in the disease cascade. Normal, heterozygote and prcd-affected dogs had measurable antibody titers to IRBP, but there was no correlation between disease state and antibody levels.

Randomized, double-masked study of cyclosporine compared to prednisolone in the treatment of endogenous uveitis

Fifty-six patients with bilateral sight-threatening noninfectious intermediate or posterior uveitis participated in a randomized double-masked study of the use of cyclosporine vs prednisolone in their treatment. Applying the end-point definitions, visual acuity or vitreal haze improved in only 13 of 28 (46%) patients in each group. The macular edema resolved in seven of 15 patients of the cyclosporine-treated group, and in ten of 16 patients of the prednisolone-treated group (P = .376). Patients whose therapies failed both cyclosporine and prednisolone trials were treated with both drugs, which resulted in additional patient improvements. Secondary effects were observed in both therapeutic alternatives, the most notable being alterations in serum creatinine concentration and hypertension with the dosage of cyclosporine used.

Experimental autoimmune retinitis in the rat induced by immunization with rhodopsin: an ultrastructural study

Experimental autoimmune retinitis induced by immunization with rhodopsin was investigated in the Lewis rat using transmission electron microscopy and light microscopy. The first signs of retinitis consisted of scattered infiltrations of lymphocytes and other mononuclear cells, predominantly in the inner nuclear layer and outer plexiform layer. Occasionally, some macrophages were detected in the photoreceptor cell layer. Eyes exhibiting a clinically moderate or severe inflammation contained areas of normal retina coexistent with mildly to severely inflamed foci. The central retina was more frequently affected than the peripheral area. In moderately inflamed foci, macrophages infiltrated the photoreceptor cell layer, damaging and eliminating its structures. Inflammatory cells penetrated the photoreceptor outer segment layer which remained unaltered so far in spite of a high serum anti-(rhod)opsin antibody titer. In stages of severe inflammation, massive infiltrations of macrophages and polymorphonuclear cells destroyed the photoreceptor cells focally, leaving the retinal pigment epithelium virtually unaffected. Adjacent to these foci the pigment epithelial cells sometimes exhibited increased numbers of phagosomes and swelling. The locations of the cell infiltrations and lesions in progressive stages of development suggest that the rod outer segments are the target for the autoimmune damage. The described patterns of inflammation were compared with those of previous studies using other animal species and inciting antigens. Especially in rhodopsin-induced retinitis, the blood-retina barrier at the level of the Bruch's membrane/pigment epithelium appears to be highly resistant to cytotoxic cells. The present observations are in agreement with the concept that the cellular immune response plays a major role in the pathogenesis of (rhod)opsin-induced retinitis.

Vascular changes in the posterior segment in clinical and experimental ocular inflammatory disease

Posterior segment inflammatory disease can have several different effects on the retinal vasculature, all of which have potentially sight threatening consequences. Blood-retinal barrier breakdown is a common feature of the disease process with resulting retinal and macula oedema. Very little is known about the mechanism of this breakdown and in particular whether it is at the endothelial cell membrane or at the tight junctions between the endothelial cells--a matter of importance if better therapeutic regimes are to be devised in the future. This paper looks at this question in two animal models of posterior uveitis using different techniques.

Localization of the gene for interphotoreceptor retinoid-binding protein to mouse chromosome 14 near Np-1

Interphotoreceptor retinoid-binding protein (IRBP) is a large glycoprotein known to bind retinoids and found primarily in the interphotoreceptor matrix of the retina between the retinal pigment epithelium and the photoreceptor cells. It is thought to transport retinoids between the retinal pigment epithelium and the photoreceptors, a critical role in the visual process. We have used a 900-bp bovine IRBP cDNA fragment to map the corresponding gene, Rbp-3, to mouse chromosome 14 with somatic cell hybrids and have positioned the gene near Np-1 (nucleoside phosphorylase-1) by analysis of the progeny of an intersubspecific backcross. In the human genome, NP maps to human chromosome 14 and RBP3 to human chromosome 10. Thus, these two genes span the putative site of a chromosomal translocation which contributed to divergent karyotype evolution of man and mouse.

Repeated determinants within the retinal interphotoreceptor retinoid-binding protein (IRBP): immunological properties of the repeats of an immunodominant determinant

Interphotoreceptor retinoid-binding protein (IRBP), a glycoprotein which localizes in the retina and pineal gland, induces inflammatory changes in these organs (EAU and EAP, respectively) when injected into various mammals. We have previously identified a determinant (residues 1169-1191) in bovine IRBP which is immunodominant and highly immunogenic and immunopathogenic in Lewis rats. IRBP exhibits a fourfold repeat structure and we report here on the comparison between the active sequence 1179-1191 and its three repeat peptides. Only one of the repeats, 271-283, cross-reacted with 1179-1191 and exhibited immunodominance, albeit of a low level. Peptide 271-283 was also immunogenic and immunopathogenic in Lewis rats, but with a minimal dose approximately 100 times higher than that of 1179-1191. Peptide 880-892, a nondominant determinant, resembled 271-283 in its immunogenicity, but was markedly less immunopathogenic. No immunological activity was detected in the fourth repeat peptide, 579-591. Peptide 1179-1191 was superior to the other repeats also in its antigenicity, i.e., the capacity to stimulate presensitized lymphocytes in culture: the minimal stimulatory concentrations of 1179-1191 was greater than 1000 times lower than those of 271-283 or 880-892. Furthermore, 1179-1191 was stimulatory at concentrations lower than those of 271-283 even when tested with lymphocytes sensitized against 271-283. A correlation was also found between the immunological activities of the repeat peptides and their amphipathicity. This study thus identifies two new immunopathogenic determinants of IRBP and provides additional data to show the association between immunodominance of peptides and their various immunological activities.

IRBP: preparation and characterization of site-specific monoclonal antibodies

Interstitial retinoid binding protein (IRBP) is a 136,000 molecular weight photoreceptor cell protein which is a highly pathogenic autoantigen for the induction of experimental autoimmune uveitis (EAU). In this study we produced a series of monoclonal antibodies (MAbs) which define different epitopes in the native molecule. These MAbs were further subdivided into three distinct groups based on a radioimmunoassay, and by ELISA assay using native IRBP and synthetic peptides corresponding to its entire amino acid sequence. Group I MAbs (MAbD7-B1 and MAbC6-B4) bound to native IRBP but not to any synthetic peptides, suggesting that their antigenic epitopes are strictly conformation dependent. Group II MAbs (MAbC7-D3 and MAbG8-H4) bound weakly to multiple peptides which shared amino acid sequence similarity located within each of four homology domains indicating that these epitopes are also conformation dependent. In group III (MAbH3-B5, MAbH7-A5, and MAbB6-D12) MAb binding was localized to a specific peptide. The MAbH3-B5 binding site was further refined to amino acid positions 361 to 367 in the native molecule. MAbH3-B5 was also useful in localizing IRBP in the mouse retina by immunohistochemical techniques. The application of these MAbs in the study of EAU and interphotoreceptor transport mechanisms is discussed.

Auxiliary production of antibodies to ocular antigens in experimental autoimmune uveoretinitis

In experimental autoimmune uveoretinitis (EAU), there are concurrent autoreactive humoral and cellular immune responses. Many studies have recently focused on T-cell reactivities in EAU, while analysis of autoantibody responses to uveitogenic epitopes has been less well characterized. In this study, a defined 16-mer uveitogenic interphotoreceptor retinoid binding protein (IRBP) peptide, designated #896, was used to induce EAU. Histological analysis of eyes at day 10 demonstrated extensive leukocyte infiltration of the anterior segment, with mononuclear and plasma cells in the posterior segment. The presence of plasma cells suggests local production of antibodies within the eye. ELISA analyses of serum, aqueous, and vitreous from rats with IRBP-induced, severe EAU revealed the presence of antibodies against peptide #896. There was little difference between the serum and intraocular antibody titers, presumably due to breakdown of the blood-ocular barriers. In addition to the anti-#896-IRBP antibodies, there were detectable antibodies reactive against separate and distinct IRBP epitopes, as well as, against epitopes on retinal-S antigen. These results indicate that in #896-peptide-induced severe EAU, humoral immune responses are induced to the primary immunogen and that there is also auxiliary production of autoreactive antibodies against other epitopes present on intraocular antigens. These auxiliary responses may contribute to the immunopathogenesis of severe EAU.

Uveitis and immune responses in primates immunized with IRBP-derived synthetic peptides

Monkeys immunized with bovine IRBP-derived synthetic peptides R4 (sequence 1158-1180) or R14 (1169-1191) developed EAU which was detected by both clinical and histological examinations. The inflammation localized mainly in the choroid, with only minor changes being noticed in the adjacent retinal tissue. EAU developed in only one of the two monkeys immunized with each of the peptides and the animals with disease also showed higher levels of cellular immunity toward the immunizing peptide than did the monkeys with no disease. The cellular immune responses, measured by the lymphocyte proliferation assay, were specific toward the immunizing peptides, with no cross responsiveness to whole IRBP. This finding suggests that the two uveitogenic peptides were non-immunodominant in the tested monkeys. In contrast, peptide R14 is highly immunodominant in the Lewis rat. Also, the fine specificity of the monkey response to R14 differed from that of the Lewis rat. The possible genetic control of the monkey susceptibility to EAU induction by the peptides is discussed and the unique finding of an autoimmune disease induction by a non-immunodominant peptide is underscored.

Identification of multiple associative and dissociative proliferative and uveitogenic T-cell sites in human interstitial retinoid-binding protein

Human interstitial retinoid-binding protein (HIRBP) is a 136 kDa retinal protein capable of inducing experimental autoimmune uveoretinitis (EAU) and experimental autoimmune pinealitis (EAP) in Lewis (LEW) rats. In order to identify the T-cell recognition sites of HIRBP responsible for uveitogenic and proliferative responses, 125 overlapping peptides corresponding to its entire 1262 amino acid sequence were synthesized. Individual peptides were tested for their ability to induce EAU in LEW rats and to stimulate lymphocyte proliferation in rats immunized with the native molecule. Our previous results showed the presence of nine uveitogenic peptides in HIRBP with a minimum requirement of eight amino acids needed to induce EAU in LEW rats. Our present studies show nine proliferative peptides, four of which are also responsible for uveitogenicity. Another four peptides known to actively induce EAU were unable to elicit proliferative responses. However, these peptides overlapped or were adjacent to peptides that elicited good proliferative responses. A single, highly proliferative peptide was located on the amino terminus of HIRBP. In addition, EAU was adoptively transferred with lymph node cells (LNC) of LEW rats previously immunized with two synthetic peptides known to be uveitogenic. Our study indicates that human IRBP is a complex molecule containing multiple and spatially distinct T-cell epitopes responsible for its uveitogenicity, adoptive transfer of EAU and proliferative responses.

The mouse as a model of experimental autoimmune uveoretinitis (EAU)

An EAU model has been developed in the mouse using the retinal soluble antigen (SAg), and the interphotoreceptor retinoid-binding protein (IRBP). Immunogenetic studies indicate that sensitivity to disease is H-2 dependent, but some data suggest that non-MHC genes may also contribute to the regulation of EAU. IRBP was a more potent uveitogen than SAg. Ability to mount lymphocyte and antibody responses was exhibited both by EAU-susceptible and by EAU-resistant strains, and could not be used as a predictive parameter. Dependence of disease induction on variables of immunization was studied in B10.A mice (I-Ak) immunized with IRBP. Use of Bordetella pertussis as additional adjuvant was a prerequisite for successful disease induction. Use of purified pertussis toxin (PTX), rather than a suspension of pertussis bacteria, allowed reduction of the immunization protocol to a single dose of IRBP in CFA. Severity and incidence of disease, as well as its clinical course, were directly affected by the dose of antigen and PTX, and could be controlled by varying their respective doses. A spectrum of disease, from hyperacute to chronic, could be obtained. The chronic type of EAU tended to relapse, with lesions reappearing after a brief period of essential quiescence. The special advantages of the murine EAU model for the study of ocular autoimmunity are discussed.

Immunological features of synthetic peptides derived from the retinal protein IRBP: differences between immunodominant and non-dominant peptides

Interphotoreceptor retinoid-binding protein (IRBP) is a glycoprotein of 1264 residues (bovine) which localizes specifically in the retina and pineal gland and induces inflammatory changes in these organs (EAU and EAP, respectively) in immunized animals. We report here on differences between the immunological activities in Lewis rats of four IRBP-derived synthetic peptides. Only one of these peptides, designated R14 (residues: 1169-1191) is immunodominant, i.e., it has the capacity to stimulate lymphocytes sensitized against whole IRBP. The remaining peptides, R4 (1158-1180), R8 (1197-1209), and R12 (248-266), are non-dominant and are not recognized by IRBP-sensitized lymphocytes. R14 differed profoundly from the other peptides in its immunogenicity, inducing cellular immunity at the low dose of 0.1 nmol/rat, whereas the non-dominant peptides initiated immune responses at doses approximately 100 times higher. R14 was also superior to the non-dominant peptides in its antigenicity, as determined by the lowest concentration required to induce sensitized lymphocytes to proliferate. Responses were stimulated by R14 at a concentration of 10(-6) microM, while the three non-dominant peptides were stimulatory at the much higher concentration of 10(-1) microM. These data support the concept that immunodominance is linked to a high binding affinity of the peptide determinant to the major histocompatibility complex antigens on antigen-presenting cells.

Immune responses to peptides derived from the retinal protein IRBP: immunopathogenic determinants are not necessarily immunodominant

Interphotoreceptor retinoid-binding protein (IRBP), a glycoprotein specific to the retina and pineal gland, induces in immunized rats inflammatory changes in these organs (EAU and EAP, respectively). We report here on the immunological activities in Lewis rats of 10 IRBP-derived peptides. Only one of these peptides (R3) was found to induce high levels of antibodies in immunized rats, as detected by ELISA. On the other hand, the majority of the tested peptides stimulated substantial cellular immune responses, measured by the lymphocyte proliferation assay. None of the tested peptides were recognized, however, by antibodies or lymphocytes from rats immunized with the whole IRBP molecule, thus indicating that these synthetic peptides are nonimmunodominant in the Lewis rat. Two of these peptides, R4 and R9 (which contains R4), were previously found to be immunopathogenic, producing EAU and EAP in immunized Lewis rats. The immune responses to peptide R4 were further examined and the data show that it induces measurable lymphocyte responses only when injected at remarkably high doses (greater than or equal to 67 microgram/rat). Yet, peptide R4 was highly antigenic when tested for stimulation of specifically sensitized lymphocytes in culture. Furthermore, lymphocytes sensitized against R4 exhibited high capacity to adoptively transfer EAU and EAP to naive recipients. The finding of immunopathogenic but nonimmunodominant peptides is discussed.

Synthesis of an immunopathogenic fusion protein derived from a bovine interphotoreceptor retinoid-binding protein cDNA clone

We have extended the cDNA sequence of bovine interphotoreceptor retinoid-binding protein (IRBP) and subcloned one of the sequenced cDNA fragments into an expression vector. The nucleotide (nt) sequences of four bovine IRBP cDNA clones have been determined. These sequences when assembled cover the 3' proximal 3629 nt of the IRBP mRNA and encode the C-terminal 551 amino acids (aa) of IRBP. This cDNA sequence validates the intron: exon boundaries predicted from the gene. A 2-kb EcoRI insert from lambda IRBP2, one of the clones sequenced, encoding the C-terminal 136 aa of IRBP was subcloned into the expression vector pWR590-1. Escherichia coli carrying this plasmid construction, pXS590-IRBP, produced a fusion protein containing 583 N-terminal aa of beta-galactosidase, three linker aa residues, 136 C-terminal aa of IRBP and possibly a number of additional C-terminal residues due to suppressed termination. This 86-kDa fusion protein, purified by detergent/chaotrope extraction followed by reverse-phase high-performance liquid chromatography, cross-reacted with anti-bovine IRBP on Western blots. This protein induced an experimental autoimmune uveo-retinitis and experimental autoimmune pinealitis in Lewis rats indistinguishable from that induced by authentic bovine IRBP. Thus, it is evident that biological activity of this region of IRBP, as manifested by immuno-pathogenicity, is retained by the fusion protein.

Rat T-cell lines specific to a nonimmunodominant determinant of a retinal protein (IRBP) produce uveoretinitis and pinealitis

Rat lymphocyte lines were established, with specificity toward two synthetic peptides derived from the interphotoreceptor retinoid-binding protein (IRBP), which specifically localizes in the retina and pineal gland. One of the peptides, R4, is immunopathogenic, producing experimental autoimmune uveoretinitis (EAU) and pinealitis (EAP) in immunized rats, while the other peptide, R3, exhibits no detectable immunopathogenicity in rats. The cell lines carry surface markers specific for the helper/inducer subset of T-lymphocytes. When tested by the proliferation assay, the line cells demonstrated major histocompatibility-restricted vigorous responses against the immunizing (homologous) peptide, but failed to recognize the intact IRBP molecule. This finding is in line with other data indicating that peptides R3 and R4 are nonimmunodominant determinants of IRBP for the Lewis rat. Yet, the cell lines specific for R4 were highly immunopathogenic, producing EAU and EAP in naive rats at numbers as low as 0.25 x 10(6), with histopathological changes similar to those induced by active immunization with this peptide. The immunological capacity of the cell lines was further demonstrated by the finding that spleen cells from recipient rats of these lines responded well against the homologous peptides. The uniqueness of this system, in which lymphocytes specific toward a nondominant determinant are immunopathogenic, is underscored and the possible mechanisms of disease induction are discussed.

Identification of an immunodominant and highly immunopathogenic determinant in the retinal interphotoreceptor retinoid-binding protein (IRBP)

Interphotoreceptor retinoid-binding protein (IRBP), a glycoprotein specific for the retina and pineal gland, induces inflammatory changes in these two organs in immunized animals. We report here on the identification of an immunodominant determinant of bovine IRBP that is highly immunogenic and immunopathogenic in the Lewis rat. The peptide, which comprises the sequence 1169-1191 of bovine IRBP, was shown to be immunodominant by its capacity to stimulate lymphocytes sensitized against whole IRBP. A comparison was made between peptide 1169-1191 and another peptide, 1158-1180, which is nondominant but is immunogenic and immunopathogenic in the Lewis rat. Peptide 1169-1191 was found to be superior in its immunological capacities; the minimal dose of 1169-1191 needed to induce cellular immune response or disease in Lewis rats (0.02-0.1 nmol/rat) is congruent to 1,000 times smaller than that of 1158-1180. In addition, unlike the ocular disease induced by 1158-1180, the disease produced by 1169-1191 resembled that induced by whole IRBP in its kinetics and histopathological features. The immunological activity of 1169-1191 in the Lewis rat was localized to the 10 residues at the COOH terminus; no such activity was exhibited by the truncated peptide 1169-1188, which comprises the 20 residues at the NH2 terminus of the full peptide. The usefulness of this unique experimental system in analyzing the role of immunodominance in peptide immunogenicity and immunopathogenicity is underscored.

Rhodopsin-induced experimental autoimmune uveoretinitis in monkeys

We present the first evidence that purified rhodopsin can induce experimental autoimmune uveoretinitis (EAU) in monkeys. Injection of a highly purified lipid-free rhodopsin preparation provokes severe chorioretinitis with concomitant anterior uveitis. The onset of disease is earlier, its frequency is higher, and the inflammation is considerably more severe than in EAU induced under similar conditions by opsin. The first inflammatory cells are observed in the ciliary body and pars plana. Within a few days the inflammation extends into the anterior chamber, choroid, and retina. Retinitis predominates in the central area, while chorioretinitis is observed in the periphery, both accompanied by damage to and elimination of the photoreceptor cells. The monkeys develop high cellular and humoral immune responses against rhodopsin and opsin. The cellular response maximum just precedes the onset of EAU. This may indicate that cellular immunity has an important role in the pathogenesis of rhodopsin-induced EAU.