Experimental autoimmune uveoretinitis (EAU) in rats: isolation of S-antigen, EAU susceptibility of rat strains, genetic control of EAU induction, and effects of cyclophosphamide and irradiation on EAU

Highly purified S-antigen was isolated from bovine retinas by high performance liquid chromatography (HPLC), and was used to induce experimental autoimmune uveoretinitis (EAU) in various rat strains. Studies were then made of the genetic control of EAU, the effects of cyclophosphamide or irradiation on EAU, and the correlation between the EAU incidence and the serum levels of antibody to S-antigen. Lewis rats were the most susceptible to EAU followed by Wistar rats. F344 rats and BN rats were resistant to EAU. (Lewis X BN)F1 rats and (LBNF1 X Lewis) rats were susceptible to EAU, while (LBNF1 X BN) rats were resistant. These results indicate that susceptibility to EAU was inherited as an autosomal dominant trait. Treatment of rats with cyclophosphamide or irradiation (200 rad/rat) on the day before immunization markedly suppressed EAU development. On the other hand, the same dose of irradiation 7 days after the immunization did not affect the disease induction, yet the antibody levels to S-antigen were very high in the rats. In addition, BN rats resistant to EAU exhibited very high levels of antibody to S-antigen. Therefore, the antibody to S-antigen seems to play a minor role, if any, in the immunopathogenic mechanisms of EAU.     

Effects of a new immunosuppressive agent, FK506, on experimental autoimmune uveoretinitis in rats

A comparative study was carried out between cyclosporine and a new immunosuppressive agent, FK506, isolated from the Streptomyces organism. This agent has the capacities to suppress the development of S-antigen-induced experimental autoimmune uveoretinitis (EAU) as well as immune responses to S-antigen in rats immunized with the antigen. When administered daily beginning on the day of immunization and for 14 days thereafter, FK506 at doses between 0.1 and 1 mg/kg suppressed EAU in a dose-dependent manner. Complete inhibition of EAU was achieved at doses of 1, 3 and 10 mg/kg. Cyclosporine (1-20 mg/kg) also produced a dose-dependent suppression of EAU and only the highest dose (20 mg/kg) caused complete inhibition of the disease. On the basis of the dose-response study, the capacity of FK506 in preventing EAU induction is 10-30 times more intense than that of cyclosporine. In addition, the FK506 (1 and 3 mg/kg) was found to be effective in preventing EAU even when administered only in the early induction phase (days 0-5) or late effector phase (days 7-12). Similar effects were obtained by cyclosporine at a daily dose of 30 mg/kg. Furthermore, none of the rats immunized with S-antigen and treated with FK506 (1 mg/kg) on days 0-14 developed EAU when reimmunized with S-antigen on day 30. In contrast, similarly treated rats were fully susceptible to the induction of experimental allergic encephalomyelitis, or even to EAU when immunized with another retinal antigen, interphotoreceptor retinoid-binding protein. Therefore, as with cyclosporine, as demonstrated in our previous study, FK506 has the capacity to induce immunological unresponsiveness specific to the S-antigen.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effects of FTY720, a novel immunosuppressant, on experimental autoimmune uveoretinitis in rats

The immunosuppressive properties of FTY720, a novel immunosuppressant obtained by structural modification of ISP-I isolated from the fermentation broth of Isaria sinclairii, were studied in experimental autoimmune uveoretinitis (EAU) in rats. Lewis rats were immunized with S-antigen and treated with FTY720 (0. 03, 0.06, 0.1 mg kg(-1)day(-1)) or distilled water for 16 days after the immunization. FTY720 suppressed the incidence and intensity of EAU in a dose-dependent manner as demonstrated by clinical and histological examinations. The drug significantly suppressed the serum levels of antibodies to S-antigen and antigens-specific lymphocyte proliferation. The number of peripheral lymphocytes, but not neutrophils, was markedly reduced by FTY720 treatment. FTY720 also suppressed the intensity of EAU when it was given from the day of EAU onset. These results indicate that FTY720 has intense immunosuppressive effects on EAU in rats and may be a potential candidate for use in the treatment of patients with autoimmune uveitis.     

Antigen-specific suppressor cells induced by FK506 in experimental autoimmune uveoretinitis in the rat.

The authors previously reported that FK506 effectively suppressed the induction of experimental autoimmune uveoretinitis (EAU) in rats with much lower doses than cyclosporine A. This study was aimed at analyzing the immune status of the FK506-treated and EAU-suppressed rats and examining the hypothesis whether the agent could induce antigen-specific suppressor T (Ts) cells. It was found that spleens from S-antigen-immunized and FK506-treated rats contained a population of Ts cells inhibiting the proliferative responses of S-antigen-sensitized lymphocytes to S-antigen, yet these cells did not affect the proliferative responses of interphotoreceptor retinoid-binding protein (IRBP)-sensitized lymphocytes to IRBP. The helper T (Th) cells did not exhibit such suppressor activities. Furthermore, transfer of Ts cells from S-antigen-immunized and FK506-treated rats to naive syngenic rats induced partial inhibition of EAU induction or delay of EAU onset after immunizing the recipient rats with S-antigen. Lymphocytes from the EAU-suppressed recipients showed low proliferative response to S-antigen and low levels of antibody to S-antigen. These data thus indicate that FK506 treatment after S-antigen immunization induces an activation of Ts cells specific to S-antigen and that the Ts cells might contribute, at least in part, to the uniquely prolonged and intensive immunosuppression by FK506.     

实验性自身免疫性葡萄膜视网膜炎中可诱导的共刺激分子的表达及意义

目的探讨可诱导的共刺激分子（ICOS）在实验性自身免疫性葡萄膜视网膜炎(EAU)中的表达及意义。方法Lewis大鼠28只，用视网膜S抗原（50 μg）和福完全佐剂免疫24只大鼠以诱导EAU模型（免疫组），另外4只作为正常对照。裂隙灯显微镜每日观察大鼠眼部变化。免疫组大鼠分别于免疫后第7、12、15、21天被处死，摘除其脾脏后制作冰冻连续切片并提取组织蛋白。使用多克隆抗ICOS抗体，用免疫组织化学细菌蛋白过氧化物酶（SP）法在上述组织切片上进行免疫组织化学染色，并对提取的蛋白进行Western blotting检测。对照组大鼠在相应各时间点做同样处理。结果正常脾组织中可见少量ICOS阳性细胞；分别在免疫后第7、12 d，脾脏中ICOS阳性细胞数量明显增加，免疫后第15天时阳性细胞数量最多，21 d时阳性细胞数量减少，但仍显著高于正常组；Western blotting检测结果显示，ICOS蛋白的动态变化与免疫组织化学显示的阳性细胞数量变化一致。结论脾脏ICOS表达升高出现于EAU发生之前，随炎症的出现和加重而升高，在EAU消退期其表达有所降低，提示ICOS参与EAU的形成、发展和消退，在EAU发病中有重要意义。(中华眼底病杂志,2005,21:114-117)     

Effects of cyclosporine and other immunosuppressive drugs on experimental autoimmune uveoretinitis in rats

Five immunosuppressive and anti-inflammatory agents were tested for their effects on development of experimental autoimmune uveoretinitis (EAU) and immune responses to S-antigen in rats immunized with this retinal antigen. When administered daily from day 0-14 after immunization, cyclosporine at 5-20 mg/Kg was nontoxic and yet effective in inhibiting the development of EAU for at least 30 days. All other tested drugs were found toxic at their immunosuppressive doses. Of these drugs, only cyclophosphamide (at 5-20 mg/Kg) was capable of inhibiting EAU in some of the treated rats for up to 30 days. Other agents, bredinin (40-100 mg/Kg), dexamethasone (0.2-0.4 mg/Kg), or colchicine (0.5 mg/Kg) produced only a delay in the disease onset. Cyclosporine was also unique in its effect on the immune responses of the rats by selectively inhibiting only the specific T-cell-mediated responses to S-antigen (delayed skin response and lymphocyte response in culture), while having no negative effect on antibody production or the lymphocyte response to the polyclonal mitogen, concanavalin A. Other drugs, when effective, inhibited all types of immune response. In addition, cyclosporine was capable of preventing EAU even when given to rats as late as from day 7 after immunization. Only cyclophosphamide (at 20 mg/Kg/day) had a similar effect on 1/3 of the rats, while other drugs only delayed or had no effect on the disease onset when given by this late schedule.     

实验性自身免疫性葡萄膜视网膜炎中T-bet的表达及意义

目的 研究实验性自身免疫性葡萄膜视网膜炎（EAU）中T-bet的表达及意义 方法 Lewis大鼠28只，用视网膜S抗原与Freund完全佐剂免疫24只大鼠以诱导EAU模型，另外4只作为正常对照。免疫组大鼠分别于免疫后7、12、15、21 d被处死，取所有大鼠的眼球和脾脏，固定后制作眼组织平片和眼球及脾脏的石蜡连续切片。使用单克隆抗T-bet 和CD4的抗体，通过免疫组织化学细菌蛋白过氧化物酶法在上述组织平片及切片上进行免疫组织化学单染和双染色，在光学显微镜下观察并计数阳性细胞，数据经SPSS 11.0统计学软件分析。 结果 正常眼和脾组织中均见少量T-bet阳性细胞；免疫后7 d，虹膜、视网膜及脾脏中T-bet的表达增加，免疫后15 d达高峰，免疫后21 d表达降低，但仍高于正常组。免疫组织化学双染色显示，T-bet阳性细胞中多数为CD4+。 结论 T-bet在EAU的发病中起着重要作用，其作用可能是通过激活辅助性T淋巴细胞1而实现的。（中华眼底病杂志，2004，20：172-174）     

Pathogenic role of retinal microglia in experimental uveoretinitis

PURPOSE: To devise methods for unequivocal identification of activated retinal microglia in experimental autoimmune uveoretinitis (EAU) and to investigate their role in the development of EAU. METHODS: A group of Lewis rats underwent optic nerve axotomy with the application of N-4-(4-didecylaminostyryl)-N methylpyridinium iodide (4Di-10ASP) at the axotomy site. On days 3, 14, and 38 after axotomy, the rats were killed, the eyes were enucleated, and the retinas were stained for OX42. Another group of such axotomized rats were immunized with S-antigen peptide and were killed on days 7 through 12 after the injection with peptide. The enucleated eyes were stained for OX42 and examined by confocal microscope. After axotomy, bone marrow (Y-->X) chimeric rats were injected with S-antigen peptide and were killed on days 10 and 12 after injection. The retinas were evaluated by PCR with Y-specific primers. Finally, a group of axotomized rats was injected with the S-antigen peptide and killed on days 6, 8, 9, and 10 after injection. Their enucleated eyes were examined for microglial expression of TNFalpha and for generation of peroxynitrite. RESULTS: In the axotomized, non-EAU eyes, 4Di-10ASP-labeled ganglion cells were detectable on days 3 and 14, and 4Di-10ASP-containing OX42-positive cells (microglia) were found in the nerve fiber and other inner retinal layers on days 14 and 38. The S-antigen peptide-injected rats showed migration of the microglia (4Di-10ASP-positive and OX42-positive) to the photoreceptor cell layer on day 9, and these cells increased in number at this site on day 10. No macrophages (OX42-positive and 4Di-10ASP-negative) were present at this early stage of EAU, but such cells appeared in the retina on days 11 and 12. PCR of the chimeric EAU retinas showed an absence of the Y chromosome-amplified product on day 10, but the presence of this product was detected on day 12. The expression of TNFalpha and generation of peroxynitrite were noted in the migrated microglia at the photoreceptor cell layer on days 9 and 10 of EAU. CONCLUSIONS: In the early phase of EAU, the microglia migrate to the photoreceptor cell layer where they generate TNFalpha and peroxynitrite. Such microglial migration and activation take place before infiltration of the macrophages. These findings indicate a novel pathogenic mechanism of EAU, in which retinal microglia may initiate retinitis with subsequent recruitment of circulation-derived phagocytes, leading to the amplification of uveoretinitis.     

Cyclosporine G and D in experimental autoimmune uveoretinitis in the rat

Two analogs of cyclosporine A (CsA), cyclosporine G (CsG) and cyclosporine D (CsD), were compared to CsA with regards to their effects on experimental autoimmune uveoretinitis (EAU) as well as their adverse effects on renal functions. When administered daily on days 0-14 after immunization with S-antigen, CsA was the most effective of all in inhibiting EAU followed by CsG: 20-30 mg/kg/day of CsG appeared to have the same effect as 5 mg/kg/day of CsA. The effect of CsD was the least. When administered from day 7 after immunization, CsA and CsG were also effective in inhibiting the development of EAU. As for the adverse side effects, CsA was the most nephrotoxic: the toxic changes were morphologically found with doses of CsA at 10 mg/kg/day or higher. CsG and CsD were not nephrotoxic even at 30 mg/kg/day. The effects of CsG on immune responses were very similar to those of CsA. Both agents exhibited selective inhibition on the cell-mediated immune responses to S-antigen, while having no effect on antibody production.     

Involvement of the pineal gland in rats with experimental autoimmune uveitis

Pineal glands of rats with experimentally induced autoimmune uveitis (EAU) were studied histologically. Inflammatory changes, characterized by mononuclear infiltration, were found in the pineal glands of one-third of the Lewis rats that developed EAU by active immunization with S-antigen. No changes in the pineal gland were observed in AVN rats which are "low responders" for EAU and did not develop ocular disease. Frequency and severity of both pineal gland and ocular involvement clearly were elevated by intravenous injection of Bordetella pertussis along with the S-antigen immunization; all B. pertussis-treated rats of both Lewis and AVN strains developed pineal and ocular changes. Inflammatory changes of the pineal gland also were found in rats in which EAU was induced passively by transfer of lymphocytes from S-antigen-immunized donors. The frequency of involvement of the pineal gland was found to be lower than that of the retinas in rats where EAU was induced by active immunization or by adoptive transfer of lymphocytes.     

Effect of Gallium Nitrate on Experimental Autoimmune Uveitis

Gallium nitrate (GN) has been shown to inhibit T cell-mediated inflammatory disease. The purpose of our study was to test the effect of gallium nitrate (GN) on experimental autoimmune uveitis (EAU). Experimental autoimmune uveitis was induced in male Lewis rats immunized with retinal S-antigen. Rats received subcutaneous injections of GN or saline one day prior to immunization and 1, 4, 7, 10, 13, 16, and 19 days after immunization. Ocular inflammation was graded clinically and histologically by masked observers, and in vitro assays of cell-mediated and humoral immunity were performed. GN significantly inhibited the development of EAU graded clinically (P=0.001) and histologically (P=0.002). Treatment with GN also resulted in a small (30–41%) decrease in the lymphocyte responses to retinal S-Antigen and a small (12–37%) reduction in antibody production to S-antigen. These data show that GN suppresses the development of EAU, and inhibits both lymphocyte proliferative responses to antigen and antibody production.     

IRBP免疫鼠血清特异性抗体的测定及动态变化

我们首次在国内提纯了光感受器间维生素 A类结合蛋白(interphotoreceptor retinoid-binding protein,IRBP),将其免疫 Lewis 大鼠后动态测定了鼠血清抗IRBP 抗体和抗视网膜 S 抗原抗体.发现抗 IRBP 抗体于免疫后第7天出现,以后逐渐上升,于第26天达高峰,未测出抗 S 抗原抗体.根据特异性抗体与实验性自身免疫性葡萄膜视网膜炎(experimental autoimmune uveoretinitis,EAU)之间的关系,讨论了特异性体液免疫反应在 EAU发生中的作用.     

T-lymphocyte and experimental autoimmune uveoretinitis

The immunopathogenic mechanisms underlying S-antigen-induced experimental autoimmune uveoretinitis (EAU) were discussed with particular emphasis on the cellular immune response on the basis of the following data: 1) athymic nude rats did not develop EAU unless sensitized lymphocytes obtained from heterozygous rats were transferred into the nude rats; 2) cyclosporine, an immunosuppressant selective to the T-lymphocytes, completely inhibited the cellular immune response to S-antigen as well as EAU induction; 3) a lymphocyte population having the capacity to produce interleukin 2 in response to S-antigen appeared prior to the onset of EAU; and 4) EAU was successfully transferred into syngenic animals by sensitized T-lymphocytes or by a T-cell line specific to S-antigen. These data were thought to indicate that the T-lymphocyte or the cellular immune response to S-antigen constitutes the essential factor for the development of EAU.     

Adoptive transfer of experimental autoimmune uveoretinitis in rats. Immunopathogenic mechanisms and histologic features

In order to learn about the immunopathogenic mechanisms of experimental autoimmune uveoretinitis (EAU), the capacity of lymphocytes to transfer the disease was studied. EAU was transferred to naive syngeneic rats by intraperitoneal injection of spleen or lymph node (LN) cells from S-antigen immunized rats, following their incubation in culture with either S-antigen or concanavalin A (Con A). In contrast, the same cells did not cause inflammatory changes in the recipient eyes when injected intravitreally. The identity of the lymphocytes that transfer EAU was determined by using monoclonal antibody enriched subsets of lymphocytes. EAU was transferred by the subset of helper/inducer T-cells, but not by T-cells of the suppressor/cytotoxic subset. Recipient rats of spleen or LN cells cultured with S-antigen exhibited both humoral and cellular immune responses to S-antigen. On the other hand, recipients of spleen cells cultured with Con A developed only cellular immune response to S-antigen. Yet, both groups of recipients fully developed EAU. The clinical and histologic changes in recipient rats closely resembled those in rats in which EAU was induced by active immunization. Severe tissue damage occurred at the photoreceptor cell layer, but inflammatory infiltration also was found in other ocular tissues. Involvement of polymorphonuclear leukocytes (PMNs) was noted throughout ocular tissues even in the eyes of recipients with no detectable antibodies to S-antigen, suggesting that the ocular PMNs infiltration in rats is not necessarily the result of an Arthus-like inflammatory process.     

Inhibition of autoimmune uveitis by anti-CD4 antibody

In this study, rats with S-antigen-induced uveitis were treated with W3/25, a monoclonal antibody that recognizes the CD4 molecule expressed by helper/inducer cells. Treatment was started on day 5 after administration of S-antigen. Groups of animals were killed 18 or 31 days after S-antigen injection. The enucleated globes were studied histologically, and in vitro T-cell response and anti-S antibody levels were determined. Results showed that the antibody treatment prevented development of experimental autoimmune uveitis (EAU) in all animals. Furthermore, there was no evidence of disease development for 14 days after cessation of therapy. These results suggest that CD4+ cells are important in the initiation of EAU, and that monoclonal antibodies directed to this subset may provide effective treatment of autoimmune uveal inflammation.     

Inhibition of experimental autoimmune uveoretinitis with anti-macrophage migration inhibitory factor antibodies

PURPOSE: The role of macrophage migration inhibitory factor (MIF) in the regulation of ocular autoimmune disease was studied in experimental autoimmune uveoretinitis (EAU) in rats following immunization with a retinal antigen (Ag), interphotoreceptor retinoid-binding protein (IRBP). METHODS: LEW rats were immunized with a single injection of IRBP derived peptide, R16(ADGSSWEGVGVVPDV). A neutralizing monoclonal antibody (mAb, IgM) to MIF was injected intraperitoneally every second day from day 0 to day 6 (group A), or from day 8 to day 14 (group B). Control rats were treated with unrelated mouse IgM or PBS. T cell proliferative responses were measured 12 days after immunization. The occurrence and severity of EAU were observed and compared among experimental and control groups. RESULTS: T cell proliferative responses against R16 were inhibited in rats treated with anti-MIF mAb compared with the control rats. The development of EAU was delayed in the rats of group A in comparison with those of group B and the control group. The mean histological EAU score on day 18 in group A was 1.11 +/- 0. 11 and significantly lower than those of the group B (1.29 +/- 0.19) and the control (1.67 +/- 0.19). CONCLUSIONS: The present result suggests that MIF plays an important role in induction of EAU.     

Characteristics of immunotolerance induced by intratesticular injection of S-antigen

Experimental autoimmune uveoretinitis (EAU) induced by immunization of male Lewis rats with bovine S-antigen (S-Ag) is prevented by injection of S-Ag into the testis prior to immunization. This protection of animals is due to the induction of systemic immunotolerance or immunosuppression, which the authors designate orchidic tolerance. In this paper they first present a brief review of several features of orchidic tolerance reported previously and features uncovered more recently, and then propose a possible sequence of events that is initiated by antigen challenge in the testis and results in the proliferation of specific subclasses of lymphocytes with immunosuppressive activity and prevention of the onset of EAU.     

Experimental autoimmune uveitis induced by immunization with retinal pigment epithelium-specific 65-kDa protein peptides

PURPOSE: To investigate the pathogenic potential and sites of retinal pigment epithelium-specific 65-kDa protein (RPE65) for inducing experimental autoimmune uveitis (EAU) in Lewis rats. METHODS: Twenty-six peptides were chemically synthesized based on the amino acid sequences of human RPE65. These peptides spanned the entire RPE65 sequence. Each peptide was injected into a footpad and the peritoneum of Lewis rats. The eyes were examined by slit-lamp biomicroscopy, and the findings were correlated with the histological findings. The serum antibody titer and lymphocyte reactivity against each peptide was also determined by enzyme-liked immunosorbent assay (ELISA) and lymphocyte proliferation assay, respectively. RESULTS: Active immunization of rats resulted in the induction of EAU with 14 (3 severe and 11 mild) of the 26 peptides. The clinical course of the EAU was similar to that induced by the injection of retinal antigens such as S-antigen or inter-photoreceptor retinoid binding protein (IRBP). However, the histopathologic changes differed from the EAU induced by these retinal antigens. The inflammation was induced mainly from the retinal pigment epithelium (RPE) and the choroid, while the retina was relatively well-preserved except for some granulomatous changes adjacent to the RPE. CONCLUSIONS: Active immunization with peptides making up RPE65 will induce EAU. RPE65 has multiple EAU-inducing sites for Lewis rats.     

Treatment of experimental autoimmune uveoretinitis with poly(lactic acid) nanoparticles encapsulating betamethasone phosphate

We have developed nanoparticles (NPs), which are capable of targeting a specific lesion and gradually releasing the agent at the site over a prolonged time period after a single intravenous administration. In this study, we evaluated the effects of intravenously administered poly(lactic acid) nanoparticles encapsulating betamethasone phosphate (BP-PLA NPs) on experimental autoimmune uveoretinitis (EAU) in Lewis rats. To determine the localization of NPs within the retina and choroid of rats with EAU, rhodamine (Rh)-encapsulated PLA NPs were injected intravenously and visualized by confocal microscopy. After the disease onset of EAU induced by S-antigen peptide in Lewis rats, either BP-PLA NPs, BP, or saline was injected intravenously, and the eyes were obtained 7 days following treatment and the histological score was determined. The clinical course of EAU was examined using pathological findings and the expression of the glial fibrillary acidic protein, rod opsin, and the surface markers of inflammatory cells (ED1 and pan T-cell) were immunohistochemically determined. Furthermore, T-cell proliferation and delayed-type hypersensitivity (DTH) to S-antigen were assessed. Intravenously injected Rh-PLA NPs accumulated in the retina and choroid of rats with EAU within 3 hr and remained over the succeeding 7-day-period. Furthermore, systemically administered BP-PLA NPs reduced the clinical scores of rats with EAU in 1 day, which were maintained for 2 weeks and decreased the histological scores. In addition, the ocular infiltration of activated T-cells and macrophages in addition to the hypertrophy of Müller cells were markedly reduced with this treatment. Meanwhile, T-cell proliferation and DTH of BP-PLA NPs-treated rats against S-antigen peptide were not significantly different from those of saline-treated rats. Systemically administered BP-PLA NPs inhibit the development of EAU due to the targeting and the sustained release of steroids in situ. The results of these studies suggest that the systemic administration of BP-PLA NPs may lead to a new therapeutic strategy in controlling intraocular inflammation.     

Suppression of experimental uveitis in rats by anti-I-A antibodies

I-region-associated (Ia) class II major histocompatibility complex (MHC) products are known to play a major role in autoimmunity. Effects of anti-I-A and anti-I-E monoclonal antibodies on development of experimental autoimmune uveitis (EAU) were investigated in Lewis rats. Prior to sensitization with S-antigen, seven groups of rats, six in each group, were injected intraperitoneally with one of the following agents. Groups 1, 2, and 3 (controls) received saline, RPMI and mouse immunoglobulin G (IgG), respectively. Groups 4 and 5 were injected with anti-I-E antibodies, 80 micrograms and 1000 micrograms, respectively. Similarly, groups 6 and 7 received anti-I-A, 100 micrograms and 750 micrograms, respectively. The treatments were repeated on days 1, 2, 5, 8, and 11 after S-antigen injection. All these animals were killed on day 18. In addition, two groups of rats sensitized with S-antigen were treated with 750 micrograms anti-I-A antibodies on days 5, 6, and 7 (group 8) and on days 7, 8 and 9 (group 9). An additional group (group 10) of Lewis rats was treated with 750 micrograms anti-I-A 1 day prior to and on days 1 and 2 after S-antigen injection. These group-10 animals were killed on day 31. Histopathologically, the enucleated globes of animals treated with high dose anti-I-A revealed marked suppression or inhibition of uveitis development. Such inhibition was virtually complete when the antibody was administered within a week of S-antigen injection, and the inhibitory effect lasted for at least 31 days.(ABSTRACT TRUNCATED AT 250 WORDS)