[Participation of sodium iodate in the induction of experimental autoimmune uveoretinitis (EAU)]

It is known that Brown Norway (BN) rats show resistance to the development of experimental autoimmune uveoretinitis (EAU). Although BN rats don't develop EAU easily when they were immunized with S antigen containing emulsified complete Freund's adjuvant, this paper reports on the development of EAU at the rate of 40-60% in BN rats when immunization is preceded by an injection of more than 0.5 mg (1.79 mg/kg of body wt) of sodium iodate which leads to the destruction of retinal pigment epithelium (RPE). It was thought that the destruction of RPE participated in the induction of EAU. Therefore, it is considered that the existence of RPE may play an important role in the induction of EAU.

Prevention of experimental autoimmune uveoretinitis and experimental autoimmune pinealitis in (Lewis x Brown-Norway) F1 rats by HgCl2 injections

Mercuric chloride (HgCl2) induces in Brown-Norway (BN) and (Lewis x Brown-Norway) F1 hybrid rats a transient autoimmune disease characterized by the production of various antibodies to self and non-self antigens and by a dramatic increase of serum IgE. Experimental autoimmune uveoretinitis (EAU) can be induced in Lewis (LEW) and (LEW x BN) F1 hybrid rats by a single immunization with retinal S-antigen (S-Ag). Besides uveoretinitis, animals immunized with S-Ag develop an autoimmune pinealitis (EAP). We demonstrate in this study that (LEW x BN) F1 hybrid rats, injected with HgCl2 7 days before S-Ag immunization, are quite efficiently protected against EAU and EAP. We also show that HgCl2-induced protection is neither due to a cytotoxic effect of HgCl2 nor to CD8+ T-cell dependent mechanisms nor to the HgCl2-induced increase of serum IgE concentration. The role of other hypothetical mechanisms, such as anti-S-Ag anti-idiotypic antibodies and/or HgCl2-induced unbalance between T-helper cell subsets, is discussed.

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.

Trials of vaccination against experimental autoimmune uveoretinitis with a T-cell receptor peptide

T lymphocytes which mediate several experimental autoimmune diseases, including encephalomyelitis (EAE) and uveoretinitis (EAU) in Lewis rats, preferentially utilize V beta 8 gene product in their receptor. Vaccination against a V beta 8.2-derived peptide was reported to inhibit EAE induction and we report here on the effect of vaccination with this peptide on the development of EAU. Experimental rats were pretreated with the V beta 8.2 peptide, emulsified in adjuvant (CFA), whereas control animals were untreated or injected with saline in CFA. Rats of all groups were immunized 30 or 40 days later with the immunopathogenic antigen, emulsified in Mycobacterium-enriched CFA. Vaccination with CFA emulsions containing either the V beta 8.2 peptide or saline, remarkably inhibited the development of the tested diseases, as compared to the untreated controls. Vaccination with the V beta 8.2 peptide had variable effects in this study on disease development: it inhibited the S-antigen-induced EAU more than did treatment with CFA in four out of six experiments, had a similar effect to that of CFA in one experiment and enhanced the disease in another experiment. Conversely, vaccination with the V beta 8.2 peptide slightly enhanced the EAU induced by the interphotoreceptor retinoid-binding protein (IRBP), or its dominant determinant, in three of four experiments and had no apparent effect in the fourth experiment. In addition, we could not reproduce the reported protective effect of vaccination with the V beta 8.2 peptide against induction of EAE. Vaccination with the V beta 8.2 peptide also had no clear effect on the development of humoral or cellular immune responses against S-antigen.(ABSTRACT TRUNCATED AT 250 WORDS)

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.

In vitro unresponsiveness to autologous sequences of the immunopathogenic autoantigen, S-antigen

Previous analyses of T cell recognition sites on immunopathogenic neural autoantigens have demonstrated, using LEW rats, the functional dissociation of in vitro proliferative responses and the ability to actively induce autoimmune diseases. In experimental autoimmune uveoretinitis, immunization of LEW rats with bovine retinal S-Ag reveals the presence of three immunodominant T cell recognition sites located in regions containing sequence differences between bovine and rat S-Ag. Immune responses of LEW rats to self (rat) and nonself (bovine and human) peptide homologues representing these three sites were compared. The immunodominant sequences of heterologous S-Ag were found to predict new pathogenic T cell recognition sites in the corresponding autologous rat sequence. Furthermore, in vitro proliferative responses to the pathogenic autologous sequences are dramatically diminished relative to the responses of lymphocytes raised to the non-self homologues. A pathogenic T cell line, R858, efficiently transferred disease, but was unresponsive to the autologous S-Ag peptide in proliferation assays. However, responses to autologous peptides were readily detected using nonirradiated splenic APC. Detection of responses to non-self peptides was independent of this radiosensitive Ag-presenting activity. The lack of in vitro proliferative responses to pathogenic autologous sequences by T cells bearing self-specific receptors, contrasted with the strong proliferation induced by non-self peptide homologues, suggests a mechanism of unresponsiveness to self.

Mechanisms of protection against herpes simplex virus type 1-induced retinal necrosis by in vitro-activated T lymphocytes

In BALB/c mice, acute retinal necrosis occurs in the uninoculated eye 8 to 10 days following uniocular anterior chamber inoculation of the KOS strain of herpes simplex virus type 1 (HSV-1). Retinitis in the uninjected eye can be prevented if HSV-1-specific immune effector cells that have been restimulated with virus in vitro are administered intravenously within 1 day of anterior chamber inoculation of virus. We explored further the mechanism of protection afforded by these activated immune effector cells. The results of our studies revealed that optimal protection from retinitis required in vitro restimulation, since infusion of 50 x 10(6) HSV-1-primed but nonrestimulated cells could not protect as well as 10 x 10(6) activated cells. Analysis of both restimulated and nonrestimulated cells showed that only in vitro-restimulated cells were cytotoxic to HSV-1-infected syngeneic target cells. From these studies, we concluded that the ability to kill virus-infected target cells contributed to optimal protection achieved by intravenous administration of activated immune effector cells. Furthermore, T-cell subset depletion of activated immune effector cells demonstrated that both L3T4+ and Lyt-2+ T cells in the transfer inoculum contributed to protection. Additional studies revealed that although the transferred immune effector cells reached the injected eye within 24 h, virus replication in the injected eye was not affected. In the uninjected eye, virus titers were low, consistent with protection of this eye from retinitis. Taken together, the virus recovery results suggest that the interaction of virus with intravenously administered HSV-1-specific immune effector cells which limits virus spread and/or replication of virus probably occurred within the central nervous system and prevented the second wave of virus from entering the uninoculated eye.

[Specific immune complexes formed by retinal S antigens and S antibodies in infectious-allergic and post-traumatic uveitis]

A method for the detection in the blood of specific circulating immune complexes (S-CIC) formed by the retinal S antigen and S antibodies. S-CICs were disintegrated by ultrasonic treatment of blood serum samples, passive hemagglutination test and specific inhibition of passive hemagglutination were used in identification of S antigen and S antibodies. S-CICs were detectable in bilateral uveoretinitis and in suspected sympathetic ophthalmia and undetectable in unilateral processes, including those involving the retina.

Murine acute retinal necrosis

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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.

Necrotizing retinopathy after intraocular inoculation of murine cytomegalovirus in immunosuppressed adult mice

A light microscopic study was done to investigate retinal changes in healthy and immunosuppressed mice after intraocular inoculation of murine cytomegalovirus (MCMV). A 0.01-ml inoculum containing 10(5) plaque-forming units of MCMV was placed behind the lens in 138 4-week-old Swiss Webster mice. Ninety-eight mice were immunosuppressed with 0.2 mg/g of cyclophosphamide given intraperitoneally at the time of inoculation and 0.1 mg/g of cyclophosphamide every 5 days thereafter. Selected eyes were examined on postinoculation days 5, 10, 15, and 16-20. Evidence of viral infection was most prominent in uveal tissue. Uveal infection developed whether or not animals received cyclophosphamide, but retinal necrosis developed only in immunosuppressed mice. Focal retinal necrosis, primarily involving the outer retinal layers and retinal pigment epithelium, was first observed in an eye examined on day 10. Retinopathy from MCMV was present in three of five eyes (60%) examined on day 15, and in six of 16 eyes (37.5%) examined between days 16-20. Retinal disease was characterized by full-thickness retinal necrosis, scattered cytomegalic cells, intranuclear and intracytoplasmic viral inclusions, and acute and chronic inflammation. These results indicate that MCMV can produce a necrotizing retinopathy in mice and that immunosuppression facilitates infection. Although ocular MCMV infection in immunosuppressed adult mice is a potential model for study of human CMV retinopathy, many differences exist between human CMV and MCMV and between the ocular diseases they produce.

[An immunohistochemical study of vitreal and epiretinal membranes in human eyes]

Macrophages, monocytes and the expression of HLA-DR antigen in 52 cases of various vitreal and epiretinal membranes in human eyes were studied with the immunohistochemical technique. The results showed that more than 80% of the specimens were macrophage positive and expressed HLA-DR antigen, and monocytes were mainly seen in the specimens of proliferative diabetic retinopathy (41.7%). Macrophages were considered to play an important role in the development of epiretinal membranes, and immuno-response was also one of the related factors.

[An immunoperoxidase study of early phase experimental retinitis induced by herpes simplex virus]

Herpes simplex virus type 1 (HSV-1) was intravitreally inoculated in domesticated rabbits, and retinitis was observed with the ABC-method using peroxidase-conjugated antibody. Trypsin digestion was used for antigen visualization. Three days after inoculation, although cell degeneration was not found in the retina, DAB was deposited on the inner limiting membrane and the nerve fiber layer, which corresponded to the basal side of Müller cells. These findings indicated that viral antigen was already present in the retina at this early stage. Four or five days after inoculation, numerous variously sized exudative retinal lesions were seen. In the small exudative foci, DAB deposition was restricted to only in the nuclei of the nerve cells of the inner nuclear layer, while it extended to the outer and inner retinal layer in the large exudative foci. These results suggested that when HSV-1 was injected intravitreally it invaded from the basal side of Müller cells to the inner nuclear layer, where it replicated. The virus spread to the outer nuclear layer and ganglion cells as infection proceeded.

Stimulation in vitro of lymphocytes for induction of uveoretinitis without any significant proliferation

Experimental autoimmune uveoretinitis can be adoptively transferred into naive recipients by lymphocytes from rats immunized with uveitogenic Ag, provided these cells are activated in vitro before being injected. The activation of sensitized lymphocytes, by the immunizing Ag, or by cross-reacting Ag, is usually accompanied by vigorous proliferation. We report, however, on a complete dissociation between the capacity of a peptide to generate uveitogenicity and to stimulate proliferation in cultured lymphocytes. This peptide, which occupies sequence 579-591 of the bovine interphotoreceptor retinoid-binding protein (IRBP), is one of the three "repeats" that exhibit partial sequence homologies with the immunodominant and highly immunogenic peptide, 1179-1191. Peptide 579-591 is nonimmunogenic and nonuveitogenic in Lewis rats and does not stimulate any significant proliferation in lymphocytes sensitized against whole IRBP, peptide 1179-1191, or another "repeat" peptide, 271-283, which is immunogenic and uveitogenic. In contrast, peptide 579-591 effectively generates uveitogenicity in the lymphocytes sensitized against these three Ag. Unlike 579-591, peptides 271-283 and 1179-1191 stimulated both proliferation and uveitogenicity in these sensitized lymphocytes. A different pattern of activities was observed with the other "repeat" peptide, 880-892. This peptide did not have any effect on the lymphocytes sensitized against IRBP, 271-283 or 1179-1191, but did stimulate both proliferation and uveitogenicity in lymphocytes sensitized against itself. The data suggest that 579-591 selectively stimulates a lymphocyte subset that is uveitogenic, but is incapable of mounting proliferative responses.

Serial adoptive transfer of experimental autoimmune uveoretinitis in rats

Experimental autoimmune uveoretinitis (EAU) and pinealitis induced by an interphotoreceptor retinoid-binding protein (IRBP)-derived peptide (R4) was serially transferred into naive recipient rats, using spleen cells from recipients of previous "orders" of transfer. The cells initiating the disease in recipients of the first order were either lymph node cells from rats immunized against peptide R4, or lymphocytes of a cell line specific toward this peptide. The serial transfer was successfully carried out through as many as four orders of sequential recipients.

Identification of a potent new pathogenic site in human retinal S-antigen which induces experimental autoimmune uveoretinitis in LEW rats

Experimental autoimmune uveoretinitis (EAU) is a T cell-mediated autoimmune disease of the eye which can be induced in LEW rats by immunization with either human or bovine S-antigen (S-Ag). In previous reports, two nonimmunodominant pathogenic sites were found using synthetic peptides corresponding to conserved sequences at amino acid residues 303-314 and 286-297 of the bovine sequence. In this report, a 20-residue synthetic peptide encompassing amino acids 343-362 located near the C-terminus was found to be highly immunopathogenic in LEW rats. The onset of EAU was observed at as early as 8 days when high doses of a peptide-encompassing residues 343-362 were used. EAU was elicited with as little as 0.5 microgram of peptide per animal. Smaller peptides from this region were also tested for uveitogenicity, further refining the site to 13 amino acids. Uveitogenic T cell lines were made to this site in two ways; first, by the in vitro selection of a bulk T cell line raised to human S-Ag with peptide 343-362. Second, by the in vitro selection of a peptide-specific line from an animal immunized with peptide 352-364, which corresponds to the minimal uveitogenic site. Both of these lines adoptively transferred EAU to LEW rats, further establishing the pathogenicity of this site. A proliferative site distinct from, but overlapping, the uveitogenic site was also found. The potent uveitopathogenicity of peptides from this region indicates that it is a major pathogenic site responsible for EAU induced in LEW rats by immunization with human S-Ag.

Experimental autoimmune uveoretinitis in mice. Induction by a single eliciting event and dependence on quantitative parameters of immunization

Experimental autoimmune uveoretinitis (EAU) in the mouse is a recently developed model of ocular autoimmunity. Dependence of disease induction on qualitative and quantitative parameters of immunization was studied in B10.A mice immunized with interphotoreceptor retinoid-binding protein (IRBP). It was found that use of Bordetella pertussis adjuvant as well as its mode of preparation was of critical importance for disease induction; no disease was induced if pertussis adjuvant was omitted. The minimal effective protocol for EAU induction when the vaccine form of B. pertussis adjuvant was used consisted of pretreatment with cyclophosphamide, two divided doses of IRBP in complete Freund's adjuvant (CFA), and two divided doses of B. pertussis vaccine. Any reduction in the immunization schedule resulted in reduced incidence of disease. In contrast, substituting purified B. pertussis toxin (PTX) for the vaccine allowed reduction of the immunization schedule to a single dose of IRBP in CFA and omission of the cyclophosphamide pretreatment. Severity and incidence of disease could be quantitatively controlled by varying the respective doses of IRBP and PTX. In addition, a chronic or an acute clinical course of EAU could be obtained by using either a low-dose or a high-dose immunization, respectively. Establishment of a single dose induction protocol and the quantitation of the immunopathogenic response as a function of the variables of immunization lay the foundation for the further development and utilization of this promising model of ocular autoimmunity.

Longitudinal study of cytomegalovirus retinitis in acquired immune deficiency syndrome

The authors prospectively evaluated 67 consecutive patients with the acquired immune deficiency syndrome (AIDS) and cytomegalovirus (CMV) retinitis during a 33-month period to assess the clinical patterns of retinal infection, efficacy of treatment, long-term survival, and relationship of retinitis to immune function. Immediately sight-threatening retinitis presented in six patients (9%) with peripapillary disease; primary foveal infection was not observed. Eighty-seven percent of patients were treated with ganciclovir. Thirty-nine patients (58%) presented with unilateral disease and contralateral infection developed in 15% of those while on ganciclovir. Smoldering (incompletely responsive) retinitis was seen in 33% of the 21 patients whose retinitis progressed while receiving ganciclovir. Progression of treated retinitis was associated with a lower lymphocyte count (P = 0.04). Median survival after diagnosis of CMV retinitis was 8 months. This represents the largest reported prospective study of CMV retinitis and indicates that (1) CMV infrequently poses an immediate threat to vision on presentation, (2) response to therapy may be related to immune function, and (3) smoldering retinitis should be recognized as an important clinical entity associated with treatment failure.

Inflammatory mediators in the vitreous humor of AIDS patients with retinitis

We measured levels of protein, of complement-derived anaphylatoxins (C3a, C4a, and C5a), and of the lymphokines interleukin-2 and gamma interferon, in vitreous humor from 10 AIDS patients with vitritis and retinitis (group 1). We compared these measurements with levels in vitreous from 7 patients with vitritis but without AIDS (group 2), 10 patients with vitreous hemorrhages (group 3), and 20 patients with retinal detachments or epiretinal membranes without clinical evidence of vitreal inflammation (group 4). Vitreous humor from 10 AIDS patients had measurable levels of interleukin-2 in three of nine samples, gamma interferon in six of nine samples, C3a and C4a in all ten samples, and C5a in only one of ten samples. Vitreous humor from group 1 did not differ significantly from vitreous from group 2. On the other hand, vitreous from group 1 had significantly higher levels of gamma interferon, C3a, and C4a, and higher ratios of these anaphylatoxins to protein, in comparison to vitreous in groups 3 and 4. The results of this study suggest that vitreous humor from AIDS patients with retinitis contains activated complement and may contain interleukin-2 and gamma interferon. Viral retinitis is associated with the presence of lymphokines in vitreous humor. Additionally, anaphylatoxin and gamma interferon levels, but not interleukin-2 levels, correlate with vitreal inflammation. This is the first study to measure interleukin-2, gamma interferon, and C5a levels in human vitreous humor.

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.

Inhibition of experimental autoimmune uveoretinitis by mercuric chloride injections in (Lewis x Brown Norway) F1 hybrid rats

Experimental autoimmune uveoretinitis (EAU), induced in (LEW X BN) F1 rats by immunization with S antigen (S-Ag) is T cell and antibody (ab) mediated and anti-S-Ag IgE ab have been involved in the occurrence of ocular lesions. (LEW X BN) F1 rats repeatedly injected with HgCl2 develop an autoimmune disease characterized by numerous auto-ab and a high increase of serum IgE level. We hypothesize that large amounts of non anti-S-Ag IgE induced by HgCl2 would compete with anti-S-Ag induced by S-Ag immunization so as to prevent EAU to occur. Indeed (LEW X BN) F1 rats immunized with S-Ag 7 days after the first HgCl2 injection are strongly protected against EAU. The putative role of the different mercury-induced autoimmune phenomena in the protection against EAU are discussed.

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.

Regulation of retinal autoimmunity via the idiotypic network

The immune response to self antigens is regulated through an interplay of idiotypes and anti-idiotypes expressed on antibodies and lymphoid cells. The equilibrium of the different components of the immune system has been modulated in various autoimmune diseases by manipulation of the idiotypic network. Experimental autoimmune uveoretinitis (EAU) was induced in rats with one foot pad injection of S-antigen (S-Ag) in complete Freund's adjuvant (CFA). 1. Injection of rats with the mouse anti-S-Ag monoclonal antibody (mAb) S2D2 either simultaneously with or before S-Ag challenge, led to an anti-idiotypic (anti-Id) response and to inhibition of EAU. 2. Suppression of the disease could be passively transferred using lymph node and/or spleen cells from donors immunized with S2D2 to naive recipients, prior to immunization with bovine S-Ag in CFA. In contrast, one injection of IgG from S2D2-immunized rats did not prevent EAU. 3. Preimmunization against a purified rat polyclonal anti-Id-S2D2 antibody (internal image of the epitope recognized by mAb S2D2) before S-Ag challenge also allowed to inhibit EAU. As S2D2 was the best of several anti-S-Ag mAbs tested for disease inhibition, the epitope recognized by S2D2 should be of particular interest in the regulation of the immune response. This epitope has been localized to the N-terminal region of S-Ag, in the amino acid sequence 40-50. The S2D2 epitope is distant from all presently known uveitogenic sites. Manipulation of the idiotypic network for selected epitopes of the autoantigen may provide a valuable approach to therapy of autoimmune disease.

Experimental autoimmune uveoretinitis: idiotypic regulation and disease suppression

Experimental autoimmune uveoretinitis (EAU), a mostly T-cell dependent disease, was induced in laboratory animals by a single immunization with retinal extract or purified S-antigen in complete Freund's adjuvant. It can be prevented or suppressed by injections of either the autoantigen or monoclonal antibodies against the autoantigen. The suppression of EAU by these antibodies was associated with an anti-idiotypic antibody response. The inhibition of the pathogenic immune response by the antigen or the antibodies could be explained, according to Jerne's hypothesis of immunoregulation, by a disturbance of the network of idiotype and anti-idiotype interactions.

Selective immunosuppression of activated T cells with the chimeric toxin IL-2-PE40. Inhibition of experimental autoimmune uveoretinitis

A characteristic of activated T lymphocytes is the expression of high affinity IL-2R. We studied a new method of selective immunosuppression directed against activated T cells by using a chimeric recombinant protein (IL-2-PE40) composed of IL-2 fused to a modified Pseudomonas exotoxin lacking its cell recognition domain. As a model of T cell-mediated disease, we used experimental autoimmune uveoretinitis (EAU) produced in Lewis rats by active immunization with the retinal S-Ag. The treatment protocol consisted of i.p. injection of IL-2-PE40 at 0.25 micrograms/g every 12 h. Controls were PBS, PE40, or IL-2-PE40asp553 a mutant form of the molecule with reduced activity. Treatment with IL-2-PE40 resulted in a significant reduction of the incidence and severity of EAU over controls. The analysis of the effect of i.p. injection of IL-2-PE40 on the popliteal draining lymph nodes of immunized animals showed a marked reduction in the lymphocytes content. Transfer experiments demonstrated that IL-2-PE40 prevented the development of EAU effector T cells. Interestingly, although activated B cells were reported to express IL-2R, there was no significant reduction of antibody production against the immunizing Ag under IL-2-PE40 treatment, suggesting sparing of the B cells.