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.

Molecular mimicry between a uveitopathogenic site of S-antigen and viral peptides. Induction of experimental autoimmune uveitis in Lewis rats

S-Antigen (S-Ag) is a well characterized 45,000 m.w. photoreceptor cell protein. When injected into susceptible animal species, including primates, it induces an experimental autoimmune uveitis, a predominantly T cell-mediated autoimmune disease of the retina and uveal tract of the eye, and of the pineal gland. In this study we found an amino acid sequence homology between a uveitopathogenic site of S-Ag, several viral proteins and one additional nonviral protein. An experimental autoimmune uveitis and pinealitis was induced in Lewis rats with these different synthetic peptides, corresponding to the amino sequence of hepatitis B virus DNA polymerase, gag-pol polyprotein of Baboon endogenous virus and gag-pol polyprotein of AKV murine leukemia virus and potato proteinase inhibitor IIa, which contain three or more consecutive amino acids identical to peptide M in S-Ag. Lymph node cells from rats immunized with either peptide M or the different synthetic peptides showed a significant degree of cross-reaction. Mononuclear cells from monkeys (Macaca fascicularis) immunized with peptide M also showed significant proliferation when incubated with either peptide M or synthetic peptides as measured by in vitro lymphocyte mitogenesis assay using [3H]TdR. Based on our findings we conclude that a viral infection may sensitize the mononuclear cells that can cross-react with self proteins by a mechanism termed molecular mimicry. Tissue injury from the resultant autoantigenic event can take place in the absence of the infectious virus that initiated the immune response.

Molecular mimicry between a uveitopathogenic site of S-antigen and viral peptides. Induction of experimental autoimmune uveitis in Lewis rats

S-Antigen (S-Ag) is a well characterized 45,000 m.w. photoreceptor cell protein. When injected into susceptible animal species, including primates, it induces an experimental autoimmune uveitis, a predominantly T cell-mediated autoimmune disease of the retina and uveal tract of the eye, and of the pineal gland. In this study we found an amino acid sequence homology between a uveitopathogenic site of S-Ag, several viral proteins and one additional nonviral protein. An experimental autoimmune uveitis and pinealitis was induced in Lewis rats with these different synthetic peptides, corresponding to the amino sequence of hepatitis B virus DNA polymerase, gag-pol polyprotein of Baboon endogenous virus and gag-pol polyprotein of AKV murine leukemia virus and potato proteinase inhibitor IIa, which contain three or more consecutive amino acids identical to peptide M in S-Ag. Lymph node cells from rats immunized with either peptide M or the different synthetic peptides showed a significant degree of cross-reaction. Mononuclear cells from monkeys (Macaca fascicularis) immunized with peptide M also showed significant proliferation when incubated with either peptide M or synthetic peptides as measured by in vitro lymphocyte mitogenesis assay using [3H]TdR. Based on our findings we conclude that a viral infection may sensitize the mononuclear cells that can cross-react with self proteins by a mechanism termed molecular mimicry. Tissue injury from the resultant autoantigenic event can take place in the absence of the infectious virus that initiated the immune response.

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.

Multiple, spatially distinct T cell epitopes within a pathogenic 123 residue cyanogen bromide peptide of bovine retinal s-antigen

We have examined the T cell specificity of a Lewis rat T cell line (R208) specific for a pathogenic, 123 residue cyanogen bromide produced peptide of bovine S-antigen by using two independent sets of overlapping synthetic peptides representing the entire length of the 123 residue fragment. S-antigen, a 48 kDa immunopathogenic photoreceptor cell autoantigen induces T cell mediated experimental autoimmune uveoretinitis (EAU) in experimental animals. Extensive analyses revealed a heterogenous response by the R208 line to the panel of synthetic peptides, proliferating weakly to 4 distinct sites. Unexpectedly, peptides representing sequences (residues 286-297 and 303-320 of bovine S-antigen) known to actively induce the autoimmune pathology were unable to significantly stimulate the R208 line as assessed by proliferation assays. Similarly, attempts to isolate T cells specific for these sequences from the R208 line have proven unsuccessful. However, two sequences, residues 253-269 and 273-289, sufficiently stimulated R208 cells to allow isolation of sub-lines, R208:26 and R208:28, respectively. Neither of these peptides actively induce an autoimmune response. R208:26 does not transfer EAU and R208:28 transfers moderate EAU. As a control, we are able to isolate a pathogenic T cell line (R502) specific for the actively pathogenic sequence, residues 303-320, when this peptide is used as the immunogen. However, the R502 line proliferates to peptides (e.g. 305-322) which do not contain residues 303 and 304 which are critical for the active induction of disease. These results show a multiplicity of distinct T cell epitopes within a relatively small region of S-antigen.(ABSTRACT TRUNCATED AT 250 WORDS)

The use of synthetic peptides in the study of experimental autoimmune uveitis

S-antigen is a highly pathogenic retinal autoantigen for the induction of experimental autoimmune uveitis (EAU). EAU is predominantly a T cell mediated autoimmune disease of the uveal tract and retina of the eye and the pinealocytes of the pineal gland. Using synthetic peptides it has been possible to identify several B cell and T cell epitopes in the molecule. In addition, synthetic peptides derived from proteins of diverse origin with amino acid sequence homology to pathogenic regions of S-antigen induce an EAU which is indistinguishable from the disease induced by native S-antigen. These studies aid in the understanding of immune mechanisms in EAU and provide a basis for the pathogenesis of uveitis in humans.

A new perspective of S-antigen from immunochemical analysis

Elucidation of the amino acid sequences of retinal S-antigens from several species has allowed the fine dissection of T cell and antibody epitopes using synthetic peptides. S-antigen, isolated from retinal rod photoreceptor cells, elicits experimental autoimmune uveoretinitis (EAU), a predominantly CD4+ T-cell mediated autoimmune disease of the retina and uveal tract of the eye and pineal gland. Three uveitogenic T cell lines, R9, R17 and R208, prepared against native bovine S-antigen, human S-antigen and cyanogen bromide peptide CB123, respectively, were used to identify the T cell recognition sites responsible for uveitogenic and proliferative responses. T cell epitopes were found to be clustered into 6 regions, some of which were species-specific. The two synthetic peptides known to actively induce EAU, residues 286-297 and 303-314 of bovine S-antigen, were unable to induce significant proliferative responses in any of the three T cell lines. However, both of these sites were adjacent to synthetic peptides, residues 273-292 and 317-328, respectively, which were unable to actively induce EAU, but elicited proliferative responses from the T cell lines. We also report the presence of a new pathogenic site, also associated with an adjacent proliferative site, together in residues 343-362 of bovine S-Ag. Our results indicate that spatially separate and distinct T cell epitopes are present in S-antigen which are responsible for the active induction of EAU, lymphocyte proliferation, and adoptive transfer of EAU.

Pharmacologic modulation of acute uveitis with aminonicotinamide

The hexose monophosphate shunt inhibitor 6-aminonicotinamide was observed to have an anti-inflammatory effect in the treatment of experimental uveitis. The electrons required for the reduction of molecular oxygen to superoxide radicals are generated by the pentose phosphate pathway in acute inflammatory cells. The inhibition of superoxide production is discussed as one of the potential antiphlogistic mechanisms.

Changing concepts in the management of retinoblastoma

For many years the most common treatment for retinoblastoma has been enucleation, generally performed on the affected eye in children with unilateral sporadic disease and on the more severely affected eye in children with bilateral disease. With refinements in conservative treatment methods, however, the affected eye now often may be salvaged and useful vision retained. Emphasizing this trend, we present our current approaches to managing retinoblastoma based on our experience with 324 patients, outlining our indications and pointing out a number of misconceptions about the role of enucleation, photocoagulation, cryotherapy, and radiotherapy in treating this condition. We also sketch some recent findings regarding the genetics of retinoblastoma and consider ways in which such research may lead to improved management of the disease.

Antigenic expression of neuron-associated class III beta-tubulin isotype (h beta 4) and microtubule-associated protein 2 (MAP2) by the human retinoblastoma cell line WERI-Rb1. A comparative immunoblot and immunocytochemical study

The antigenic expression of two neuron-associated microtubule proteins, class III beta-tubulin isotype (h beta 4) and microtubule-associated protein 2 (MAP2), was evaluated in a comparative immunoblot and immunocytochemical study of the human retinoblastoma cell line WERI-Rb1 maintained for up to 30 days in three different in vitro conditions. Western blots were performed on whole sodium dodecyl sulfate extracts of cells grown in floating suspensions, on Gelfoam matrices and on coverslips. Immunoperoxidase histochemistry was performed on matrix cultures. Immunoblotting demonstrated that h beta 4 and MAP2 were present under all culture conditions. By immunocytochemistry, staining of cytologically undifferentiated cells with anti-h beta 4 and anti-MAP2 monoclonal antibodies was found on Gelfoam matrix explants. In contrast, glial fibrillary acidic protein was not detected by either immunoblots or immunocytochemistry. These findings are in keeping with the solely neuroblastic nature of this line and provide no evidence for its divergent (i.e. neuronal and glial) differentiation capacity.

Identification of T cell recognition sites in S-antigen: dissociation of proliferative and pathogenic sites

Experimental autoimmune uveoretinitis (EAU) is a predominantly CD4+ T cell-mediated autoimmune inflammatory disease of the retina and uveal tract of the eye and the pineal gland. S-antigen, a protein found in retinal photoreceptor cells and pinealocytes, is a potent agent for the induction of EAU in susceptible species and strains. In order to identify the T cell recognition sites of S-antigen responsible for its uveitogenicity and proliferative responses, cyanogen bromide (CB) fragments as well as synthetic peptides were used to test the proliferative responses of two uveitogenic T cell lines, R9 and R17, prepared against native bovine and human S-antigen, respectively. Two nonoverlapping synthetic peptides which are known to actively induce EAU, amino acid residues 286-297 and 303-314 of the bovine sequence, were unable to induce proliferative responses in either S-antigen-specific T cell line. However, both of these sites were adjacent to synthetic peptides, residues 273-292 and 317-328, respectively, which were unable to actively induce EAU, but elicited strong proliferative responses from T cell lines raised to bovine and human S-antigen. Repeated in vitro selection of the R9 T cell line with a synthetic peptide containing one of these proliferative sites, residues 317-328, gave rise to a transiently uveitogenic T cell line. Several species-specific T cell epitopes were identified, but none of these were found to be involved in a uveitogenic response. Our results indicate that spatially separated and distinct T cell epitopes are present in S-antigen which are responsible for the active induction of EAU, lymphocyte proliferation, and the ability to adoptively transfer EAU.

Selection of antibody epitopes in an immunopathogenic neural autoantigen

Results with two well-characterized self-antigens, cytochrome c and myelin basic protein, have led to differing opinions regarding the predominant specificities of autoantibodies, whether regions of sequence diversity or 'structurally inherent features' of a protein determine favored antigenic sites. To further examine this question, 16 antibody epitopes have been mapped on a highly immunopathogenic autoantigen, retinal S-antigen (S-Ag). The epitopes were characterized for: (1) sequence diversity and cross-reactivity on S-antigens from several species; (2) conformational dependency; and (3) probability of their occurrence on the surface of S-antigen. A single C-terminal region containing sequence diversity was most frequently recognized, but no evidence for recognition of any other regions of sequence diversity was found. Thirteen of 16 monoclonal antibodies raised to native S-Ag bound epitopes strongly predicted to be on the surface of S-antigen. Conversely, only one of six antibody preparations raised to peptides or affinity-purified on peptides was found to recognize an epitope predicted to be on the surface, suggesting a good correlation between specificity for conformation-dependent sites and surface probability based on the surface prediction algorithm. Three of these six antibodies which preferred denatured epitopes bound sites which overlapped or coincided with T cell sites; two of these T cell sites are immunopathogenic. The epitopes recognized on denatured antigen and peptides were similar whether the antibodies were elicited with intact human or bovine S-antigen or with cyanogen bromide-cleaved peptides. Our data suggests that in the case of S-antigen, structural features are more significant factors in epitope selection than sequence diversity.

The early natural history of subfoveal neovascular membranes in eyes with age-related macular degeneration

During the course of age-related macular degeneration, the visual prognosis is abruptly changed when the presence of a subretinal neovascular membrane (SRNVM) is established by intravenous fluorescein angiography (IVFA). Patients who have been alerted to this condition may notice distortion on the Amsler grid and report within days of the onset of symptoms. Unfortunately most patients either do not notice the early changes in central vision or incorrectly attribute these symptoms to the development of cataracts and defer proper retinal evaluation for several months. We reviewed our records to determine the natural history of those SRNVMs which on initial IVFA either originated or extended into the foveal portion of the macula. Our results clearly indicate that treatment must be undertaken early in the course of this disease to maintain useful visual function for as long as possible.

Choroidal neovascularization in an eye with a macular hole

We report the case of a 68-year-old woman who initially presented with an idiopathic macular hole OD and atrophic macular degenerative changes and who subsequently developed subretinal neovascularization OU. The subretinal neovascularization evolved through the macular hole OD and decreased visual acuity to counts fingers, but the membrane was successfully treated OS with krypton laser photocoagulation and stabilization of visual acuity at 20/50 over the eight-year postoperative follow-up. This is the first report, to our knowledge, of a membrane developing through a macular hole. This may be a more common occurrence than reported due to obscuring of details from hemorrhage and exudate as part of the disciform process.

Relationship of the demonstration of intermediate filament protein to kinetics of three human neuroepithelial tumor cell lines. Lack of neural-related proteins in most cells in S phase: a double-labeled immunohistochemical study on matrix cultures

The immunocytochemical demonstration of intermediate filament proteins in three human neuroepithelial tumor cell lines maintained in vitro on a three-dimensional matrix was correlated with the proportion of cells in S phase. The cell lines of a medulloblastoma (D283 Med), a retinoblastoma (WERI-Rb1), and an astrocytic glioma (U-251 MG) were cultured in an organ culture system, pulse-fed with bromodeoxyuridine, and double-labeled by immunoperoxidase and by the avidin-biotin peroxidase complex method for bromodeoxyuridine and for intermediate filament proteins [each triplet of neurofilament proteins, as well as vimentin and glial fibrillary acidic (GFA) protein] using eight different antibodies. The average percentages of bromodeoxyuridine-labeled cells for the D283 Med, WERI-Rb1, and U-251 MG lines were respectively, 25, 32, and 12% 30 minutes after pulse labeling. In the D283 Med line, 15- greater than 95% of the cells were positive for each neurofilament protein, and 80% of the cells were positive for vimentin; less than 10% of the cells in S phase were positive with each of the five antineurofilament protein monoclonal antibodies (Mabs), but 20% of the vimentin-positive cells were in S phase. In the WERI-Rb1 line, 44 and greater than 96% of the cells were positive for the high-molecular-weight neurofilament subunit and high- and middle-molecular-weight neurofilament subunits proteins, respectively, but only 5% of the high-molecular-weight neurofilament positive cells were in S phase. In the U-251 MG line, 37 and 98% of the cells were positive for GFA protein and vimentin, respectively; only 3% of the GFA protein-positive cells, but 13% of the vimentin-positive cells, were in S phase. The results indicate that, when maintained in a matrix culture system, most cells in S phase in these lines lack markers of neural differentiation.

Human interstitial retinoid binding protein. A potent uveitopathogenic agent for the induction of experimental autoimmune uveitis

Human interstitial retinoid binding protein (HIRBP) is a 136,000 m.w. photoreceptor cell protein which transports retinoids between the retina and the retinal pigment epithelium of the eye. The amino acid sequence of HIRBP suggests that the molecule consists of four continuous homology domains which arose by several gene duplications some 600 to 800 million years ago. When injected into susceptible animal species, including primates, it induces an experimental autoimmune uveitis (EAU), a predominantly T cell-mediated autoimmune disease of the retina and uveal tract of the eye, and the pineal gland. In order to further refine specific sites in HIRBP responsible for its uveitopathogenicity, we synthesized 120 overlapping peptide corresponding to its entire 1262 amino acid sequence, and tested each peptide for its ability to induce an EAU in Lewis rats. Five peptides with extensive amino acid sequence homology, designated HIRBP 715, HIRBP greater than 730 and HIRBP 745, HIRBP 778, and HIRBP 808 were uveitopathogenic when used at a 50 micrograms immunizing dose. The most potent peptide for the induction of EAU was HIRBP 715 (amino acid positions 521 to 540). In dose response studies as little as 0.1 microgram/animal was capable of inducing an inflammatory response. In addition, peptide HIRBP 946 which corresponds to the mid portion of peptide HIRBP 715 and contains only eight amino acids (RTATAAEE) was uveitopathogenic under our experimental conditions. Our study identifies multiple uveitopathogenic sites in HIRBP and further defines the amino acids necessary for the induction of EAU in one of these sites.

An 18-mer peptide derived from the retinal S antigen induces uveitis and pinealitis in primates

S-antigen, a photoreceptor cell protein, induces a predominantly T-cell mediated autoimmune uveitis in many vertebrate animals, including primates. Because of this activity and the finding of immune responses to S antigen in patients with uveitis, this protein has been implicated in the pathogenesis of uveitis in humans. Peptide M, an 18-amino acid component of S antigen, has previously been shown to be highly uveitopathogenic in rats and guinea pigs. We report here that peptide M is immunopathogenic in some monkeys, producing inflammatory changes in eyes and pineal glands similar to those induced by native S antigen. Monkeys with disease also developed intense immune responses to peptide M, measured by the lymphocyte proliferation assay. In addition, lymphocytes from these monkeys reacted against whole S antigen. Furthermore, lymphocytes from certain monkeys immunized with whole S antigen responded well against peptide M, thus indicating that this peptide is an immunodominant epitope in these animals. Two of the four monkeys immunized with peptide M did not develop disease. Lymphocytes from these two animals did not respond in culture against the peptide. Following immunization with the whole protein, these monkeys were capable, however, of developing cellular immunity against S antigen and one of them developed disease. The possible involvement of peptide M in the pathogenesis of uveitis in humans is discussed.

Rod cell-specific antigens in retinoblastoma

We investigated rhodopsin immunoreactivity in five well-differentiated retinoblastomas using a panel of monoclonal antibodies directed against specific antigenic sites in the amino- and carboxyl-terminal portions of rhodopsin. All five monoclonal antibodies bound to the rod cell outer segment of nontumorous retina in all 10% formaldehyde solution-fixed, paraffin-embedded tissue sections. A characteristic "halo" cell surface staining pattern was observed in four (80%) of five tumors treated with two monoclonal antibodies, B6-30 (rhodopsin amino-terminal specific) and K16-107 (rhodopsin carboxyl-terminal specific). In each case, the staining pattern was limited to well-differentiated areas of the tumor containing Flexner-Wintersteiner rosettes or fleurettes. One tumor was not stained by any monoclonal antibody, whereas all monoclonal antibodies stained the rod cell outer segments of nontumorous retina. Our studies indicate that selected retinoblastomas may be differentiated along a rod photoreceptorlike cell lineage.

Human interstitial retinoid binding protein. A potent uveitopathogenic agent for the induction of experimental autoimmune uveitis

Human interstitial retinoid binding protein (HIRBP) is a 136,000 m.w. photoreceptor cell protein which transports retinoids between the retina and the retinal pigment epithelium of the eye. The amino acid sequence of HIRBP suggests that the molecule consists of four continuous homology domains which arose by several gene duplications some 600 to 800 million years ago. When injected into susceptible animal species, including primates, it induces an experimental autoimmune uveitis (EAU), a predominantly T cell-mediated autoimmune disease of the retina and uveal tract of the eye, and the pineal gland. In order to further refine specific sites in HIRBP responsible for its uveitopathogenicity, we synthesized 120 overlapping peptide corresponding to its entire 1262 amino acid sequence, and tested each peptide for its ability to induce an EAU in Lewis rats. Five peptides with extensive amino acid sequence homology, designated HIRBP 715, HIRBP greater than 730 and HIRBP 745, HIRBP 778, and HIRBP 808 were uveitopathogenic when used at a 50 micrograms immunizing dose. The most potent peptide for the induction of EAU was HIRBP 715 (amino acid positions 521 to 540). In dose response studies as little as 0.1 microgram/animal was capable of inducing an inflammatory response. In addition, peptide HIRBP 946 which corresponds to the mid portion of peptide HIRBP 715 and contains only eight amino acids (RTATAAEE) was uveitopathogenic under our experimental conditions. Our study identifies multiple uveitopathogenic sites in HIRBP and further defines the amino acids necessary for the induction of EAU in one of these sites.

Rat pineal S-antigen: sequence analysis reveals presence of alpha-transducin homologous sequence

S-antigen (S-Ag) is a soluble, highly antigenic protein, the administration of which induces autoimmune uveitis. This protein is found in the retina and pineal. Retinal S-Ag from three species has been sequenced. In this study rat pineal S-Ag was sequenced. Clones were isolated from a rat pineal lambda gt11 cDNA library by probing with a 300 bp fragment of mouse retinal S-Ag cDNA containing the 5'-coding region. The largest clone isolated (RPS-118; 1364 bp) contained the entire coding sequence. Comparison of the rat pineal and mouse retinal S-Ag nucleotide sequences indicated a high homology (95%). The deduced amino acid sequence was found to contain 403 residues (congruent to 44 992 Da). Comparison of the rat pineal and mouse retinal S-Ag amino acid sequences also revealed high homology (97%). The similarity of both the nucleotide and amino acid sequences of rat pineal and mouse retinal S-Ag indicates that expression of the S-Ag gene in both tissues is similar. Further analysis of the rat pineal S-Ag sequence indicated that it contained essentially the same major uveitopathogenic region of S-Ag present in bovine retina; minor uveitopathogenic sites were somewhat different. As is true of retinal S-Ag, rat pineal S-Ag contains the same consensus phosphoryl-binding site present in many GTP/GDP-binding proteins and a homologous sequence found in the C-terminus of alpha-transducin. These sequences may play a role in the action of pineal S-Ag in transmembrane signal transduction.

Immunohistochemistry of retinoblastoma. A review

Various studies which relate to the immunohistochemical identification of neuronal, glial, carbohydrate and nucleic acid associated antigens in retinoblastoma will be reviewed. The majority of these studies appear to support the concept that retinoblastomas arise, in situ, from neuron committed cells and in some cases specifically into photoreceptor-like cells. In selected cases, however, glial cell differentiation may be a feature of the tumor. In addition, the molecular biology of the retinoblastoma gene and the immunohistochemical characterization of its gene product will be discussed.

Sequence homology between yeast histone H3 and uveitopathogenic site of S-antigen: lymphocyte cross-reaction and adoptive transfer of the disease

Experimental autoimmune uveitis (EAU) serves as an animal model of ocular inflammation. The disease is caused by the immunization of microgram amounts of a soluble retinal protein, designated S-antigen, in susceptible animal strains, including primates. We induced EAU and experimental autoimmune pinealitis (EAP) in Lewis rats with a small synthetic peptide corresponding to amino acid positions 106-121 in yeast histone H3. This peptide contains five consecutive amino acids identical to a uveitopathogenic site (peptide M) in human S-antigen. Lymph node or mononuclear cells from different species of animals immunized either with histone H3 or with peptide M showed significant cross-reaction as measured by in vitro lymphocyte mitogenesis assay using [3H]thymidine. Also, we adoptively transferred the EAU and EAP in naive rats by immune lymph node cells. These findings support the fact that selected bacterial, viral, or fungal proteins with amino acid sequence homologies to normal retinal proteins are uveitopathogenic and, as such, provide a basis for autoimmune inflammatory diseases.

Molecular mimicry. Yeast histone H3-induced experimental autoimmune uveitis

Experimental autoimmune uveitis (EAU) serves as an animal model of ocular inflammation. The disease is caused by the immunization with microgram amounts of a soluble retinal protein, designated S-Ag, in susceptible animal strains, including primates. We induced EAU and pinealitis in Lewis rats with a small synthetic peptide, corresponding to amino acid positions 106 to 121 in yeast histone H3, which contains five consecutive amino acids identical to a uveitopathogenic site in human S-Ag. In addition, native yeast histone was also capable of inducing an EAU in Lewis rats. Lymph node cells from animals immunized with either peptide M (uveitopathogenic site of S-Ag), histone H3 peptide, or native histone showed significant cross-reaction. Also, we adoptively transferred the EAU in naive rats by lymph node cells. These findings provide a basis for studying autoimmune inflammatory diseases of the eye in humans.