Inhibition of Experimental Autoimmune Uveoretinitis by Oral Administration of S-Antigen and Synthetic Peptides

S-Antigen, a photoreceptor cell protein, is highly efficient in inducing experimental autoimmune uveoretinitis (EAU), a severe inflammation of the uveal tract and retina of the eye. S-Antigen and six synthetic peptides, all of which correspond to known T-cell or B-cell recognition sites, were tested for their ability to induce oral tolerance to EAU in LEW rats. Feeding three 1-mg doses of native S-Antigen or three doses of one synthetic peptide, designated BSA(343-362) (200 micrograms per dose), reduced the incidence and severity of EAU induced by immunization with 50 micrograms of S-Antigen. Another peptide, BSA(270-289), was able to inhibit EAU only when a low dose (10 micrograms) of the uveitogenic S-Antigen was used to induce EAU. Animals which received 200 micrograms doses of four other immunologically active peptides, BSA(31-51), BSA(143-162), BSA(303-327) and BSA(333-352), were not significantly protected. Furthermore, animals fed BSA(343-362) were significantly less susceptible to EAU induced by adoptive transfer (tEAU) of the uveitogenic R9 T-cell lines. Con A-activated lymphocytes purified from spleens of rats fed peptide BSA(343-362) transferred partial resistance to tEAU induced by adoptive transfer of R9 line cells. The resistance of orally tolerized rats to induction of EAU by adoptive transfer of an activated, pathogenic T-cell line, and the ability of lymphocytes from orally-tolerized animals to transfer resistance to tEAU shows that effector mechanisms can be inhibited by oral feeding as well as the afferent mechanisms reported here and elsewhere. Circulating levels of IgG specific for S-Antigen were not affected by feeding any of the peptides.

Ocular surface epithelium induces expression of human mucosal lymphocyte antigen (HML-1) on peripheral blood lymphocytes

BACKGROUND/AIMS

Peripheral blood CD8+ lymphocytes that home to mucosal surfaces express the human mucosal lymphocyte antigen (HML-1). At mucosal surfaces, including the ocular surface, only intraepithelial CD8+ lymphocytes express HML-1. These lymphocytes are retained in the intraepithelial compartment by virtue of the interaction between HML-1 and its natural ligand, E-cadherin, which is expressed on epithelial cells. The purpose of this study was to determine whether ocular surface epithelial cells (ocular mucosa) could induce the expression of human mucosal lymphocyte antigen on peripheral blood lymphocytes.

METHODS

Human corneal and conjunctival epithelial cells were co-cultured with peripheral blood lymphocytes. Both non-activated and activated lymphocytes were used in the experiments. After 7 days of incubation, lymphocytes were recovered and analysed for the antigens CD8/HML-1, CD4/HML-1, CD3/CD8, CD3/CD4, CD3/CD25, CD8/CD25, and CD4/CD25 by flowcytometry.

RESULTS

Significant statistical differences were observed in the CD8/HML-1 expression when conjunctival epithelial cells were co-cultured with non-activated and activated lymphocytes (p = 0.04 for each) and when corneal epithelial cells were co-cultured with non-activated lymphocytes (p = 0.03). Significant statistical difference in CD4/HML-1 expression was observed only when conjunctival epithelial cells were co-cultured with activated lymphocytes (p = 0.02).

CONCLUSION

Ocular surface epithelial cells can induce the expression of human mucosal lymphocyte antigen on CD8+ (and to some extent on CD4+) lymphocytes. This may allow the retention of CD8+ and CD4+ lymphocytes within the epithelial compartment of the conjunctiva and play a part in mucosal homing of lymphocytes.

A novel gene for autosomal dominant Stargardt-like macular dystrophy with homology to the SUR4 protein family

PURPOSE

To describe a novel gene causing a Stargardt-like phenotype in a family with dominant macular dystrophy and the exclusion of all known genes within the disease locus.

METHODS

Meiotic breakpoint mapping in a family of 2314 individuals enabled refinement of the location of the disease gene. The genomic organization and expression profile of known and putative genes within the critical region were determined using bioinformatics, cDNA cloning, and RT-PCR. The coding sequence of genes expressed within the retina was scanned for mutations, by using DNA sequencing.

RESULTS

The disease-causing gene (STGD3) was further localized to 562 kb on chromosome 6 between D6S460 and a new polymorphic marker centromeric to D6S1707. Of the four genes identified within this region, all were expressed in the retina or retinal pigment epithelium. The only coding DNA sequence variant identified in these four genes was a 5-bp deletion in exon 6 of ELOVL4. The deletion is predicted to lead to a truncated protein with a net loss of 44 amino acids, including a dilysine endoplasmic reticulum retention motif. The ELOVL4 gene is the fourth known example of a predicted human protein with homology to mammalian and yeast enzymes involved in the membrane-bound fatty acid chain elongation system. The genomic organization of ELOVL4 and primer sets for exon amplification are presented.

CONCLUSIONS

ELOVL4 causes macular dystrophy in this large family distributed throughout North America and implicates fatty acid biosynthesis in the pathogenesis of macular degeneration. The PCR-based assay for the 5-bp deletion will facilitate more accurate genetic counseling and identification of other branches of the family.

Autosomal dominant Stargardt-like macular dystrophy

Autosomal dominant Stargardt-like macular dystrophy is one of the early onset macular dystrophies. It is characterized clinically in its early stages by visual loss and by the presence of atrophic macular changes with or without the presence of yellowish flecks. It is an important retinal dystrophy to study, not only because it has implications in the care and treatment of patients with the condition, but because it also provides important information regarding retinal function. Review of the literature suggests that many of the reported families are linked to chromosome 6q. Genetic and genealogical evidence suggests that these families have descended from a common ancestor or founder. The recent identification of a disease-causing gene that is involved in fatty acid metabolism may have implications in the study of the more common age-related macular degeneration. We review the recent clinical, genetic, and genealogical aspects of autosomal dominant Stargardt-like macular dystrophy.

Experimental autoimmune uveoretinitis in mice (Biozzi ABH and NOD) expressing the autoimmune-associated H-2A(g7) molecule: identification of a uveitogenic epitope

To determine whether Biozzi ABH (H-2A(g7)) mice were susceptible to chronic experimental autoimmune uveoretinitis (EAU). Biozzi ABH were immunized with the two retinal antigens, interphotoreceptor retinoid binding protein (IRBP) and soluble antigen (S-Ag). Biozzi ABH mice were found to be susceptible to EAU induction with native bovine IRBP. Recombinant protein domains were used to identify IRBP domain 2 (EcR2) as the uveitogenic domain. Histopathological examination indicated that EcR2-induced disease was of a chronic, non-destructive nature in the Biozzi ABH. Using synthetic overlapping peptides corresponding to EcR2, a uveitogenic and immunogenic epitope was identified corresponding to human IRBP511-530. Non-obese diabetic (NOD) mice share the same MHC class II (H-2A(g7)) molecule as the Biozzi ABH, and were also found to be susceptible to EAU induction with EcR2. This study has identified a novel mouse model of EAU, whereby disease is of a chronic, non-destructive nature, which has potential to be used in immune manipulation and neuroprotection studies.

Malattia leventinese presenting with subretinal neovascular membrane and hemorrhage

PURPOSE

To report a case of malattia leventinese involving subretinal hemorrhage.

METHODS

Case report.

RESULTS

Two weeks after initial presentation, the visual acuity of this 34-year-old man decreased to LE: 20/100. Funduscopic evaluation revealed a subretinal hemorrhage involving the center of the foveal in the left eye that was interpreted as secondary to a neovascular membrane on fluorescein angiography. The patient did well after the removal of the submacular material by pars plana vitrectomy.

CONCLUSION

Patients with malattia leventinese may occasionally present with submacular hemorrhage. Prompt diagnosis and intervention may enhance the patient's chance for visual improvement.

Autosomal dominant Stargardt-like macular dystrophy: founder effect and reassessment of genetic heterogeneity

OBJECTIVES

To characterize a disease-associated haplotype in 7 families with autosomal dominant Stargardt-like macular dystrophy and to determine whether these families share a common ancestor.

METHODS

Twenty-five polymorphic DNA markers spanning known dominant Stargardt-like gene loci were used to determine the haplotype associated with disease. In addition, an extensive genealogical investigation searching for a common ancestor shared by all of the 7 families was performed.

RESULTS

We clinically evaluated 171 patients and genotyped 145 samples. The same DNA haplotype on chromosome 6q16 was shared by all evaluated affected members within the 7 families. In addition, we were able to genealogically join all of the families into one larger family consisting of 31 branches and 2314 individuals. Twenty-seven branches have known living descendants, with 7 branches having affected family members. In addition, we refined the critical region for the gene to approximately 1000 kilobases (kb) and eliminated part or all of 9 candidate disease-causing genes.

CONCLUSIONS

Our study indicates that most reported cases of autosomal dominant Stargardt-like macular dystrophy in North America are part of a single larger family associated with a gene locus on chromosome 6q16. Furthermore, the DNA haplotype associated with disease is useful in excluding individuals with phenotypically similar retinal conditions.

CLINICAL RELEVANCE

The disease-associated haplotype allows for more accurate genetic counseling to be given to individuals with a Stargardt-like phenotype inherited in an autosomal dominant pattern.

Stargardt's macular dystrophy--a patient's perspective

PURPOSE

The purpose of this paper was to evaluate life experience, including disease characteristics, daily-living activities, employment, interactions with health care professionals, and support services in patients diagnosed with Stargardt's macular dystrophy.

METHODS

More than 200 patients with Stargardt's disease responded to a 68-question survey. Results were analyzed using SAS Statistical Analysis Package.

RESULTS

Of 203 responders, 142 (70%) were women. Early disease onset occurred in more than 60% of patients. Blurred vision (134, 66%) and glare (183, 90.1%) were the leading symptoms reported. Reading (116, 57.1%), driving (86, 42.4%), and recognizing faces (66, 32.5%) were daily-living activities most difficult to perform. Patients with early disease onset had worse vision at presentation (p = 0.001), faster progression of visual loss (p = 0.007), and were more often diagnosed with a non-physiological visual loss (p = 0.007). Patients with late disease onset had more difficulty with orientation and coping skills (p = 0.02). Sixty-five percent of evaluated adults (108 of 165) were employed.

CONCLUSIONS

Although the study illustrates that patients with Stargardt's disease can contribute and function well in contemporary society, issues related to depression, and availability and quality of health care, are still major concerns for this patient population. The study shows differences in progression of visual loss between patients, with early versus late disease onset indicating that age at onset and visual acuity at presentation might be two important factors influencing patient's visual prognosis. Finally, the study suggests parallels in psychological profiles between late age at onset Stargardt's disease and age-related macular degeneration patients.

A possible hot spot in exon 21 of the retinoblastoma gene predisposing to a low penetrant retinoblastoma phenotype?

PURPOSE

To identify the mutation in the RB1 gene in a Syrian family showing incomplete penetrance of retinoblastoma (RB).

METHODS

Genomic DNA was used as a template for the PCR reaction to amplify all exons as well as the promoter region of RB1 gene. These PCR products were screened by conformational sensitive gel electrophoresis and the 331-bp product containing exon 21 showing anomalous migration was sequenced directly to identify the mutation.

RESULTS

We identified the missense point mutation in exon 21 of the RB1 gene converting a Cys-->Arg (codon 712) in one family with a low penetrant phenotype. The proband was unilaterally affected, whereas the paternal uncle was bilaterally affected and the mutation carrier father was unaffected. The T-->C substitution abolished a cleavage site for the Nde I restriction enzyme, enabling rapid detection of the mutant allele.

CONCLUSION

Phenotypically, this family is different from the previously described low penetrant phenotype pedigree with the same mutation whose affected members all had unilateral tumors. These results suggest that codon 712 may represent a mutational 'hot spot' for the low penetrant phenotypes and that the mutation codes for retinoblastoma protein with an apparently residual tumor-suppressive function give rise to low penetrance. These results also raise the interesting question: what other factors influence the phenotype of mutation carriers in addition to the predisposing missense mutation.

Cloning of the human monocarboxylate transporter MCT3 gene: localization to chromosome 22q12.3-q13.2

Lactate transport across cell membranes is mediated by a family of proton-coupled monocarboxylate transporters (MCTs). The retinal pigment epithelium (RPE) expresses a unique member of this family, MCT3. A portion of the human MCT3 gene was cloned by polymerase chain reaction using primers designed from rat RPE MCT3 cDNA sequence. The human genomic sequence was used to design primers to clone human MCT3 cDNA and to identify a bacterial artificial chromosome clone containing the human MCT3 gene. The human MCT3 cDNA contained a 1512-nucleotide open reading frame with a deduced amino sequence 85% identical to rat MCT3. Comparison of the cDNA and genomic sequences revealed that the MCT3 gene was composed of five exons distributed over 5 kb of DNA. The exon-intron borders were conserved between the human and the chicken MCT3 genes. Using radiation hybrid mapping, the MCT3 gene was mapped to chromosome 22 between markers WI11639 and SGC30687. A search of chromosome 22 in the Sanger Centre database confirmed the location of the human MCT3 gene at 22q12.3-q13.2.

Lymphocyte subsets in conjunctival mucosa-associated-lymphoid-tissue after exposure to retinal-S-antigen

PURPOSE

To evaluate the immune cell subsets in conjunctival mucosa-associated-lymphoid-tissue (C-MALT) following challenge with antigen.

METHODS

Ten adult female Lewis rats were studied. Five rats received one drop (5 microL) of retinal S-antigen (500 microg/mL in phosphate buffered saline, PBS) instilled into the lower fornix twice daily for 10 consecutive days. Five rats received PBS only and served as controls for the experiment. Two days after the last instillation the animals were sacrificed and the orbital contents prepared for immunohistological staining. A panel of monoclonal antibodies was used: CD5, CD4, CD8, CD25, and CD45RA. The number of positive cells were counted in sections of epibulbar, forniceal, and tarsal conjunctiva.

RESULTS

There was a significant increase in the number of CD8+ T lymphocytes in the conjunctiva of animals receiving retinal S-antigen when compared to control animals.

CONCLUSION

Conjunctival instillation of retinal S-antigen causes an immune response in the C-MALT with a significant increase in the CD8+ T lymphocyte subset in this tissue. This response may be involved in the induction of tolerance to the encountered antigen.

Autosomal dominant Stargardt-like macular dystrophy: I. Clinical characterization, longitudinal follow-up, and evidence for a common ancestry in families linked to chromosome 6q14

PURPOSE

Characterize the phenotype of autosomal dominant Stargardt-like macular dystrophy in two families linked to chromosome 6q14 and determine whether they share a common ancestry.

METHODS

Two families spanning 10 generations were identified and studied independently. Participating members were examined and genetic linkage and genotyping performed.

RESULTS

Presenting symptoms included decreased vision, hemeralopia, and mild photophobia. The subjective onset of visual loss ranged from age 3 to 50 with a mean of 14 years. A Snellen acuity of 20/200 occurred at a mean age of 22 years. Over decades, the macular lesion enlarged and visual acuity decreased to 20/300 to 20/800. The typical phenotype was well-circumscribed, homogenous atrophy of the retinal pigment epithelium and choriocapillaris in the macula, with surrounding yellow flecks and temporal optic nerve pallor. The phenotypic spectrum included a pattern dystrophy-like appearance, diffuse geographic atrophy, and extensive fundus flecks. Genotyping revealed that the two families were linked to chromosome 6q14 and shared a common haplotype spanning 21 cM between D6S430 and D6S300. The two families were subsequently shown by genealogic investigation to represent different branches of a common kindred.

CONCLUSIONS

Families with autosomal dominant Stargardt-like macular dystrophy linked to chromosome 6q14 share a common phenotype and in some cases can be distinguished from similar dystrophies by inheritance pattern and clinical features. The finding that these two families shared a common ancestor suggests the existence of a founder effect. Characterization of the gene for autosomal dominant Stargardt-like macular dystrophy may enable better understanding of this condition and elucidation of its potential role in other forms of macular degeneration.

Genetic aspects of uveal melanoma: a brief review

Uveal melanoma usually occurs sporadically in the absence of obvious genetic predisposing factors. However, in rare patients, there is a suggestion that there may be genetic predisposition. Rare occurrences of familial uveal melanoma are believed to be inherited in an autosomal dominant mode. There are a few clinical conditions that can predispose to or be associated with uveal melanoma, including ocular melanocytosis, neurofibromatosis type I, and familial atypical mole and melanoma syndrome. Nonrandom cytogenetic changes in uveal melanoma are characterized by monosomy 3, trisomy 8, and structural or numerical abnormalities of chromosome 6. Alterations of chromosome 9p are less frequently observed. CDKN2 gene, a cutaneous melanoma predisposition gene, is probably not a uveal melanoma predisposition gene as evidenced by the lack of somatic mutations involving this gene in uveal melanoma samples and the absence of germline mutations in familial uveal melanoma patients. Transgenic mouse models developed using a tyrosinase promoter tagged with a mutated ras gene or SV40-Tag oncoprotein develop retinal pigment epithelium tumors that resemble uveal melanoma. We propose that uveal melanoma cases be categorized on genetic basis according to a new classification system. This classification scheme will help to identify and uniformly categorize uveal melanoma patients with genetic predisposition. Such patients offer unique opportunities for studying the genetic aspects of uveal melanoma and, therefore, appropriate tissue samples should be obtained from them for molecular genetic studies. Further studies are needed to fully understand the genetic aspects of uveal melanoma.

Is the occurrence of familial uveal melanoma coincidental?

OBJECTIVE

To ascertain whether the familial occurrence of uveal melanoma was coincidental in kindreds in which 1 first-degree relative of the proband had also been affected with primary uveal melanoma.

PATIENTS

In a series of 4500 patients with primary uveal melanoma, 17 kindreds were identified in which a first-degree relative of the proband had also been affected with primary uveal melanoma.

DESIGN

In the 17 families in which a first-degree relative of the proband had been affected, primary uveal melanoma was classified as familial. In the remaining 4483 families, primary uveal melanoma was classified as sporadic. The expected number of affected first-degree relatives of probands for a family was estimated, assuming an incidence rate of 6 cases per million population per year in each type of family.

RESULTS

The expected number of affected first-degree relatives was calculated to be 0.81, with an SE of 0.08, compared with 17 observed affected first-degree relatives (P < .001).

CONCLUSION

Our study provides strong statistical evidence that occurrence of familial uveal melanoma is not coincidental.

The effect of topical cyclosporin on conjunctiva-associated lymphoid tissue (CALT)

Topical cyclosporin A is increasingly being used in the treatment of ocular surface immune-mediated disorders. The availability of the drug in oil-based vehicles or collagen shields has restricted its use because of ocular irritation or blurring of vision. Although topical cyclosporin is being used more frequently, its effect on the immunocompetent cells of the conjunctiva is not known. Our aim was to study the effect of cyclosporin instillation on the immunocomponent cells of conjunctiva-associated lymphoid tissue (CALT) of Lewis rat, using a novel method of topical drug delivery. A suspension of collagen bits impregnated with cyclosporin A was instilled into eyes of Lewis rats for 4 days (group 1) or 8 days (group 2). Control rats (group 3) received the suspension without cyclosporin. Frozen sections of eyelids and conjunctiva were immunostained with the following monoclonal antibody markers: W3/13 (CD3), W3/25 (CD4, macrophages), OX-8 (CD8), MARD-3 (B cells), ED1, ED2 (macro/monocytes), OX-6 (class II MHC, Ia) and OX-39 (CD25, IL-2 receptor). Intraepithelial (IE) and substantia propria cells for each subset were counted and expressed as numbers per section. By day 8, intraepithelial and substantia propria cells for all the above markers, except B cells, showed a significant reduction in numbers. The p values were < 0.02 for W3/13 (CD3), W3/25 (CD4), OX-8 (CD8), OX-39 (CD25) (IE only), ED1, ED2 and OX-6 positive cells. Goblet cells of control animals showed strong positive reaction with OX-39 (CD25) antibody. This was completely abolished following 8 days of topical cyclosporin. This study demonstrated that topical cyclosporin A induces a marked reduction in numbers of all subtypes of immunocompetent cells in the conjunctival epithelium and substantia propria.

Vortex or whorl formation of cultured human corneal epithelial cells induced by magnetic fields

The terms 'vortex keratopathy' and 'hurricane keratopathy' describe two similar conditions affecting the corneal surface. In the former, a vortex or whorl pattern is seen on the corneal surface and is due to the deposition of substances such as pigment, iron or drugs in the epithelial cells. In the latter, a similar pattern is presented by migrating epithelial cells but, unlike the former, the pattern is rendered more visible by fluorescein staining. Both represent the migratory pattern of normal epithelial cells which is otherwise not visible due to the slow rate of epithelial turnover and migration. The whorl pattern has a clockwise predisposition in the majority of cases and is hypothesised to be due to the influence of ocular electro-magnetic fields on the migrating epithelial cells. In this study we tested in vitro the effect of static magnetic fields on corneal epithelial cells. We were able to reproduce dramatic vortex or whorl patterns in response to magnetic fields, but without preferential migration towards the North or South Pole.

Retinoblastoma-like phenotype expressed in medulloblastomas

The previous demonstration of rod-opsin and S-antigen (S-Ag), a protein which arrests visual phototransduction, in retinoblastomas and in a subgroup of medulloblastomas has suggested a relationship between these tumors. We examined 17 medulloblastomas for the presence of a retinoblastoma-like phenotype. Overall 41% of the tumors were immunoreactive for S-Ag. Two tumors with well-differentiated Flexner-Wintersteiner rosettes were also immunoreactive for S-Ag, but not for epithelial membrane antigen (EMA). In contrast, most ependymal rosettes in two ependymomas stained positive for EMA along the luminal surface, consistent with a previous study, and were negative for S-Ag. Because calcification in areas of necrosis is a near constant finding in retinoblastomas, the medulloblastomas were evaluated for the presence of calcification, using Von Kossa staining. Forty-one percent showed calcification in areas of necrosis and 29% were positive for both calcification and S-Ag immunoreactivity. There was a statistically significant concordance between calcification and S-Ag immunoreactivity in the medulloblastomas (p < 0.05). Despite similar phenotypic features, a shared mechanism of tumori-genesis for retinoblastomas and the subgroup of medulloblastomas with photoreceptor differentiation could not be identified since all 17 medulloblastomas were found to express functional Rb protein, as indicated by positive nuclear immunoreactivity.

Genetic and molecular studies of macular dystrophies: recent developments

Macular degeneration is a heterogeneous group of disorders characterized by progressive central visual loss and degeneration of the macula and underlying retinal pigment epithelium (RPE) of the eye. Age-related macular degeneration (ARMD), the most common form of the disease, is the leading cause of legal blindness in the elderly population in the United States and in the many developed countries throughout the world. Despite its prevalence, its etiology and pathogenesis are poorly understood, and effective treatment options are limited for most patients. Inherited macular dystrophies share many important features with ARMD but are more readily studied by molecular genetic approaches. Over the past few years, significant progress has been made in the molecular genetics of inherited macular dystrophies. Genes responsible for dominant and recessive Stargardt's macular dystrophy as well as Best's disease have been localized to specific chromosomal regions. The peripherin/RDS gene when defective is associated with butterfly-shaped pattern dystrophy. Molecular studies of genes involved in macular dystrophies may yield insights into the mechanisms of pathogenesis of macular degeneration and provide new rationale for the management and treatment of patients with these diseases.

Recent advances in the molecular genetics of retinitis pigmentosa

In recent years a rapid development in gene cloning techniques has been seen which has, in part, been responsible for the elucidation of the molecular mechanisms involved in many hereditary diseases. Most noteworthy is the rapid detection of mutations in various genes Most noteworthy is the rapid detection of mutations in various genes associated with various retinal degenerations and disorders. There is an increasing need for ophthalmologists to keep abreast with these new developments to better understand disease processes and recognize new opportunities for the diagnosis and treatment of these conditions. In addition, more recent discoveries in molecular genetics have revealed previously unrecognized associations between different clinical entities that share common gene mutations (gene sharing), as well as distinctly different molecular alterations within the spectrum of what traditionally was believed to be the same disease (locus heterogeneity). These findings will most likely, in the future, invoke the need to redefine disease categories at the molecular level. This article reviews basic molecular genetics useful to ophthalmologists and examines in detail these concepts with regard to one representative hereditary retinal disease--retinitis pigmentosa.

The ocular surface as part of the mucosal immune system: conjunctival mucosa-specific lymphocytes in ocular surface pathology

The mucosal immune system includes mucus membranes of the gut, respiratory and urogenital tracts. Mucosa-specific, intraepithelial lymphocytes (IELs), that correspond to the suppressor/cytotoxic subset and also express the human mucosal lymphocyte antigen (HML-1), are a unique component of this system. We have recently demonstrated these cells in the human conjunctiva, establishing the ocular surface as an integral part of the mucosal immune system. In this study we examined the distribution of lymphocyte subsets, with particular attention to mucosa-specific lymphocytes, in two ocular surface disorders, namely conjunctival intraepithelial neoplasia (CIN) and ocular cicatricial pemphigoid (OCP). Cryosections of biopsy specimen were immunostained using a panel of monoclonal antibodies against different lymphocyte subsets. In CIN, the CD8/HML ratio was decreased (1 +/- 0) and CD8/CD4 ratio was reversed (0.54 +/- 0.21). HML-1+ cells were distributed throughout the epithelial layers of dysplastic tissue. Biopsy specimens of OCP showed normal ratios of CD8/HML (1.4 +/- 0.16) but the CD8/CD4 was low (1.29 +/- 0.88). Association of HML-1+ cells with the basal layer of normal epithelium and with all layers of dysplastic epithelium suggests that expression of HML-1 antigen may be induced by actively dividing cells. HML-1+ cells may have a role in immune mechanisms associated with ocular surface disorders.

Identification of a major pathogenic epitope in the human IRBP molecule recognized by mice of the H-2r haplotype

PURPOSE

Mice of the H-2b, H-2k, and H-2r haplotypes develop experimental autoimmune uveoretinitis (EAU) after immunization with interphotoreceptor retinoid-binding protein (IRBP) of bovine or monkey origin. The purpose of this study was to identify putative pathogenic epitope(s) of IRBP and to establish their immunodominance within the IRBP molecule.

METHODS

Overlapping 20-amino acid peptides, spanning the entire human IRBP molecule, were synthesized and used to immunize C57BL/10 (H-2b), B10.BR (H-2k), and B10.RIII (H-2r) mice. Bovine IRBP was used as a positive control. Experimental autoimmune uveoretinitis was examined by histopathology 21 days after immunization. Immunologic responses were assessed by delayed-type hypersensitivity (DH) and lymphocyte proliferation assays.

RESULTS

Peptide 161-180, spanning the sequence SGIPYIISYLHPGNTILHVD, was found to be highly pathogenic for B10.RIII mice but not for the other strains. A dose-response curve showed that peptide 161-180 was maximally pathogenic at 50 micrograms, but incidence and scores were reduced at 10 micrograms. The truncated 13-mer 165-177 was also highly pathogenic (100 to 200 micrograms), suggesting that it contained the pathogenic epitope. Mice immunized with the peptide, or with whole IRBP, had positive DH and lymphocyte responses to the immunizing as well as to the reciprocal antigen. A cell line derived to peptide 161-180 was also pathogenic for B10.RIII mice after adoptive transfer and responded (proliferation) to native IRBP.

CONCLUSIONS

High incidence and high severity scores, as well as immunologic cross-recognition of peptide 161-180 and native IRBP in vivo and in vitro, suggest that this peptide contains a major epitope recognized as pathogenic by B10.RIII mice.

Modification of standard proteinase K/phenol method for DNA isolation to improve yield and purity from frozen blood

Research in medical genetics may frequently involve freezing of large numbers of peripheral blood samples. This is a convenient method for storing blood for subsequent DNA isolation and analysis. An area of potential concern is the low yield of DNA from blood samples that have been frozen. Here we report a modification of the widely used standard proteinase K/phenol DNA isolation method for improving the yield and purity of DNA from frozen blood samples, by an initial trypsinisation of whole blood before cell lysis to obtain lymphocytic nuclei and subsequent DNA purification. We report an increased total yield of DNA with pretrypsinised blood as well as improved purity. These results indicate that trypsinisation of thawed whole blood helps the deproteinisation process, reducing the amount of protein associated with the nuclear pellet. This modification to improve yield and purity of DNA from frozen blood samples should be useful to laboratories performing DNA based diagnostic work or studying molecular genetic mechanisms of disease.

Immunological mimicry between retinal S-antigen and group A streptococcal M proteins

Immunological mimicry between host and microbial proteins has been suggested as a potential mechanism in the development of uveitis in humans. In this study immunological crossreactivity between anti-streptococcal monoclonal antibodies (MAbs) and the human eye was investigated. In indirect immunofluorescence, we demonstrated novel immunological crossreactivity of two anti-streptococcal MAbs (27 and 112) with the rod outer (and inner) segments of the retina of the human eye. In further studies, retinal S-Ag, a uveitogenic protein in the rod outer (and inner) segments, was found to react with the anti-streptococcal MAbs. In addition, several uveitogenic peptides of S-Ag were recognized by the anti-streptococcal MAbs. In the ELISA and Western immunoblot, anti-S-Ag MAbs crossreacted with group A streptococci and the streptococcal M protein further demonstrating sites of antigenic similarity. Homology between the retinal S-Ag and streptococcal M protein was observed in amino acid sequences repeated in the B repeat region of the streptococcal M5 protein. These data show that retinal S-antigen has immunological similarities with streptococcal M protein, a major virulence determinant and strong bacterial cell surface antigen.

Isolation and expression of an arrestin cDNA from the horseshoe crab lateral eye

Electrophysiological studies of photoreceptors from the horseshoe crab Limulus polyphemus continue to provide fundamental new knowledge of the photoresponse in invertebrates. Therefore, it is of particular interest to characterize the molecular components of the photoresponse in this system. Here we describe an arrestin cloned from a cDNA library constructed using poly(A)+ RNA isolated from Limulus lateral eyes. The protein, deduced from the arrestin cDNA, is most similar to arrestin from locust antennae (56% identity) and Drosophila phosrestin I (53% identity). Limulus arrestin was expressed in a heterologous system, and its properties were compared with those of a 46-kDa light-regulated phosphoprotein (pp46A) in Limulus photoreceptors described in previous studies from this laboratory. Arrestin and pp46A (a) have the same apparent molecular weight on sodium dodecyl sulfate-polyacrylamide gel electrophoresis, (b) have an isoelectric point in the basic pH range, (c) require calmodulin and elevated Ca2+ levels for phosphorylation, (d) are immunoreactive with monoclonal antibody C10C10 directed against a sequence in bovine arrestin (S-antigen) that is perfectly conserved in the deduced arrestin protein, and (e) are associated with photoreceptors. We conclude that the arrestin described here and pp46A are the same protein. The results of this and previous studies show that in Limulus photoreceptors, light regulates the phosphorylation of arrestin in complex ways.

A dominant Stargardt's macular dystrophy locus maps to chromosome 13q34

OBJECTIVE

To identify the chromosomal location of a mutated gene that causes an autosomal dominant Stargardt's macular dystrophy.

METHODS

Ocular examinations were performed on 67 members of a large kindred to identify those with macular dystrophy. DNA analyses defined the genotype of all family members at 49 polymorphic loci. Linkage between the gene defect responsible for this macular dystrophy and each polymorphic locus was assessed by lodscore calculations.

RESULTS

Diminished visual acuity and funduscopic abnormalities were found in 29 family members, which was diagnostic of macular dystrophy. Genetic analyses demonstrated that polymorphic loci from chromosome 13 band q34 were linked to the gene defect in this family. Haplotype analyses localized the disease locus to an 8-centimorgan interval between loci D13S159 and D13S158/D13S174.

CONCLUSION

A disease locus responsible for an autosomal dominant Stargardt's macular dystrophy is located on chromosome 13 band q34. Identification of the mutated gene at this locus will lead to a better understanding of macular degeneration.

Effect of hydroxylamine on the subcellular distribution of arrestin (S-antigen) in rod photoreceptors

The immunocytochemical labeling of arrestin (S-antigen) in photoreceptors of the ovine retina was examined following incubation of the retina with hydroxylamine (NH2OH), an agent known to inhibit the phosphorylation of photoactivated rhodopsin. Intact, isolated retinas bathed in medium containing 20 mM NH2OH, or in control medium lacking NH2OH, were maintained in darkness or exposed to bright light for 3 min (dark-adapted and light-adapted conditions, respectively); further incubated in darkness for 10 min; and then fixed and prepared for cryosectioning. Cryosections were incubated with anti-S-antigen monoclonal antibody MAb A2G5; with secondary antibodies that were conjugated with horseradish peroxidase; and with either 3-amino-9-ethyl carbazole or diaminobenzidine as chromogen. Anti-arrestin labeling in cryosections was then analyzed densitometrically using a light-microscopic image processing system. In dark-adapted control retinas, labeling density of the photoreceptor outer segment (OS) layer (0.061 +/- 0.004; average +/- S.E.M.) was less than that of the inner segment (IS) layer (0.138 +/- 0.011). In light-adapted control retinas, OS labeling density (0.139 +/- 0.007) exceeded IS labeling density (0.095 +/- 0.005). Incubation with NH2OH eliminated this light-dependent increase in labeling of the OS relative to that of the IS, i.e. eliminated the increase in relative OS/IS labeling. Densities of labeling were 0.110 +/- 0.006 (OS) and 0.183 +/- 0.006 (IS) in NH2OH-treated dark-adapted retinas vs. 0.078 +/- 0.004 (OS) and 0.182 +/- 0.008 (IS) in NH2OH-treated light-adapted retinas. Anti-arrestin labeling was also examined in retinas that were exposed to 3 min or 13 min of bright light and then immediately fixed.(ABSTRACT TRUNCATED AT 250 WORDS)

Cytogenetic findings in primary uveal melanoma

We analyzed cytogenetic abnormalities in 10 cases of primary uveal melanoma. Clonal chromosomal abnormalities were present in nine cases. Chromosome 6 was most commonly affected (seven cases) and included gain of material from 6 and/or loss of material from 6q. Trisomy of chromosome 8 or gain in material from 8q, mostly in the form of an i(8q) resulting in three to five copies of the 8q segment was seen in six cases. Monosomy of chromosome 3 and rearrangements of chromosome 9 were less frequent and were altered in three cases each. Clinical, histopathologic, and cytogenetic abnormalities are correlated.

Identification and rapid screening of a DraI RFLP by PCR in the retinoblastoma gene

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Mucosa specific lymphocytes in the human conjunctiva, corneoscleral limbus and lacrimal gland

Conjunctiva associated lymphoid tissue shows several similarities to mucosa associated lymphoid tissue of the gut and respiratory tract. These similarities have been described in relation to lymphocyte subpopulations and epithelial cell morphology. However, unlike the lymphoid tissue of the gut and respiratory tract, mucosa specific lymphocytes have not been described in the ocular mucosa. In this study we demonstrated the presence of mucosa specific lymphocytes bearing the Human Mucosal Lymphocyte-1 antigen (beta 7 integrin), in the human conjunctiva, limbus and lacrimal gland. The distribution of this subset of lymphocytes corresponded to the distribution of CD8+ T-cells and was found maximally in the epithelium of the epibulbar conjunctiva and in the lacrimal gland. The Human mucosal lymphocyte antigen may function to determine mucosal homing of this particular subset of CD8+ T-cells, which in turn, may have special function in immunological defense and tolerance mechanisms occurring at mucosal surfaces.

S-antigen immunoreactivity in tumors of the choroid plexus

Using monoclonal antibodies (MAbs) directed against retinal S-antigen, the authors demonstrated the presence of S-antigen immunoreactivity in six of six (100%) tumors of the human choroid plexus, a tissue rich in β-adrenergic receptor activity. An anti-retinal S-antigen MAb F4C1, showed S-antigen immunoreactivity in one papilloma of the choroid plexus and in five of five (100%) carcinomas of the choroid plexus. In contrast, a papillary ependymoma of the spinal cord, an astrocytoma, an oligodendroglioma, metastatic oat cell carcinoma and metastatic adenocarcinoma to the brain did not stain. Our study indicates that MAb F4C1 may prove to be a useful immunohistochemical marker of tumors originating from the choroid plexus.

Oral tolerance in experimental autoimmune uveoretinitis. Distinct mechanisms of resistance are induced by low dose vs high dose feeding protocols

Studies of oral tolerance in LEW rat models of autoimmune diseases including S-antigen (S-Ag)-mediated experimental autoimmune uveoretinitis (EAU), and myelin basic protein-induced experimental autoimmune encephalomyelitis have produced conflicting evidence for the roles of clonal anergy and suppression. Using subpeptides from a region of S-Ag known to induce oral tolerance a protective site was localized to a nonamer of residues 347-355. This site was also uveitogenic, providing the basis for testable hypotheses for tolerance to be due to clonal anergy in pathogenic T cells specific for that site, or to suppression. Evidence for suppression was strongly supported by several observations. 1) Induction of oral tolerance with low dose feedings (250 micrograms/feeding) of peptide 343-362 conferred resistance to EAU induction by intact S-Ag, which should not be possible if only T cells specific for epitopes in 343-362 were rendered unresponsive, since there are several other pathogenic sites in S-Ag. 2) Low dose feeding induced resistance to EAU induction by a distinct, spatially separate peptide, residues 270-289, of S-Ag. 3) The requirement for linked recognition was shown by the inability of tolerance induced by feeding 343-362 to protect from EAU induction by a peptide, residues 521-540, derived from interphotoreceptor retinoid binding protein, a different uveitogenic retinal protein. 4) Resistance could be adoptively transferred. Conversely, induction of tolerance with high doses of peptide (5 mg/feeding) resulted in loss of resistance to EAU induced by S-Ag, although disease induction by the fed peptide was inhibited; observations that are consistent with clonal anergy. The apparent lack of suppression after high dose feeding could mean that suppressor T cells can also be rendered unresponsive or that induction of T suppressor cells is dependent on CD4+ Th cells, which were rendered anergic, leading to lack of T suppressor development. We suggest that oral tolerance operates by at least two distinct mechanisms that depend on the feeding dose; low doses induce suppression, whereas high doses induce unresponsiveness.

Oral tolerance in experimental autoimmune uveoretinitis. Distinct mechanisms of resistance are induced by low dose vs high dose feeding protocols

Studies of oral tolerance in LEW rat models of autoimmune diseases including S-antigen (S-Ag)-mediated experimental autoimmune uveoretinitis (EAU), and myelin basic protein-induced experimental autoimmune encephalomyelitis have produced conflicting evidence for the roles of clonal anergy and suppression. Using subpeptides from a region of S-Ag known to induce oral tolerance a protective site was localized to a nonamer of residues 347-355. This site was also uveitogenic, providing the basis for testable hypotheses for tolerance to be due to clonal anergy in pathogenic T cells specific for that site, or to suppression. Evidence for suppression was strongly supported by several observations. 1) Induction of oral tolerance with low dose feedings (250 micrograms/feeding) of peptide 343-362 conferred resistance to EAU induction by intact S-Ag, which should not be possible if only T cells specific for epitopes in 343-362 were rendered unresponsive, since there are several other pathogenic sites in S-Ag. 2) Low dose feeding induced resistance to EAU induction by a distinct, spatially separate peptide, residues 270-289, of S-Ag. 3) The requirement for linked recognition was shown by the inability of tolerance induced by feeding 343-362 to protect from EAU induction by a peptide, residues 521-540, derived from interphotoreceptor retinoid binding protein, a different uveitogenic retinal protein. 4) Resistance could be adoptively transferred. Conversely, induction of tolerance with high doses of peptide (5 mg/feeding) resulted in loss of resistance to EAU induced by S-Ag, although disease induction by the fed peptide was inhibited; observations that are consistent with clonal anergy. The apparent lack of suppression after high dose feeding could mean that suppressor T cells can also be rendered unresponsive or that induction of T suppressor cells is dependent on CD4+ Th cells, which were rendered anergic, leading to lack of T suppressor development. We suggest that oral tolerance operates by at least two distinct mechanisms that depend on the feeding dose; low doses induce suppression, whereas high doses induce unresponsiveness.

Pseudo low penetrance in retinoblastoma. Fortuitous familial aggregation of sporadic cases caused by independently derived mutations in two large pedigrees

OBJECTIVE

The disparate occurrence of few cases of retinoblastoma in the same extended pedigree confronts us with the unsolved problem of a low-penetrant autosomal-dominant trait vs fortuitous familial aggregation of sporadic cases. Determination as to whether the disease arises from a common inherited mutation or sporadic mutations has important implications for genetic counseling. This is illustrated in this report of two presumed low-penetrant retinoblastoma pedigrees characterized by two distantly affected relatives connected through apparently healthy carriers.

DESIGN

We mathematically modeled the inheritance patterns and calculated the a priori relative probabilities of heredity with low penetrance vs chance occurrence of independent mutations for each pedigree. The derived odds clearly show that the disease, which occurred twice in each family, most likely resulted from unrelated mutations. To prove this, extensive DNA testing was conducted, including determination of intragenic RB1 DNA sequence polymorphisms and screening for mutation using the polymerase chain reaction coupled with single-strand conformation polymorphism analysis.

PATIENTS

All living key members from both pedigrees were included.

RESULTS

Consistent with our initial expectation, there was no common intragenic haplotype or common germ-line mutation that segregated with the disease phenotype in either of these two families.

CONCLUSIONS

We therefore conclude that collateral incidence of retinoblastoma in these two pedigrees occurred by chance and not according to autosomal-dominant inheritance with low penetrance. Furthermore, our data provide the first evidence, to our knowledge, that related individuals may have independent mutations involving an identical gene locus, giving rise to an artefactual inheritance pattern.

Polypeptide variants of beta-arrestin and arrestin3

Retinal arrestin (S-antigen) inactivates the phototransduction cascade by binding to light-activated phosphorylated rhodopsin and thereby "arresting" coupling to the G protein transducin. beta-Arrestin (beta arr), a ubiquitous arrestin homolog, acts analogously to desensitize the beta 2-adrenergic receptor by disrupting Gs receptor interaction. In an attempt to identify additional "arrestins" which might regulate the multitude of G protein-coupled receptors, we have isolated two bovine brain cDNAs which encode polypeptide variants of an arrestin homolog which we have designated arrestin3 (arr3). The open reading frames of these two cDNAs are identical except that the long form, arr3L, contains an 11-amino-acid insert between residues 361 and 362. Arr3 is more closely related to bovine beta arr (78% identity) than to bovine visual arrestin (56% identity). Polymerase chain reaction amplification of RNA and immunoblotting of lysates with an arr3-specific antibody suggest that the short form, arr3S, is the major form of arr3 in all bovine tissues and that it is most abundant in the spleen. Furthermore, polymerase chain reaction amplification of beta arr mRNA indicates that in several tissues (lung, liver, spleen, and pituitary), the major form of beta arr lacks 8 amino acids which are present in brain beta arr. Immunoblotting with an antibody which recognizes beta arr and arr3 with equal sensitivity demonstrates that beta arr (either the long or the short polypeptide) is the major arrestin in all (non-photoreceptor bearing) tissues examined. These observations suggest that in some tissues, as many as four arrestin homolog variants may play a role in the regulation of G protein-coupled receptors.

S-antigen-like protein in porcine ciliary epithelium

A soluble protein with a molecular weight of approximately 52,000 Da (from SDS-polyacrylamide gel electrophoresis) was purified from porcine ciliary body, vitreous body and retina by ammonium sulfate fractionation, Sephacryl S-300 gel filtration, and DEAE-cellulose ion exchange chromatography. The protein has a higher molecular weight than bovine S-antigen which is a highly pathogenic retinal antigen, and was eluted from DEAE-cellulose at a slightly higher NaCl concentration than the concentration at which bovine S-antigen was eluted. By reaction with anti-bovine S-antigen polyclonal antibodies, the porcine protein and bovine S-antigen showed full immunological identity. Using a panel of five monoclonal antibodies (MAbs) directed against epitopes spanning the entire length of bovine S-antigen, the porcine protein was analyzed by the enzyme immunoassay and found to react with all MAbs except one that is specific for a species-specific epitope of bovine S-antigen. Immunocytochemical labeling of porcine ciliary body using all of the MAbs demonstrated that the 52,000-Da protein was primarily localized to the nonpigmented epithelial cells rather than the pigmented epithelial cells. Consistent with this localization, the 52,000-Da protein was synthesized by in vitro translation of mRNA extracted from the nonpigmented cells. When injected into Lewis rats, the porcine protein was found to be far less effective in inducing uveoretinitis than native bovine S-antigen.

Identification of an S-antigen-like molecule in human choroid plexus and cerebrospinal fluid

Sensitisation to retinal S-antigen has been implicated in the pathogenesis of several clinical forms of posterior uveitis. S-antigen-like molecules have recently been demonstrated in the brain and choroid plexus of experimental animals. We used a panel of four monoclonal antibodies (MAbs), MAbF4-C1, MAbC10-C10, MAbA2-G5 and MAbA9-C6, which define specific epitopes in the amino, mid and carboxyl terminal portions of S-antigen in order to identify an S-antigen-like molecule in human choroid plexus and cerebrospinal fluid (CSF). Three MAbs, MAbF4-C1, MAbC10-C10 and MAbA9-C6, localised an S-antigen-like molecule to the cytoplasm of the epithelial cells of the human choroid plexus. Polymerase chain reaction of cDNA from choroid plexus verified the presence of S-antigen homologues in the choroid plexus. The presence of an S-antigen-like molecule in the CSF was demonstrated by western blots in seven CSF samples from patients with a variety of neuropathological disorders. It is proposed that immunological cross-reactivity and biochemical similarity between retinal S-antigen and an S-antigen-like molecule in human choroid plexus and CSF could form a basis for neurological manifestations observed in certain clinical forms of uveitides.

The effect of retinal autoantigens and their peptides on the inhibition of experimental autoimmune uveitis

Experimental autoimmune uveitis is an immune-mediated inflammation of the retina and uveal tract. Such inflammation can be induced in eyes of experimental animals by inoculating them with retinal autoantigens. This animal model of uveitis closely resembles idiopathic uveitis in humans and lends itself ideally for the study of mechanisms involved in the aetiopathogenesis of uveitis and for the evaluation of methods used to control or prevent immune-mediated intraocular inflammation. In this study we used the retinal proteins S-antigen, interphotoreceptor retinoid binding protein and some synthetic peptides of S-antigen to modulate the immune response of Lewis rats. Following immunomodulation these animals did not develop uveitis when challenged with the retinal proteins. The discovery of small, non-pathogenic peptides of retinal antigens that down-regulate the immune response has relevance in developing strategies for immune intervention in human uveitis.

ME491 melanoma-associated glycoprotein family: antigenic identity of ME491, NKI/C-3, neuroglandular antigen (NGA), and CD63 proteins

BACKGROUND

Numerous monoclonal antibodies (MAbs) have been produced to antigens found in human melanomas. Three of the best characterized melanoma antigens include the melanoma-associated glycoproteins (MAGs) defined by two reagent families--the ME491 family (including ME491, 8-1H, and 8-2A) and the NKI/C-3 family (including NKI/C-3 and NKI/black-13)--as well as the neuroglandular antigen (NGA) defined by MAbs LS59, LS62, and LS140. These three antigens have significant similarities in tissue distribution, biosynthesis, and structure. The ME491 MAG has been cloned, mapped, and sequenced. Numerous non-melanoma-associated proteins (Sm23, CO-029, R2, TAPA-1, CD9, CD37, CD53, and CD63) have recently been shown to have significant homology to this sequence.

PURPOSE

We conducted this study to investigate the similarity between the two MAG antigens and NGA.

METHODS

Several reagents defining the three different melanoma antigens were compared, using competition immunoprecipitation, immunoassay, and inhibition radioimmunoassay techniques.

RESULTS

Immunoassay experiments show that MAbs defining the three melanoma antigens bind to affinity-purified ME491 antigen and inhibit each other from binding in an inhibition radioimmunoassay. Competition immunoprecipitation experiments demonstrate that the ME491 and NKI/C-3 antibodies bind to NGA. Rabbit anti-ME491 idiotype serum recognizes determinants shared by NKI/C-3 and the anti-NGA MAbs. A competition immunoprecipitation experiment also confirms the identity of CD63, as defined by MAb RUU-SP 2.28, with the three melanoma antigens.

CONCLUSION

These data indicate that the MAGs defined by ME491 and NKI/C-3 as well as the anti-NGA antibodies are epitopes of the same molecule, which is identical to CD63 by both immunochemical and molecular genetic investigations.

IMPLICATIONS

Our results indicate that the data obtained in studies of these three melanoma antigens may be pooled, and we propose that the molecule recognized by these reagents be classified as CD63.

Transient, cyclic changes in mouse visual cell gene products during the light-dark cycle

Temporal and spatial changes in the cellular and subcellular concentrations of photoreceptor cell gene products appear to be important features of phototransduction in rod photoreceptor cells. The time course of the rapid, light-dependent movement of S-antigen (S-Ag) (48k; Arrestin) from the inner segments to the outer segments was analyzed using polyclonal and monoclonal antibodies. The concentrations of mRNA change about threefold for rhodopsin and about sixfold for S-Ag in cyclic, independent modes during the normal light-dark cycle. Kinetic analysis indicates that the oscillations of S-Ag mRNA levels are due to changes in the transcriptional activity of the gene itself. An experimental model is presented summarizing the relationships between mRNA levels, protein localization, disc shedding, and phototransduction in the photoreceptors cells.