The role of a computed tomography-based image registered navigation system for natural orifice transluminal endoscopic surgery: a comparative study in a porcine model.

BACKGROUND AND STUDY AIMS: Most natural orifice transluminal endoscopic surgery (NOTES) procedures have been performed in animal models through the anterior stomach wall, but this approach does not provide efficient access to all anatomic areas of interest. Moreover, injury of the adjacent structures has been reported when using a blind access. The aim of the current study was to assess the utility of a CT-based (CT: computed tomography) image registered navigation system in identifying safe gastrointestinal access sites for NOTES and identifying intraperitoneal structures. METHODS: A total of 30 access procedures were performed in 30 pigs: anterior gastric wall (n = 10), posterior gastric wall (n = 10), and anterior rectal wall (n = 10). Of these, 15 procedures used image registered guidance (IR-NOTES) and 15 procedures used a blind access (NOTES only). Timed abdominal exploration was performed with identification of 11 organs. The location of the endoscopic tip was tracked using an electromagnetic tracking system and was recorded for each case. Necropsy was performed immediately after the procedure. The primary outcome was the rate of complications; secondary outcome variables were number of organs identified and kinematic measurements. RESULTS: A total of 30 animals weighting a mean (± SD) of 30.2 ± 6.8 kg were included in the study. The incision point was correctly placed in 11 out of 15 animals in each group (73.3 %). The mean peritoneoscopy time and the number of properly identified organs were equivalent in the two groups. There were eight minor complications (26.7 %), two (13.3 %) in the IR-NOTES group and six (40.0 %) in the NOTES only group ( P = n. s.). Characteristics of the endoscope tip path showed a statistically significant improvement in trajectory smoothness of motion for all organs in the IR-NOTES group. CONCLUSION: The image registered system appears to be feasible in NOTES procedures and results from this study suggest that image registered guidance might be useful for supporting navigation with an increased smoothness of motion.

Magnetic resonance for assessment of disease activity and severity in ileocolonic Crohn's disease.

OBJECTIVE: Assessment of disease extension and activity is crucial to guide treatment in Crohn's disease. The objective of the current cross-sectional study was to determine the accuracy of MR for this assessment. DESIGN: 50 patients with clinically active (n = 35) or inactive (n = 15) Crohn's disease underwent ileocolonoscopy (reference standard) and MR. T2-weighted and precontrast and postcontrast-enhanced T1-weighted sequences were acquired. Endoscopic activity was evaluated by CDEIS (Crohn's Disease Endoscopic Index of Severity); in addition endoscopic lesions were classified as absent, mild (inflammation without ulcers) or severe (presence of ulceration). RESULTS: The comparison of intestinal segments with absent, mild and severe inflammation demonstrated a progressive and significant (p<0.001) increase in the following MR parameters: wall thickness, postcontrast wall signal intensity, relative contrast enhancement, presence of oedema, ulcers, pseudopolyps and lymph node enlargement. Independent predictors for CDEIS in a segment were wall thickness (p = 0.007), relative contrast enhancement (p = 0.01), presence of oedema (p = 0.02) and presence of ulcers at MR (p = 0.003). There was a significant correlation (r = 0.82, p<0.001) between the CDEIS of the segment and the MR index calculated according to the logistic regression analysis coefficients. The MR index had a high accuracy for the detection of disease activity (area under the receiver operating characteristic (ROC) curve 0.891, sensitivity 0.81, specificity 0.89) and for the detection of ulcerative lesions (area under the ROC curve 0.978, sensitivity 0.95, specificity 0.91) in the colon and terminal ileum. CONCLUSION: The accuracy of MR for detecting disease activity and assessing severity brings about the possibility of using MR as an alternative to endoscopy in the evaluation of ileocolonic Crohn's disease.

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.

Efectos de los opioides en endocrinología / Opioids effects in endocrinology

El uso de opioides ha aumentado en forma significativa en las últimas décadas, lo que nos ha permitido conocer sus diversos efectos en el sistema endocrino. Estos efectos están sub diagnosticados, en parte porque los síntomas se confunden con los de la misma enfermedad que lleva al uso de opioides y porque no los buscamos de forma dirigida. El hipogonadismo y la insuficiencia suprarrenal son sus efectos más establecidos, sin embargo, otros efectos como los provocados en el tejido óseo requieren de especial atención. La evaluación de los ejes gonadotropo, adrenal y de la salud ósea debe tenerse en consideración en los usuarios crónicos de opioides, particularmente frente a la presencia de síntomas. La suspensión o reducción del uso de opioides es el primer tratamiento del compromiso endocrinológico.

The use of opioids has increased significantly in recent decades, which has allowed us to understand its effects on the endocrine system. These effects are underdiagnosed, the symptoms are confused with those of the same disease that leads to the use of opioids and we do not look for them in a targeted way. Hypogonadism and adrenal insufficiency are its most established effects, however, other effects such as the ones caused on bone tissue require special attention. Evaluation of gonadotropic and adrenal axes as well as bone health should be taken into consideration in chronic opioid users, particularly in the presence of symptoms. Stopping or reducing opioid use is the first treatment for endocrine compromise.

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.

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.

Photodynamic immunopotentiation: in vitro activation of macrophages by treatment of mouse peritoneal cells with haematoporphyrin derivative and light.

Peritoneal macrophages treated in vivo with haematoporphyrin derivative (HPD) exhibited significant enhancement of Fc receptor mediated ingestion activity. To examine this process more rigorously, we studied photodynamic activation of macrophages by exposure in vitro of mouse peritoneal cell cultures (containing macrophages and B and T-lymphocytes) to HPD and red fluorescent light. A short (10 s) exposure of peritoneal cells in medium containing 0.03 ng HPD/ml produced the maximal level of ingestion activity of macrophages. A singlet oxygen quencher, DABCO, inhibited the effect of HPD. Photodynamic treatment of macrophages alone did not activate the cells and activation was only observed when macrophages were mixed with photodynamically treated non-adherent cells (B and T-lymphocytes). These results imply that activation of macrophage is a consequence of peroxidation of lymphocyte membrane lipids by photodynamically generated singlet oxygen.

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.

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.

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.

Tissue distribution and biochemical properties of an ocular melanoma-associated antigen.

A screening method is described to select monoclonal antibodies (Mabs) that bind to ocular melanoma-associated antigens (MAAs) retained in formalin-fixed, paraffin-embedded tissue sections. Small sections of epithelioid or spindle-cell-type uveal melanomas were cut into 2 mm cubes and reembedded in one block. Microslides were cut from this block and used to screen hybridoma supernatant fluid. Using this screening method, three MAbs were selected from two separate fusions of mouse myeloma cells with spleen cells of mice immunized previously with either ocular melanoma cells obtained fresh at enucleation or cells of a cutaneous melanoma cell line. Although all three MAbs showed similar specificities, MAb8-1H showed the strongest immunohistochemical reaction and was studied further in detail. MAb8-1H bound to 91% (71/79) of the choroidal or ciliochoroidal melanomas tested, indicating a high prevalence of this antigen in uveal melanomas. The antigen defined by MAb8-1H was isolated, purified, and partially characterized as a 40,000-50,000 dalton, highly glycosylated protein rich in glycine, serine, and glutamic acid, as is typical of a mucin-type glycoprotein.

Surface and cytoplasmic antigens in retinoblastoma.

Surface and cytoplasmic antigens in retinoblastoma were examined by antisera prepared against two tissue-cultured retinoblastoma cell lines. In addition, several other antisera, including anti-rhodopsin, anti-rod outer segment, anti-large-molecular-weight protein, anti-S, and anti-P antigen, were also utilized in a complement-dependent cytotoxicity assay in order to explore the tumor cell surface. Antisera to tissue-cultured retinoblastoma cell lines were cross-reactive to both cell lines as was rod outer segment antiserum.

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.

Human retinal S-antigen. Isolation, purification, and characterization.

S-antigen, a highly pathogenic agent for the inducation of experimental autoimmune uveitis ( EAU ), was obtained in a pure state from human retina by conventional salt fractionation, molecular sieve and ion exchange chromatography. The physical and chemical properties of the purified protein including the molecular weight, isoelectric point and amino acid composition were determined. The physical properties of the purified human retinal S-antigen were similar, but not identical, to those previously reported for bovine retinal S-antigen (J Immunol 119:1949, 1977). Following the injection of 50 micrograms of human retinal S-antigen into the footpads of guinea pigs, EAU was documented both clinically and histopathologically. The relationship between S-antigen, uveitis, and the pineal gland is discussed.

S-antigen in the developing retina and pineal gland: a monoclonal antibody study.

Spleen cells of BALB/c mice, previously immunized with bovine retinal S-antigen, were fused with Sp2/0-Ag14 mouse myeloma cells. Two monoclonal antibodies (MAbs) MAbA9-C6 (IgG2a isotype) and MAbA1-G5 (IgG1 isotype) were selected on the basis of reactivity in an ELISA and immunofluorescent assay. In radioimmunoassay MAbA9-C6 and MAbA1-G5 do not compete and appear to define unrelated epitopes of S-antigen. Both MAbs reacted in the ELISA assay, whereas only MAbA9-C6 bound to S-antigen in fixed tissue sections. Because MAbA9-C6 was useful for immunocytochemistry, it was studied in more detail. MAbA9-C6 bound to all vertebrate retinas tested including human, bovine, guinea pig, and mice. The immunoreactivity of MAbA9-C6 also was studied in the developing rat retina and pineal gland. In the morphologically undifferentiated retina, assessed by conventional light microscopy, there was an incomplete separation of the outer neuroblastic cells. However, in the same retina a distinct zone, corresponding to S-antigen immunoreactivity, was present indicating antigenic differentiation with regard to S-antigen at this stage of retinal development. In the pineal gland, S-antigen immunoreactivity was first observed in the three day old rat and at all stages examined thereafter. The usefulness of these two MAbs in the study of the embryologic development of the retina and of the antigenic epitopes of S-antigen is discussed.

Retinal S-antigen and retinoblastoma: a monoclonal antibody and flow cytometric study.

Retinal S-antigen was demonstrated in the WERI-Rb1 and to a lesser extent the Y-79 tissue cultured retinoblastoma cell lines as well as an ethanol-fixed, paraffin-embedded retinoblastoma by an indirect immunoperoxidase technique using monoclonal antibody MAbA9-C6, and by flow cytometric analysis (FCM) using MAbA9-C6 and MAbA1-G5. In fixed tissue sections, S-antigen immunoreactivity was restricted and localized to small numbers of retinoblastoma cells, including Flexner-Wintersteiner rosettes. By FCM, MAbA9-C6 bound to 15.4% of WERI-Rb1 cells and to 10.99.7% of Y-79 cells whereas MAbA1-G5 bound to 14.66% of WERI-Rb1 and to 4.23% of Y-79 cells respectively. Cell cycle analysis showed that S-antigen was predominately expressed in the resting (G0/G1) phase. The usefulness of MAbA9-C6 in studying the embryological development of the retina and as a marker protein for studying antigenic expression and modulation in retinoblastomas is discussed.

Comparison of direct and microslide pathology measurements of uveal melanomas.

Many investigators have shown that large cilio-choroidal melanomas are more likely to be associated with an unfavorable outcome than small tumors by using data retrieved and measured from pathology files. In the past, the measurement of largest tumor dimension (LTD) may not have been recorded at the time of the gross examination, because the significance of this observation was not appreciated. If this information is not available, authors can eliminate cases from their studies, take all their measurements directly from glass microslides, or combine clinical estimates of tumor size for some cases with gross measurements for others. To date, there has been no formal study to compare the measurement of tumor dimensions from glass microslides with measurements made at the time of gross examination by the pathologist. This study of 112 cilio-choroidal melanomas reveals that measurements of the LTD made from the glass microslide correlate with direct measurements taken from the cut surface of the globe at the time of sectioning. Additionally, measurements of the LTD from the glass microslide are at least as effective in predicting patient outcome as direct measurements. These findings suggest that measurements of the LTD from the glass microslide provide as much prognostic information as direct measurements if it is known that the eye was cut to obtain representative sections of the tumor.

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.

Identification of the main immunogenic region of retinal S-antigen: subordinate influence of MHC, IGH, species or strain differences on the specificity of the antibody response.

The factors which lead to selection of dominant antigenic sites concentrated in discreet regions of proteins and polypeptides are important to the development of antigen-specific immunotherapies for autoimmune diseases and for vaccine design. In this study, the main immunogenic regions of the immunopathogenic autoantigen, retinal S-antigen, have been identified by examination of the specificity of antibody responses of different species. Using cyanogen bromide and synthetic peptides in western blots and the ELISA, the specificities of antisera from rabbits, guinea pigs, rats and 19 inbred strains of mice were tested. All animals produced high titers of antibody to S-antigen with the exception of PL/J mice. Antibodies which bound epitopes contained in peptide CB46, a 46 amino acid-containing peptide located at the C-terminus of S-antigen, were dominant in all species and strains tested. The epitopes in CB46 were multiple, overlapping, and concentrated in a stretch of approximately 30 residues. Two overlapping synthetic peptides from that region substantially competed the anti-CB46 response of all animals. Antibodies which recognized peptide CB47, a 47 residue peptide from the N-terminus, comprised the next most common group. This epitope was similar in all mice and overlapped the epitope defined by rat antibodies. All anti-CB47 antibodies mapped to an 11 residue region of CB47. Eleven strains of mice did not respond to CB47 after one immunization with S-antigen; however, multiple immunizations readily converted all animals so tested to CB47 responders. Rabbits and guinea pigs exhibited very weak responses to CB47 following one immunization; multiple immunizations increased the response minimally. Rats produced a strong antibody response to peptide CB123, which contains the known uveitogenic sites, while very little activity to CB123 was raised in rabbits and guinea pigs. Only 3 murine strains, LP, LP.R3, and B10.R3-71, responded with antibodies to CB123 and the epitope was mapped to a 30 residue region which in rats also contains two distinct pathogenic sites and an antibody epitope. Only rats and rabbits made antibody to the CB35 peptide; the epitopes were contained within an 18 residue sequence. The results show that a main immunogenic region is located in S-antigen near the C-terminus and is independent of species or MHC. Less dominant, species and strain-dependent immunogenic regions were found in three other areas, i.e. peptides CB47, CB123 and CB35.