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Chi-Chao Chan

Publications and source records attributed to Chi-Chao Chan.

At least 73 records · Page 4Linked to original sources
PubMed2004

Central immunotolerance in transgenic mice expressing a foreign antigen under control of the rhodopsin promoter.

PURPOSE: Different conclusions have been reached in recent studies concerning the immune response or tolerance of transgenic (Tg) mice expressing foreign antigens under control of retinal antigen promoters. The present study was aimed at analyzing the state of tolerance in Tg mice expressing hen egg lysozyme (HEL) under control of the rhodopsin promoter. METHODS: Tg mice expressing HEL under control of the rhodopsin promoter (RhHEL-Tg) were generated and tested by conventional methods for immune responses against HEL. These Tg mice were also mated with Tg mice expressing HEL-specific receptor on their T lymphocytes and the double-Tg mice were examined for increased apoptosis in their thymi by the TUNEL assay, as well as for loss of HEL-specific T cells, by flow cytometry and proliferative response. The presence of HEL mRNA in mouse thymi was determined by RT-PCR. RESULTS: RhHEL-Tg mice developed tolerance to HEL, shown by reduced cellular and humoral responses to HEL, as well as by the failure of ocular inflammation to develop after immunization with HEL. RhHEL-Tg mice expressed HEL mRNA in their thymus, and the tolerogenic mechanism in these mice was shown to be thymic deletion of HEL-specific T cells by the following observations in the double-Tg mice: (1) increased apoptosis in their thymi, (2) remarkable reduction in the proportion of the HEL-specific T cells, and (3) loss of lymphocyte response to low concentrations of HEL. CONCLUSIONS: Tg mice expressing HEL under control of the rhodopsin promoter develop a tolerance for the foreign antigen, apparently as a result of thymic expression of HEL and deletion of T cells specific to this antigen.

Animals↗
PubMed2004

Encapsulated cell-based intraocular delivery of ciliary neurotrophic factor in normal rabbit: dose-dependent effects on ERG and retinal histology.

PURPOSE: ERG and histologic changes were investigated in normal rabbits after intravitreal implantation of encapsulated cell technology (ECT) devices releasing ciliary neurotrophic factor (CNTF). METHODS: Fifteen adult New Zealand White albino rabbits had ECT devices secreting CNTF at 22, 5, or 0 ng/d implanted in the superior temporal quadrant of the left eye. The low dose has been shown to produce substantial rescue of photoreceptors in the rcd1 canine model of retinal degeneration. Right eyes were untreated. Ganzfeld dark- and light-adapted ERGs and clinical observations were performed at 5, 15, and 25 days after implantation. Rod a-waves and rod and cone b-waves and outer nuclear layer (ONL) morphology were evaluated at 25 days. RESULTS: Clinical examination showed minimal changes in a few CNTF-treated eyes, including vitreous membranes and engorgement of iris vessels at day 25. Retinas appeared normal. CNTF did not significantly affect the rod a- or b-waves, although the b-wave amplitude tended to be larger in CNTF-treated retinas at low flash intensities. The cone b-wave amplitude was significantly reduced in high-dose eyes at some flash intensities. The ONL area in high-dose eyes was significantly greater because of increased thickness than in fellow retinas. ONL cell size was significantly increased, and staining density decreased in CNTF-treated retinas. CONCLUSIONS: CNTF, given by intravitreal ECT device at doses that protect photoreceptors in a canine model of retinal degeneration (5 ng/d), did not adversely affect either rod or cone ERG function of normal rabbit retina. The cone ERG was more sensitive to suppression being reduced, at low flash intensities, by 22 ng/d. Dose-related changes in the ONL and photoreceptor cell nuclei did not represent a toxic effect, because they were not associated with deficits in the rod ERG over a broad range of intensities.

Animals↗
PubMed2004

Von Hippel-Lindau gene deletion and expression of hypoxia-inducible factor and ubiquitin in optic nerve hemangioma.

PURPOSE: Von Hippel-Lindau (VHL) disease is a hereditary cancer syndrome expressed in multiple organs caused by germline alterations of the VHL gene. We have shown VHL deletion in the "stromal" cells of retinal angiomas. The VHL protein-associated complex is a primary ubiquitin ligase for the ubiquitination of hypoxia-inducible factor (HIF). This study examines VHL and ubiquitin expression in optic nerve hemangiomas and juxtapapillary angiomas. METHODS: Using microdissection and polymerase chain reaction, four optic nerve hemangiomas (one also had juxtapapillary angioma) associated with VHL disease were analyzed for loss of heterozygosity in the VHL gene. In addition, expression of HIF and ubiquitin was evaluated in these tumors by immunohistochemistry. RESULTS: All informative optic nerve and juxtapapillary lesions showed loss of heterozygosity in the VHL gene detected in vacuolated "stromal" cells. Both HIF and ubiquitin were highly expressed in the hemangiomas of all four VHL cases. CONCLUSIONS: Like retinal angiomas and other VHL tumor lesions, VHL gene deletion is found in optic nerve hemangiomas and juxtapapillary angiomas. These tumor cells also express HIF and ubiquitin, the protein responsible for the negative regulation of HIF that results in the hypervascularization characteristic of VHL disease.

Adolescent↗
PubMed2003

An immunologically privileged retinal antigen elicits tolerance: major role for central selection mechanisms.

Immunologically privileged retinal antigens can serve as targets of experimental autoimmune uveitis (EAU), a model for human uveitis. The tolerance status of susceptible strains, whose target antigen is not expressed in the thymus at detectable levels, is unclear. Here, we address this issue directly by analyzing the consequences of genetic deficiency versus sufficiency of a uveitogenic retinal antigen, interphotoreceptor retinoid-binding protein (IRBP). IRBP-knockout (KO) and wild-type (WT) mice on a highly EAU-susceptible background were challenged with IRBP. The KO mice had greatly elevated responses to IRBP, an altered recognition of IRBP epitopes, and their primed T cells induced exacerbated disease in WT recipients. Ultrasensitive immunohistochemical staining visualized sparse IRBP-positive cells, undetectable by conventional assays, in thymi of WT (but not of KO) mice. IRBP message was PCR amplified from these cells after microdissection. Thymus transplantation between KO and WT hosts demonstrated that this level of expression is functionally relevant and sets the threshold of immune (and autoimmune) reactivity. Namely, KO recipients of WT thymi generated reduced IRBP-specific responses, and WT recipients of KO thymi developed enhanced responses and a highly exacerbated disease. Repertoire culling and thymus-dependent CD25+ T cells were implicated in this effect. Thus, uveitis-susceptible individuals display a detectable and functionally significant tolerance to their target antigen, in which central mechanisms play a prominent role.

Animals↗
PubMed2003

Dissociating the enhancing and inhibitory effects of pertussis toxin on autoimmune disease.

Pertussis toxin (PT) has both enhancing and inhibitory effects on experimental autoimmune disease, depending on its time of administration relative to immunization. The inhibitory effect is due to blocking of G(i)-coupled receptors by the enzymatic A subunit. In this study, we attribute the enhancing effect of PT to the cell-binding B subunit (PT-B). C57BL/6 mice, a strain that requires PT to develop experimental uveitis, were immunized with a retinal Ag and were injected with whole PT, PT-B, or vehicle. Disease and associated immunological responses were evaluated. The results showed that PT-B, determined to be free of biologically significant contamination with whole PT or with endotoxin, was able to mimic all the effects of PT with respect to disease induction, enhancement of delayed-type hypersensitivity, enhancement of lymphocyte proliferation, induction of an innate IL-12 response, and promotion of an adaptive IFN-gamma response to the uveitogenic Ag. Our results suggest that PT-B is largely responsible for the disease-enhancing properties of PT.

Adjuvants, Immunologic↗
PubMed2003

Detection of histoplasma capsulatum DNA in lesions of chronic ocular histoplasmosis syndrome.

OBJECTIVE: To evaluate choroidal lesions in histological sections from the enucleated eye of a patient with chronic ocular histoplasmosis syndrome for the presence of Histoplasma capsulatum DNA. METHODS: Laser-capture microdissection was used to procure cells from macular and midperipheral choroidal lesions in a deparaffinized hematoxylin-eosin-stained section prepared from the enucleated left eye of a patient with an ipsilateral choroidal melanoma and bilateral chronic histoplasmosis syndrome. The captured cells were initially subjected to polymerase chain reaction (PCR) amplification using a pair of primers unique to each end of the nucleotide sequences that are complementary to the DNA known to flank the internal transcribed spacer regions of the ribosomal RNA genes of H capsulatum. This product was then reamplified using a second set of internally situated nested primers. The results were compared with a positive control sample of H capsulatum DNA and with a negative microdissected sample from noninflamed choroid in the same slide. RESULTS: Products of H capsulatum DNA were identified in both samples of microdissected tissue and the positive control. They were absent in the negative control. CONCLUSION: The observations provide molecular biological evidence linking the chronic choroidal lesions to earlier infection by H capsulatum.

Choroid↗
PubMed2003

Effects of aldose reductase inhibitors and galactose withdrawal on fluorescein angiographic lesions in galactose-fed dogs.

OBJECTIVE: To assess the effect of aldose reductase inhibitor (ARI) M79175 (2-methyl-6-fluoro-spiro-chroman-4-5'-imidazolidine-2',4'-dione) administration and galactose withdrawal on the progression of retinal changes using fluorescein angiography in galactose-fed dogs. METHODS: Thirty male beagles were randomized into 4 groups. Three dogs were fed a normal control diet containing 30% nonnutritive fiber for 74 months (control group), 11 dogs a 30% galactose diet for 74 months (continuous galactose group), 8 dogs a 30% galactose diet for 36 months followed by replacement with a normal diet for 36 months (galactose withdrawal group), and 8 dogs a 30% galactose diet supplemented with M79175 for 34 months followed by replacement with a normal diet and removal of M79175 treatment for 38 months (ARI-treated galactose withdrawal group). Stereoscopic color fundus photography and fluorescein angiography, performed at baseline and follow-up, were assessed for the clinical development of retinopathy, including the first appearance of hyperfluorescence, varying severity of retinal nonperfusion, and retinal neovascularization. Histopathologic features were examined in selected dogs. RESULTS: All dogs in the 3 groups fed the 30% galactose diet developed areas of hyperfluorescence and nonperfusion. Of these dogs, only those supplemented with the ARI did not develop areas of nonperfusion greater than or equal to half the field and retinal neovascularization. Parametric survival analysis showed significant differences (galactose withdrawal group vs ARI-treated galactose withdrawal group) in the median times to the development of nonperfusion greater than or equal to half the field (P =.003) and retinal neovascularization (P =.03). CONCLUSION: Normalization of glycemic control with galactose withdrawal and ARI treatment may delay the onset and progression of retinal lesions in galactose-fed dogs. Clinical Relevance Perfect glycemic control after a period of poor control does not completely prevent the progression of retinal lesions. Therapy with ARIs may potentially be important in the prevention of retinal lesions associated with diabetic eye disease.

Aldehyde Reductase↗
PubMed2003

Interphotoreceptor retinoid-binding protein (IRBP)-deficient C57BL/6 mice have enhanced immunological and immunopathogenic responses to IRBP and an altered recognition of IRBP epitopes.

Experimental autoimmune uveitis (EAU) and pinealitis (EAP) can be induced in susceptible mice by immunization with immunologically privileged retinal antigens. In the present study, we analyzed the immunologic and immunopathologic responses of mice deficient in the retinal autoantigen interphotoreceptor retinoid-binding protein (IRBP). The consequences of IRBP deficiency on the T-cell repertoire were also investigated. IRBP+/+, IRBP+/- and IRBP-/- mice on the C57BL/6 background were immunized with IRBP or with a pathogenic epitope, IRBP(1-20) peptide in adjuvant, and were evaluated for disease severity and immunological responses. C57BL/6 IRBP-/- mice were completely resistant to EAU and EAP, and had enhanced immunological responses to IRBP and to its pathogenic peptide 1-20, as compared to their IRBP+/+ counterparts. IRBP-/- mice exhibited an altered IRBP epitope recognition. T cell epitope mapping revealed a response to IRBP peptide 271-290 in IRBP-/- mice, that was absent in the wild type. Primed T cells of IRBP-/- mice transferred an exacerbated form of EAU to nai;ve wild type recipients. A gene-dose effect was evident in that C57BL/6 IRBP+/- mice, exhibited intermediate immunological responses and lower disease scores compared to wild type. We conclude that expression of IRBP in target tissues is a necessary prerequisite for disease induction, excluding other retinoid-binding or vision-related proteins as surrogate targets. Furthermore, endogenous expression of IRBP is directly responsible for lowering the threshold of susceptibility to uveitic disease.

Adoptive Transfer↗
PubMed2003

Histopathology and regression of retinal hard exudates in diabetic retinopathy after reduction of elevated serum lipid levels.

PURPOSE: To describe a regression of retinal hard exudates in 2 patients with diabetic maculopathy, and to report immunohistologic findings reflecting lipid deposition in the retina. DESIGN: Two interventional case reports. METHODS: Two patients with exudative diabetic maculopathy were treated to normalize serum lipids. Histologic examination and immunohistochemistry of each patient's eyes were performed to assess the localization of apolipoprotein B and cholesteryl ester, both of which are principal components of low-density lipoprotein. RESULTS: Both patients showed a dramatic regression of retinal hard exudates after correction of dyslipidemia. Histopathology revealed diffuse lipids and cholesteryl ester in the retina. Apolipoprotein B and macrophages were colocalized in the perivascular space. CONCLUSIONS: The regression of hard exudates was most likely due to the aggressive lipid lowering in both patients. The novel histopathologic findings of hard exudate and diabetic maculopathy are similar to the pathologic changes observed in larger atherosclerotic lesions, except that they occur in the intraretinal perivascular space.

Adult↗
PubMed2003

Expression of chemokine receptors, CXCR4 and CXCR5, and chemokines, BLC and SDF-1, in the eyes of patients with primary intraocular lymphoma.

OBJECTIVE: Chemokines have a range of biologic activities, including regulation of leukocyte trafficking, modulation of hematopoietic cell proliferation, and adhesion to extracellular matrix molecules. Specifically, B-lymphocyte chemoattractant (BLC); BCA-1; CXCL13, SCYB13) and stromal cell-derived factor-1 (SDF-1, CXCL12, SCYB12) are chemotactic for human B cells, and their ligands CXCR4 and CXCR5 are differentially expressed on B cells, including malignant B cells. We investigated the expression of these chemokine/chemokine receptors in eyes with primary intraocular B-cell lymphoma (PIOL). DESIGN: Observational case series (human tissue study). METHODS: Three freshly enucleated eyes with PIOL and a normal autopsied eye were frozen and sectioned. The sections were evaluated using immunohistochemistry (avidin-biotin-complex immunoperoxidase technique) for CXCR4, CXCR5, BLC, and SDF-1 to detect the expression and location. Reverse transcriptase-polymerase chain reaction was used to detect chemokine transcripts of CXCR4, CXCR5, BLC, and SDF-1 in PIOL and retinal pigment epithelium (RPE) cells after microdissection-either by laser capture (Arcturus) or by manual dissection-from frozen sections. MAIN OUTCOME MEASURES AND RESULTS: The three PIOL eyes showed similar pathology, with typical diffuse large B-lymphoma cells subjacent to the RPE. The eyes also demonstrated a similar chemokine profile. High expression levels of CXCR4 and CXCR5 were found limited to the lymphoma cells. In contrast, BLC protein was expressed in the RPE but not located in other ocular resident cells. SDF-1 was barely detected in a few RPE cells. CXCR4 and CXCR5 transcripts were detected abundantly in lymphoma cells, whereas BLC and SDF-1 transcripts were detected only in the RPE and not the malignant cells. No chemokine expression was detected on the RPE cells in the normal control eye. CONCLUSIONS: Chemokines and chemokine receptors selective for B cells were identified in RPE and malignant B cells, respectively. BLC, and possibly SDF-1, attracts both normal and malignant B-cells while promoting migration of only small numbers of T cells and macrophages. We propose that B-cell chemokines may be involved in the pathogenesis of PIOL by selectively attracting lymphoma cells to the RPE from the choroidal circulation. Our data suggest that inhibition of B-cell chemoattractants could be a future strategy for the treatment of PIOL.

B-Lymphocytes↗
PubMed2003

Resting CD8 T cells recognize beta-galactosidase expressed in the immune-privileged retina and mediate autoimmune disease when activated.

Although the expression of class II major histocompatibility complex (MHC) in retina is extremely low, it is an established fact that activated CD4 T cells, specific for retinal antigens (Ags), mediate experimental autoimmune uveoretinitis (EAU). Conversely, CD8 T cells have not been shown to recognize Ag in the retina. This study investigated whether retinal-specific Ags are detected by class I MHC-restricted CD8 T cells. Using a CD8 T-cell clone (beta3) specific for an immunodominant epitope of beta-galactosidase (beta-gal), local Ag recognition was shown by transfer of activated beta3 cells into beta-gal transgenic (Tg) mice expressing beta-gal in the retina (hi-arr-beta-gal mice), or in the brain and eye (GFAP-beta-gal mice). Beta-gal-positive photoreceptor cells were damaged in the retina of hi-arr-beta-gal mice, and anterior segment disease was found in the eyes of GFAP-beta-gal mice. Ag recognition by resting CD8 T cells was also evaluated. Recovery of 5(6)-carboxyfluorescein diacetate N-succinimidyl ester (CFSE)-labelled beta3 cells from hi-arr-beta-gal mice was slightly decreased compared to recovery from B10.A mice, while recovery from GFAP-beta-gal mice was transiently increased. Conversely, recovery of CFSE- cells increased in hi-arr-beta-gal mice, consistent with an Ag-dependent response. The CFSE content of the CFSE+ population was unchanged relative to beta3 cells recovered from controls. Intracellular cytokine responses of beta3 cells recovered from hi-arr-beta-gal and GFAP-beta-gal mice correlated with the number of cells recovered, regardless of CFSE content. Even though their production of interferon-gamma and tumour necrosis factor-alpha was affected little by transfer into hi-arr-beta-gal recipients, the ability of beta3 cells to mediate delayed-type hypersensitivity was inhibited in hi-arr-beta-gal mice. These results show that resting CD8 T cells are affected by the presence of Ag that originates in retina and, when activated prior to transfer, mediate pathogenic autoimmunity against retinal and other ocular targets.

Adoptive Transfer↗
PubMed2003

Effect of sex hormones on experimental autoimmune uveoretinitis (EAU).

PURPOSE: Sex hormones have been associated with the prevalence, susceptibility, and severity of autoimmune disease. Although the exact mechanism is unknown, sex hormones are reported to influence cytokine production, specifically by affecting the balance of Th1 and Th2 effector cells. We evaluated the effect of estrogen, progesterone, and testosterone in autoimmune uveoretinitis (EAU), a rodent model of human ocular autoimmune disease. METHODS: Lewis rats implanted with either beta-estradiol (estrogen), 5-dihydrotestosterone (5-DHT), norgestrel (progesterone), or estrogen plus progesterone were immunized with the retinal antigen interphotoreceptor retinoid binding protein (IRBP) peptide. Evaluation of EAU was based on histology of the eyes and measurement of peripheral immunological responses of DTH and lymphocyte proliferation to S-antigen. Quantitative RT-PCR was used to measure IFN-gamma and IL-10 mRNA in the eyes. RESULTS: In female rats 5-DHT significantly decreased, estrogen slightly enhanced, but progesterone or estrogen + progesterone did not affect EAU. In contrast, in male rats 5-DHT slightly decreased, estrogen moderately decreased, progesterone did not effect, but, estrogen + progesterone slightly decreased EAU. The results correlated with the ocular levels of Th1 (IFN-gamma) and Th2 (IL-10) cytokine messengers. CONCLUSION: The data support the hypothesis that sex hormones may affect autoimmune diseases by inducing changes in the cytokine balance. This suggests that sex hormone therapy could be considered as an adjunct to anti-inflammatory agents to treat ocular autoimmune diseases in humans.

Animals↗
PubMed2003

Tgf-beta inhibits activation and uveitogenicity of primary but not of fully polarized retinal antigen-specific memory-effector T cells.

PURPOSE: TGF-beta exerts suppressive effects on immunity, but its potential applications in therapy of ocular autoimmunity have not been widely explored. In the present study, the effects of TGF-beta on uveitogenic T cells were examined. METHODS: The effects of TGF-beta on newly primed cells from mice given a uveitogenic regimen of interphotoreceptor retinoid-binding protein (IRBP) were compared with the effects on fully polarized Th1 cells from a long-term uveitogenic T-cell line. The parameters measured were T-cell proliferation, IFN-gamma production, induction of IL-12R expression, triggering of pathogenicity, and expression of costimulatory molecules on antigen-presenting cells (APCs) during in vitro exposure to antigen. RESULTS: TGF-beta suppressed B7.1 expression on APCs in cultures of lymph node cells from immunized mice. It also suppressed T-cell proliferation, IFN-gamma production, IL-12 receptor accumulation, and the IL-12-promoted acquisition of uveitogenic function. In contrast, the polarized Th1 cells were either resistant to suppression or were enhanced by TGF-beta. CONCLUSIONS: The results suggest that TGF-beta suppresses acquisition of effector functions by autopathogenic T cells, in part by interfering with their response to IL-12 through downregulation of IL-12R expression and in part through inhibition of APC function. The data suggest that although TGF-beta may effectively inhibit activation and recruitment of new T cells into the effector pool, it may be less effective in suppressing the reactivation of already polarized memory T cells that are less dependent on IL-12 and costimulation.

Animals↗
PubMed2003

A humanized model of experimental autoimmune uveitis in HLA class II transgenic mice.

Experimental autoimmune uveitis (EAU) is a disease of the neural retina induced by immunization with retinal antigens, such as interphotoreceptor retinoid-binding protein (IRBP) and arrestin (retinal soluble antigen, S-Ag). EAU serves as a model for human autoimmune uveitic diseases associated with major histocompatibility complex (HLA) genes, in which patients exhibit immunological responses to retinal antigens. Here we report the development of a humanized EAU model in HLA transgenic (TG) mice. HLA-DR3, -DR4, -DQ6, and -DQ8 TG mice were susceptible to IRBP-induced EAU. Importantly, HLA-DR3 TG mice developed severe EAU with S-Ag, to which wild-type mice are highly resistant. Lymphocyte proliferation was blocked by anti-HLA antibodies, confirming that antigen is functionally presented by the human MHC molecules. Disease could be transferred by immune cells with a Th1-like cytokine profile. Antigen-specific T cell repertoire, as manifested by responses to overlapping peptides derived from S-Ag or IRBP, differed from that of wild-type mice. Interestingly, DR3 TG mice, but not wild-type mice, recognized an immunodominant S-Ag epitope between residues 291 and 310 that overlaps with a region of S-Ag recognized by uveitis patients. Thus, EAU in HLA TG mice offers a new model of uveitis that should represent human disease more faithfully than currently existing models.

Amino Acid Sequence↗