Biomedical subjects

J T Ernest

Publications and source records attributed to J T Ernest.

At least 19 recordsLinked to original sources

PubMed2002

Visual acuity outcomes following vitreous loss in glaucoma and diabetic patients.

PURPOSE: To analyze the visual acuity (VA) of patients with and without vitreous loss, while concurrently analyzing the effects of the pre-existing pathologies of glaucoma and diabetes on VA. METHODS: A retrospective study on 1013 cataract extractions from 1995 to 1999 was performed. Patients included in this study had intraocular lens implantation during phacoemulsification surgery, no intraoperative complications besides vitreous loss, had no other prior ophthalmic condition other than glaucoma or diabetes, and had a postoperative follow-up interval between one and 4 months. When indicated, vitrectomy was performed concurrently with phacoemulsification following vitreous loss. Patients diagnosed with both glaucoma and diabetes were excluded. The identified subjects were then placed into six groups: (1) patients with uncomplicated surgery; (2) patients with surgery complicated by vitreous loss; (3) glaucoma patients with uncomplicated surgery; (4) glaucoma patients with surgery complicated by vitreous loss; (5) diabetic patients with uncomplicated surgery; and (6) diabetic patients with surgery complicated by vitreous loss. A two-tailed, heteroscedastic t-test and power calculation were performed on the preoperative and postoperative visual acuities of the groups. RESULTS: There were statistically significant differences (P < 0.05) in the postoperative VA between patients with and without vitreous loss at the time of surgery. Patients with the pre-surgical conditions of diabetes or glaucoma did not display a statistically significant difference in postoperative VA when compared to controls. However, the pre-surgical condition of glaucoma displayed a trend, which showed it may contribute to a poorer postoperative VA (P = 0.072, power = 0.430). CONCLUSIONS: Vitreous loss is a risk factor for a decreased postoperative VA. Also while the pre-surgical condition of glaucoma may play a role in decreasing postoperative VA, diabetes does not.

Adult↗

PubMed2000

A model for xenogenic immune response.

PURPOSE: To develop a model for analyzing the immune response after xenogenic human fetal retinal pigment epithelium (HFRPE) transplantation. MATERIALS AND METHODS: Pure sheets of HFRPE cells were isolated and attached to poly (DL-lactide-co-glycolide) polymer films and HFRPE spheroids were formed. The spheroids were transplanted into the subretinal space of New Zealand albino rabbits and were observed for 5 months. Bare polymer films were transplanted into the subretinal space of Dutch Belted pigmented rabbits, serving as control. RESULTS: The polymer film was biodegraded within 3 weeks in the subretinal space. No signs of inflammation in the retina or choroid were observed. The HFRPE spheroids were easily transplanted into the subretinal space. The immune response was followed with ophthalmoscopy. Light microscopy indicated a localized immune response in the transplanted area in which the retina and the choroid were infiltrated with immune cells. This infiltration was denser in the choroid. CONCLUSIONS: HFRPE spheroid transplantation may be utilized as a model for studying the xenogenic immune response after HFRPE transplantation. This model may also have applications in evaluating the role of immune suppressive agents in preventing rejection after HFRPE transplantation.

Absorbable Implants↗

PubMed2000

Human fetal retinal pigment epithelium-induced cell cycle arrest, loss of mitochondrial membrane potential and apoptosis.

PURPOSE: To investigate the mechanism of action of the soluble immune suppressive product secreted by human fetal retinal pigment epithelial (HFRPE) cells in a model system using the human T-cell line Jurkat (Jkt). METHODS: Pure HFRPE cells were isolated and cultured. The supernatants of both nonactivated and IFN-gamma-activated HFRPE cells were isolated. Cells from the human T-cell line Jkt were incubated either in standard culture medium or in the supernatant isolated from HFRPE cells. In the first assay Jkt cell proliferation was measured by [(3)H]thymidine incorporation. In the second assay Jkt cell apoptosis was examined for annexin V staining by flow cytometry. In the third assay Jkt cell division was evaluated with carboxyfluorescein succinimidyl ester (CFSE) fluorescent dye. In the last assay the mitochondrial transmembrane potential of Jkt cells was measured with the cationic lipophilic fluorochrome 3,3'-dihexyloxacarbocyanine iodide [DiOC(6)]. In all the assays the effect of supernatants isolated from both nonactivated and IFN-gamma-activated HFRPE cells were compared with standard culture medium. The involvement of antiapoptotic human gene bcl-x(L:)was determined by using a Jkt cell line that was stably transfected with bcl-x(L:). RESULTS: The supernatant isolated from HFRPE cells significantly suppressed the cell division in Jkt cells and induced apoptosis. These effects were stronger when the supernatant was isolated from IFN-gamma-activated HFRPE cells. The apoptosis pathway induced by the secreted product of HFRPE cells involved the early disruption of mitochondrial transmembrane potential. Although the overexpression of bcl-x(L) gene rescued the Jkt cells from supernatant-induced apoptosis, it could not restore the proliferation of Jkt cells. CONCLUSIONS: These data suggest that HFRPE cells secrete a product that initiates an early cell cycle arrest in the human T-cell line Jkt, which is followed by the activation of an apoptotic pathway that involves the loss of mitochondrial membrane potential. The latter could be prevented by bcl-x(L) overexpression. Also these data suggest that the HFRPE-induced T-cell apoptosis may play a significant role in maintaining the immune privilege in the subretinal space.

Annexin A5↗

PubMed1999

A new model of retinal pigment epithelium transplantation with microspheres.

OBJECTIVES: To develop a 3-dimensional carrier system for subretinal transplantation of human fetal retinal pigment epithelial (HFRPE) cells and to assess their growth pattern in the rabbit subretinal space. METHODS: After a standard 3-port vitrectomy, HFRPE cells grown as microspheres on cross-linked fibrinogen were introduced into the subretinal space of rabbits. The eyes were studied at 7, 14, and 30 days after surgery by ophthalmoscopy and light microscopy. RESULTS: Ophthalmoscopically, at day 7, 11 (61%) of the 18 eyes showed radiating hyperpigmentation around the transplanted HFRPE microspheres. The results of a histological examination revealed a monolayer outgrowth of HFRPE cells, overlying host retinal pigment epithelium. The control eyes revealed a patch of chorioretinal atrophy with lymphocytic infiltration around the microspheres. CONCLUSIONS: Human fetal retinal pigment epithelial cells grown as microspheres on cross-linked fibrinogen can be successfully transplanted into the subretinal space. Cells can survive for at least 1 month and form a monolayer over the host retinal pigment epithelium cells, with a mild local inflammatory response. The difference in inflammatory responses between the eyes that underwent transplantation and the control eyes may suggest a modulating effect of the HFRPE cells on inflammation, immunity, or both. This new xenogenic model may have importance in the study of subretinal transplant cell biology and the associated immune response. CLINICAL RELEVANCE: The results of this study may be important for better understanding of the mechanisms of retinal pigment epithelium cell behavior after transplantation. The proposed model may be applicable for future clinical and experimental investigations in the area of retinal pigment epithelium transplantation.

Animals↗

PubMed1999

Growth of human fetal retinal pigment epithelium as microspheres.

BACKGROUND: The aim was to develop a three-dimensional cell culture system for human fetal retinal pigment epithelial (HFRPE) cells for in vitro cellular studies and for possible application in subretinal transplantation. METHODS: Pieces of freshly isolated HFRPE monolayer tissue were grown on crosslinked fibrinogen (CLF) films. The growth pattern and morphologic characteristics of the implanted tissue were studied using phase-contrast microscopy, photography, and light and electron microscopy. The cells were screened immunohistochemically for HLA-ABC, HLA-DR, ICAM-1, B7, and Cytokeratin. Cell proliferation was studied using 5-bromo-2-deoxyuridine incorporation. RESULTS: After attachment to CLF, HFRPE monolayer tissue formed small tumor-like formations, i.e. microspheres. HFRPE microspheres survived and proliferated in a floating state for at least 4 months. After attachment of the microspheres to the culture dish floor, formation of a confluent HFRPE cell monolayer with high proliferative activity was noted around the microspheres. HFRPE cells stained positive for HLA-ABC, ICAM-1, and cytokeratin and negative for B7 and HLA-DR. The microspheres could be easily detached from the dish and they were able to initiate similar growth after reattachment. CONCLUSION: HFRPE grown on CLF resemble a three-dimensional culture system with high yield of pure cells that can be useful for a wide variety of in vitro studies. Because of their adjustable size, spherical shape, and ability to initiate growth of cells with a high proliferative potential, HFRPE microspheres may be successfully utilized as a source of donor cells for subretinal transplantation.

B7-1 Antigen↗

PubMed1999

Cellular response in rabbit eyes after human fetal RPE cell transplantation.

BACKGROUND: This study was carried out to study inflammatory and proliferative cellular responses in the rabbit eye after subretinal transplantation of human fetal retinal pigment epithelial (HFRPE) cells. METHODS: 5-Bromo-2-deoxyuridine (BrdU)-labeled HFRPE cells were injected subretinally into rabbit eyes at three different concentrations. Macrophage, glial, and proliferative responses of the eye tissues were studied by immunohistochemistry and light microscopy at different times after the surgery. RESULTS: In transplanted eyes, the HFRPE cells were distributed irregularly either as multilayers or monolayers. In eyes receiving high-density cell suspensions, retinal breaks were seen. No retinal breaks were noted in the eyes receiving low-density HFRPE cell suspensions. The highest intensity of inflammatory response was seen at 4-14 days after surgery, with greater expression in transplanted eyes receiving high-density cell suspensions. The host cellular response was characterized initially by local infiltration of the retina and subretinal space by macrophages and glial cells. After day 14, a decline in the number of donor cells was noted in all eyes. At later stages the host cellular response was characterized mainly by local choroidal thickening and infiltration by inflammatory cells. Proliferative response was expressed mainly by retinal cells. CONCLUSION: Initial inflammatory and proliferative responses after the xenogenic human to rabbit HFRPE cell transplantation were expressed by retinal cells with later involvement of the choroid. Our results showed a decline in the number of donor cells starting from day 14 after the transplantation. This may suggest a possibility of rejection. The initial quantity of injected cells may be critical for the intensity of the immune and inflammatory responses.

Animals↗

PubMed1999

Human fetal retinal pigment epithelium suppresses the activation of CD4(+) and CD8(+) T-cells.

BACKGROUND: The suppressive effect of human fetal retinal pigment epithelium (HFRPE) on the activation of human CD4(+) and CD8(+) T-cells was evaluated in vitro. METHODS: Pure populations of CD4(+) and CD8(+) T-cells were isolated from human peripheral blood-derived buffy coats by negative immunomagnetic selection. The purity of the cells was examined by flow cytometry using anti-CD3-FITC, anti-CD4-FITC, anti-CD8-PE, and anti-CD20-PE mAbs. HFRPE cells were isolated from fetal eyes and pure cultures were obtained. The effect of normal or IFN-gamma-activated HFRPE cells at early (P3) or late (P6) passages on the activation of CD4(+) and CD8(+) T-cells was assessed in two different T-cell activation assays. In both activation models anti-CD3 mAb (OKT3) provided the antigen-specific signal. The secondary signal for the activation of CD4(+) and CD8(+) T-cells was provided with anti-CD18 mAb (TS1/18) and anti-CD28 mAb (9.3) in the first and the second assay respectively. Cross-linking of these soluble mAbs was performed with sheep-anti-mouse IgG-coated latex beads. The T-cell activation was determined by cell proliferation measured by [(3)H]thymidine incorporation. In each activation assay T-cells were incubated with HFRPE cells in a ratio of T-cells to HFRPE of 1:1 or 1:4. RESULTS: CD4(+) and CD8(+) T-cells were activated by cross-linking CD3 and CD18 in the first assay (CD3/CD18) and CD3 and CD28 in the second assay (CD3/CD28). In both assays HFRPE inhibited the activation of CD4(+) and CD8(+) T-cells. IFN-gamma-activated HFRPE cells totally suppressed the T-cell activation at a 1:1 ratio. This suppressive effect was weaker at lower cell ratios. Some donor variation was observed in the inhibition at the lower cell ratios, especially for the inhibition of CD8(+) T-cell activation with anti-CD3/CD18. The passaging of HFRPE cells did not alter their suppressive effect on CD4(+) and CD8(+) T-cells. CONCLUSIONS: HFRPE cells suppressed the activation of both CD4(+) and CD8(+) T-cells in vitro. These findings suggest that RPE-induced immune suppression may play a significant role in maintaining immune privilege in the subretinal space.

Antibodies, Monoclonal↗

PubMed1999

Human fetal retinal pigment epithelial cells induce apoptosis in allogenic T-cells in a Fas ligand and PGE2 independent pathway.

PURPOSE: To evaluate the inhibitory effect of human fetal retinal pigment epithelium (HFRPE) on the activation of human T-cells. METHODS: Pure cultures of HFRPE cells were incubated with purified human T-cells in three different activation assays: 1) allogenic peripheral blood mononuclear cells; 2) OKT3 coated beads in the presence of accessory cells; and 3) stimulation with phorbol ester and phytohemagglutinin. RESULTS: HFRPE cells suppressed the activation of T-cells in all three assays. The mechanism of HFRPE mediated T-cell suppression was apoptosis. The role of Fas ligand(FasL)/Fas-mediated T-cell suppression was excluded, since FasL protein or mRNA could not be detected on HFRPE cells with flow cytometry and by reverse transcriptase polymerase chain reaction, respectively. Additionally, the inhibitory effect of HFRPE cells could not be blocked by anti-Fas ligand or antagonistic anti-Fas antibodies. Moreover, HFRPE cells suppressed the proliferation of anti-CD3 mAb mediated T-cell proliferation of murine splenocytes isolated from lpr mice. The inhibitory effect of HFRPE cells was not PGE2 mediated, since indomethacin could not restore the T-cell activation. Although the HFRPE mediated T-cell apoptosis was cell-cell contact independent, it was not induced by secretion of TNF-alpha, TGF-beta, or IL-10. The ratio between HFRPE and T-cells had a major impact on the HFRPE's inhibitory effect. CONCLUSIONS: HFRPE cells suppressed the activation of human T-cells by induction of T-cell apoptosis through a process that involves the secretion of soluble factors. The HFRPE mediated T-cell suppression was dependent on the ratio between HFRPE and T-cells. This undefined pathway of T-cell apoptosis may play a role in the maintenance of immune privilege in the subretinal space and may reduce the severity of the immune response after HFRPE transplantation.

Animals↗

PubMed1999

Cryoprecipitate: An autologous substrate for human fetal retinal pigment epithelium.

PURPOSE: To harvest thin membranes from cryoprecipitates isolated from human blood donors and utilize them as substrates for the adhesion of human fetal retinal pigment epithelial (HFRPE) cells. METHODS: Frozen human cryoprecipitates from anonymous blood donors were obtained from the blood bank. Thin cryo-membranes were harvested by their mixture with riboflavin-5-phosphate (R5P) and overnight exposure to ultra-violet light. Sheets of retinal pigment epithelium (RPE) were isolated from fetal eyes at 17-22 weeks gestational age. The sheets were subsequently attached to cryo-membranes. The morphology of the cells was examined with phase contrast and electron microscope. Cell proliferation was evaluated by their incorporation of 5-bromo-2'-deoxyuridine (BrdU). Functional viability was assessed by rod outer segment (ROS) phagocytosis. RESULTS: Thin membrane films were made from isolated human cryoprecipitates. Isolated sheets of pure HFRPE cells were attached to the membranes. The cells maintained their cuboidal morphology and did not dedifferentiate. The cells subsequently proliferated and migrated onto the culture plate, forming cellular monolayers. The cultured cells phagocytized isolated ROS. CONCLUSIONS: Cryoprecipitate membranes may provide an ideal source for the adhesion, cultivation, and transfer of HFRPE cells. Their autologous isolation from the recipient's blood grants an additional advantage for their application as a carrier for HFRPE transplantation into the subretinal space.

Blood Preservation↗

PubMed1999

Biodegradable polymer film as a source for formation of human fetal retinal pigment epithelium spheroids.

PURPOSE: To evaluate the attachment of human fetal rctinal pigment epithelial (HFRPE) cells to a biodegradable polymer film with subsequent formation of spheroids in vitro. METHODS: Ten biodegradable polymer films with different compositions were examined for their physical properties and ease of manipulation under a dissecting microscope. The film with the most suitable handling characteristics was chosen, and a purely isolated sheet of HFRPE cells was attached to it. The purity of the cells was assessed by their pigmentation and expression of cytokeratin. Proliferation was assessed by incorporation of 5-bromo-2'-deoxyuridine (BrdtJ). Cellular structure was analyzed under light and electron microscopes, and the functional capability of the cells was evaluated by rod outer segment (ROS) phagocytosis. RESULTS: The polymer film with composition 50:50 poly (DL-lactide) (PLA)/poly (DL-lactide-co-glycolide) (PLG) with an inherent viscosity of 1.03 dl/g was found to be the most suitable for handling under the microscope. Sheets of HFRPE cells attached to the polymer films within 48 hours and began to form spheroids. All the isolated cells were pigmented and expressed cytokeratin. They possessed a cuboidal morphology, numerous apical microvilli, and no sign of dedifferentiation. HFRPE cells produced extracellular matrix (collagen filaments) on their basal side, filling the cavities of the polymer film. The cells subsequently proliferated, incorporated BrdU, migrated onto the culture plate to form monolayers, and phagocytized ROS. CONCLUSIONS: Biodegradable polymer films can be used as a scaffold for the adhesion of the HFRPE sheet and formation of spheroids. Spheroids represent a source of high density and well-differentiated HFRPE cells that are easy to transfer. Furthermore, the stricture of the membrane makes it suitable for additional applications.

Biodegradation, Environmental↗

PubMed1999

Human fetal retinal pigment epithelial cells induce apoptosis in the T-cell line Jurkat.

PURPOSE: To investigate the mechanism(s) involved in human fetal retinal pigment epithelium (HFRPE)-mediated T-cell death. METHODS: Pure HFRPE cells were isolated and cultured. Normal and interferon (IFN)-gamma-activated HFRPE from early and late in vitro passages were incubated with cells from the human T-cell leukemia line Jurkat (Jkt). Cultures were pulsed with [3H]-thymidine to measure Jkt cell proliferation. Jkt cells were evaluated for apoptosis either by staining with an ethidium bromide/acridine orange mixture (AO/EB) or with Annexin V-phycoerythrin. The role of Fas ligand (FasL) molecule in HFRPE-mediated apoptosis was assessed by using a mutant Jkt cell line (DD3), which is deficient in Fas-mediated signaling. The involvement of the antiapoptotic human gene bcl-xL was determined by using Jkt cells that were stably transfected with bcl-x(L). The role of cell- cell contact in the induction of apoptosis was evaluated in a transwell system in the presence or absence of neutralizing antibodies against IFN-gamma and tumor necrosis factor (TNF)-alpha. RESULTS: HFRPE cells inhibited the proliferation of Jkt cells by inducing apoptosis through a FasL-independent pathway. Passaging and IFN-gamma activation strengthened the inhibitory effect of HFRPE cells on the proliferation of Jkt cells. At lower HFRPE passages (P2), bcl-alphaL, overexpression rescued the HFRPE cell-mediated apoptosis. The separation of the cells by the transwell system did not affect the HFRPE cell-mediated suppression. This suppressive effect was not mediated by the secretion of IFN-gamma or TNF-alpha molecules. CONCLUSIONS: HFRPE cells suppressed the proliferation of Jkt cells by inducing apoptosis. HFRPE cells induced a stronger inhibitory effect on Jkt cells at higher in vitro passages. The HFRPE-induced apoptosis was not mediated through the FasL/Fas pathway or through the secretion of the apoptosis-inducing cytokines IFN-gamma and TNF-alpha. The bcl-xL gene may play a role in preventing HFRPE cell-induced apoptosis in Jkt cells. These combined results suggest that the HFRPE-mediated suppression of primary T cells may also be mediated by the induction of apoptosis. Therefore, the retinal pigment epithelium may play a role in the induction of immune privilege in the subretinal space.

Apoptosis↗

PubMed1998

What is glaucoma?

Explore the source record for details and available documents.

Glaucoma↗

PubMed1998

Outcomes of extracapsular cataract extraction and phacoemulsification performed in a university training program.

BACKGROUND AND OBJECTIVES: As the number of older Americans increases, more patients will need cataract extraction surgery. Outcome studies will be necessary to assess and improve the quality of care. This study documents the outcomes of extracapsular cataract extraction (ECCE) performed at Oak Forest County Hospital (OFH) and phacoemulsification (PE) performed at the University of Chicago Hospitals (UCH) by residents who were training at the University of Chicago. PATIENTS AND METHODS: Residents train using ECCE during their second year at OFH, and learn PE at the UCH during their third year. The authors performed a chart review of all patients who had undergone ECCE at OFH (N = 52) and all patients who had undergone PE at the UCH (N = 343) from 1995 through 1997. Complete preoperative, intraoperative, and postoperative clinical data were recorded on the American Society of Cataract and Refractive Surgery database. RESULTS: There were no intraoperative complications at OFH, and 23 of 52 (44%) of the eyes had a final best-corrected visual acuity (BCVA) of 20/40 or better. At the UCH, vitreous loss occurred in 16 of 343 (5%) of the PE patients. A final BCVA of 20/40 or better was achieved in 300 of 343 (87%) of the PE eyes. CONCLUSIONS: The visual outcomes of patients who undergo ECCE at a county hospital are poor, but the surgical complications are minimal. The visual outcomes of patients who undergo PE at a university hospital are good, but the complication rates are slightly higher.

Adolescent↗

PubMed1997

Photodynamic biologic tissue glue to enhance corneal wound healing after radial keratotomy.

PURPOSE: To evaluate the effect of photodynamic biologic tissue glue (PBTG) on corneal wound healing after radial keratotomy (RK). SETTING: Cornea Research Laboratory, The University of Chicago, Chicago, Illinois, USA. METHODS: Bidirectional, eight-incision RK was done in one eye of eight Dutch pigmented rabbits. Then, PBTG was inserted into the RK incisions and activated with an argon blue-green laser in four treatment eyes. The rabbits were divided into three groups: early, in which corneal wound healing was assessed at 1 and 3 weeks; late, in which corneal wound healing was assessed at 8 weeks; enhancement. RESULTS: The PBTG-treated keratotomy wounds had a more prominent epithelial healing response immediately after RK and a decreased propensity for wound dehiscence. Collagen fiber arrangement in the PBTG-treated incisions was sagittal to the keratotomy wound 1 to 3 weeks after RK and then changed to a transverse orientation across the keratotomy wound by 8 weeks. The control keratotomy wounds had a less prominent epithelial healing response and developed late disorganization of the posterior keratotomy wound at 8 weeks. Keratometry measurements 2 months after RK showed corneal flattening of 1.0 diopter (D) in the PBTG-treated eye and 6.5 D in the control eye, which is consistent with histologic studies showing more advanced wound healing in the PBTG-treated eyes. After RK enhancement, the PBTG-treated eye resisted further corneal flattening and had 4.5 D of corneal steepening; the control eye had 2.0 D of additional corneal flattening. CONCLUSION: The nontoxic, laser-activated adhesive PBTG accelerated corneal wound healing after RK and simulated the placement of sutures into the RK wound. Thus, PBTG may be an alternative to sutures to correct hyperopia after RK in humans.

Animals↗

PubMed1997

A new method of culturing and transferring iris pigment epithelium.

PURPOSE: To optimize a culture technique and transfer iris pigment epithelial (IPE) cells for cellular studies in vitro. METHODS: Porcine iris tissues were obtained, and IPE cells were isolated and cultured at high densities by plating them in the form of drops. Spherically shaped structures containing a high concentration of cells were formed after 7 to 10 days of culture. Cells were subcultured by transferring spheres to new culture dishes without employing enzymatic dissociation. The purity of IPE cells was determined by pigmentation and cytokeratin labeling. Proliferation was assessed by incorporation of 5-bromo-2'-deoxyuridine. Cellular structure was analyzed under the light and electron microscopes and function was assayed by rod outer segment phagocytosis. RESULTS: Iris pigment epithelial cells, when cultured at high densities, tended to form elevated spherical structures containing viable cells. The cultured cells were pigmented and showed positive labeling with a monoclonal cytokeratin antibody. The IPE cells proliferated and migrated from the spheres to form monolayers. Cells originating from the transferred spheres also continued to proliferate and to migrate in a similar manner to the originally cultivated cells to form monolayers after 7 to 10 days. These cells were able to phagocytose rod outer segments. CONCLUSIONS: This new method provides a simple method of culturing a large quantity of IPE cells. The high yield of pure IPE cells and the ease of transfer provide an ideal means to study them at the cellular level.

Animals↗

PubMed1997

The immunogenic potential of human fetal retinal pigment epithelium and its relation to transplantation.

PURPOSE: To perform a quantitative analysis of the expression of major histocompatibility molecules (MHC classes I and II) and costimulatory molecules by human fetal retinal pigment epithelial (HFRPE) cells and to evaluate their potential role in providing costimulatory signals for the activation of human T cells in vitro. METHODS: Pure HFRPE cells were isolated and cultured. The ability of HFRPE cells to express MHC class I and II and costimulatory molecules before and after incubation with interferon (IFN)-gamma was quantitatively analyzed by flow cytometry. The potential of HFRPE cells to activate human T cells was assessed in three different lymphocyte activation models. In the first model, anti-CD3 (OKT3)-coated beads were used to provide the T-cell receptor (TcR) signal. In the second model, the allogenic potential of HFRPE cells was assessed, and in the third assay a potent superantigen (SEA) was used to provide the TcR signal. T-cell activation was determined by cell proliferation, measured by [3H]-thymidine incorporation. RESULTS: The cultured HFRPE cells expressed low levels of MHC class I and ICAM-1 molecules. After incubation with IFN-gamma, the expression of MHC class I and ICAM-1 molecules was further upregulated, and the expression of MHC class II and VCAM-1 molecules was induced. The expression of the costimulatory molecules B7-1 and B7-2 was not observed in normal or activated HFRPE cells. In the first T-cell activation model, neither normal nor IFN-gamma-activated HFRPE cells could provide T-cell costimulation for anti-CD3 (OKT3)-coated beads. However, the autologous peripheral blood mononuclear cells (PBMCs; used here as the source of antigen-presenting cells) could provide costimulation for the T cells, inducing their proliferation. In the second T-cell activation assay, normal or IFN-gamma-activated HFRPE cells could not stimulate an alloresponse from the T cells, but they could induce a significant alloimmune T-cell response in the presence of PBMCs. In the third T-cell activation assay, the IFN-gamma-activated HFRPE cells were able to provide T-cell costimulation for the SEA-mediated activation. CONCLUSIONS: In these in vitro experiments, the IFN-gamma-activated HFRPE cells stimulated only the T cells with the potent superantigen SEA. In the absence of antigen-presenting cells, the HFRPE cells did not provide T-cell costimulation in an anti-CD3 mAb-coated bead system or induce significant alloimmune response. These results suggest that in transplantation between donors and recipients with different MHC molecules, the direct MHC peptide presentation by HFRPE cells may not induce a significant allospecific immune response. Nevertheless, an allospecific immune response could occur as a consequence of the indirect presentation, to the host T cells by the host antigen-presenting cells, of the HFRPE cells' derived MHC alloantigens.

Antigen-Presenting Cells↗

PubMed1996

AIDS and the eyes.

The eye is affected in 50-75% of adult AIDS patients. This rate of ocular involvement is much higher than that in symptom-free HIV-seropositive patients, and seems to increase in incidence with severity of disease. These observations indicate that regular screening of HIV-positive patients is warranted to allow early identification of potential vision and life threatening disease.

AIDS-Related Opportunistic Infections↗

PubMed1996

Isovolemic hemodilution increases retinal tissue oxygen tension.

BACKGROUND: Therapeutic isovolemic hemodilution has been reported to improve blood flow and oxygen delivery. Few reliable measurements have been made, however, showing the effect of hemodilution on tissue oxygen tension. METHODS: We measured retinal oxygen tension during experimental isovolemic hemodilution in normal cats. Polarographic oxygen microelectrodes were placed in the vitreous humor within 100-200 microns of the retinal surface. RESULTS: Tissue oxygen tension increased initially during isovolemic hemodilution to a maximum approximately 50% above baseline at approximately two thirds of the original hematocrit level. Hemodilution beyond this point to lower hematocrits caused a steady decline in tissue oxygen tension. Cardiac output measured in one cat undergoing isovolemic hemodilution increased as hematocrit was lowered, but the cardiac erythrocyte flux actually decreased steadily. CONCLUSION: The observed increase in tissue oxygen tension with hemodilution appears to be explained by a lesser reduction in capillary than in systemic hematocrit, coupled with an increased capillary blood flow. The increase in tissue oxygen tension we observed could in part explain the clinically beneficial effects of hemodilution.

Animals↗