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J Y Niederkorn

Publications and source records attributed to J Y Niederkorn.

At least 19 recordsLinked to original sources
PubMed2006

Oral immunization with Acanthamoeba castellanii mannose-binding protein ameliorates amoebic keratitis.

Acanthamoeba castellanii mannose-binding protein (MBP) mediates adhesion of the amoebae to corneal epithelial cells, a key first step in the pathogenesis of Acanthamoeba keratitis (AK), a devastating corneal infection. In the present study, we demonstrate that oral immunization with recombinant MBP ameliorates AK in a hamster animal model and that this protection is associated with the presence of elevated levels of anti-MBP immunoglobulin A in the tear fluid of the immunized animals.

Acanthamoeba Keratitis↗
PubMed2006

Differential roles of CD8+ and CD8- T lymphocytes in corneal allograft rejection in 'high-risk' hosts.

We examined the role of perforin and FasL in corneal allograft rejection mediated by CD8+ and CD8 T cells. BALB/c corneas were transplanted orthotopically into vascularized, 'high-risk' graft beds in C57BL/6 mice, perforin knockout mice and FasL-defective gld/gld mice. CD8+ and CD8 T cells were collected following graft rejection and adoptively transferred to SCID mice, which were then challenged with BALB/c corneal allografts. In every case, CD8 T cells could mediate graft rejection when adoptively transferred to SCID mice that received BALB/c corneal allografts. Although CD8+ T cells also mediated graft rejection, the tempo was slower. Moreover, CD8+ T cells collected FasL-defective donors that had rejected corneal allografts, mediated corneal allograft rejection in only 50% of the SCID mice that received the adoptively transferred cells. In some cases, CD8+ T-cell-mediated rejection occurred in the absence of delayed-type hypersensitivity and cytotoxic T-lymphocyte activity, but was associated with CD8+ T-cell-mediated apoptosis of BALB/c corneal cells in vitro. The results demonstrate the redundancy in immune mechanisms of corneal allograft rejection. Either CD8+ or CD8 T cells can produce corneal allograft rejection, however functional FasL is necessary for optimal rejection, even in a high-risk setting.

Animals↗
PubMed2002

Resistance of Acanthamoeba castellanii cysts to physical, chemical, and radiological conditions.

Resistance of Acanthamoeba castellanii cysts to disinfection agents, antimicrobial agents, heat, freeze-thawing, ultraviolet radiation (UV), gamma irradiation, and cellulase were evaluated in vitro. Following exposure to different agents, the cysts were removed and cultured for A. castellanii trophozoites for 3-14 days. Solutions containing 20% isopropyl alcohol or 10% formalin effectively killed A. castellanii cysts. Hydrogen peroxide (3%, AOSept Disinfectant) effectively killed A. castellanii cysts after 4 hr of exposure. Polyhexamethylene biguanide (0.02%), clotrimazole (0.1%), or propamidine isethionate (Brolene) were effective in killing A. castellanii cysts in vitro. Acanthamoeba castellanii cysts were resistant to both 250 K rads of gamma irradiation and 800 mJ/cm2 of UV irradiation. Excystment of trophozoites was accelerated after exposure to 10, 100, and, 1,000 units of cellulase. These results suggest that A. castellanii cysts benefit by enhanced survival because of their resistance to very harsh environmental conditions.

2-Propanol↗
PubMed2001

Gamma delta T cells are needed for ocular immune privilege and corneal graft survival.

It has been recognized for over a century that the anterior chamber of the eye is endowed with a remarkable immune privilege. One contributing component is the Ag-specific down-regulation of systemic delayed-type hypersensitivity (DTH) that is induced when Ags are introduced into the anterior chamber. This phenomenon, termed anterior chamber-associated immune deviation (ACAID), culminates in the generation of regulatory cells that inhibit the induction (afferent suppression) and expression (efferent suppression) of DTH. Since gamma delta T cells play a major role in other forms of immune regulation, we suspected they might contribute to the induction and expression of ACAID. Mice treated with anti-gamma delta Ab failed to develop ACAID following anterior chamber injection of either soluble Ag (OVA) or alloantigens (spleen cells). Additional experiments with knockout mice confirmed that mice lacking functional gamma delta T cells also fail to develop ACAID. Using a local adoptive transfer of DTH assay, we found that gamma delta T cells were required for the generation of regulatory T cells, but did not function as the efferent regulatory cells of ACAID. The importance of gamma delta T cells in corneal allograft survival was confirmed by blocking gamma delta T cells with GL3 Ab before corneal transplantation. While in vivo treatment with normal hamster serum had no effect on corneal graft survival, infusion of anti-gamma delta Ab resulted in a profound increase in corneal allograft rejection. Thus, gamma delta T cells are needed for sustaining at least one aspect of ocular immune privilege and for promoting corneal allograft survival.

Animals↗
PubMed2001

Ocular immune privilege promoted by the presentation of peptide on tolerogenic B cells in the spleen. II. Evidence for presentation by Qa-1.

Ocular immune privilege is the result of several unique features of the eye, including the systemic down-regulation of Th1 immune responses to Ags encountered in the anterior chamber of the eye-a phenomenon termed anterior chamber-associated immune deviation (ACAID). The induction of ACAID requires the participation of three cell populations: the ocular ACAID APC, the splenic B cell, and the splenic T cell. Because B cells have been implicated in tolerogenic Ag presentation in other systems, we hypothesized that B cells were responsible for the induction of regulatory T cells in ACAID. The central hypothesis for this study is that APC from the eye migrate to the spleen where they release antigenic peptides (OVA) that are captured and presented to T cells by splenic B cells. A combination of in vitro and in vivo studies demonstrated that splenic B cells, incubated with ACAID APC in vitro, were capable of inducing ACAID when transferred to naive mice. The induction of ACAID required the normal expression of ss(2)-microglobulin on both the B cell and ACAID APC, but not on the T suppressor cells. Moreover, the induction of ACAID regulatory cells required histocompatibility between the B cells and regulatory T cells at the TL/Qa region. The results indicate that: 1) B cells are necessary for the induction of ACAID; 2) ACAID B cells do not directly suppress the expression of delayed-type hypersensitivity; and 3) the induction of Ag-specific regulatory T cells by ACAID B cells requires histocompatibility at the TL/Qa region.

Adoptive Transfer↗
PubMed2001

Angiostatin produced by certain primary uveal melanoma cell lines impedes the development of liver metastases.

OBJECTIVES: To evaluate the ability of human uveal melanomas to produce angiostatin in vitro and the effect of angiostatin on the development of liver metastases in vivo. METHODS: Human uveal melanoma cell lines (OCM1, OCM3, MEL202, MEL285, 92-1, OM431, and OMM1) were assayed for their ability to produce angiostatin in vitro by an angiostatin bioassay and by Western blot analysis. The OCM3 and OMM1 tumor cells were inoculated either in the posterior or the anterior segment of nude mice. One group of mice in each experiment underwent enucleation and hepatic metastases were assayed by histopathologic and liver function analysis. RESULTS: OCM1, OCM3, and 92-1 cell lines significantly inhibited bovine endothelial cell proliferation in vitro and generated 38-Kd angiostatin molecules. Enucleation of eyes containing OCM3 in the posterior segment resulted in a higher number of metastatic foci (26.5) in that group compared with the nonenucleated group of mice (11.17). After enucleation, elevated levels of serum aspartate transaminase and alanine aminotransferase were observed in mice bearing OCM3 in either anterior or posterior segments. The enucleation of eyes containing OMM1 (nonangiostatin-producing cells) had no significant effect on liver metastasis. CONCLUSION: By removing a source of angiostatin, enucleation of melanoma-containing eyes may unwittingly exacerbate the metastatic potential of uveal melanomas. CLINICAL RELEVANCE: In certain circumstances, enucleating a melanoma-containing eye may unwittingly exacerbate metastatic disease. The results also suggest that exogenous angiostatin may have potential therapeutic implications in the management of patients with primary intraocular melanomas.

Alanine Transaminase↗
PubMed2001

Role of fas ligand in uveal melanoma-induced liver damage.

BACKGROUND: Uveal melanoma, the most common adult intraocular malignancy, metastasizes preferentially to the liver. Areas of cell death surrounding uveal melanoma metastases were observed in the livers of mice. We hypothesized that uveal melanoma cells might express Fas ligand (FasL), facilitating FasL-mediated apoptosis of Fas-expressing hepatocytes. PURPOSE: To determine whether Fas ligand (FasL)-expressing human uveal melanoma cells induce apoptosis of human hepatocytes in vitro and in vivo. METHODS: Human uveal melanoma cell lines were assayed for FasL expression by flow cytometry and immunohistology. A human hepatocyte cell line was assayed for Fas expression by flow cytometry. Apoptosis of hepatocytes was detected by annexin V staining in vitro, and terminal deoxynucleotidyl transferase nick end labeling (TUNEL) in vivo. RESULTS: Human uveal melanoma cell lines expressed FasL, as determined by flow cytometry and immunohistology. Human hepatocytes were Fas-positive by flow cytometry. In vitro, annexin V staining revealed that human uveal melanoma cells induced apoptosis of human hepatocytes. TUNEL staining of liver metastases revealed apoptosis of murine hepatocytes in contact with metastatic human uveal melanoma cells. CONCLUSION: FasL-induced apoptosis of hepatocytes in contact with FasL-positive human uveal melanoma cells may contribute to hepatic failure during metastatic disease.

Animals↗
PubMed2001

Tear IgA and serum IgG antibodies against Acanthamoeba in patients with Acanthamoeba keratitis.

PURPOSE: Exposure to Acanthamoebaspecies appears to be ubiquitous, as 50% to 100% of healthy human subjects display anti-Acanthamoebaantibodies. However, the presence of specific anti-Acanthamoebaantibodies in the serum and tears of patients has not been investigated. The prevalence of serum immunoglobulin G (IgG) and tear IgA against three species of Acanthamoebawas assessed in healthy subjects and patients with Acanthamoebakeratitis. METHODS: The level of specific serum IgG and tear IgA against A. castellanii, A. astronyxis, and A. culbertsoniin the sera of 23 patients and 25 healthy subjects was tested by enzyme-linked immunosorbent assays. Total serum IgM, IgG, and IgA concentrations were measured by nephelometry. Acanthamoebakeratitis was diagnosed clinically and confirmed by in vivo confocal microscopy. In some patients, corneal biopsies were also performed and trophozoites were cultured on lawns of Escherichia colion non-nutrient agar. RESULTS: All healthy subjects and patients with Acanthamoebakeratitis had detectable serum IgG antibodies against all Acanthamoebaantigens. However, patients with Acanthamoebakeratitis had significantly higher anti-AcanthamoebaIgG antibody titers than healthy subjects. In contrast, Acanthamoeba-specific tear IgA was significantly lower in patients with Acanthamoebakeratitis in comparison with healthy subjects. Total serum immunoglobulins did not differ significantly between healthy subjects and patients with Acanthamoebakeratitis. CONCLUSIONS: The results suggest that a low level of anti-AcanthamoebaIgA antibody in the tears appears to be associated with Acanthamoebakeratitis.

Acanthamoeba↗
PubMed2001

Mechanisms of corneal graft rejection: the sixth annual Thygeson Lecture, presented at the Ocular Microbiology and Immunology Group meeting, October 21, 2000.

The history of corneal transplantation reaches back over 150 years. Kissam performed one of the first penetrating keratoplasties when he transplanted a pig cornea onto a human in 1838. Only two interrupted sutures were used, and the surgery was performed without anesthesia! In retrospect, no one would be surprised to learn that the porcine corneal xenograft was rejected. Thirty years later, May transplanted rabbit corneal grafts to humans, but concluded that the failures in the first 24 attempts were the result of "imperfect technique and the inability to keep the eyes properly bandaged." The first documented report of a successful penetrating keratoplasty in a human subject was performed by Zirm in 1905. As we enter the new millennium, corneal transplantation remains the oldest, most common, and, arguably, the most successful form of solid tissue transplantation. In the United States alone, approximately 36,000 corneal transplants are performed each year. The success rate for corneal transplants is in excess of 90% in uncomplicated cases, even though HLA tissue typing is not performed and systemic immunosuppressive drugs are not administered. In spite of this extraordinary success, immune rejection remains the leading cause of corneal graft failure. Many inferences about the immunobiology of corneal graft rejection have been based on clinical observations; however, confirmation of these hypotheses requires prospective studies under controlled settings. The prudent use of animal models has fostered analytic studies on the immunobiology of corneal allografts without the complicating and confounding effects of topical steroids that are typically used on most keratoplasty patients. Although animal models of penetrating keratoplasty have been in use for almost a half-century, until recently, progress in understanding the immune mechanisms of corneal graft rejection has been slow. However, the widespread use of rodent models of orthotopic corneal transplantation has shed new light on the pathogenesis of corneal graft rejection.

Animals↗
PubMed2001

Effect of steroids on Acanthamoeba cysts and trophozoites.

PURPOSE: Topical steroids are frequently used to control corneal inflammation and uveitis or is administered after surgery, to prevent corneal graft rejection. This study was undertaken to determine whether steroids could affect the pathogenicity of Acanthamoeba castellanii. METHODS: The effect of dexamethasone phosphate on excystment, proliferation, and encystment of trophozoites and cysts of A. castellanii was examined in vitro. Cytolysis capacity of steroid-treated Acanthamoeba was quantified by a spectrophotometric assay, and plasminogen activators were measured by a fibrinolysis assay. The influence of steroid treatment on corneal infection in a Chinese hamster model of Acanthamoeba keratitis was examined in vivo. RESULTS: Treatment of Acanthamoeba cysts with dexamethasone induced 4- to 10-fold increases in the number of trophozoites compared with untreated control cultures. Acceleration of trophozoite proliferation was observed when trophozoites were treated with dexamethasone. However, dexamethasone treatment did not affect encystment of Acanthamoeba trophozoites. Dexamethasone-treated trophozoites or cysts induced a significant cytopathic effect on corneal epithelial cells compared with untreated organisms. Supernatants collected from either dexamethasone-treated or untreated organisms failed to lyse corneal epithelial cells. Treatment of organisms with dexamethasone had no effect on production of plasminogen activators by Acanthamoeba trophozoites. Intramuscular injection of dexamethasone had a profound effect on the incidence, severity, and chronicity of keratitis. Keratitis in dexamethasone-treated hamsters was significantly more severe at all time points than in untreated animals (P < 0.05). CONCLUSIONS: These findings indicate that exposure of Acanthamoeba trophozoites and cysts to dexamethasone increases the pathogenicity of the organisms. The results emphasize the importance of maintaining adequate amebicidal therapy if a topical steroid is used in the management of Acanthamoeba keratitis.

Acanthamoeba↗
PubMed2000

Human uveal melanoma cells produce macrophage migration-inhibitory factor to prevent lysis by NK cells.

Human uveal melanoma arises in an immune privileged ocular environment in which both adaptive and innate immune effector mechanisms are suppressed. Uveal melanoma is the most common intraocular tumor in adults and is derived from tissues in the eye that produce macrophage migration-inhibitory factor (MIF), a cytokine that has recently been demonstrated to produce immediate inhibition of NK cell-mediated lytic activity. Although NK cell-mediated lysis of uveal melanomas is inhibited in the eye, melanoma cells that disseminate from the eye are at risk for surveillance by NK cells. Moreover, uveal melanoma cells demonstrate a propensity to metastasize to the liver, an organ with one of the highest levels of NK activity in the body. Therefore, we speculated that uveal melanomas produced MIF as a means of escaping NK cell-mediated lysis. Accordingly, seven primary uveal melanoma cell lines and two cell lines derived from uveal melanoma metastases were examined for their production of MIF. MIF was detected in melanoma culture supernatants by both ELISA and the classical bioassay of macrophage migration inhibition. Melanoma-derived MIF inhibited NK cell-mediated lysis of YAC-1 and uveal melanoma cells. Cell lines derived from uveal melanoma metastases produced approximately twice as much biologically active MIF as cultures from primary uveal melanomas. Inhibition of NK cell-mediated killing by uveal melanoma-derived MIF was specifically inhibited in a dose-dependent manner by anti-MIF Ab. The results suggest that human uveal melanoma cells maintain a microenvironment of immune privilege by secreting active MIF that protects against NK cell-mediated killing.

Animals↗
PubMed2000

The diagnosis and management of Acanthamoeba keratitis.

PURPOSE: The purpose of this study was to evaluate the immunology, pathogenesis and therapy of Acanthamoeba keratitis. METHODS: The recent development of an animal model of Acanthamoeba keratitis and its impact on the medical treatment and immunology of Acanthamoeba keratitis was reviewed. RESULTS: After initial reports, Acanthamoeba infection of the cornea remained a rare disease until an association with contact lens wear was first recognized. Although the disease is closely associated with contact lens wear, it appeared that the contaminated solutions that were coming into contact with the lenses caused the disease. All types of contact lenses can be associated with development of Acanthamoeba keratitis. Therefore, the contact lens serves as a carrier of Acanthamoeba to the surface of the eye. The typical patient with Acanthamoeba keratitis is a young healthy individual who is either a contact lens wearer or has had significant exposure to water contaminated with Acanthamoeba. There are several risk factors such as corneal trauma, contaminated solution and contact lenses that have been reported to be associated with Acanthamoeba keratitis. In spite of significant improvement in the diagnosis of Acanthamoeba keratitis, progress in developing and utilizing effective antimicrobial agents for treating this disease have been disappointing. A growing body of evidence suggests that the mammalian immune system, if properly activated, is capable of preventing and controlling ocular infections. CONCLUSIONS: In order to develop effective immunotherapeutic modalities, and to better understand the immune effector mechanisms that protect the cornea against Acanthamoeba infection, it is necessary to fully characterize and evaluate the immunobiology of Acanthamoeba keratitis.

Acanthamoeba↗
PubMed2000

The role of cytotoxic T lymphocytes in corneal allograft rejection.

PURPOSE: Immunologic rejection constitutes a major barrier to the success of allogeneic corneal transplants, but the specific mediators and mechanisms of graft rejection are poorly understood. Several studies have implicated cytotoxic T-lymphocyte (CTL) responses, typically associated with CD8(+) T cells, in promoting corneal graft rejection. This study sought to test the hypothesis that CTLs are essential in promoting corneal graft rejection. METHODS: BALB/c donor corneas were grafted orthotopically onto C57BL/6, perforin knockout, or CD8(+) T-cell knockout mice. The tempo and incidence of graft rejection were observed for each group. In separate experiments, donor-specific CTL and delayed-type hypersensitivity (DTH) responses were tested at the time of graft rejection by a standard chromium release assay and an ear swelling assay, respectively. RESULTS: Perforin knockout and CD8(+) T-cell knockout mice were as effective as wild-type C57BL/6 control mice in rejecting BALB/c donor corneas. Furthermore, animals in all three groups were found to develop robust donor-specific DTH, not CTL, responses at the time of graft rejection. Histopathologically, the rejected corneas from all three groups contained a predominantly mononuclear cellular infiltrate. CONCLUSIONS: This study rejects the hypothesis that CD8(+) CTLs are essential in promoting corneal graft rejection and instead further implicates donor-specific DTH reactions as the relevant immune response during graft failure.

Animals↗
PubMed1999

Expression of a nonclassical MHC class Ib molecule in the eye.

BACKGROUND: MHC class Ia molecules are absent, or expressed at low levels, on cells lining the anterior chamber of the eye, an immune-privileged site. Although the scarcity of class Ia MHC antigens may protect cells from T cell-mediated tissue injury, it may also render them vulnerable to natural killer cell-mediated cytolysis. There is growing evidence that MHC class Ib molecules share similar functions to class Ia. In this study, we examine the expression and distribution of Qa-2, one of the best-characterized murine MHC class Ib molecules in the eye. METHODS: The transcription of Qa-2 mRNA in whole eye and eye-derived cells was analyzed by sensitive and specific RNase protection and reverse transcription-polymerase chain reaction assays. Immunohistochemistry, flow cytometry, and ELISA were used to determine whether Qa-2 was expressed as cell surface proteins. Expression levels of Qa-2 were monitored in resting cells and cells stimulated with interferon-gamma. RESULTS: Expression of membrane-bound and soluble Qa-2 isoforms was detected in various tissues of the eye, including cell subsets lining the anterior chamber. Immunohistological staining revealed Qa-2 expression on corneal epithelium as well as endothelium, iris ciliary bodies, and retina. These observations were confirmed by analysis of cultured, eye-derived cells. Qa-2 expression was inducible by interferon-gamma. Qa-2 was not detected in lens cells. CONCLUSIONS: The results demonstrate that membrane-bound and soluble MHC class Ib molecules are expressed by eye cells. Expression of Qa-2 in the corneal endothelium and other substructures lining the anterior chamber suggests that this class Ib protein may contribute to the immune-privileged status of the anterior chamber.

Animals↗
PubMed1999

The immune privilege of corneal allografts.

BACKGROUND: Corneal transplantation is the oldest, most common, and arguably, the most successful form of tissue transplantation. In the United States alone, over 40,000 corneal transplantations are performed each year. Less than 10% of the uncomplicated, first-time corneal grafts will undergo immune rejection even though HLA matching is not routinely performed and the use of immunosuppressive drugs is limited to the topical application of corticosteroids. The success of corneal transplantations predates the use of corticosteroids and further emphasizes the remarkable privilege of corneal allografts. METHODS: Several laboratories have used rat and mouse models of orthotopic corneal transplantation (keratoplasty) in an attempt to understand the basis for the immune privilege of corneal allografts. RESULTS: The time-honored explanation for the immune privilege of corneal allografts was based on the conspicuous avascularity of the cornea, which was believed to sequester the graft from the immune apparatus. However, results from several laboratories indicate that at least three additional features of the corneal graft contribute to its immune privileged status: (a) absence of donor-derived, antigen-presenting passenger Langerhans cells in the corneal graft; (b) expression of Fas ligand on the epithelium and endothelium of the corneal allograft; and (c) capacity of the corneal allograft to induce immune deviation of the systemic immune response. CONCLUSIONS: The immune privilege of corneal allografts is a product of at least three unique qualities of the corneal allograft that conspire to interfere with the induction and expression of allodestructive immune responses.

Animals↗
PubMed1999

Monoclonal IgA antibodies protect against Acanthamoeba keratitis.

Acanthamoeba keratitis is a rare, yet sight-threatening corneal infection. Ocular infection does not appear to induce protective immunity as repeated corneal infections occur in both humans and experimental animals. However, we have recently demonstrated that activation of the common mucosal immune system by oral immunization with Acanthamoeba antigens protects both Chinese hamsters and pigs against ocular infection with A. castellanii. Protection correlates closely with the appearance of anti- Acanthamoeba antibodies in the tears. To test the hypothesis that oral immunization induces specific protective IgA antibodies, two monoclonal IgA antibodies specific for Acanthamoeba antigens were generated. Both antibodies detected epitopes on the surface of fixed Acanthamoeba trophozoites. When delivered intraperitoneally, one monoclonal antibody (14E4) was detected in stool and tear samples. This clone also protected naive animals against ocular challenge with Acanthamoeba trophozoites (43% infection rate compared to a 91% infection rate in animals receiving control IgA). In vitro functional studies showed that neither antibody induced encystment or directly killed Acanthamoeba trophozoites. However, both monoclonal anti- Acanthamoeba IgA antibodies produced a three-fold inhibition in the adherence of trophozoites to corneal epithelial cells in vitro. These data show that monoclonal anti- Acanthamoeba IgA antibodies can protect against Acanthamoeba keratitis and suggest that this occurs by inhibiting adhesion of the parasite to the corneal epithelium.

Acanthamoeba↗