Anterior Chamber Flare as a Non-Invasive Assessment of Intraocular Immune Status and Ocular Complications in Proliferative Diabetic Retinopathy.

Proliferative diabetic retinopathy (PDR) is a vision-threatening complication of diabetes mellitus (DM). Anterior chamber (AC) flare and intraocular cytokines are potent biomarkers reflecting the intraocular immune status in PDR. This study aimed to elucidate the complex interrelationship between AC flare and intraocular cytokines in PDR eyes. A retrospective observational study was conducted on 19 PDR eyes of 19 patients with type 2 DM, and on 19 eyes of 19 patients with idiopathic macular hole or epiretinal membrane as controls. AC flare was measured before pars plana vitrectomy (PPV). Aqueous humor (AH) and vitreous fluid (VF) samples were collected at the time of PPV, and the quantities of 27 cytokines in both intraocular fluids were analyzed. In the PDR and control groups, Spearman's rank correlation analysis revealed a positive correlation between AC flare and IL-8 level in both AH and VF. Additionally, IL-8 levels in AH correlated positively with IL-8 levels in VF. In the PDR group, receiver operating characteristic curve analysis identified IL-8 level in AH as a significant predictor for both diabetic macular edema (DME) and vitreous hemorrhage (VH) complications. The cut-off values of IL-8 were established at ≥26.6 pg/mL for DME and ≥7.96 pg/mL for VH. Given the positive correlation between AC flare and AH IL-8 level, the present findings suggest that AC flare value may potentially be a non-invasive biomarker for predicting DME.

Adipose-derived stem cells integrate into trabecular meshwork with glaucoma treatment potential.

The trabecular meshwork (TM) is an ocular tissue that maintains intraocular pressure (IOP) within a physiologic range. Glaucoma patients have reduced TM cellularity and, frequently, elevated IOP. To establish a stem cell-based approach to restoring TM function and normalizing IOP, human adipose-derived stem cells (ADSCs) were induced to differentiate to TM cells in vitro. These ADSC-TM cells displayed a TM cell-like genotypic profile, became phagocytic, and responded to dexamethasone stimulation, characteristic of TM cells. After transplantation into naive mouse eyes, ADSCs and ADSC-TM cells integrated into the TM tissue, expressed TM cell markers, and maintained normal IOP, outflow facility, and extracellular matrix. Cell migration and affinity results indicated that the chemokine pair CXCR4/SDF1 may play an important role in ADSC-TM cell homing. Our study demonstrates the possibility of applying autologous or allogeneic ADSCs and ADSC-TM cells as a potential treatment to restore TM structure and function in glaucoma.

Investigation of Cytotoxic T Lymphocyte Function during Allorejection in the Anterior Chamber of the Eye.

Cytotoxic T lymphocytes (CTL) are an essential part of our immune system by killing infected and malignant cells. To fully understand this process, it is necessary to study CTL function in the physiological setting of a living organism to account for their interplay with other immune cells like CD4+ T helper cells and macrophages. The anterior chamber of the eye (ACE), originally developed for diabetes research, is ideally suited for non-invasive and longitudinal in vivo imaging. We take advantage of the ACE window to observe immune responses, particularly allorejection of islets of Langerhans cells by CTLs. We follow the onset of the rejection after vascularization on islets until the end of the rejection process for about a month by repetitive two-photon microscopy. We find that CTLs show reduced migration on allogeneic islets in vivo compared to in vitro data, indicating CTL activation. Interestingly, the temporal infiltration pattern of T cells during rejection is precisely regulated, showing enrichment of CD4+ T helper cells on the islets before arrival of CD8+ CTLs. The adaptation of the ACE to immune responses enables the examination of the mechanism and regulation of CTL-mediated killing in vivo and to further investigate the killing in gene-deficient mice that resemble severe human immune diseases.

Immune Checkpoints Contribute Corneal Immune Privilege: Implications for Dry Eye Associated with Checkpoint Inhibitors.

The eye is provided with immune protection against pathogens in a manner that greatly reduces the threat of inflammation-induced vision loss. Immune-mediated inflammation and allograft rejection are greatly reduced in the eye, a phenomenon called 'immune privilege'. Corneal tissue has inherent immune privilege properties with underlying three mechanisms: (1) anatomical, cellular, and molecular barriers in the cornea; (2) an immunosuppressive microenvironment; and (3) tolerance related to regulatory T cells and anterior chamber-associated immune deviation. This review describes the molecular mechanisms of the immunosuppressive microenvironment and regulatory T cells in the cornea that have been elucidated from animal models of ocular inflammation, especially those involving corneal transplantation, it also provides an update on immune checkpoint molecules in corneal and systemic immune regulation, and its relevance for dry eye associated with checkpoint inhibitor therapy.

The efficacy of systemic and intravitreal infliximab treatments in an endotoxin-induced uveitis model.

Purpose: To compare the efficacy of systemic and intravitreal infliximab treatments in an experimental endotoxin-induced uveitis (EIU) model. Methods: Twenty-eight white New Zealand rabbits were equally divided into 4 groups. Group 1 received an intravitreal injection of 0.1 cc saline, group 2 received an intravitreal injection of 2 µg/0.1 cc lipopolysaccharide (LPS), group 3 received an intravitreal injection of 2 µg/0.1 cc LPS and 2 mg/0.1 cc infliximab, and group 4 received intravitreal injection of 2 µg/0.1 cc LPS and intravenous injection of 5 mg/kg infliximab. Clinical, biochemical (aqueous and vitreous humour protein levels and TNF-α concentrations), and histopathological evaluations were performed. Results: The clinical examination score was lower in group 4 than in group 2 (p = 0.006); but there was no significant difference between groups 2 and 3 (Bonferroni correction, p = 0.016). No statistically significant difference was found among groups 2, 3, and 4 for aqueous humour protein levels (p > 0.05). Significantly higher aqueous humour concentrations of TNF-α was measured in group 3 comparing to both group 1 and 4 (p = 0.003 and p = 0.002, respectively). No significant difference was found in vitreous protein levels or TNF-α concentrations among all study groups (Bonferroni correction, p = 0.026 and p = 0.101, respectively). Histopathological evaluation of the uveal tissue and anterior chamber reaction revealed the highest inflammation in group 3 (p < 0.001). In group 4, histopathological evaluation of uveal tissue was lower than in groups 2 and 3 (p < 0.001 and p = 0.001, respectively); whereas there was no difference in anterior chamber inflammation between groups 2 and 4 (p = 1.00). Conclusion: Intravitreal 2 mg/0.1 cc infliximab injection exacerbated inflammation in an EIU model; whereas systemic infliximab treatment at a dose of 5 mg/kg suppressed inflammation effectively and rapidly.

CD4- and CD8-expressing cells found in the bovine and porcine anterior chamber of the eye.

The aim of the present study was to investigate whether the anterior chamber constitutes part of the normal migratory pathway of CD4+ and CD8+ lymphocytes in cattle and swine. The cells obtained from aqueous humor of cows and pigs were stained for CD4 and CD8 receptors, and subsequently analyzed with flow cytometry. The mean percentage of CD4+CD8-, CD4-CD8+ and CD4+CD8+ cells within the total lymphocyte population of the bovine anterior chamber was, respectively, 17.88, 12.64 and 27.26%. In turn, the mean values of these parameters in pigs were 1.77, 38.48 and 17.45, respectively. Among bovine and porcine CD4+CD8+ cells prevalent were those displaying CD4lowCD8low and CD4lowCD8high phenotypes, respectively. The results suggest that the anterior chamber in cattle and swine is an element in the normal migratory pathway of CD4+, CD8+ and CD4+CD8+ cells. Furthermore, the contribution of these subsets in the anterior chamber lymphocyte population can differ considerably between animal species.

Eye-mediated immune tolerance to Type II collagen in arthritis-prone strains of mice.

Type II collagen (CII) is a cartilage structural protein that plays important roles in joint function, arthritis and ageing. In studying the ability of CII to induce eye-mediated specific immune tolerance, we have recently proven that CII is capable of inducing anterior chamber-associated immune deviation (ACAID) in Balb/c mice. Here, we study the ability of CII to induce eye-mediated immune tolerance in strains of mice that are prone to the induction of rheumatoid arthritis. Thus, we hypothesized that CII induces ACAID in DBA/1 mice and in C57BL/6 mice through the AC route (direct injection) or the intravenous route (adoptive transfer of in vitro-generated CII-specific ACAID macrophages or of CII-specific in vitro-generated T regulatory cells). Specific immune tolerance induction was assessed using both delayed-type hypersensitivity (DTH) and local adoptive transfer (LAT) assays. Results indicated the ability of CII to generate CII-specific ACAID-mediated immune tolerance in vivo and in vitro in both DBA/1 mice and C57BL/6 mice. These findings could be beneficial in studies of immune tolerance induction using CII.

In vitro-induced cell-mediated immune deviation to encephalitogenic antigens.

The injection of antigens into the Anterior Chamber (AC) of the eye induces Anterior Chamber Associated Immune Deviation (ACAID), which is a potent form of immune deviation that is largely attributed to the effect of TGFß2 in the aqueous humor on ocular antigen-presenting cells (APCs). ACAID antigen presentation via APCs and B cells leads to the generation of antigen-specific T regulatory cells. The encephalitogenic antigens Myelin oligodendrocyte glycoprotein (MOG) and Myelin basic protein (MBP) have an obvious clinical relevance. We hypothesized that the intravenous injection of in vitro-generated ACAID APCs or in vitro-generated ACAID B cells specific to the encephalitogenic antigens MOG35-55/MBP induces specific peripheral tolerance in recipient BALB/c mice. We examined the suppression of MOG35-55-specific/MBP-specific inflammatory responses using delayed-type hypersensitivity (DTH) assays and Local Adoptive Transfer (LAT) assays. Results indicated that MOG35-55-specific/MBP-specific tolerance was generated after the intravenous injections of MOG35-55-specific/MBP-specific ACAID APCs, MOG35-55-specific/MBP-specific ACAID B cells, and MOG35-55-specific/MBP-specific ACAID T regulatory cells. The specific immune deviation was in vitro-induced, cell-mediated, and specific to the encephalitogenic antigens MOG35-55/MBP. This in vitro-mediated approach for the generation of MOG35-55/MBP-specific tolerance opens up avenues for the application of ACAID as a tool for the therapy of Multiple Sclerosis, Schizophrenia, and other diseases.

The in vivo and in vitro induction of anterior chamber associated immune deviation to myelin antigens in C57BL/6 mice.

Introduction of antigens into the anterior chamber (AC) of the eye generates a specific systemic form of tolerance that is termed AC-associated immune deviation (ACAID). Experimental autoimmune encephalomyelitis (EAE) is an animal model of the human CNS demyelinating diseases, including multiple sclerosis (MS) and acute disseminated encephalomyelitis. We investigated whether the encephalitogenic antigens myelin oligodendrocyte glycoprotein (MOG35-55) or myelin basic protein (MBP) induce ACAID in the EAE-prone C57BL/6 mice. We hypothesized that injection of MOG35-55/MBP induces antigen-specific tolerance whether via the AC route, the adoptive transfer of in vitro-generated MOG35-55-specific/MBP-specific ACAID antigen presenting cells (APCs), or the adoptive transfer of MOG35-55-specific/MBP-specific ACAID T regulatory cells (Tregs). ACAID is characterized by the specific impairment of delayed-type hypersensitivity (DTH) responses. Thus, DTH assays were used to test for ACAID following the AC injection of MOG35-55/MBP, or the intravenous injection of MOG35-55-specific/MBP-specific ACAID APCs. The functional local adoptive transfer (LAT) assays were used to examine the putative regulatory functions of in vitro generated MOG35-55-specific/MBP-specific Tregs. This report is the first to demonstrate the in vivo and in vitro induction of MOG35-55-specific/MBP-specific ACAID-mediated tolerance in C57BL/6 mice. These findings highlight the need for novel immunotherapeutic strategies for MS and optic neuritis.

Pigment Dispersion Contributes to Ocular Immune Privilege in a DBA/2J Mouse Model of Pigmentary Glaucoma.

Purpose: To investigate the effects of anterior chamber pigment dispersion on ocular immune privilege and the possible mechanisms involved in a DBA/2J mouse model of pigmentary glaucoma. Methods: DBA/2J mice were utilized as a pigment dispersion model, and age-matched C57BL/6J mice were used as the control group in this study. Proteins in the aqueous humor (AH) and serum were quantified using the bicinchoninic acid assay. Immune cells in the AH were detected using hematoxylin and eosin staining and immunocytochemistry. The expression of TGF-ß2 in the AH and cytokine levels (IL-10, IFN-γ) in serum were measured using ELISA. Anterior chamber-associated immune deviation (ACAID) was induced in DBA/2J mice by injecting antigens into the anterior chamber. Delayed-type hypersensitivity (DTH) assays were used to assess the induction of ACAID. In DBA/2J mice, before and after pigment dispersion, following anterior chamber injection of pigment particles, and after ACAID modeling, the expression of regulatory T cells (Tregs) was detected using flow cytometry. Results: Compared to C57BL/6J mice, the protein concentration, immune cell count, and TGF-ß2 levels in the AH were elevated in DBA/2J mice. Protein concentration and IL-10 levels in serum were increased, while IFN-γ levels were decreased in DBA/2J. Additionally, the expression of Treg cells in the spleen of DBA/2J mice was significantly increased after pigment dispersion and anterior chamber injection of pigment particles. At 3 and 6 months, DTH responses in DBA/2J mice were not inhibited, thus preventing ACAID induction. However, the opposite was observed at 9 months in DBA/2J mice. Furthermore, the ACAID group exhibited an augmented expression of Treg cells. Conclusions: Dispersion of pigment particles in the anterior chamber of the eye enhances the state of ocular immune privilege by influencing the immunosuppressive microenvironment and inducing more Treg cells to reestablish ACAID.

Implanted islets in the anterior chamber of the eye are prone to autoimmune attack in a mouse model of diabetes.

AIMS/HYPOTHESIS: Type 1 diabetes is an autoimmune disease resulting from the destruction of insulin-producing beta cells. Along with advances in generating replacement beta cells for treating diabetes, there is also increasing demand for non-invasive tools to evaluate the recurrence of autoimmune attack on transplanted tissue. Here, we examined the anterior chamber of the eye as a potential islet transplant site, and also evaluated whether in vivo imaging of the islets transplanted in the eye could enable real-time visualisation of autoimmune processes underway in the pancreas. METHODS: Syngeneic islet equivalents were transplanted into the eye or kidney capsule of streptozotocin-induced diabetic C57BL/6 mice to compare islet dose (25-125 islet equivalents) and function across transplant sites. Autoimmune attack of syngeneic islets was evaluated in the pancreas and eye tissues of NOD and NOD-severe combined immunodeficient (SCID) mice given diabetogenic splenocytes. RESULTS: Islet transplantation in the eye decreased fasting plasma glucose levels and increased weight gain and survival in an islet-dose-dependent manner. Even 50 islets in the eye reduced blood glucose levels, whereas ≥ 200 islets were required in the kidney for a similar effect. Autoimmune destruction of pancreatic islets in the eye mirrored that in the pancreas and could be visualised in real time by non-invasive imaging. CONCLUSIONS/INTERPRETATION: We found that far fewer islets were required to restore normoglycaemia when transplanted into the anterior chamber of the eye vs the kidney capsule. However, our results suggest that islets are not protected against autoimmune attack in the eye, making this a suitable site for visualising autoimmune processes against transplanted tissue.

Imaging dynamics of CD11c⁺ cells and Foxp3⁺ cells in progressive autoimmune insulitis in the NOD mouse model of type 1 diabetes.

AIMS/HYPOTHESIS: The aim of this study was to visualise the dynamics and interactions of the cells involved in autoimmune-driven inflammation in type 1 diabetes. METHODS: We adopted the anterior chamber of the eye (ACE) transplantation model to perform non-invasive imaging of leucocytes infiltrating the endocrine pancreas during initiation and progression of insulitis in the NOD mouse. Individual, ACE-transplanted islets of Langerhans were longitudinally and repetitively imaged by stereomicroscopy and two-photon microscopy to follow fluorescently labelled leucocyte subsets. RESULTS: We demonstrate that, in spite of the immune privileged status of the eye, the ACE-transplanted islets develop infiltration and beta cell destruction, recapitulating the autoimmune insulitis of the pancreas, and exemplify this by analysing reporter cell populations expressing green fluorescent protein under the Cd11c or Foxp3 promoters. We also provide evidence that differences in morphological appearance of subpopulations of infiltrating leucocytes can be correlated to their distinct dynamic behaviour. CONCLUSIONS/INTERPRETATION: Together, these findings demonstrate that the kinetics and dynamics of these key cellular components of autoimmune diabetes can be elucidated using this imaging platform for single cell resolution, non-invasive and repetitive monitoring of the individual islets of Langerhans during the natural development of autoimmune diabetes.

Systemic immunological tolerance to ocular antigens is mediated by TRAIL-expressing CD8+ T cells.

Systemic immunological tolerance to Ag encountered in the eye restricts the formation of potentially damaging immune responses that would otherwise be initiated at other anatomical locations. We previously demonstrated that tolerance to Ag administered via the anterior chamber (AC) of the eye required Fas ligand-mediated apoptotic death of inflammatory cells that enter the eye in response to the antigenic challenge. Moreover, the systemic tolerance induced after AC injection of Ag was mediated by CD8(+) regulatory T cells. This study examined the mechanism by which these CD8(+) regulatory T cells mediate tolerance after AC injection of Ag. AC injection of Ag did not prime CD4(+) T cells and led to increased TRAIL expression by splenic CD8(+) T cells. Unlike wild-type mice, Trail(-/-) or Dr5(-/-) mice did not develop tolerance to Ag injected into the eye, even though responding lymphocytes underwent apoptosis in the AC of the eyes of these mice. CD8(+) T cells from Trail(-/-) mice that were first injected via the AC with Ag were unable to transfer tolerance to naive recipient wild-type mice, but CD8(+) T cells from AC-injected wild-type or Dr5(-/-) mice could transfer tolerance. Importantly, the transferred wild-type (Trail(+/+)) CD8(+) T cells were also able to decrease the number of infiltrating inflammatory cells into the eye; however, Trail(-/-) CD8(+) T cells were unable to limit the inflammatory cell ingress. Together, our data suggest that "helpless" CD8(+) regulatory T cells generated after AC injection of Ag enforce systemic tolerance in a TRAIL-dependent manner to inhibit inflammation in the eye.

[Post-operational acute iridocyclitis and immune shifts in intraocular humor of patients with cataracts].

The negative tendency of cataracts growth, which is a consequence of various diseases of the organism including those of eyes, combined in the concept "the complicated cataract" is clearly traced now. In the concept of such a complication of cataracts as the acute autoimmune iridocyclitis, the important role, in our opinion, should be given to regional immunopathological disorders, which testify to the withdrawal of the known phenomenon underlying in the immunological tolerance of post-barrier eye membrane "a syndrome of eye anterior chamber-associated immune deviation (ACAID). Microcoaxial phacoemulsification was carried in three hundred patients with senile and complicated cataracts. The intraocular humor of the operated patients was subjected to immune-enzyme immunomorphological analysis for СD4, СD8, IgG and B-lymphocytic populations. On the base of performed clinical-laboratory research we found that the gravest inflammatory process in eye tissues manifested in the form of autoimmune aseptic iridocyclitis was observed particularly in patients with complicated cataracts, proceeding on the background of glaucoma, diabetes and the previous trauma of an eye. The high indicators of IgG, СD4 were registered on the background of low СD8 indicators in the intraocular humour at these patients. The revealed regional inflammatory reaction in eye tissues testifies, in our opinion, in favour of in situ withdrawal of ACAID; this latter brings to origination of acute aseptic autoimmune iridocyclitis in the early post-operational course of the complicated cataracts.

Ocular pathogenesis and immune reaction after intravitreal dispase injection in mice.

PURPOSE: The purpose of the current study was to examine the ocular pathogenesis and immune reaction in mice after intravitreal dispase injection. METHODS: Three microliters of dispase at a concentration of 0.2 U/µl were injected into the vitreal cavities of 4-6-week-old mice. Hematoxylin and eosin staining, immunofluorescence analysis, and electroretinograms of the eyes were then performed to assess ocular changes, and enzyme-linked immunospot assays and intracellular staining of single-cell suspensions of the spleens were used to detect immune changes during an 8 week observation period. RESULTS: Neutrophils were the main inflammatory infiltrating cells appearing at the anterior chamber. No cluster of differentiation (CD)3+ labeled T cells, F4/80+ labeled macrophages, or CD56+ labeled natural killer cells were found in the vitreal cavities or retinas in dispase-injected mice within 5 days after injection. Proliferative vitreoretinopathy (PVR)-like signs first appeared at 2 weeks, gradually increased thereafter, and reached peak values at 8 weeks. There was a statistically significant difference in b-wave amplitudes between the PVR and saline-control eyes. Enzyme-linked immunospot assays and intracellular staining showed that specific CD4+ and CD8+ labeled T cells were not involved in dispase-injected mice. CONCLUSIONS: Our data show that neutrophils in the anterior chamber and PVR-like signs in the retinas were found, and that specific immune reactions were not involved after intravitreal dispase injection in mice.

[Anti-inflammatory Strategies by Focusing on the Particularity of Ocular Immunity].

Particularity of ocular immunity is manifested by "Immune privilege". For example, it has been generally known that corneal transplantation is a typically successful organ transplantation compared with other organs. This immune privilege can be explained by "immune-suppressive ocular microenvironment" and "anterior chamber-associated immune deviation, ACAID". This review focused on molecular mechanisms of the "immune-suppressive ocular microenvironment" and "ACAID", so that possible anti-inflammatory strategies could be raised. Especially, in murine ACAID model, anti-inflammatory actions were induced probably through induction of Treg cells. As an anti-inflammatory strategy, anti-inflammatory Treg cells could be induced in vitro. Treg cells that are specifically responsive for a specific antigen can be induced by culturing spleen cells with the antigen and transforming growth factor-ß (TGF-ß). The induced Treg cells were activated by stimulation with the specific antigen. When the induced Treg cells were adoptively transferred to recipient mice, antigen-induced inflammation was effectively suppressed. The Treg cells may be able to be efficiently induced by eye-based mechanisms. Further analyses of mechanisms underlying the ocular immune privilege can be useful for development of new anti-inflammatory strategies on the eye basis.

Induction of anterior chamber-associated immune deviation requires an intact, functional spleen.

Anterior chamber-associated immune deviation (ACAID) expresses itself in BALB/c mice inoculated intracamerally with P815 cells in three ways: progressive growth of the tumor within the eye, transient growth of P815 cells injected subcutaneously, and prolonged acceptance of DBA/2 skin allografts. The spleen was found to play a crucial role in the development of ACAID. Splenectomized animals bearing intracameral P815 tumors reject DBA/2 skin grafts in an accelerated manner. A functioning spleen was required during the first 10 d after intracameral inoculation of P815 cells, but not thereafter. Reconstitution experiments revealed that the spleen's ability to support the induction of ACAID depends partly upon its constituent lymphoid cells, but also upon either a stromal component or a unique architectural arrangement that can only be restored with splenic fragments. The data hold promise that therapeutic protocols using appropriately timed splenectomy and specific immunization can be devised to induce hosts bearing intraocular tumors to mount an immune response sufficiently vigorous to destroy the tumor within the eye, and sufficiently precise to preserve the functional and anatomic integrity of the eye.

Systemic immune unresponsiveness induced in adult mice by anterior chamber presentation of minor histocompatibility antigens.

The ability to introduce carefully controlled numbers of viable cells into the anterior chamber of mouse eyes made it possible to examine the interrelationship between presentation of antigens into the anteior chamber and into conventional body sites and their synergistic/antagonistic effects on the immune system. P815 mastocytoma (DBA/2; H-2d) cells are syngeneic with BALB/c hosts at the major histocompatibility locus, but differ at multiple minor histocompatibility loci. When P815 cells were injected subcutaneously, they were rejected by BALB/c recipients who became specifically immune. By contrast, when P815 cells were injected intracamerally, they grew progressively into massive intraocular tumors; moreover, these BALB/c hosts proved subsequently unable to reject subcutaneously injected P815 cells, and, more impressively, failed to reject DBA/2 skin allografts placed orthotopically. Minor histocompatibility antigens, presented first through the anterior chamber of mouse eyes, elicit a suppressive rather than an aggressive host immune response that protects cells that bear these antigens from a destructive alloimmune reaction at both intracameral and systemic sites.

By altering ocular immune privilege, bone marrow-derived cells pathogenically contribute to DBA/2J pigmentary glaucoma.

Pigment dispersion syndrome causes iris pigment release and often progresses to elevated intraocular pressure and pigmentary glaucoma (PG). Because melanin pigment can have adjuvant like properties and because the Gpnmb gene, which contributes to pigment dispersion in DBA/2J (D2) mice, is expressed in dendritic cells, we tested the hypothesis that ocular immune abnormalities participate in PG phenotypes. Strikingly, we show that D2 eyes exhibit defects of the normally immunosuppressive ocular microenvironment including inability of aqueous humor to inhibit T cell activation, failure to support anterior chamber (AC)-associated immune deviation, and loss of ocular immune privilege. Histologic analysis demonstrates infiltration of inflammatory leukocytes into the AC and their accumulation within the iris, whereas clinical indications of inflammation are typically very mild to undetectable. Importantly, some of these abnormalities precede clinical indications of pigment dispersal, suggesting an early role in disease etiology. Using bone marrow chimeras, we show that lymphohematopoietic cell lineages largely dictate the progression of pigment dispersion, the ability of the eye to support induction of AC-associated immune deviation, and the integrity of the blood/ocular barrier. These results suggest previously unsuspected roles for bone marrow-derived cells and ocular immune privilege in the pathogenesis of PG.

Antiinflammatory effects of CD95 ligand (FasL)-induced apoptosis.

Apoptosis is critical to homeostasis of multicellular organisms. In immune privileged sites such as the eye, CD95 ligand (FasL)-induced apoptosis controls dangerous inflammatory reactions that can cause blindness. Recently, we demonstrated that apoptotic cell death of inflammatory cells was a prerequisite for the induction of immune deviation after antigen presentation in the eye. In this report, we examine the mechanism by which this takes place. Our results show that Fas- mediated apoptosis of lymphoid cells leads to rapid production of interleukin (IL)-10 in these cells. The apoptotic cells containing IL-10 are responsible for the activation of immune deviation through interaction with antigen-presenting cells (APC). In support of this, we found that apoptotic cells from IL-10(+/+) animals fed to APC in vitro promote Th2 cell differentiation, whereas apoptotic IL-10(-/-) cells, as well as nonapoptotic cells, favor Th1 induction. Thus, apoptotic cell death and tolerance are linked through the production of an antiinflammatory cytokine to prevent dangerous and unwanted immune responses that might compromise organ integrity.