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.

Anterior chamber associated immune deviation used as a neuroprotective strategy in rats with spinal cord injury

The inflammatory response is probably one of the main destructive events occurring after spinal cord injury (SCI). Its progression depends mostly on the autoimmune response developed against neural constituents. Therefore, modulation or inhibition of this self-reactive reaction could help to reduce tissue destruction. Anterior chamber associated immune deviation (ACAID) is a phenomenon that induces immune-tolerance to antigens injected into the eye´s anterior chamber, provoking the reduction of such immune response. In the light of this notion, induction of ACAID to neural constituents could be used as a potential prophylactic therapy to promote neuroprotection. In order to evaluate this approach, three experiments were performed. In the first one, the capability to induce ACAID of the spinal cord extract (SCE) and the myelin basic protein (MBP) was evaluated. Using the delayed type hypersensibility assay (DTH) we demonstrated that both, SCE and MBP were capable of inducing ACAID. In the second experiment we evaluated the effect of SCE-induced ACAID on neurological and morphological recovery after SCI. In the results, there was a significant improvement of motor recovery, nociceptive hypersensitivity and motoneuron survival in rats with SCE-induced ACAID. Moreover, ACAID also up-regulated the expression of genes encoding for anti-inflammatory cytokines and FoxP3 but down-regulated those for pro-inflamatory cytokines. Finally, in the third experiment, the effect of a more simple and practical strategy was evaluated: MBP-induced ACAID, we also found significant neurological and morphological outcomes. In the present study we demonstrate that the induction of ACAID against neural antigens in rats, promotes neuroprotection after SCI.

Intravital imaging of cytotoxic T lymphocytes

Intravital imaging approaches are proving to be essential to address new questions to better understand how the immune system operates. These approaches are especially valuable to characterize the complex organization of immune responses in vivo. Here, we examine how to take advantage of the cornea as a natural body window to apply noninvasive imaging techniques to assess cytotoxic T lymphocyte involvement in the immune rejection process in a model of intraocular allogeneic islet transplantation.

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.

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.

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.

[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.

An intracameral injection of antigen induces in situ chemokines and cytokines required for the generation of circulating immunoregulatory monocytes

Anterior Chamber-Associated Immune Deviation (ACAID) induced by an intracameral injection of antigen generates antigen-specific regulatory splenic T cells that suppress specifically cell-mediated immunity specific for the injected antigen. Circulating F4/80⁺ cells recovered from mice receiving an intracameral injection of antigen are thought to be ocular in origin and induce the development of thymic and splenic regulatory T cells. We have shown previously that after the intracameral injection of antigen there is a CCR2/CCL2-dependent infiltration of circulating F4/80⁺ cells into the anterior chamber associated with the generation of circulating, ACAID-inducing F4/80⁺ monocytes. Here we tested the hypothesis that the intracameral injection of antigen induces events in the anterior chamber that are associated with the induction of circulating immunoregulatory monocytes that induce the suppression of cell-mediated immunity. The intracameral injection of antigen resulted in aqueous humor (i) a time- dependent increase of CCL2 and CCL7, (ii) a transient increase in TNF-α, and (iii) an infiltration of CD11b^hi, Gr1^hi and F4/80⁺ as well as F4/80⁻ and Gr1^hi peripheral blood cells into the anterior chamber. Further characterization of these F4/80⁺ cells revealed that they are Ly 6C^hi, LY6G^lo or negative, 7/4 (LY6B)^hi, CD115⁺, CD45⁺, CD49B⁺, and CD62 L⁺. Antibody-mediated neutralization of TGF-β in situ in the anterior chamber prevented the induction of circulating, ACAID-inducing monocytes and ACAID. These cells did not increase in the irides of ACAID-refractory CCR2–/– and CCL2–/– mice that received an intracameral injection of antigen. Our results extend our suggestion that ACAID is initiated as the result of a mild proinflammatory response to intracameral injection that results in the infiltration of a CCR2⁺ subset of monocytes into the anterior chamber where there is a TGF-β-dependent induction of an immunosuppressive phenotype in the infiltrated monocytes that recirculate to induce antigen-specific regulatory T cells.

Ocular immune privilege sites

The eye is one of the immune privilege sites of the body that is consequently protected from the detrimental and potentially blinding influences of immunologic inflammation. Within the eye, the anterior chamber has been recognized for its immune privilege property for many years now; however, a similar property detectable in the subretinal space has only recently been appreciated. These ocular sites are not only equipped with specialized mechanisms that barricade local inflammatory responses, but also induce systemic regulatory immune response. Numerous studies have characterized molecular and cellular mechanisms involved in conferring both these sites with an immune privilege status. Pigmented epithelial cells lining the anterior chamber in the iris and ciliary body area as well as those in the retina are endowed with immunomodulatory properties that contribute to ocular immune privilege. These cells, via expression of either soluble factors or membrane molecules, inhibit inflammatory T cell activation and promote the generation of regulatory T cells. In the anterior chamber resident antigen-presenting cells, influenced by the various immunosuppressive factors present in the aqueous humor, capture ocular antigens and present them in the spleen to T cells in association with NKT cells and marginal zone B cells. Immunomodulatory microenvironment created by these cells helps generate regulatory T cells, capable of interrupting the induction as well as expression of inflammatory responses. Furthermore, neural regulation of both intraocular and systemic regulatory mechanisms also contributes to ocular immune privilege.

Antigen-presenting cells are targets of regulatory T cells similar to those that mediate anterior chamber-associated immune deviation

PURPOSE

To identify the means by which in-vitro-generated regulatory T cells, similar to those in anterior chamber-associated immune deviation (ACAID), suppress antigen-specific T-cell responses.

METHODS

T regulators (T regs), generated by stimulating ovalbumin (OVA)-specific Tcr transgenic DO11.10 T cells with OVA-pulsed, TGF-beta2-treated peritoneal exudates cells (PEC), or their supernatants were added to OVA-pulsed PEC that were used to activate DO11.10 T cells in vitro or to suppress OVA-specific delayed hypersensitivity (DH) induction in vivo.

RESULTS

OVA-pulsed PECs exposed in vitro to TGF-beta-producing T regs or their supernatants failed to activate DO11.10 T cells in vitro, and suppressed DH in mice immunized with OVA plus adjuvant.

CONCLUSION

T cells exposed to TGF-beta2-pretreated, antigen-pulsed PECs secrete soluble factors, including active TGF-beta that regulate OVA-specific responses by forcing antigen-presenting cells to promote deviant T-cell activation in vitro and in vivo.

A Privileged View of NKT Cells and Peripheral Tolerance Through the Eye

The eye is an immune-privileged site that uses specialized mechanisms to protect itself from damage and to preserve its visual acuity. Among the mechanisms that contribute to the eye's privileged existence is its ability to induce both local and peripheral tolerance to antigens that may transgress its chambers. Experimentally, antigens that are inoculated into the anterior chamber induce an associated immune deviation of immune lymphocytes from their potential T-helper inflammatory responses to T regulatory cells. The prominent role of a somewhat rare cell called invariant (i)NKT cell in the process of tolerance induced through the anterior chamber-associated immune deviation model, ACAID, has revealed novel biological characteristics for the iNKT cell, as well as novel mechanisms for the induction of tolerance that have not been previously known or considered. The role of the iNKT cell in ACAID and its novel story is discussed in this mini-review.

Qa-1, a Nonclassical MHC Molecule with Immunomodulatory Functions, Is Ubiquitously Expressed in the Immune-Privileged Anterior Chamber of the Eye

PURPOSE

To determine whether the MHC class Ib gene, Qa-1, is expressed in the tissues that surround the immune-privileged anterior chamber (AC) of the murine eye.

METHODS

Transcription of Qa-1 mRNA in BALB/c ocular tissues was analyzed by reverse transcription-polymerase chain reaction. Expression of Qa-1 protein was assessed on ocular frozen tissue sections by immunohistochemistry, and within aqueous humor by western blotting.

RESULTS

Transcription of Qa-1 was found in all tissues surrounding the AC of the eye. Immunohistological staining revealed Qa-1 expression on corneal endothelium, corneal epithelium, and lens epithelium. No soluble Qa-1 was detected in aqueous humor.

CONCLUSIONS

Qa-1, unlike other MHC class I molecules, is ubiquitously expressed in tissues surrounding the AC of the eye, raising the possibility that Qa-1 plays a role in creating and maintaining ocular immune privilege.

Expression of Tim-3 Is Transiently Increased before Development of Anterior Chamber-Associated Immune Deviation

PURPOSE

To assess the expression of T-cell immunoglobulin- and mucin-domain-containing molecule 3 (Tim-3) in the spleens of BALB/c mice undergoing anterior chamber-associated immune deviation (ACAID).

METHODS

ACAID was generated after intracameral (i.c.) injection of ovalbumin (OVA) into BALB/c mice and evaluated by assessing the delayed-type hypersensitivity (DTH) response following a subsequent subcutaneous (s.c.) injection of OVA emulsified in complete Freund's adjuvant (CFA) on Days 0, 3, 7, 14, 21 and 28. Tim-3 mRNA levels were detected using real-time RT-PCR, and the frequency of CD4+Tim-3+ T cells in splenocytes as well as the coexpression of Tim-3 with CD25 on CD4+ T cells were assessed by flow cytometry.

RESULTS

A significantly suppressed DTH response was observed on Days 7, 14, 21, and 28, but not on Days 0 and 3 during the development of ACAID. The levels of Tim-3 mRNA and the frequency of CD4+CD25+Tim-3+ T cells in the splenocytes reached a peak on Day 3, declined on Day 7, and returned to basal levels thereafter.

CONCLUSIONS

A transient upregulation of Tim-3 expression was observed in the early stage of ACAID, suggesting its possible involvement in the development of ACAID.

Termination of Systemic Immunity in the Presence of Intraocular Tumors: Influence of Ocular Immune Privilege on Tumor Vaccines

Ocular immune privilege preserves the visual axis by preventing the induction of sight-threatening nonspecific inflammation. Although privilege is essential for maintaining visual integrity, intraocular tumors exploit the privileged environment and grow progressively within the anterior chamber of the eye. Recently, a large number of laboratories have constructed genetically engineered tumor cell vaccines that express high levels of costimulatory signals. These vaccines are designed to bypass the normal pathways of T-cell activation and directly activate CD8+ tumor-specific T cells. In the following series of experiments, we determined whether a tumor cell vaccine that uses costimulatory signals (CD80 and IL-12) is capable of eliminating tumors within the immune-privileged anterior chamber. As expected, vaccine-immunized mice rejected subcutaneous flank tumors (a non-privileged site). However, the vaccine failed to protect mice from even a small number of tumor cells transplanted into the immune-privileged anterior chamber. Surprisingly, immunized mice that were simultaneously challenged with subcutaneous and anterior chamber tumors were unable to eliminate tumors at either site. The failure of systemic protective immunity coincided with the loss of tumor-specific delayed hypersensitivity and cytotoxic T cells. We conclude that tumor cell vaccines that induce complete protection against tumors in non-immune-privileged sites fail to protect against the same tumor within an ocular immune-privileged site. Moreover, a tumor that escapes elimination within the eye can terminate systemic protective immunity that is induced by the tumor cell vaccine.

[The influence of glaucoma filtration surgery on anterior chamber associated immune deviation in mice]

OBJECTIVE

To study glaucoma infiltration surgery induced the anterior chamber associated immune deviation (ACAID) by with or without anterior chamber (AC) implantation of foreign epithelium removed corneal graft in mice.

METHODS

In this study, fifty Wistar mice were randomly divided into five groups (ten in each group) and additional five SD and one Wistar mouse were used as the providers of epithelium removed corneal grafts to induce ACAID as follows: Group A: corneal grafts from Wistar mouse were implanted into the AC 1 week after the infiltration surgery. Group B: the spleen cells were injected into the nape of neck 1 week after the glaucoma infiltration surgery. In group C, D, and E, the corneal grafts from SD mice were implanted into the AC at 1 week, 4 week, and 8 week after the glaucoma infiltration surgery, respectively. To induce the delayed type hypersensitivity (DTH), spleen cells were injected into the right ear pinna 1 week after the neck injection in group B, 2 weeks after the AC implantation of corneal grafts in other groups. At the same time points as the induction of DTH, heart blood was collected to detect the concentration of IL-4 and IL-10. The spleens were removed to evaluate the expression of the GATA-3 mRNA by RT-PCR. The eyeballs were enucleated and used to evaluate the histopathological changes.

RESULTS

(1) The DTH were found in group B, C, D, and E with corneal grafts of SD, but not in group A with that of Wistar. (2) The serum concentrations of IL-4 and IL-10 were statistically different in group C, D, and E (F = 49.124, 6.336; P < 0.01). The concentrations of IL-4 and IL-10 were significantly (P = 0.002) lower in group D than those in group C and E (3.759 +/- 0.250 vs 5.916 +/- 0.500 or 4.566 +/- 0.518, and 17.170 +/- 3.943 vs 44.447 +/- 17.167 or 35.643 +/- 21.233 microg/L, n = 10, respectively), which showed a biphase response fluctuation of ILs. (3) The GATA-3 mRNA was obviously up-regulated in group D and E. (4) The exudation and a few inflammatory cells in the AC were observed in group C, but not in group D and E.

CONCLUSIONS

The eye with the glaucoma infiltration surgery results in a temporary incapable of inducing ACAID, which is gradually recovered following the diminish of intraocular inflammation and the increase of levels of IL4, IL-10 and GATA-3 mRNA.

[Expression of programmed death 1 and its ligands in iris-ciliary body from mice with anterior chamber-associated immune deviation]

OBJECTIVE

To study the expression and possible implication of programmed death 1 (PD-1) and its ligands in the iris-ciliary body from mice with anterior chamber-associated immune deviation (ACAID).

METHODS

This was an experimental study. Twenty-four BALB/c mice were divided into ACAID group, negative controls, positive controls and phosphate-buffer saline controls. ACAID was evaluated by delayed-type hypersensitivity response. Expressions of PD-1 and its ligands (PD-L1, PD-L2) in the iris-ciliary body from ACAID mice were determined by real-time polymerase chain reaction and immunohistochemical studies.

RESULTS

Delayed-type hypersensitivity was not detected in ACAID group, indicating that ACAID was induced successfully. The expression of PD-1 mRNA in ACAID group was higher than that in all other groups (F = 248. 109, P < 0.05). The positive controls showed a high expression of PD-L1 mRNA (F = 179. 033, P < 0.05). PD-1 and PD-L1 positive cells with round or oval shapes were found in whole iris-ciliary body, especially in the iris base and pupil margin. Expression of PD-1 and PD-L1 proteins were similar to their expression at mRNA levels. Neither mRNA nor protein of PD-L2 was detected in the iris-ciliary body in all groups.

CONCLUSION

An increased expression of PD-1 in the iris-ciliary body of ACAID mice indicates that this is involved in the induction of ACAID.

[The influence of lens and vitreous resection on anterior chamber associated immune deviation in mice model]

OBJECTIVE

To explore the impact of lens and vitreous resection on the induction of the anterior chamber associated immune deviation (ACAID) in the mice, and its relationship with the time duration postoperatively.

METHODS

The current study was an experimental research. Fifty-one Wistar mice were chosen to involve this study. After the surgeries, 50 Wistar mice were randomly divided into 5 groups. Other 5 SD mice and 1 Wistar mouse were used as the providers of epithelium removed corneal grafts to induce ACAID. Group A: corneal grafts from wistar mouse were implanted into the anterior chamber 1 week after the lens and vitreous resection. Group B: the spleen cells were injected into the nape of neck 1 week after the lens and vitreous resection. The corneal grafts from SD mice were implanted into the anterior chamber 1 week, 4 week and 8 week after the lens and vitreous resection in group C, D and E respectively. To induce the delayed type hypersensitivity (DTH), spleen cells were injected into the right ear pinna 1 week after the neck injection in group B, 2 weeks after the corneal grafts anterior chamber implantation in other groups. At the same time point as the DTH inducement, aqueous humor was collected to measure the concentration of transforming growth factor (TGF) -beta2 and interleukin (IL)-10; heart blood was collected to detect the concentration of IL-4 and IL-10. And the spleens were removed to evaluate the expression of the GATA-3 mRNA by RT-PCR. The eyeballs were enucleated to evaluate the histopathologic changes.

RESULTS

(1) The evaluation of DTH. The DTH were found in group B, C, D and E. (2) The analysis of the TGF-beta2 and IL-10 concentrations in aqueous humor and the IL-4, IL-10 concentrations in serum. The concentrations of IL-4 in serum were (4.073 +/- 0.198) ng/L in group A, (5.806 +/- 0.635) ng/L in group B, (5.535 +/- 0.278) ng/L in group C, (4.102 +/- 0.344) ng/L in group D and (5.313 +/- 0.317) ng/L in group E. The concentrations of IL-10 in serum in group A to group E were (7.854 +/- 2.349) ng/L, (25.633 +/- 6.307) ng/L, (40.103 +/- 16.010) ng/L, (14.321 +/- 2.983) ng/L and (28.620 +/- 5.251) ng/L. The IL-10 concentrations in the aqueous humor were (8.857 +/- 0.401) ng/L, (22.882 +/- 3.315) ng/L, (21.548 +/- 0.477) ng/L, (7.742 +/- 0.952) ng/L and (12.119 +/- 0.477) ng/L, respectively. The concentrations of TGF-beta in the aqueous humor were (5.800 +/- 2.899) ng/L in group A, (60.010 +/- 0.000) ng/L in group B, (57.055 +/- 4.179) ng/L in group C, (28.490 +/- 4.144) ng/L in group D and (36.370 +/- 3.169) ng/L in group E. Significant differences were found in concentrations of TGF-beta2 and IL-10 in aqueous humor and the concentrations of IL-4 and IL-10 in serum in group C, D and E. The concentrations of TGF-beta2, IL-4 and IL-10 were significantly lower in group D than those in group C and E. The trend that the concentrations of TGF-beta2, IL-4 and IL-10 increased after one week postoperatively, then decreased, and finally increased again was observed. (3) The expression of GATA-3 mRNA in spleen. The expression values of GATA-3 mRNA were 662.5 +/- 114.4 in group A, 730.7 +/- 53.8 in group B, 881.9 +/- 10.7 in group C, 1288.3 +/- 258.0 in group D and 1129.7 +/- 95.7 in group E. An obvious up-regulation of the GATA-3 mRNA was noted in group D and E.

CONCLUSIONS

The eye after the lens and vitreous resection lost the ability to induce ACAID in the research duration of this study. But with the gradually decrease of the intraocular inflammation, the ability to induce ACAID might recover with the time.

NKT cell-derived urokinase-type plasminogen activator promotes peripheral tolerance associated with eye

In a model of peripheral tolerance called anterior chamber-associated immune deviation (ACAID), the differentiation of the T regulatory cells depends on NKT cells and occurs in the spleen. In this study, we show that NKT cells that express the invariant (i) TCR and are the CD1d-reactive NKT cells (required for development of peripheral tolerance) actually produced urokinase-type plasminogen activator (uPA) during tolerance induction. The RT-PCR and in vitro plasmin assay showed that splenic iNKT cells derived uPA-converted plasminogen to plasmin. Moreover, uPA was required for tolerance induction because uPA knockout (KO) mice did not develop peripheral tolerance or develop CD8(+) T regulatory cells after Ag inoculation into the anterior chamber. In contrast, other aspects of ACAID-induced tolerance, including recruitment of iNKT cells to the spleen and production of IL-10 by iNKT cells, were unchanged in uPA-deficient mice. The adoptive transfer of splenic NKT cells from wild-type mice restored ACAID in Jalpha18 KO mice (iNKT cell deficient), but NKT cells from uPA KO mice did not. We postulate that the mechanism of action of uPA is through its binding to the uPAR receptor, and enzymatic cleavage of plasminogen to plasmin, which in turn activates latent TGFbeta. In conclusion, uPA derived from iNKT cells is required to induce peripheral tolerance via the eye.

NK1.1 Cells Downregulate Murine Endotoxin-Induced Uveitis Following Intraocular Administration of Interleukin-12

To evaluate the role of IFN-gamma (interferon gamma) in IL-12- (interleukin-12)-induced inhibition of the inflammatory response in the eye during endotoxin-induced uveitis (EIU). C57BL/6 wild type mice and IFN-gamma-deficient (GKO) mice were injected with 250 microg of Salmonella typhymurium endotoxin as a model for EIU. Animals were then injected intraocularly with 100 ng of rIL-12 or the equivalent volume of Phosphate-buffer saline (PBS). Histopathologic grading of disease was performed 12, 36 and 72 h after endotoxin injection. Chemokine mRNA expression in the eye was evaluated by reverse transcriptase-polymerase chain reaction. Depletion of NK1.1+ cells in vivo was performed using a PK136 antibody. Depletion of IFN-gamma was performed using the R4-6A2 antibody. C57BL/6 mice treated with rIL-12 intraocularly were protected from the development of EIU. Neutralization of IFN-gamma with a monoclonal antibody abrogated such protection. The IL-12 protective effects were lost in NK1.1-depleted mice. Intraocular IL-12 decreased the expression of keratinocyte-derived chemokines (KC) gene but had no effect on macrophage inflammatory protein (MIP-2) gene. The protective effect of IL-12 during EIU occurs through production of IFN-gamma by NK1.1+ cells. IL-12-induced higher levels of IFN-gamma are also correlated with lower expression of the chemokine KC, resulting in diminished attraction of neutrophils to the inflammatory site.

Expansion of B cells is necessary for the induction of T-cell tolerance elicited through the anterior chamber of the eye

Antigens injected into the anterior chamber (AC) of the eye induce a form of peripheral immune tolerance termed anterior chamber-associated immune deviation (ACAID). ACAID is initiated by F4/80+ ocular antigen-presenting cells (APC) which capture ocular antigens and migrate to the spleen where they transfer antigenic peptides to B cells, which act as ancillary APC for the induction of T-regulatory cells (T(reg)) that inhibit delayed-type hypersensitivity (DTH) responses. Here we show that ocular-like APC induce the expansion of tolerogenic splenic B cells. Furthermore, we show that inhibiting B-cell proliferation with either mitomycin-c or gamma-irradiation abolishes the ability of B cells to induce T(reg). To our knowledge, this is the first study to report that B-cell proliferation is needed for B-cell-induced T-cell tolerance.

Increased expression of Foxp3 in splenic CD8+ T cells from mice with anterior chamber-associated immune deviation

PURPOSE

To examine the expression of Foxp3 on CD8+ T cells in the spleen during anterior chamber-associated immune deviation (ACAID).

METHODS

Ovalbumin (OVA) was injected into the anterior chamber (AC) of C57BL/6 mice, and the delayed-type hypersensitivity (DTH) response was measured to evaluate the development of ACAID. The suppressive effect of CD8+ T cells in ACAID mice was determined by a local adoptive transfer (LAT) assay. Flow cytometry was used to assay the frequency of CD8+ Foxp3+ T cells from normal mice, ACAID mice, and control mice receiving an AC injection of PBS (PBS-AC-injected mice). These frequencies were also tested after polyclonal or specific antigen stimulation. The mRNA level of Foxp3 in CD8+ splenocytes from different groups with or without stimulation were determined by reverse transcription-polymerase chain reaction.

RESULTS

OVA injection into the AC induced ACAID, and CD8+ T cells from ACAID mice inhibited the ear-swelling response by OVA-primed responder cells in LAT assay. Flow cytometry analysis showed that the frequency of CD8+ Foxp3+ cells in splenocytes was upregulated in ACAID mice following polyclonal or specific antigen stimulation. Foxp3 mRNA was only detected in CD8+ T cells from ACAID mice after polyclonal stimulation.

CONCLUSIONS

An upregulated Foxp3 expression in CD8+ T cells is associated with the development of ACAID, suggesting an involvement of CD8+ Foxp3+ T cells in this model of immune tolerance.

CD8+ T cells circumvent immune privilege in the eye and mediate intraocular tumor rejection by a TNF-alpha-dependent mechanism

Although intraocular tumors reside in an immune-privileged environment, T cells can circumvent immune privilege and mediate tumor rejection without inducing damage to normal ocular tissue. In this study, we used a well-characterized tumor, Ad5E1 (adenovirus type 5 early region 1), to analyze the role of CD8+ T cells in the pristine rejection of intraocular tumors. It has been previously documented that Ad5E1 tumor rejection can occur in the absence of CD8+ T cells. However, here we find that CD8+ T cells infiltrated intraocular Ad5E1 tumors in C57BL/6 mice. Surprisingly, CD8+ T cells from tumor-rejector mice could mediate intraocular tumor rejection following adoptive transfer to SCID mice. In determining the mechanisms behind CD8+ T cell-mediated tumor rejection, we discovered that antitumor CTL activity was neither observed nor necessary for rejection of the intraocular tumors. CD8+ T cells from rejector mice did not produce IFN-gamma in response to Ad5E1 tumor Ags or use FasL to mediate intraocular tumor rejection. Also, CD8+ T cells did not use perforin or TRAIL, as CD8+ T cells from perforin knockout (KO) and TRAIL KO mice conferred protection to SCID recipient mice following adoptive transfer. We discovered that CD8+ T cells used TNF-alpha to mediate tumor rejection, because Ad5E1 tumor cells were highly sensitive to TNF-alpha-induced apoptosis and CD8+ T cells from TNF-alpha KO mice did not protect SCID mice from progressive Ad5E1 tumor growth. The results indicate that CD8+ T cells circumvent immune privilege and mediate intraocular tumor rejection by a TNF-alpha-dependent manner while leaving the eye intact and vision preserved.

CD4+CD25+Tregs express an increased LAG-3 and CTLA-4 in anterior chamber-associated immune deviation

BACKGROUND

Regulatory CD4(+)CD25(+) T cells have been proven to be essential for maintenance of peripheral tolerance and autoimmune diseases. ACAID is a model of immune privilege in the eye. Relatively little is known about the role and phenotype of these regulatory CD4(+)CD25(+) T cells in ACAID.

METHODS

Injection of OVA into the anterior chamber of BALB/C mice was performed to induce ACAID. The frequencies of splenic CD4(+)CD25(+) Tregs and the expression of CTLA-4 and LAG-3 on these cells were determined by flow cytometry. Magnetic cell sorting was used to isolate CD4(+)CD25(+) and CD4(+)CD25(-)T cells. The function of CD4(+)CD25(+) T cells was detected by in vitro immunosuppression assays and in vivo adoptive transfer.

RESULTS

ACAID was successfully induced following an i.c. injection of OVA. Frequencies of CD4(+)CD25(+) and Tregs were significantly increased in ACAID mice as compared to those in controls. The CD4(+)CD25(+) T cells stimulated with OVA in ACAID mice showed a stronger suppressive ability in vitro than those seen in non-ACAID mice. CD4(+)CD25(+) T cells from ACAID mice, but not from non-ACAID mice, were able to suppress DTH responses in an antigen-specific manner following adoptive transfer. The frequencies of CTLA-4 or LAG-3 on Tregs in ACAID mice were higher as compared with those in naive mice.

CONCLUSION

Splenic CD4(+)CD25(+)Foxp3(+)T cells expressing CTLA4 and LAG3 play an important role in the induction of ACAID.

The induction of anterior chamber-associated immune deviation

Evidence of ocular immune privilege was noted almost 130 years ago. The past 30 years have witnessed an explosion in research on ocular immune privilege. One of the primary mechanisms that contribute to ocular immune privilege is the unique form of immune deviation that is invoked when antigens are introduced into the anterior chamber (AC) of the eye - a phenomenon termed AC-associated immune deviation (ACAID). ACAID embodies a constellation of cellular interactions and at least four different organ systems: eye, thymus, spleen, and sympathetic nervous system. At least four different cell populations interact to generate CD8+ T regulatory cells that suppress both Th1- and Th2-mediated inflammation. The interactions that occur between F4/80+ antigen-presenting cells, CD4+ T regulatory cells, NK1.1+ T cells, gammadelta T cells, B cells, and CD8+ T cells remain to be fully elucidated. Ocular immune privilege was originally perceived as a simple anatomic anomaly that has evolved to be one of the most sophisticated and intriguing forms of immune regulation.

Impact of inflammation on ocular immune privilege

The immune-privileged status of the anterior chamber of the eye is altered in experimentally induced intraocular inflammation and in the pigment dispersion syndrome of DBA/2J mice. However, the eye has developed multiple mechanisms to maintain ocular immune privilege even in the presence of intraocular inflammation.

Acute retinal necrosis

Acute retinal necrosis (ARN) is a rare disease that is usually caused by one of the three neurotropic human herpesviruses - herpes simplex virus type 1(HSV-1), HSV-2 and varicella-zoster virus (VZV). Although much is known about the clinical course of the disease and its treatment and about the viruses that cause it, comparatively little is known about its pathogenesis. This article will review the history of ARN, the typical clinical findings, and methods of diagnosis. Information from studies of the mouse model of ARN including development of anterior chamber-associated immune deviation (ACAID) and routes of spread will be reconsidered, and the combined information from human and mouse studies will be discussed to suggest mechanisms that contribute to the pathogenesis of ARN in human patients. Finally, puzzles and questions about the disease will be considered.

Therapies based on principles of ocular immune privilege

Anterior chamber (AC)-associated immune deviation (ACAID) is a form of ocularderived peripheral tolerance that helps to maintain the immune privilege of the eye by suppressing both the priming and elicitation of adaptive immune responses. ACAID is known to facilitate the survival of corneal grafts and suppression autoimmune uveitis in the eye. Intravenous inoculation of in vitro generated ACAID tolerance-inducing antigen presenting cells (APCs) treated with transforming growth factor-Beta2 (tolerogenic APCs) generates the kind of T regulatory cells found in in vivo ACAID when antigen is inoculated into the AC of the eye. Here, we review the application of peripheral tolerance induction by ACAID with either AC inoculation or in vitro generated tolerogenic ACAID-APCs in suppressing ongoing Th1- and Th2-mediated immune pathogenesis in naive and presensitized hosts. Transfer of tolerogenic APCs has suppressed antigen-specific immune inflammation in animal models of experimental autoimmune encephalomyelitis, hapten immune pulmonary interstitial fibrosis, and ovalbumin-induced allergic pulmonary inflammation. The possibility of immune therapy by in vitro generated ACAID-like tolerogenic APCs in humans is discussed.

Gammadelta T cells promote anterior chamber-associated immune deviation and immune privilege through their production of IL-10

Anterior chamber-associated immune deviation (ACAID) is a form of peripheral tolerance that is induced by introducing Ags into the anterior chamber (AC) of the eye, and is maintained by Ag-specific regulatory T cells (Tregs). ACAID regulates harmful immune responses that can lead to irreparable injury to innocent bystander cells that are incapable of regeneration. This form of immune privilege in the eye is mediated through Tregs and is a product of complex cellular interactions. These involve F4/80+ ocular APCs, B cells, NKT cells, CD4+CD25+ Tregs, and CD8+ Tregs. gammadelta T cells are crucial for the generation of ACAID and for corneal allograft survival. However, the functions of gammadelta T cells in ACAID are unknown. Several hypotheses were proposed for determining the functions of gammadelta T cells in ACAID. The results indicate that gammadelta T cells do not cause direct suppression of delayed-type hypersensitivity nor do they act as tolerogenic APCs. In contrast, gammadelta T cells were shown to secrete IL-10 and facilitate the generation of ACAID Tregs. Moreover, the contribution of gammadelta T cells ACAID generation could be replaced by adding exogenous recombinant mouse IL-10 to ACAID spleen cell cultures lacking gammadelta T cells.

Cross talk among cells promoting anterior chamber-associated immune deviation

The visual axis of the eye focuses light images precisely on the retina. The retina is intolerant of distortion that might be induced by innate or immune inflammation. In addition, the corneal endothelium and the neurosensory retina are unable to regenerate if injured by trauma or inflammation. Within the environment of this visual organ a phenomenon called ocular immune privilege provides the eye with the necessary immune protection against infectious agents by allowing the expression of the least deleterious immune effector mechanisms. Moreover, the mechanisms of immune privilege are multiple, overlapping, and include both active and passive suppression of innate and immune inflammation. At the very basis of an effective immune response are cellular interactions and their cross talk. Central to the ability of cells to communicate are the intercellular channels that are established to isolate signals and movement of proteins between cells. Within this secure nano-environment, cells signal each other and even exchange proteins. Studies reviewed here are centered on knowledge and exploration of the tolerogenic synapse rather than the immunogenic synapse. The unique cells (invariant natural killer T cells, F4/80+ antigen-presenting cells, and T and B lymphocytes) that cluster within the marginal zone following injection of antigen in the anterior chamber (AC) express a phenotype of cell surface molecules that that seem to be uniquely critical for the development of AC-associated immune deviation. How these cell surface molecules behave during the cellular interactions that result in the development of regulatory T cells and peripheral tolerance induced through the eye is discussed.

Complement, innate immunity and ocular disease

The complement system is a major component of innate immunity. During an inflammatory reaction, the eye is potentially threatened by homologous complement attack, and unregulated complement activation could lead to tissue damage and vision loss. The complement system is continuously activated at low levels in the normal eye, and intraocular complement-regulatory proteins (CRPs) tightly regulate this spontaneous complement activation so that there is elimination of potential pathogens without the induction of destructive intraocular inflammation. The presence of a complement activation product (iC3b) during the early phase of antigen and antigen-presenting cell contact is essential for the induction of systemic tolerance to antigen injected into the anterior chamber of the eye and the establishment of ocular immune privilege. The complement system and complement-regulatory proteins control intraocular inflammation in autoimmune anterior uveitis and may play an important role in the development of age-related macular degeneration. Thus, in the eye, complement functions as a double-edged sword - on one hand it provides innate immunity against pathogens while simultaneously instructing the adaptive immune response to develop tolerance to such pathogens to avoid inadvertent tissue damage in a critical organ.

Evaluation of anterior chamber inflammatory activity in eyes treated with intravitreal bevacizumab

PURPOSE

To evaluate the effect of intravitreal bevacizumab on anterior chamber inflammatory activity.

METHODS

Sixty-one consecutive patients with neovascular age-related macular degeneration were examined before, 1 day, and 1 week after intravitreal administration of 1 mg of bevacizumab (0.04 mL) for neovascular age-related macular degeneration. The intravitreal injection was performed under sterile conditions. Twenty-one fellow eyes served as controls. The anterior chamber inflammatory activity was evaluated using biomicroscopy and the laser flare meter (Kowa FM-500, Kowa Company, Ltd., Tokyo, Japan).

RESULTS

None of the 61 consecutive patients had a significant, clinically detectable inflammatory response within 1 week of follow-up. Anterior chamber inflammatory activity measured by the laser flare meter ranged from 1.9 counts/ms to 70.0 counts/ms (mean +/- SD, 13.2 +/- 16.9 counts/ms; 95% confidence interval [CI], 7.8-18.6) before treatment. One day and 1 week after injection, values were between 3.2 counts/ms and 30.0 counts/ms (mean +/- SD, 9.1 +/- 6.2 counts/ms; 95% CI, 7.2-11.1) and 2.0 counts/ms and 25.1 counts/ms (mean +/- SD, 7.3 +/- 4.6 counts/ms; 95% CI, 5.8-8.8), respectively. There was a significant reduction of anterior chamber flare at 1 week compared with baseline (P = 0.031). The control eyes had constantly low flare measures.

CONCLUSION

No inflammatory response was detected clinically and by the laser flare meter after intravitreal bevacizumab administration. The slight reduction in anterior chamber flare could be due to the known antiinflammatory effect of anti-vascular endothelial growth factor therapy.

Ocular immune privilege is circumvented by CD4+ T cells, leading to the rejection of intraocular tumors in an IFN-{gamma}-dependent manner

Although intraocular tumors reside in an immune-privileged site, they can circumvent immune privilege and undergo rejection, which typically follows one of two pathways. One pathway involves CD4(+) T cells, delayed-type hypersensitivity (DTH), and the culmination in ischemic necrosis of the tumor and phthisis (atrophy) of the eye. The second pathway is DTH-independent and does not inflict collateral injury to ocular tissues, and the eye is preserved. In this study, we used a well-characterized tumor, Ad5E1, to analyze the role of IFN-gamma in the nonphthisical form of intraocular tumor rejection. The results showed that IFN-gamma induced tumor cell apoptosis, inhibited tumor cell proliferation, and promoted rejection by inhibiting angiogenesis. Microarray analysis revealed that IFN-gamma induced up-regulation of five antiangiogenic genes and down-regulation of four proangiogenic genes in Ad5E1 tumor cells. Although IFN-gamma knockout (KO) mice have progressively growing intraocular tumors, IFN-gamma was not needed for the elimination of extraocular tumors, as all IFN-gamma KO mice rejected s.c. tumor inocula. This represents a heretofore unrecognized role for IFN-gamma in circumventing ocular immune privilege and eliminating intraocular tumors. The findings also reveal that some IFN-gamma-independent tumor rejection processes are excluded from the eye and may represent a new facet of ocular immune privilege.

CD4+PD-1+ T cells acting as regulatory cells during the induction of anterior chamber-associated immune deviation

PURPOSE

To study the expression and functional characteristics of programmed death-1 (PD-1) and its ligands in the spleens of mice undergoing anterior chamber-associated immune deviation (ACAID).

METHODS

ACAID was induced in BALB/c mice by intracameral injection of ovalbumin (OVA). The expression of PD-1 and its ligands in the spleens of ACAID mice was determined by quantitative real-time PCR, Western blotting, and flow cytometry. In vitro proliferation assays, enzyme-linked immunosorbent assays, and adoptive transfer assays were used to investigate the functional characteristics of splenic CD4+PD-1+ T cells of ACAID mice.

RESULTS

Both mRNA and protein of PD-1, PD-L1, and PD-L2 were markedly upregulated in the spleens of ACAID mice compared with controls. CD4+PD-1+ T cells from ACAID mice produced large amounts of IL-10 and exhibited in vitro antigen-specific suppressive activity. CD4+PD-1+ T cells from ACAID mice were able to significantly inhibit the antigen-specific, delayed-type hypersensitivity response when adoptively transferred to naive mice.

CONCLUSIONS

CD4+PD-1+ T cells from ACAID mice, as regulatory cells, are involved in the induction of antigen-specific suppression in association with enhanced expression of IL-10. CD4+PD-1+ T cells in the murine spleen may represent a substantial population of regulatory T cells possibly responsible for the induction of ACAID after intracameral injection of antigen.

The suppression of delayed-type hypersensitivity by CD8+ regulatory T cells requires interferon-gamma

CD8(+) regulatory (suppressor) T cells are induced by complex cellular pathways in the spleens of mice that have received an injection of antigen into the anterior chamber (AC) of an eye, an immune-privileged site. Although these CD8(+) regulatory T cells perform an antigen-specific regulatory function for an immune response to self and non-self antigens, the mechanisms of the activation or function of these regulatory cells are not clear. Here, we describe a novel mechanism for the activation of splenic CD8(+) regulatory T cells induced by injection of antigen into the AC. Immunization of mice with trinitrophenyl and bovine serum albumin (TNP-BSA) amplified AC-induced splenic CD8(+) regulatory T cells that suppressed the initiation of contact sensitivity when transferred to immunized, challenged mice. These CD8(+) regulatory T cells were produced independently of perforin, indicating that they are not canonical cytotoxic T cells. Fas ligand (FasL)-deficient CD8(+) regulatory T-cell function was rescued by inclusion of exogenous interferon-gamma (IFN-gamma), demonstrating that the expression of FasL by CD8(+) regulatory T cells was dispensable, but IFN-gamma was not. Ultimately, we demonstrated that the generation of these CD8(+) regulatory T cells occurred independently of IFN-gamma, but their suppressor function required IFN-gamma receptor stimulation.

Possibility of inducing anterior chamber-associated immune deviation by TGF-β2 treatment of monocytes isolated from Behcet's patients

Murine macrophages treated with TGF-beta2 are capable of inducing anterior chamber-associated immune deviation (ACAID), and these macrophages are characterized by impaired IL-12 production and CD40 expression, consequently failing to promote Th1 cell differentiation. In this study, we investigated whether human monocytes can also acquire the specific functions by TGF-beta2 treatment, even when the monocytes are isolated from patients with Behcet's disease (BD). Adherent monocytes isolated from peripheral blood mononuclear cells (PBMC) of 16 BD patients and 16 healthy controls, were cultured overnight with or without 5 ng/ml of TGF-beta2. Then, TGF-beta2-treated or untreated adherent cells were co-cultured with allogeneic CD4(+) T cells obtained from healthy subjects. TGF-beta2 treatment inhibited the abilities of adherent monocytes obtained from BD patients to stimulate the proliferation and IFN-gamma production of allogeneic CD4(+) T cells. The reduced IFN-gamma production was also confirmed by IFN-gamma mRNA expression in the co-cultured T cells. IL-12 production and CD40 molecule expression by adherent monocytes obtained from BD patients were strikingly reduced by TGF-beta2 treatment. These results suggest a possibility that adherent monocytes isolated from BD patients may acquire a property to induce ACAID by treatment with TGF-beta2.

Indoleamine 2,3-dioxygenase (IDO) is involved in promoting the development of anterior chamber-associated immune deviation

Indoleamine 2,3-dioxygenase (IDO), a rate-limiting enzyme in the tryptophan catabolism, has been shown to play an important role in various forms of immune tolerance. Since anterior chamber associated immune deviation (ACAID) is a systemic immune tolerance elicited by introducing exogenous antigens into the anterior chamber of the eye, we investigated the expression and function of IDO in the development of this ocular tolerance. ACAID was induced in BALB/c mice by an intracameral injection of 50mug ovalbumin (OVA). The IDO expression in the splenocytes during ACAID was determined by fluorescent quantitative real-time PCR, Western blot analysis and immunohistochemistry. The development of ACAID was evaluated by the delayed-type hypersensitivity (DTH) response after intraperitoneal injection of an IDO inhibitor 1-methyl-dl-tryptophan (1-MT). Secretion of IFN-gamma and IL-4 by splenocytes and lymph node cells from the mice treated with or without 1-MT were also evaluated using intracellular cytokine staining. Our results showed that the IDO expression was significantly increased at both mRNA and protein levels following OVA intracameral injection. Inhibition of IDO with 1-MT prevented the development of ACAID, which was indicated by the re-appearance of the OVA-specific DTH response. IL-4 was significantly reduced and IFN-gamma was partially recovered after the treatment of 1-MT. Our study reveal that IDO is up-regulated during ACAID and IDO inhibitor prevents ACAID generation, suggesting that IDO is involved in the development of this immune tolerance.

Accumulation of immunosuppressive CD11b+ myeloid cells correlates with the failure to prevent tumor growth in the anterior chamber of the eye

The purpose of these studies is to determine why an immunogenic tumor grows unchecked in the anterior chamber (a.c.) of the eye. The OVA-expressing EL4 tumor, E.G7-OVA, was injected into the a.c. or skin of immunocompetent and immunodeficient mice. Tumor growth and tumor-specific immune responses were monitored. Ocular tumor-infiltrating leukocytes were characterized phenotypically and functionally. Growth of E.G7-OVA was inhibited when limiting numbers of cells were injected in the skin but not in the a.c. of C57BL/6 mice, although both routes primed OVA-specific immune responses, which prevented the growth of a subsequent injection with E.G7-OVA in the skin or opposite eye. Tumor regression was OVA-specific because growth of the parental EL-4 tumor was not inhibited in primed mice. E.G7-OVA growth in the skin was not inhibited in immunodeficient Rag(-/-) or CD8 T cell-deficient mice, suggesting that CD8(+) CTLs mediate tumor elimination. CD8(+) T cell numbers were significantly increased in eyes of mice primed with E.G7-OVA, but few were detected in primary ocular tumors. Nevertheless, growth of E.G7-OVA was retarded in the a.c. of TCR-transgenic OT-I mice, and CD8(+) T cell numbers were increased within eyes, suggesting that tumor-specific CD8(+) CTLs migrated into and controlled primary ocular tumor growth. E.G7-OVA did not lose antigenicity or become immunosuppressive after 13 days of growth in the eye. However, CD11b(+) cells accumulated in primary ocular tumors and contained potent immunosuppressive activity when assayed in vitro. Thus, CD11b(+) cells that accumulate within the eye as tumors develop in the a.c. may contribute to immune evasion by primary ocular tumors by inhibiting CTLs within the eye.

Tumor escape mutants develop within an immune-privileged environment in the absence of T cell selection

The establishment of tumor escape mutants, which can be driven by innate and/or adaptive immune effector cells, presents a significant obstacle in the development of successful tumor immunotherapies. Our study documents that tumors growing within an immune-privileged site within the eye develop a tumor escape phenotype in the absence of selective T cell pressure. P815 tumor cells that are recovered from progressively growing tumors within the anterior chamber of the eye escape elimination when injected into the flanks of a second group of syngeneic DBA/2 mice that were previously immunized against P815 tumor cells. The escape phenotype of eye-derived P815 tumors was stable and permanent when the tumor cells were cultured in vitro. Eye-derived tumor cells recovered from the anterior chamber of CB-17 SCID mice also escaped elimination when injected into the flanks of immunized mice, demonstrating that selective pressure by tumor Ag-specific T cells did not contribute to the development of the escape phenotype. In vitro studies demonstrated that eye-derived tumor cells were not lysed by specific CTL and were unable to restimulate primed Ag-specific T cells. Immune escape of eye-derived tumor cells was not due to down-regulation of either MHC class I or ICAM-1. Our data demonstrate that the immune-privileged environment within the eye induces a tumor escape phenotype that is not driven by selective T cell pressure. We predict that immune escape within the eye is driven by the unique ocular environment that permanently alters gene expression in eye-derived tumor cells.

Peripheral tolerance via the anterior chamber of the eye: role of B cells in MHC class I and II antigen presentation

Ags introduced into the anterior chamber (AC) of the eye induce a form of peripheral immune tolerance termed AC-associated immune deviation (ACAID). ACAID mitigates ocular autoimmune diseases and promotes corneal allograft survival. Ags injected into the AC are processed by F4/80(+) APCs, which migrate to the thymus and spleen. In the spleen, ocular APCs induce the development of Ag-specific B cells that act as ancillary APCs and are required for ACAID induction. In this study, we show that ocular-like APCs elicit the generation of Ag-specific splenic B cells that induce ACAID. However, direct cell contact between ocular-like APCs and splenic B cells is not necessary for the induction of ACAID B cells. Peripheral tolerance produced by ACAID requires the participation of ACAID B cells, which induce the generation of both CD4(+) regulatory T cells (Tregs) and CD8(+) Tregs. Using in vitro and in vivo models of ACAID, we demonstrate that ACAID B cells must express both MHC class I and II molecules for the generation of Tregs. These results suggest that peripheral tolerance induced through the eye requires Ag-presenting B cells that simultaneously present Ags on both MHC class I and II molecules.

Phenotypic and immunoregulatory characteristics of monocytic iris cells

The introduction of antigen into the anterior chamber of an eye induces the antigen-specific suppression of cell-mediated immunity and the antigen-induced production of immunoglobulin G2 antibodies. To define further the role of iris monocytic cells in the systemic suppression of cell-mediated immunity that follows the entry of foreign antigen into the anterior chamber, murine iris wholemounts or cell suspensions of iris cells were stained with fluorescent anti-F4/80 and/or anti-CD11c, anti-CD11b antibodies and examined by confocal microscopy or flow cytometry, respectively. Monocytic cells in iris cell suspensions were recovered from mice receiving an injection of trinitrophenylated bovine serum albumin (TNP-BSA) into an anterior chamber and Percoll-enriched iris cells separated into cells expressing F4/80 or CD11c were injected intravenously into TNP-BSA-immunized or naive recipients. The recipients were challenged to induce delayed-type hypersensitivity (DTH) or were provided with splenocytes or thymocytes that transfer the suppression of DTH. The homing of monocytic bone marrow cells to the iris was determined by the intravenous injection of bone marrow cells from green fluorescent protein (GFP)-transgenic donors into C57 mice, and the staining of recipient iris wholemounts with anti-F4/80 antibodies. Iris cells with a dendritic morphology expressing both F4/80 and/or CD11c and CD11b, some cells expressing only F4/80 or CD11c, were detected. The irides of irradiated GFP- mice that received intravenous GFP+ bone marrow cells contained GFP+ F4/80+ cells. F4/80+ and CD11c+ cells from the irides of donors that received intracameral TNP-BSA transferred the suppression of DTH when injected intravenously into TNP-BSA-immunized recipients, activated immunoregulatory thymocytes and activated antigen-specific splenic regulatory effector cells. These results support the hypothesis that iris monocytic cells may participate in the systemic induction of regulatory T cells.

Immunogenicity and antigenicity of allogeneic amniotic epithelial transplants grafted to the cornea, conjunctiva, and anterior chamber

PURPOSE

To determine the immunogenic characterization of amniotic epithelium (AE), by examining the fate of allogeneic AE grafts heterotopically transplanted in the eye.

METHODS

Intact AE from enhanced green fluorescence protein (EGFP) transgenic mice (C57BL/6 background) and wild-type C57BL/6 mice were transplanted onto cornea or conjunctiva, or inserted into the anterior chamber (AC) of normal BALB/c mice, C57BL/6 mice, or BALB/c mice presensitized to donor antigens. For repeated AE transplantation experiments, AE was grafted in the other eye 7 days after the first grafting. Graft fate was assessed clinically and histologically at selected intervals after grafting. Infiltrating inflammatory cells were examined immunohistochemically. Sensitization to alloantigens by AE was assessed by the delayed hypersensitivity (DH) response.

RESULTS

In normal recipients, GFP+ cells were absent in EGFP donor-derived AE grafts by day 21 on cornea and by day 7 on conjunctiva. AE grafts implanted in the AC survived for >8 weeks. In presensitized recipients and recipients that underwent repeated AE implantation, graft survival was markedly shorter than in normal recipients. DH was induced at 2 weeks, but failed to be induced at 4 weeks after grafting on cornea or at 8 weeks after grafting on conjunctiva and in the AC of normal recipients.

CONCLUSIONS

Fresh allogeneic AE expressed immunogenicity when placed on the ocular surface, although no memory of allospecific DH was acquired. Allogeneic AE is clearly vulnerable to immune rejection in specifically sensitized recipients.

Induction of eye-derived tolerance does not depend on naturally occurring CD4+CD25+ T regulatory cells

PURPOSE

Regulatory CD4+ T cells (T regs) arise in the spleens of mice with anterior chamber-associated immune deviation (ACAID), an eye-derived tolerance evoked by injection of antigen into the ocular anterior chamber (AC). The current study was conducted to investigate the possibility that these T regs express CD25 and are derived from natural CD4+CD25+ T cells.

METHODS

Naïve T cells from DO11.10 mice were activated in vitro by ovalbumin (OVA)-pulsed, TGFbeta-treated antigen-presenting cells (APCs), and the expression of CD25 assayed by flow cytometry. OVA-specific ACAID T regs were obtained from the spleens of DO11.10 mice with ACAID to OVA. Immunomagnetic enrichment was used to sort out CD4+CD25+, and CD4+CD25- ACAID T cells before they were injected into OVA-immunized mice or examined for mRNA expression of the regulatory T-cell transcription factor Foxp3. In addition, before AC injection of OVA, systemic depletion of CD25+ T cells was performed with injections of anti-IL-2 receptor antibody into the mice.

RESULTS

OVA-specific T cells from DO11.10 mice expressed CD25 when exposed to OVA-pulsed, TGFbeta-treated APCs, even when the DO11.10 T cells were depleted of CD25+ cells before their in vitro stimulation. In addition, DH was suppressed in naïve mice that were injected with CD4+CD25+ or CD4+CD25- ACAID T cells. The CD4+CD25+, but not the CD4+CD25-, ACAID T regs expressed Foxp3. Finally, OVA induced ACAID in mice depleted of CD25+ cells.

CONCLUSIONS

Some of the CD4+ T regs of ACAID arise from CD25- precursors, and the induction of ACAID is not dependent on the presence of natural CD4+CD25+ T regs.

OVA-specific CD8+ T cells do not express granzyme B during anterior chamber associated immune deviation

PURPOSE

To examine antigen (Ag)-specific CTL response during anterior chamber associated immune deviation (ACAID).

METHODS

OVA or OVA257-264 peptide was injected into the anterior chamber (AC) of C57BL/6 mice. There were 16 mice in each ACAID group induced with OVA or OVA257-264 peptide. The mice were primed by SC injection with OVA or OVA 257-264 peptide in complete Freund's adjuvant (CFA) on day 7. Ag-specific CD8+ T cells in spleens were analyzed on day 14 using Pentamer H-2K(b)-SIINFEKL(OVA257-264 peptide). IFN-gamma ELISPOT and intracellular granzyme B staining were used to characterize the CTL response. Twelve mice in each group immunized with OVA or OVA257-264 peptide in CFA served as positive controls. Twelve normal mice served as negative controls and 12 receiving injection of CFA as CFA controls for studying the influence of CFA on the Ag-specific CTL response.

RESULT

The results showed that anterior chamber inoculation of OVA or OVA257-264 peptide could induce ACAID as evidenced by an impaired DTH response. The frequency of Ag-specific CD8+ T cells in ACAID mice was not different from that in mice challenged with Ags in CFA only (positive controls). IFN-gamma production by these cells in ACAID mice was not different compared to positive controls. However, Ag-specific CD8+ T cells in ACAID mice failed to secrete granzyme B. Mice challenged only with OVA peptide and CFA also showed a granzyme B negative CD8+ T cell response. Ag-specific CTL response induced by CFA alone was similar with the negative control.

CONCLUSION

These results show that the frequency of Ag-specific CD8+ T cells is not altered during ACAID. The Ag-specific CTL response during ACAID is characterized by the absence of granzyme B expression.

Abnormal anterior chamber associated immune deviation (ACAID) in 129-strain mice

PURPOSE

To characterize anterior chamber immune deviation (ACAID) in 129-strain and mixed 129-strain mice.

METHODS

ACAID was assayed using standard protocols with herpes simplex-1 (HSV-1) and trinitrophenol-hapten-spleen cells (TNP-spleen) in C57B1/6, 129P2, 129X1, and intercrossed strains. Systemic tolerance induction was assayed using an ultraviolet light skin tolerance protocol to 2,-4,6-trinitro-l-chlorobenzene (TNCB).

RESULTS

129X1 and C57Bl/6xl29Xl Fl mice did not show ACAID to HSV-1. C57Bl/6xl29P2 mice did not show ACAID to TNP-spleen. C57Bl/6xl29P2 mice did show normal peripheral immune deviation to TNCB. (C57Bl/6xl29Xl) x C57B1/6 N2 backcrossed mice showed a bimodal ACAID response to HSV-1 suggesting a single dominant allele in the 129X1 background responsible for suppressing ACAID.

CONCLUSION

ACAID to multiple antigens is significantly reduced in 129-strain mice and their outcrossed progeny. Since 129-strain embryonic stem cells are widely used to generate knockout and transgenic mice, care must be taken to extensively backcross resultant strains in order to assess the effect of particular genes on ACAID.

GATA-3 expression in the development of anterior chamber associated immune deviation

BACKGROUND

Anterior chamber associated immune deviation (ACAID) is characterized by a Th2 cell response. GATA-3 has been shown to be necessary for the activation of Th2 cells. This study was designed to examine the expression of GATA-3 in the development of ACAID.

METHODS

ACAID was induced by injection of 50 microg interphotoreceptor retinoid binding protein (IRBP) into the anterior chamber (AC) of Wistar rats. Delayed-type hypersensitivity (DTH) was evaluated on day 3, 7, 14, 21, 28 after IRBP inoculation. GATA-3 expression was detected using immunohistochemical staining. The expression of GATA-3 mRNA at different time points after AC injection of IRBP was assayed by reverse transcriptase polymerase chain reaction (RT-PCR).

RESULTS

A significant DTH reaction was observed in Wistar rats on day 3 and 5 after IRBP inoculation. The DTH reaction was decreased 7 days after IRBP inoculation. GATA-3 expression was weak at both mRNA and protein levels in the normal spleen, but was significantly increased on day 5, 7, 14, and 21 after AC injection of IRBP.

CONCLUSION

The expression of GATA-3 is increased during ACAID, suggesting that GATA-3 may be involved in the development of ACAID.

Inhibition of Experimental Autoimmune Anterior Uveitis by Adenovirus-Mediated Transfer of the Interleukin-10 Gene

AIMS

The aim of this study was to investigate the efficiency of adenoviral-mediated transfer of the interleukin (IL)-10 gene for inhibition of experimental autoimmune anterior uveitis, a rat model of human acute anterior uveitis. Uveitis was induced in the Lewis rat by simultaneous injection of melanin-associated antigen intraperitoneally (i.p.) and into the left footpad. The animals were treated by systemic administration of adenoviral construct expressing IL-10 (Ad-IL-10) or Ad-Mock carrying no cytokine transgene.

RESULTS

A significant reduction in ocular inflammation was noted for rats that received one or two divided i.p. administrations of Ad-IL-10 (one 10 x 10(9) and two 5 x 10(9) particles of adenoviral construct, respectively), as judged by reduced clinical scores and decreased leukocyte infiltration in the anterior chamber and confirmed by histological examinations, relative to control animals. Systemic Ad-IL-10, treatment also revealed a higher serum level of IL-10, compared to the controls.

CONCLUSIONS

The results suggest that systemic adenovirus-mediated IL-10 gene therapy has an anti-inflammatory effect on immune-mediated ocular inflammation and that this approach may be promising for the treatment of acute anterior uveitis.