Impact of inflammation on ocular immune privilege

The anterior chamber of the eye technology and its anatomical, optical, and immunological bases

The anterior chamber of the eye (ACE) is distinct in its anatomy, optics, and immunology. This guarantees that the eye perceives visual information in the context of physiology even when encountering adverse incidents like inflammation. In addition, this endows the ACE with the special nursery bed iris enriched in vasculatures and nerves. The ACE constitutes a confined space enclosing an oxygen/nutrient-rich, immune-privileged, and less stressful milieu as well as an optically transparent medium. Therefore, aside from visual perception, the ACE unexpectedly serves as an excellent transplantation site for different body parts and a unique platform for noninvasive, longitudinal, and intravital microimaging of different grafts. On the basis of these merits, the ACE technology has evolved from the prototypical through the conventional to the advanced version. Studies using this technology as a versatile biomedical research platform have led to a diverse range of basic knowledge and in-depth understanding of a variety of cells, tissues, and organs as well as artificial biomaterials, pharmaceuticals, and abiotic substances. Remarkably, the technology turns in vivo dynamic imaging of the morphological characteristics, organotypic features, developmental fates, and specific functions of intracameral grafts into reality under physiological and pathological conditions. Here we review the anatomical, optical, and immunological bases as well as technical details of the ACE technology. Moreover, we discuss major achievements obtained and potential prospective avenues for this technology.

Mechanisms and Treatment of Light-Induced Retinal Degeneration-Associated Inflammation: Insights from Biochemical Profiling of the Aqueous Humor

Ocular inflammation contributes to the pathogenesis of blind-causing retinal degenerative diseases, such as age-related macular degeneration (AMD) or photic maculopathy. Here, we report on inflammatory mechanisms that are associated with retinal degeneration induced by bright visible light, which were revealed while using a rabbit model. Histologically and electrophysiologically noticeable degeneration of the retina is preceded and accompanied by oxidative stress and inflammation, as evidenced by granulocyte infiltration and edema in this tissue, as well as the upregulation of total protein, pro-inflammatory cytokines, and oxidative stress markers in aqueous humor (AH). Consistently, quantitative lipidomic studies of AH elucidated increase in the concentration of arachidonic (AA) and docosahexaenoic (DHA) acids and lyso-platelet activating factor (lyso-PAF), together with pronounced oxidative and inflammatory alterations in content of lipid mediators oxylipins. These alterations include long-term elevation of prostaglandins, which are synthesized from AA via cyclooxygenase-dependent pathways, as well as a short burst of linoleic acid derivatives that can be produced by both enzymatic and non-enzymatic free radical-dependent mechanisms. The upregulation of all oxylipins is inhibited by the premedication of the eyes while using mitochondria-targeted antioxidant SkQ1, whereas the accumulation of prostaglandins and lyso-PAF can be specifically suppressed by topical treatment with cyclooxygenase inhibitor Nepafenac. Interestingly, the most prominent antioxidant and anti-inflammatory benefits and overall retinal protective effects are achieved by simultaneous administrating of both drugs indicating their synergistic action. Taken together, these findings provide a rationale for using a combination of mitochondria-targeted antioxidant and cyclooxygenase inhibitor for the treatment of inflammatory components of retinal degenerative diseases.

Molecular Genetics of Pigment Dispersion Syndrome and Pigmentary Glaucoma: New Insights into Mechanisms

We explore the ideas and advances surrounding the genetic basis of pigment dispersion syndrome (PDS) and pigmentary glaucoma (PG). As PG is the leading cause of nontraumatic blindness in young adults and current tailored interventions have proven ineffective, a better understanding of the underlying causes of PDS, PG, and their relationship is essential. Despite PDS being a subclinical disease, a large proportion of patients progress to PG with associated vision loss. Decades of research have supported a genetic component both for PDS and conversion to PG. We review the body of evidence supporting a genetic basis in humans and animal models and reevaluate classical mechanisms of PDS/PG considering this new evidence.

Myeloid suppressor cells induced by retinal pigment epithelial cells inhibit autoreactive T-cell responses that lead to experimental autoimmune uveitis

PURPOSE

To test whether retinal pigment epithelial (RPE) cells are able to induce myeloid-derived suppressor cell (MDSC) differentiation from bone marrow (BM) progenitors.

METHODS

BM cells were cocultured with or without RPE cells in the presence of GM-CSF and IL-4. Numbers of resultant MDSCs were assessed by flow cytometry after 6 days of incubation. The ability of the RPE cell-induced MDSCs to inhibit T cells was evaluated by a CFSE-based T-cell proliferation assay. To explore the mechanism by which RPE cells induce MDSC differentiation, PD-L1-deficient RPE cells and blocking antibodies against TGF-β, CTLA-2α, and IL-6 were used. RPE cell-induced MDSCs were adoptively transferred into mice immunized with interphotoreceptor retinoid-binding protein in complete Freund's adjuvant to test their efficacy in suppressing autoreactive T-cell responses in experimental autoimmune uveitis (EAU).

RESULTS

RPE cells induced the differentiation of MDSCs. These RPE cell-induced MDSCs significantly inhibited T-cell proliferation in a dose-dependent manner. PD-L1-deficient RPE cells induced MDSC differentiation as efficiently as wild-type RPE cells, and neutralizing TGF-β or CTLA-2α did not alter the numbers of induced MDSCs. However, blocking IL-6 reduced the efficacy of RPE cell-induced MDSC differentiation. Finally, adoptive transfer of RPE cell-induced MDSCs suppressed IRBP-specific T-cell responses that led to EAU.

CONCLUSIONS

RPE cells induce the differentiation of MDSCs from bone marrow progenitors. Both cell surface molecules and soluble factors are important in inducing MDSC differentiation. PD-L1, TGF-β, and CTLA-2α were not measurably involved in RPE cell-induced MDSC differentiation, whereas IL-6 was important in the process. The induction of MDSCs could be another mechanism by which RPE cells control immune reactions in the retina, and RPE cell-induced MDSCs should be further investigated as a potential approach to therapy for autoimmune posterior uveitis.

Equine immune-mediated keratopathies

Immune mediated keratopathies (IMMKs) are a relatively commonly occurring group of heterogeneous corneal disorders. This paper describes the currently recognised clinical presentations of the IMMKs in the USA and in the UK. Although a clinical diagnosis is relatively straightforward in most cases, the specific aetiopathogeneses of the IMMKs remains elusive and largely speculative, but are thought to be based upon upregulated immunoreactivity in the normally immunologically passive cornea. Treatment protocols, both medical and surgical, are based primarily on collective clinical experience and are variably successful, and in some cases recurrence or refractoriness to treatment is possible.

Rapid bilateral intraocular cocktail sampling method for West Nile virus detection in dead corvids

Corvids can be a sensitive indicator for West Nile virus (WNV) prevalence and are a component of many WNV surveillance programs. An improved sampling procedure using a bilateral intraocular cocktail (BIC) was developed for testing corvid carcasses for WNV. This new procedure was substantially faster than harvesting internal organs, required less specialized equipment and training, and yielded excellent diagnostic sensitivity.

Brucellar uveitis: intraocular fluids and biopsy studies

BACKGROUND

Ocular brucellosis is usually diagnosed by clinical criteria and serological tests. Little is known with regard to the ocular immunology of brucellosis and the use of intraocular diagnostic tests. We report retrospectively the laboratory findings of patients with ocular involvement associated with brucellosis.

MATERIALS AND METHODS

Patients with uveitis with no evident etiologic diagnosis were evaluated at the Instituto de Medicina Tropical "Alexander von Humboldt" of the Universidad Peruana Cayetano Heredia and the Hospital Nacional Cayetano Heredia. Patients were tested for brucellosis, tuberculosis, syphilis, toxoplasmosis, toxocariasis, and human T-cell lymphotropic virus-1. Blood and intraocular fluid samples were examined. Patients with a diagnosis of brucellar uveitis were selected as cases and patients with a diagnosis of uveitis of other etiology were included as controls. The Goldmann-Witmer coefficient was determined.

RESULTS

Twelve patients with clinical and laboratory findings suggestive of brucellar uveitis were considered as cases. Seven patients with uveitis of other etiology were selected as controls. Four (33.3%) patients with ocular brucellosis had negative ocular agglutinations and eight (66.7%) had positive agglutinations. No control cases had positive agglutinations for Brucella melitensis. The sensitivity of the test was 66.7% and the specificity 100%. Only one patient had a positive culture for B. melitensis in subretinal fluid. The Goldmann-Witmer coefficient was calculated in six cases of brucellosis uveitis and five uveitis controls. It was highly positive in three patients with ocular brucellosis. Tissue samples showed lymphoplasmacytic infiltrates.

CONCLUSIONS

Intraocular serological tests could be used to support the diagnosis of ocular brucellosis.