Capacity of ocular infiltrating T helper type 1 cells of patients with non-infectious uveitis to produce chemokines

Behçet's Disease: A Comprehensive Review on the Role of HLA-B*51, Antigen Presentation, and Inflammatory Cascade

Behçet's disease (BD) is a complex, recurring inflammatory disorder with autoinflammatory and autoimmune components. This comprehensive review aims to explore BD's pathogenesis, focusing on established genetic factors. Studies reveal that HLA-B*51 is the primary genetic risk factor, but non-HLA genes (ERAP1, IL-10, IL23R/IL-12RB2), as well as innate immunity genes (FUT2, MICA, TLRs), also contribute. Genome-wide studies emphasize the significance of ERAP1 and HLA-I epistasis. These variants influence antigen presentation, enzymatic activity, and HLA-I peptidomes, potentially leading to distinct autoimmune responses. We conducted a systematic review of the literature to identify studies exploring the association between HLA-B*51 and BD and further highlighted the roles of innate and adaptive immunity in BD. Dysregulations in Th1/Th2 and Th17/Th1 ratios, heightened clonal cytotoxic (CD8+) T cells, and reduced T regulatory cells characterize BD's complex immune responses. Various immune cell types (neutrophils, γδ T cells, natural killer cells) further contribute by releasing cytokines (IL-17, IL-8, GM-CSF) that enhance neutrophil activation and mediate interactions between innate and adaptive immunity. In summary, this review advances our understanding of BD pathogenesis while acknowledging the research limitations. Further exploration of genetic interactions, immune dysregulation, and immune cell roles is crucial. Future studies may unveil novel diagnostic and therapeutic strategies, offering improved management for this complex disease.

Machine Learning Approach for Intraocular Disease Prediction Based on Aqueous Humor Immune Mediator Profiles

PURPOSE

Various immune mediators have crucial roles in the pathogenesis of intraocular diseases. Machine learning can be used to automatically select and weigh various predictors to develop models maximizing predictive power. However, these techniques have not yet been applied extensively in studies focused on intraocular diseases. We evaluated whether 5 machine learning algorithms applied to the data of immune-mediator levels in aqueous humor can predict the actual diagnoses of 17 selected intraocular diseases and identified which immune mediators drive the predictive power of a machine learning model.

DESIGN

Cross-sectional study.

PARTICIPANTS

Five hundred twelve eyes with diagnoses from among 17 intraocular diseases.

METHODS

Aqueous humor samples were collected, and the concentrations of 28 immune mediators were determined using a cytometric bead array. Each immune mediator was ranked according to its importance using 5 machine learning algorithms. Stratified k-fold cross-validation was used in evaluation of algorithms with the dataset divided into training and test datasets.

MAIN OUTCOME MEASURES

The algorithms were evaluated in terms of precision, recall, accuracy, F-score, area under the receiver operating characteristic curve, area under the precision-recall curve, and mean decrease in Gini index.

RESULTS

Among the 5 machine learning models, random forest (RF) yielded the highest classification accuracy in multiclass differentiation of 17 intraocular diseases. The RF prediction models for vitreoretinal lymphoma, acute retinal necrosis, endophthalmitis, rhegmatogenous retinal detachment, and primary open-angle glaucoma achieved the highest classification accuracy, precision, and recall. Random forest recognized vitreoretinal lymphoma, acute retinal necrosis, endophthalmitis, rhegmatogenous retinal detachment, and primary open-angle glaucoma with the top 5 F-scores. The 3 highest-ranking relevant immune mediators were interleukin (IL)-10, interferon-γ-inducible protein (IP)-10, and angiogenin for prediction of vitreoretinal lymphoma; monokine induced by interferon γ, interferon γ, and IP-10 for acute retinal necrosis; and IL-6, granulocyte colony-stimulating factor, and IL-8 for endophthalmitis.

CONCLUSIONS

Random forest algorithms based on 28 immune mediators in aqueous humor successfully predicted the diagnosis of vitreoretinal lymphoma, acute retinal necrosis, and endophthalmitis. Overall, the findings of the present study contribute to increased knowledge on new biomarkers that potentially can facilitate diagnosis of intraocular diseases in the future.

Retinal Pigment Epithelial Cells Derived from Induced Pluripotent Stem (iPS) Cells Suppress or Activate T Cells via Costimulatory Signals

Human retinal pigment epithelial (RPE) cells derived from induced pluripotent stem (iPS) cells have immunosuppressive properties. However, RPE cells are also known as immunogenic cells, and they have major histocompatibility complex expression and produce inflammatory proteins, and thus experience immune rejection after transplantation. In this study, to confirm the immunological properties of IPS-RPE cells, we examined whether human RPE cells derived from iPS cells could suppress or stimulate inflammatory T cells from uveitis patients via costimulatory signals. We established T cells from patients with active uveitis as target cells and used iPS-RPE cells as effector cells. As a result, cultured iPS-RPE cells inhibited cell proliferation and the production of IFN-γ by activated uveitis CD4⁺ T cells, especially Th1-type T cells. In contrast, iPS-RPE cells stimulated T cells of uveitis patients. The iPS-RPE cells constitutively expressed B7-H1/CD274 and B7-DC/CD273, and suppressed the activation of T cells via the PD-1 receptor. iPS-RPE expressed these negative costimulatory molecules, especially when RPE cells were pretreated with recombinant IFN-γ. In addition, iPS-RPE cells also expressed B7-H3/CD276 costimulatory molecules and activated uveitis T cells through the B7-H3-TLT-2 receptor. Thus, cultured iPS-derived retinal cells can suppress or activate inflammatory T cells in vitro through costimulatory interactions.

Detection of Complement Activators in Immune Attack Eyes After iPS-Derived Retinal Pigment Epithelial Cell Transplantation

Purpose

To determine whether human induced pluripotent stem (iPS) cell-derived retinal pigment epithelial (RPE) cells (iPS-RPE) can express complement factors.

Methods

To confirm expression of complement factors in human iPS-RPE cells, we performed flow cytometry, immunohistochemistry, ELISA, and quantitative RT-PCR for the following: C3, C5, CFB (Factor B), C5b-9 (membrane attack complex [MAC]), CFH (Factor H), CFI (Factor I), CD46, CD55, CD59, clusterin, and vitronectin. We also prepared iPS-RPE cells in the presence of recombinant IFN-γ, recombinant TNF-α, lipopolysaccharide, supernatants of naïve T cells, and T helper 1 (Th1) cells. For the transplantation, after preparation of iPS-RPE cells from cynomolgus monkeys, the iPS-RPE cells (allografts) were transplanted into the subretinal space in monkeys. After surgery, monkeys were euthanized for IHC evaluation of the retinal section and determination of complement factors (C3, C5, CFB, MAC, and C1q), cytokines, and immunoglobulin G (IgG).

Results

Human iPS-RPE cells expressed complement activators and inhibitors. iPS-RPE cells highly expressed complement factors during inflammatory conditions, especially IFN-γ exposure including Th1 cell supernatants. In immune attack eyes after allogeneic iPS-RPE cell transplantation, complement activators such as C3, CFB, C5, and MAC were detected around the host RPE layer, grafted RPE cells, inflammatory retinal lesions, and transplanted subretinal space. In addition, we observed a large number of C1q and IgG double positive and IFN-γ positive inflammatory cells in the retinal sections.

Conclusions

iPS-derived RPE cells greatly expressed complement factors. Thus, RPE cells might be activated and produce complement factors after exposure to infiltrating inflammatory cells in the eye.

Therapeutic potency of Poly I:C in HSV-induced inflammation through up-regulation of IL-15 receptor alpha

Interleukin-15 receptor alpha (IL-15Rα) forms stable complex with IL-15 on the cell surface of activated monocytes and mediates the proliferation of memory CD8+ T cells. Recent studies informed that polyinosinic:polycytidylic acid (Poly I:C) is an immunostimulant which boosts the generation of memory T cells through induction of IL-15Rα. The aim of this study is to evaluate the relevance of IL-15Rα in Herpes simplex virus (HSV)-induced Behçet's disease (BD) mouse model and BD patients. The frequencies of IL-15Rα expression in PBMCs of BD patients and BD-like symptomatic mice were analyzed by flow cytometry. In addition, Poly I:C supplementation could reduce inflammation through the up-regulation of memory T cells and IL-15Rα+ cells accompany with down-regulation of pro-inflammatory cytokine, IL-17A in BD mice. In BD patients, the frequencies of IL-15Rα expression in PBMCs were also significantly different between the inactive and active disease states. These results suggest that IL-15Rα is a relevant factor in BD.

Neutrophil-dominant experimental autoimmune uveitis in CC-chemokine receptor 2 knockout mice

PURPOSE

Murine experimental autoimmune uveitis (EAU) is an animal model of human uveitis. It has been demonstrated that ocular-infiltrating macrophages are crucial for EAU induction, and monocyte chemoattractant protein-1 (MCP-1) was actually upregulated in the eye. CC chemokine receptor-2 (CCR2) is the receptor of MCP-1, and macrophages fail to recruit particular lesions in CCR2 knockout (KO) mice. To confirm the role of macrophages in EAU, we examined EAU in CCR2 KO mice.

METHODS

CCR2 KO mice and wild-type (WT) mice that had the same genetic background were immunized with human interphotoreceptor retinoid-binding protein peptide 1-20 emulsified in complete Freund's adjuvant. At multiple time-points, EAU severity was evaluated based on microscopic fundus observation and histological examination. To examine the phenotype of retinal-infiltrating cells, single cells were prepared from the eye and analysed by flow cytometry.

RESULTS

In WT mice, EAU was induced at the peak of day 16 and marked macrophage infiltration was observed. Although macrophages failed to be recruited into the eye in CCR2 KO mice, severe uveitis was induced unexpectedly. Flow cytometry and histology revealed that most of the infiltrating cells were neutrophils. We also compared the intraocular chemokine concentrations between WT mice and KO mice. Two CXC chemokine (monokine induced by interferon-γ and interferon-γ-inducible protein-10) were upregulated in KO mice.

CONCLUSION

Interphotoreceptor retinoid-binding protein peptide immunization caused neutrophil-dominant uveitis in CCR2 KO mice. In the absence of macrophages, neutrophils can be alternatively recruited and can cause tissue damage.

Emerging biologics in the treatment of uveitis

The pathogenic mechanisms underlying uveitis syndromes continue to be evaluated using animal models and in the clinical setting. As the complex interactions between ocular immune cells, proinflammatory cytokines, chemokines and cellular adhesion molecules are uncovered, targeted therapies directed against these immune mediators will continue to be developed. Traditional immunosuppressive medications, such as corticosteroids and steroid-sparing immunomodulatory agents, have demonstrated efficacy in the treatment of uveitic syndromes, but side effects and drug toxicities often limit the use of these medications. The biologic agents, a newer class of medications, target specific immune pathways and have demonstrated efficacy in rheumatologic, dermatologic and neurologic conditions. Biologic therapies (e.g., TNF-alpha inhibitors and IL-2 receptor inhibitor) targeting ocular immune cell surface receptors, cytokines and chemokines continue to be developed and have shown promise in the treatment of uveitis and ocular inflammatory diseases. Clinical and basic aspects of monoclonal antibody therapy for uveitis are presented in this review. Additional studies are needed to further evaluate the role of monoclonal antibodies in the therapeutic armamentarium for uveitis.

CD4+Foxp3+ T-regulatory cells in noninfectious uveitis

OBJECTIVE

To evaluate CD4(+)Foxp3(+) (forkhead box P3) T-regulatory cell populations in patients with uveitis and to determine if T-regulatory cell populations are associated with disease features.

METHODS

Patients with uveitis were evaluated for CD4(+)Foxp3(+) T-regulatory cells by flow cytometry. Systemic and ocular diagnoses, disease activity, and the presence of cystoid macular edema were reviewed. Percentages of CD4(+)Foxp3(+) lymphocytes were compared for patients with inactive vs active disease, systemic vs ocular diagnoses, and the presence or absence of cystoid macular edema. Real-time polymerase chain reaction testing was performed on 2 patients with extremely low CD4(+)Foxp3(+) cell populations to assess Foxp3 mRNA.

RESULTS

A total of 20 patients with intermediate uveitis, posterior uveitis, and panuveitis were evaluated. The mean age was 40.6 years and the mean visual acuity was 20/57. Percentages of CD4(+)Foxp3(+) cells were lower in patients with active compared with inactive uveitis (P< .05). No differences in T-regulatory cells were observed between the other subgroups. Two patients with recalcitrant uveitis who demonstrated less than 1% CD4(+)Foxp3(+) lymphocytes showed extremely low or absent Foxp3 mRNA.

CONCLUSION

T-regulatory cells are reduced in patients with active compared with inactive disease. Severe depletion of CD4(+)Foxp3(+) T cells and Foxp3 mRNA in 2 patients with severe uveitis suggests that loss of the T-regulatory cells of uveitis may be a salient feature in certain patients.

The role of chemokines and their receptors in uveitis

T-cell-dependent immunological events are increasingly being regarded as extremely important in the pathogenesis of uveitis. Several studies have also shown that macrophages are major effectors of tissue damage in uveitis. Neutrophils are also thought to play a central role in the pathogenesis of Behçet's disease. Chemokines are a superfamily of 8 to 10-kDa secreted proteins that direct the recruitment of leukocytes to sites of inflammation. The specific biological effects of chemokines are mediated by a family of seven transmembrane-spanning G-protein-coupled receptors. Recent studies of animals and humans suggest that chemokines and their receptors play a key role in leukocyte recruitment into the eye in uveitis. A strategy for blocking chemokines or chemokine receptors could be a new approach for treatment of uveitis.

Inflammatory mediators of uveitis: cytokines and chemokines

PURPOSE OF REVIEW

The study of uveitis has been restricted by the difficulty in obtaining sufficient intraocular material from both human disease and experimental models. Recent developments in cytokine and chemokine detection have overcome many of these problems. This review presents a summary of the technologic advances in this area.

RECENT FINDINGS

Recent advances in cytokine analysis, in particular multiplexed bead immunoassays, have allowed the measurement of an extensive array of cytokines and chemokines from very small sample volumes. This has revolutionized uveitis research, enabling measurement of a large profile of cytokines and chemokines in intraocular fluid, such as aqueous humour. This allows us to recognize complex patterns of cytokines and chemokines from different forms of uveitis and to examine relationships between different molecules.

SUMMARY

The spectrum of proinflammatory cytokines and chemokines known to be implicated in uveitis has increased over recent years. Many of these molecules have also been found in experimental models of disease and may represent attractive therapeutic targets for the future. With recent advances in cytokine detection, an extension of these techniques with a more detailed analysis of different uveitis conditions may provide useful diagnostic and prognostic information for this potentially blinding group of diseases.