Induction of antigen-specific Treg cells in treating autoimmune uveitis via bystander suppressive pathways without compromising anti-tumor immunity

RBPJ Knockdown Promotes M2 Macrophage Polarization Through Mitochondrial ROS-mediated Notch1-Jagged1-Hes1 Signaling Pathway in Uveitis

Uveitis is an autoimmune eye disease that can be involved in the entire body and is one of the leading causes of blindness. Therefore, comprehending the mechanisms underlying the development and regulation of ocular immune responses in uveitis is crucial for designing effective therapeutic interventions. In this study, we investigated how RBPJ regulates macrophage polarization in uveitis. We demonstrated that targeted RBPJ knockdown (RBPJKD) promotes M2 macrophage polarization and ameliorates uveitis through the mtROS-mediated Notch1-Jagged1-Hes1 signaling pathway. Real-time quantitative (Q-PCR) analysis revealed that the Notch1-Jagged1-Hes1 signaling pathway was active in the eye tissues of experimental autoimmune uveitis (EAU) rats. Immunofluorescence double staining confirmed enhanced signaling primarily occurring in macrophages, establishing a correlation between the Notch1 signaling pathway and macrophages. Transmission electron microscopy evaluated the morphological and functional changes of mitochondria in each group's eye tissues. It demonstrated significant swelling and disorganization in the EAU group, which were effectively restored upon RBPJ knockdown intervention. Finally, by employing an antioxidant N-acetyl-L-cysteine (NAC) to eliminate mtROS in vivo, we observed a decrease in the M2 macrophage polarization level, which prevented the cytoprotective effect conferred by RBPJKD. These findings underscore the relevance of the Notch signaling pathway to the immune system while highlighting the potential role of mtROS as a therapeutic target for inflammation and other related diseases.

A comprehensive overview of tolerogenic vaccine adjuvants and their modes of action

Tolerogenic vaccines represent a therapeutic approach to induce antigen-specific immune tolerance to disease-relevant antigens. As general immunosuppression comes with significant side effects, including heightened risk of infections and reduced anti-tumor immunity, antigen-specific tolerance by vaccination would be game changing in the treatment of immunological conditions such as autoimmunity, anti-drug antibody responses, transplantation rejection, and hypersensitivity. Tolerogenic vaccines induce antigen-specific tolerance by promoting tolerogenic antigen presenting cells, regulatory T cells, and regulatory B cells, or by suppressing or depleting antigen-specific pathogenic T and B cells. The design of tolerogenic vaccines vary greatly, but they all deliver a disease-relevant antigen with or without a tolerogenic adjuvant. Tolerogenic adjuvants are molecules which mediate anti-inflammatory or immunoregulatory effects and enhance vaccine efficacy by modulating the immune environment to favor a tolerogenic immune response to the vaccine antigen. Tolerogenic adjuvants act through several mechanisms, including immunosuppression, modulation of cytokine signaling, vitamin signaling, and modulation of immunological synapse signaling. This review seeks to provide a comprehensive examination of tolerogenic adjuvants currently utilized in tolerogenic vaccines, describing their mechanism of action and examples of their use in human clinical trials and animal models of disease.

The immunopathogenesis of sarcoidosis

Sarcoidosis is a granulomatous multiorgan disease, thought to result from exposure to yet unidentified antigens in genetically susceptible individuals. The exaggerated inflammatory response that leads to granuloma formation is highly complex and involves the innate and adaptive immune system. Consecutive immunological studies using advanced technology have increased our understanding of aberrantly activated immune cells, mediators and pathways that influence the formation, maintenance and resolution of granulomas. Over the years, it has become increasingly clear that disease immunopathogenesis can only be understood if the clinical heterogeneity of sarcoidosis is taken into consideration, along with the distribution of immune cells in peripheral blood and involved organs. Most studies offer an immunological snapshot during disease course, while the cellular composition of both the circulation and tissue microenvironment may change over time. Despite these challenges, novel insights on the role of the immune system are continuously published, thus bringing the field forward. This review highlights current knowledge on the innate and adaptive immune responses involved in sarcoidosis pathogenesis, as well as the pathways involved in non-resolving disease and fibrosis development. Additionally, we describe proposed immunological mechanisms responsible for drug-induced sarcoid like reactions. Although many aspects of disease immunopathogenesis remain to be unraveled, the identification of crucial immune reactions in sarcoidosis may help identify new treatment targets. We therefore also discuss potential therapies and future strategies based on the latest immunological findings.

Dysregulated Th17/Treg cell axis is correlated with local and systemic immune response in human intermediate uveitis

Th17/Treg cell balance is essential for immune homeostasis and when disrupted, is associated with the occurrence and development of inflammation in numerous autoimmune diseases. However, its contribution in pathophysiology of uveitis remains unexplored. In this study, we deciphered the role of Th17/Treg cell balance in autoimmune uveitis subjects. Using flow cytometry, we detected the frequencies and absolute count of both Th17 and Treg cells in the aqueous humor and peripheral blood of patients and healthy controls. Our results for the first time reveal a significant increase (p < 0.01 and p < 0.005) in Th17 population alongside a significant decrease (p < 0.001 and p < 0.003) in Treg cell population in both the aqueous humor and PBMCs of uveitis patients. Further we analyzed the expression of Th17-Treg associated genes and cytokines via qPCR and ELISA respectively. These findings align with our flow cytometry results, as evident by a significant (p < 0.002) up-regulation of IL-17 and a concurrent down regulation of IL-10 at transcriptional levels. Moreover, IL-17A cytokine was found to be substantially high (p < 0.001) and IL-10 (p < 0.02) down regulated in serum. Interestingly, we demonstrated a significant correlation of Th17/Treg cells in aqueous humor with those in peripheral blood. Conclusively, our results suggest the pivotal role of Th17/Treg cell axis in the immuno-pathophysiology of human uveitis. Further we propose the therapeutic potential of targeting this novel axis for ameliorating the disease burden associated with uveitis.

Microglial mediators in autoimmune Uveitis: Bridging neuroprotection and neurotoxicity

Autoimmune uveitis, a severe inflammatory condition of the eye, poses significant challenges due to its complex pathophysiology and the critical balance between protective and detrimental immune responses. Central to this balance are microglia, the resident immune cells of the central nervous system, whose roles in autoimmune uveitis are multifaceted and dynamic. This review article delves into the dual nature of microglial functions, oscillating between neuroprotective and neurotoxic outcomes in the context of autoimmune uveitis. Initially, we explore the fundamental aspects of microglia, including their activation states and basic functions, setting the stage for a deeper understanding of their involvement in autoimmune uveitis. The review then navigates through the intricate mechanisms by which microglia contribute to disease onset and progression, highlighting both their protective actions in immune regulation and tissue repair, and their shift towards a pro-inflammatory, neurotoxic profile. Special emphasis is placed on the detailed pathways and cellular interactions underpinning these dual roles. Additionally, the review examines the potential of microglial markers as diagnostic and prognostic indicators, offering insights into their clinical relevance. The article culminates in discussing future research directions, and the ongoing challenges in translating these findings into effective clinical applications. By providing a comprehensive overview of microglial mechanisms in autoimmune uveitis, this review underscores the critical balance of microglial activities and its implications for disease management and therapy development.

Immunostimulatory effects of Toll-like receptor ligands as adjuvants in establishing a novel mouse model for pemphigus vulgaris

BACKGROUND

The meticulous selection of appropriate vaccine adjuvants is crucial for optimizing immune responses. Traditionally, pemphigus vulgaris (PV), an autoimmune disorder, has been modelled using complete Freund's adjuvant (CFA). In this study, we aimed to discern potential variations in immune responses elicited by Toll-like receptor (TLR) ligands as compared to CFA.

METHODS

A comprehensive investigation was conducted, comparing the effects of these adjuvants in conjunction with ovalbumin or desmoglein-3. Flow cytometry was employed to analyse distinct cell subsets, while enzyme-linked immunosorbent assay quantified antigen-specific antibodies and cytokine levels. Histological examination of harvested skin tissues and transcriptome analysis of skin lesions were performed to identify differentially expressed genes.

RESULTS

TLR ligands demonstrated efficacy in inducing PV-like symptoms in wild-type mice, in contrast to CFA. This underscored the substantial impact of the adjuvant on self-antigen tolerance. Furthermore, we proposed an enhanced method for establishing a PV model through adoptive transfer, substituting CFA with TLR ligands. Our results revealed that in contrast to the perception that CFA being the most potent immunopotentiator reported, CFA promoted regulatory T cells (Treg), follicular regulatory T cells and IL-10-producing neutrophils, whereas TLR ligands downregulated CCL17 and IL-10. This suggested potential implications for the recruitment and activation of Treg subsets. While B cell and CD8+ T cell responses exhibited similarity, CFA induced less activation in dendritic cell subsets. A novel mouse model of PV and systemic comparison of immunostimulatory effects of adjuvants were provided by this study.

CONCLUSIONS

The systematic comparison of CFA and TLR ligands shed light on the distinctive properties of these adjuvants, presenting innovative mouse models for the investigation of pemphigus. This study significantly contributes to adjuvant research and advances our understanding of PV pathogenesis.

KEY POINTS/HIGHLIGHTS

Immunization with desmoglein 3 and Toll-like receptor (TLR) ligands effectively induces pemphigus symptoms in wild-type mice, whereas complete Freund's adjuvant (CFA) fails. TLR ligands heightened the autoreactivity of donor cells in the adoptive transfer pemphigus model. CFA promoted regulatory T cells and IL-10-producing neutrophils, whereas TLR ligands downregulated CCL17 and IL-10, leading to more effective immune responses.

Beneficial mechanisms of dimethyl fumarate in autoimmune uveitis: insights from single-cell RNA sequencing

BACKGROUND

Dimethyl fumarate (DMF) is a fumaric acid ester that exhibits immunoregulatory and anti-inflammatory properties. However, the function of DMF in autoimmune uveitis (AU) is incompletely understood, and studies comprehensively exploring the impact of DMF on immune cells are still lacking.

METHODS

To explore the function of DMF in uveitis and its underlying mechanisms, we conducted single-cell RNA sequencing (scRNA-seq) on the cervical draining lymph node (CDLN) cells of normal, experimental autoimmune uveitis (EAU), and DMF-treated EAU mice. Additionally, we integrated scRNA-seq data of the retina and CDLNs to identify the potential impact of DMF on ocular immune cell infiltration. Flow cytometry was conducted to verify the potential target molecules of DMF.

RESULTS

Our study showed that DMF treatment effectively ameliorated EAU symptoms. The proportional and transcriptional alterations in each immune cell type during EAU were reversed by DMF treatment. Bioinformatics analysis in our study indicated that the enhanced expression of Pim1 and Cxcr4 in EAU was reversed by DMF treatment. Further experiments demonstrated that DMF restored the balance between effector T (Teff) /regulatory T (Treg) cells through inhibiting the pathway of PIM1-protein kinase B (AKT)-Forkhead box O1 (FOXO1). By incorporating the scRNA-seq data of the retina from EAU mice into analysis, our study identified that T cells highly expressing Pim1 and Cxcr4 were enriched in the retina. DMF repressed the ocular infiltration of Teff cells, and this effect might depend on its inhibition of PIM1 and CXCR4 expression. Additionally, our study indicated that DMF might reduce the proportion of plasma cells by inhibiting PIM1 expression in B cells.

CONCLUSIONS

DMF effectively attenuated EAU symptoms. During EAU, DMF reversed the Teff/Treg cell imbalance and suppressed the ocular infiltration of Teff cells by inhibiting PIM1 and CXCR4 expression. Thus, DMF may act as a new drug option for the treatment of AU.

Inflammatory cytokines as mediators of retinal endothelial barrier dysfunction in non-infectious uveitis

Characterised by intraocular inflammation, non-infectious uveitis includes a large group of autoimmune and autoinflammatory diseases that either involve the eye alone or have both ocular and systemic manifestations. When non-infectious uveitis involves the posterior segment of the eye, specifically the retina, there is substantial risk of vision loss, often linked to breakdown of the inner blood-retinal barrier. This barrier is formed by non-fenestrated retinal vascular endothelial cells, reinforced by supporting cells that include pericytes, Müller cells and astrocytes. Across the published literature, a group of inflammatory cytokines stand out as prominent mediators of intraocular inflammation, with effects on the retinal endothelium that may contribute to breakdown of the inner blood-retinal barrier, namely tumour necrosis factor (TNF)-α, interleukin (IL)-1β, IL-6, IL-8, IL-17 and chemokine C-C motif ligand (CCL)2. This article reviews the function of each cytokine and discusses the evidence for their involvement in retinal endothelial barrier dysfunction in non-infectious uveitis, including basic laboratory investigations, studies of ocular fluids collected from patients with non-infectious uveitis, and results of clinical treatment trials. The review also outlines gaps in knowledge in this area. Understanding the disease processes at a molecular level can suggest treatment alternatives that are directed against appropriate biological targets to protect the posterior segment of eye and preserve vision in non-infectious uveitis.

TGF-β1 signaling and Smad7 control T-cell responses in health and immune-mediated disorders

Transforming growth factor (TGF)-β1, a member of the TGF-β superfamily, is produced by many immune and nonimmune cells and has pleiotropic effects on both innate and adaptive immunity, especially in the control of T-cell differentiation and function. Consistently, loss of TGF-β1 function is associated with exacerbated T-cell-dependent inflammatory responses that culminate in pathological processes in allergic and immune-mediated diseases. In this review, we highlight the roles of TGF-β1 in immunity, focusing mainly on its ability to promote differentiation of regulatory T cells, T helper (Th)-17, and Th9 cells, thus contributing to amplifying or restricting T-cell responses in health and human diseases (e.g., inflammatory bowel diseases, type 1 diabetes, asthma, and MS). In addition, we discuss the involvement of Smad7, an inhibitor of TGF-β1 signaling, in immune-mediated disorders (e.g., psoriasis, rheumatoid arthritis, MS, and inflammatory bowel diseases), as well as the discordant results of clinical trials with mongersen, an oral pharmaceutical compound containing a Smad7 antisense oligonucleotide, in patients with Crohn's disease. Further work is needed to ascertain the reasons for such a discrepancy as well as to identify better candidates for treatment with Smad7 inhibitors.

Interleukin-17 receptor C is essential for the pro-inflammatory pathogenicity of granulocyte-macrophage-colony-stimulating factor-producing T helper cells in experimental autoimmune uveitis

Autoimmune uveitis is an inflammatory disorder of the eye triggered by the responses of autoreactive T cells to ocular autoantigens. This study aims to understand the role of granulocyte-macrophage-colony-stimulating factor (GM-CSF)-producing T helper (ThGM) cells in the pathophysiology of mouse experimental autoimmune uveitis (EAU). We established an EAU model by immunizing mice with interphotoreceptor retinoid-binding protein (IRBP) 651-670. Splenic or eye-infiltrating ThGM cells were analyzed and enriched by flow cytometry according to the levels of an array of surface markers, transcription factors, and cytokines. Lentiviral transduction was conducted to silence or overexpress the target gene in differentiated ThGM cells. The adoptive transfer was applied to determine the pathogenicity of ThGM cells in vivo. We found that ThGM cells were present in the spleen and the eye after EAU induction. Both splenic and eye-infiltrating ThGM cells were phenotypically CD4⁺CCR7^-CXCR3^-CCR6^-CCR10^hi. Eye-infiltrating ThGM cells up-regulated interleukin-1β (IL-1β), interleukin-6 (IL-6), and IL-17 receptor C (IL-17RC) relative to splenic ThGM cells. IL-17RC overexpression enabled interleukin-17A (IL-17A)-induced up-regulation of IL-1β and IL-6 production in ThGM cells. Adoptive transfer of IL-17RC overexpressing ThGM cells exacerbated EAU severity, as evidenced by a higher histology score as well as increased pro-inflammatory cytokines and inflammatory cells in the eye. However, IL-17RC-silenced ThGM cells did not impact EAU. Therefore, for the first time, this study unveils the essential pro-inflammatory role of IL-17RC-expressing ThGM cells in EAU pathophysiology. We discovered a novel mechanism underlying the pathophysiology of autoimmune uveitis.

Regulatory T Cells: Therapeutic Opportunities in Uveitis

Regulatory T cells (Tregs) are critical for the maintenance of immune tolerance and the suppression of excessive inflammation. Many inflammatory autoimmune disorders, including autoimmune uveitis, involve the loss of the suppressive capacities of Tregs. Over the past decade, Tregs' therapeutic potential in uveitis has garnered increasing attention. Specific subsets of Tregs, including TIGIT+ and PD-1+ Tregs, have emerged as potent immunosuppressors that may be particularly well-suited to cell-based therapeutics. Studies have elucidated the interaction between Treg development and the gut microbiome as well as various intracellular signaling pathways. Numerous cell-based therapies and therapeutic molecules have been proposed and investigated using the murine experimental autoimmune uveitis (EAU) model. However, certain challenges remain to be addressed. Studies involving the use of Tregs in human patients with uveitis are lacking, and there are concerns regarding Tregs' production and purification for practical use, their plasticity towards inflammatory phenotypes, immunogenicity, and tumorigenicity. Nevertheless, recent research has brought Tregs closer to yielding viable treatment options for uveitis.