Pre-incubation of corneal donor tissue with sCD83 improves graft survival via the induction of alternatively activated macrophages and tolerogenic dendritic cells.

Immune responses reflect a complex interplay of cellular and extracellular components which define the microenvironment of a tissue. Therefore, factors that locally influence the microenvironment and re-establish tolerance might be beneficial to mitigate immune-mediated reactions, including the rejection of a transplant. In this study, we demonstrate that pre-incubation of donor tissue with the immune modulator soluble CD83 (sCD83) significantly improves graft survival using a high-risk corneal transplantation model. The induction of tolerogenic mechanisms in graft recipients was achieved by a significant upregulation of Tgfb, Foxp3, Il27, and Il10 in the transplant and an increase of regulatory dendritic cells (DCs), macrophages (Mφ), and T cells (Tregs) in eye-draining lymph nodes. The presence of sCD83 during in vitro DC and Mφ generation directed these cells toward a tolerogenic phenotype leading to reduced proliferation-stimulating activity in MLRs. Mechanistically, sCD83 induced a tolerogenic Mφ and DC phenotype, which favors Treg induction and significantly increased transplant survival after adoptive cell transfer. Conclusively, pre-incubation of corneal grafts with sCD83 significantly prolongs graft survival by modulating recipient Mφ and DCs toward tolerance and thereby establishing a tolerogenic microenvironment. This functional strategy of donor graft pre-treatment paves the way for new therapeutic options in the field of transplantation.

Soluble CD83 inhibits human monocyte differentiation into dendritic cells in vitro.

Human CD83 is type I transmembrane glycoprotein, mainly expressed on mature dendritic cells (DCs), so it was first described as a molecular marker for mature DC. However, increasing evidence has demonstrated that CD83 is also an immunomodulatory molecule either its membrane-bound CD83 (mCD83) or soluble CD83 (sCD83) released from DCs. Intriguingly, the mCD83 possesses stimulatory effects on immune response, on the contrary, the sCD83 has inhibitory effects. Whether the sCD83 has the inhibitory effects on human monocyte differentiation into DCs is unknown. To this end, we prepared the recombinant human sCD83 in HEK293T cells and treated human monocytes being differentiated into DCs in vitro with the sCD83, and evaluate sCD83 inhibitory effects on immune response by analyzing the surface marker pattern of the cells. The results showed that the sCD83, especially glycosylated sCD83 could bind the monocytes and significantly inhibited the depression of CD14 expressions (P<0.01) and reduced CD1a, CD80, CD86 and MHC II expressions (P<0.01 or P<0.05) during the differentiation, indicating that the sCD83 can inhibit monocyte differentiation into DCs, and suggesting that a negative feedback regulation may exist in monocyte differentiation into DCs based on sCD83 released from the mature DCs.

Soluble CD83 modulates human-monocyte-derived macrophages toward alternative phenotype, function, and metabolism.

Alterations in macrophage (Mφ) polarization, function, and metabolic signature can foster development of chronic diseases, such as autoimmunity or fibrotic tissue remodeling. Thus, identification of novel therapeutic agents that modulate human Mφ biology is crucial for treatment of such conditions. Herein, we demonstrate that the soluble CD83 (sCD83) protein induces pro-resolving features in human monocyte-derived Mφ biology. We show that sCD83 strikingly increases the expression of inhibitory molecules including ILT-2 (immunoglobulin-like transcript 2), ILT-4, ILT-5, and CD163, whereas activation markers, such as MHC-II and MSR-1, were significantly downregulated. This goes along with a decreased capacity to stimulate alloreactive T cells in mixed lymphocyte reaction (MLR) assays. Bulk RNA sequencing and pathway analyses revealed that sCD83 downregulates pathways associated with pro-inflammatory, classically activated Mφ (CAM) differentiation including HIF-1A, IL-6, and cytokine storm, whereas pathways related to alternative Mφ activation and liver X receptor were significantly induced. By using the LXR pathway antagonist GSK2033, we show that transcription of specific genes (e.g., PPARG, ABCA1, ABCG1, CD36) induced by sCD83 is dependent on LXR activation. In summary, we herein reveal for the first time mechanistic insights into the modulation of human Mφ biology by sCD83, which is a further crucial preclinical study for the establishment of sCD83 as a new therapeutical agent to treat inflammatory conditions.

The soluble CD83 protein prevents bone destruction by inhibiting the formation of osteoclasts and inducing resolution of inflammation in arthritis.

Here we show that soluble CD83 induces the resolution of inflammation in an antigen-induced arthritis (AIA) model. Joint swelling and the arthritis-related expression levels of IL-1ß, IL-6, RANKL, MMP9, and OC-Stamp were strongly reduced, while Foxp3 was induced. In addition, we observed a significant inhibition of TRAP+ osteoclast formation, correlating with the reduced arthritic disease score. In contrast, cell-specific deletion of CD83 in human and murine precursor cells resulted in an enhanced formation of mature osteoclasts. RNA sequencing analyses, comparing sCD83- with mock treated cells, revealed a strong downregulation of osteoclastogenic factors, such as Oc-Stamp, Mmp9 and Nfatc1, Ctsk, and Trap. Concomitantly, transcripts typical for pro-resolving macrophages, e.g., Mrc1/2, Marco, Klf4, and Mertk, were upregulated. Interestingly, members of the metallothionein (MT) family, which have been associated with a reduced arthritic disease severity, were also highly induced by sCD83 in samples derived from RA patients. Finally, we elucidated the sCD83-induced signaling cascade downstream to its binding to the Toll-like receptor 4/(TLR4/MD2) receptor complex using CRISPR/Cas9-induced knockdowns of TLR4/MyD88/TRIF and MTs, revealing that sCD83 acts via the TRIF-signaling cascade. In conclusion, sCD83 represents a promising therapeutic approach to induce the resolution of inflammation and to prevent bone erosion in autoimmune arthritis.

Soluble CD83 inhibits acute rejection by up regulating TGF-ß and IDO secretion in rat liver transplantation.

BACKGROUND: Allogeneic transplantation immune tolerance is currently a hot research issue and soluble CD83(sCD83) is a novel immunomodulator with great potential in inducing transplantation tolerance. OBJECTIVE: To investigate the mechanism of the immune tolerance effect of sCD83 on rat liver transplantation. METHOD: A rat liver transplantation model was established to study the effects of sCD83 on the expression levels of IL-2, IL-10, and TGF-ß in peripheral blood and the mRNA expressions of foxp3, TGF-ß, and Indoleamine 2,3-dioxygenase (IDO) in liver. The expression changes of costimulatory molecules CD80, CD86, and MHC-II on the surface of DC cells and the expressions of IDO + DC cell, TGF-ß + CD4 + T cell, and CD4 + CD25 + Foxp3 + T cell were analyzed and compared. RESULTS: sCD83 alleviated the rejection activity index (RAI) of rat liver transplantation in the early stage, increased the expressions of TGF-ß, IL-10 in peripheral blood and the mRNAs of IDO, TGF-ß and foxp3 in the transplanted liver, and down-regulated the expressions of MHC-II, CD86, and CD80 in DC cells, resulting in significant increased numbers of tolerogenic TGF-ß + CD4 + T cells, Treg cells, and IDO + DC cells with low expression. CONCLUSION: sCD83 inhibited acute rejection after liver transplantation in an allogeneic rat, and the mechanism was associated with the effect that sCD83 increased the expression of TGF-ß, activated IDO immunosuppressive pathway, and increased tolerogenic DC cells and Treg cells.

Porcine soluble CD83 alleviates LPS-induced abortion in mice by promoting Th2 cytokine production, Treg cell generation and trophoblast invasion.

CD83, either in its membrance-bound form (mCD83) or soluble form (sCD83), is an important immunomodulatory molecule in humans and mice. While mCD83 is immunostimulatory, sCD83 exhibits striking immunosuppressive activities, suggesting that sCD83 may be used to combat inflammatory diseases, such as rheumatoid arthritis, graft-versus-host disease and habitual abortion. Although many studies had shed lights on the role of CD83 in humans and mice, little is known about CD83 in other animals. Recently, we showed that porcine CD83 had similar biochemical characteristics and immunoregulatory functions as its human counterpart. However, whether porcine sCD83 (psCD83) is involved in maintaining the immunological tolerance at the maternal-fetal interface and thereby prevents embryo loss and abortion during pregnancy is unclear. In this study, we used LPS-induced animal model to analyze the effect of porcine sCD83 on the mouse abortion. Results showed that psCD83 could significantly alleviate LPS-induced abortion in mice, indicating that the psCD83 had the function of fetal protection. Mechanically, psCD83-mediated fetal protection was related to the promotion on Th2 cytokine production, Treg cell differentiation and trophoblast invasion. This study provides a molecular basis for the fetal protection of psCD83, as well as a potential target for the regulation of maternal-fetal interfacial immune tolerance.

Soluble CD83 suppresses experimental food allergy via regulating aberrant T helper 2 responses.

Aberrant T helper-2 (Th2) responses play a critical role in the pathogenesis of allergic diseases. The underlying mechanism is to be further investigated. It is reported that soluble CD83 (sCD83) has immune-regulatory effects. This study aims to investigate the role of sCD83 in the regulation of Th2 polarization. Blood samples were collected from pediatric patients with food allergy (FA). The Th2 response was analyzed by pertinent immunological approaches. An FA murine model was developed to test the role of sCD83 in the regulation of FA response. We found that the serum sCD83 levels were lower in FA patients. A negative correlation was detected between serum sCD83 levels and serum Th2 cytokine levels. The presence of sCD83 suppressed Th2 cell differentiation and antigen-specific Th2 cell activation. sCD83 upregulated the T-bet expression and suppressed the GATA3 expression in CD4+ T cells. Administration of sCD83 suppressed experimental FA. Pediatric FA patients have low serum sCD83 levels. Administration of sCD83 can alleviate experimental FA via suppression of aberrant Th2 polarization.

Soluble CD83 Triggers Resolution of Arthritis and Sustained Inflammation Control in IDO Dependent Manner.

Interference with autoimmune-mediated cytokine production is a key yet poorly developed approach to treat autoimmune and inflammatory diseases such as rheumatoid arthritis. Herein, we show that soluble CD83 (sCD83) enhances the resolution of autoimmune antigen-induced arthritis (AIA) by strongly reducing the expression levels of cytokines such as IL-17A, IFNγ, IL-6, and TNFα within the joints. Noteworthy, also the expression of RANKL, osteoclast differentiation, and joint destruction was significantly inhibited by sCD83. In addition, osteoclasts which were cultured in the presence of synovial T cells, derived from sCD83 treated AIA mice, showed a strongly reduced number of multinuclear large osteoclasts compared to mock controls. Enhanced resolution of arthritis by sCD83 was mechanistically based on IDO, since inhibition of IDO by 1-methyltryptophan completely abrogated sCD83 effects on AIA. Blocking experiments, using anti-TGF-ß antibodies further revealed that also TGF-ß is mechanistically involved in the sCD83 induced reduction of bone destruction and cartilage damage as well as enhanced resolution of inflammation. Resolution of arthritis was associated with increased numbers of regulatory T cells, which are induced in a sCD83-IDO-TGF-ß dependent manner. Taken together, sCD83 represents an interesting approach for downregulating cytokine production, inducing regulatory T cells and inducing resolution of autoimmune arthritis.

Porcine CD83 is a glycosylated dimeric protein existing naturally in membrane-bound and soluble forms.

Human and mouse CD83 have been well characteized, however, the other mammalian CD83 genes have not been cloned and characterized. In this study, the porcine CD83 (pCD83) was cloned, expressed and characterized, and showed that the pCD83 gene has 81% and 74% homologies with humans and mice, respectively, which was identified to be glycosylated when expressed in eukaryotic cells, existing naturally in two forms: membrance-bound CD83 (mCD83) and soluble CD83 (sCD83), the latter was identified to be generated mainly from mCD83 by proteolytic shedding. The pCD83 was a dimmer mediated by intermolecular disulfide bond formed by the fifth cysteine in the exrtracellular domain. Functionally, the recombinant porcine sCD83 was preliminarily tested to have the ability to inhibit DC-mediated T cell activition. This study provided necessary fundation for further investigation on pCD83 functions.

Putative loss of CD83 immunosuppressive activity in long-standing complication-free juvenile diabetic patients during disease progression.

The CD83 molecule is a known marker of dendritic cell differentiation process, and its soluble form (sCD83) exerts immunosuppressive functions. In our research, we examined whether the sCD83 plasma concentration is impaired in DM1 children and if the expected changes are in line with the disturbed process of monocyte's transformation into mCD83+ monocyte-derived cells. 28 newly diagnosed (ND-DM1) and 30 long-standing (LS-DM1) patients were enrolled into our study. We revealed that the examined cells show a high mCD83 expression level in ND-DM1, which was significantly downregulated by the TNF-α stimulation. The results were in line with those from healthy controls. We also observed that monocyte differentiation process into CD83+ cells was much defective in LS-DM1 children and the mCD83 expression level seems not to be controlled by TNF-α. Moreover, the sCD83 level was significantly decreased in plasma from LS-DM1 children and it was negatively related to HbA1c levels, while no correlations were observed between TNF-α plasma concentration or disease duration. Summarizing, our results suggest that reduced sCD83 levels may correspond with a poor metabolic control in LS-DM1 patients and therapeutic administration of this molecule may indicate a new therapy approach in the chronic phase of diabetes.

An Expanded Neuroimmunomodulation Axis: sCD83-Indoleamine 2,3-Dioxygenase-Kynurenine Pathway and Updates of Kynurenine Pathway in Neurologic Diseases.

Many neurologic diseases are related to autoimmune dysfunction and a variety of molecules or reaction pathways are involved in the regulation of immune function of the nervous system. Soluble CD83 (sCD83) is the soluble form of CD83, a specific marker of mature dendritic cell, which has recently been shown to have an immunomodulatory effect. Indoleamine 2,3-dioxygenase (IDO; corresponding enzyme intrahepatic, tryptophan 2,3-dioxygenase, TDO), a rate-limiting enzyme of extrahepatic tryptophan kynurenine pathway (KP) participates in the immunoregulation through a variety of mechanisms solely or with the synergy of sCD83, and the imbalances of metabolites of KP were associated with immune dysfunction. With the complement of sCD83 to IDO-KP, a previously known immunomodulatory axis, this review focused on an expanded neuroimmunomodulation axis: sCD83-IDO-KP and its involvement in nervous system diseases.

The levels of soluble forms of CD21 and CD83 in multiple sclerosis.

Multiple Sclerosis (MS) is a neuroinflammatory disease of the central nervous system (CNS) in which immune system plays a crucial role in progression of the disease. An enormous amount of research has been shown that immune mediators such as cytokines and chemokines are the culprits of MS propagation suggesting that modulation of such molecules may pave the path to hinder the disease development. It has been shown that both CD21 and CD83 contribute to the resolution of inflammation occurred in MS. CD21 and CD83 have also been ascribed to Epstein Barr virus (EBV) infection (the prime suspect of MS causality) and the levels of vitamin D, respectively. Hence, in this study, we measured the serum concentrations of soluble forms of CD21 and CD83 in 255 patients with MS divided into two groups who were receiving interferon-beta (185 MS patients) and fingolimod (70 MS patients) in comparison to 384 healthy individuals. The levels of EBV titers including anti-VCA IgM, anti-VCA IgG and anti-EBNA-1 IgG were also measured. The results showed that the concentration of soluble CD21 (sCD21) was markedly decreased in serum samples of MS patients with respect of controls. Contrarily, the level of soluble CD83 (sCD83) was elevated in MS patients compared to healthy individuals. In addition, the levels of sCD21 and sCD83 were correlated with the titers of EBV. The data showed the significant association between the expanded disability status scale (EDSS) and the levels of both sCD21 and sCD83. It seems that both sCD21 and sCD83 might be good candidate for disease monitoring and can be considered potential biomarkers for the disease activity.

Soluble CD83 Alleviates Experimental Autoimmune Uveitis by Inhibiting Filamentous Actin-Dependent Calcium Release in Dendritic Cells.

Soluble CD83 (sCD83) is the extracellular domain of the membrane-bound CD83 molecule, and known for its immunoregulatory functions. Whether and how sCD83 participates in the pathogenesis of uveitis, a serious inflammatory disease of the eye that can cause visual disability and blindness, is unknown. By flow cytometry and imaging studies, we show that sCD83 alleviates experimental autoimmune uveitis (EAU) through a novel mechanism. During onset and recovery of EAU, the level of sCD83 rises in the serum and aqueous humor, and CD83+ leukocytes infiltrate the inflamed eye. Systemic or topical application of sCD83 exerts a protective effect by decreasing inflammatory cytokine expression, reducing ocular and splenic leukocyte including CD4+ T cells and dendritic cells (DCs). Mechanistically, sCD83 induces tolerogenic DCs by decreasing the synaptic expression of co-stimulatory molecules and hampering the calcium response in DCs. These changes are caused by a disruption of the cytoskeletal rearrangements at the DC-T cell contact zone, leading to altered localization of calcium microdomains and suppressed T-cell activation. Thus, the ability of sCD83 to modulate DC-mediated inflammation in the eye could be harnessed to develop new immunosuppressive therapeutics for autoimmune uveitis.