Association of T and B Cells Infiltrating Orbital Tissues With Clinical Features of Graves Orbitopathy

Graves disease: latest understanding of pathogenesis and treatment options

Graves disease is the most common cause of hyperthyroidism in iodine-sufficient areas. The main responsible mechanism is related to autoantibodies that bind and activate the thyrotropin receptor (TSHR). Although Graves hyperthyroidism is relatively common, no causal treatment options are available. Established treatment modalities are antithyroid drugs, which reduce thyroid hormone synthesis, radioactive iodine and surgery. However, emerging drugs that target the main autoantigen (monoclonal antibodies, small molecules, peptides) or block the immune pathway have been recently tested in clinical trials. Graves disease can involve the thyroid exclusively or it can be associated with extrathyroidal manifestations, among which Graves orbitopathy is the most common. The presence of Graves orbitopathy can change the management of the disease. An established treatment for moderate-to-severe Graves orbitopathy is intravenous glucocorticoids. However, recent advances in understanding the pathogenesis of Graves orbitopathy have allowed the development of new target-based therapies by blocking pro-inflammatory cytokine receptors, lymphocytic infiltration or the insulin-like growth factor 1 receptor (IGF1R), with several clinical trials providing promising results. This article reviews the new discoveries in the pathogenesis of Graves hyperthyroidism and Graves orbitopathy that offer several important tools in disease management.

Plasma exosomes from patients with active thyroid-associated orbitopathy induce inflammation and fibrosis in orbital fibroblasts

BACKGROUND

The pathogenesis of thyroid-associated orbitopathy (TAO) remains incompletely understand. The interaction between immunocytes and orbital fibroblasts (OFs) play a critical role in orbital inflammatory and fibrosis. Accumulating reports indicate that a significant portion of plasma exosomes (Pla-Exos) are derived from immune cells; however, their impact upon OFs function is unclear.

METHODS

OFs were primary cultured from inactive TAO patients. Exosomes isolated from plasma samples of patients with active TAO and healthy controls (HCs) were utilized for functional and RNA cargo analysis. Functional analysis in thymocyte differentiation antigen-1+ (Thy-1+) OFs measured expression of inflammatory and fibrotic markers (mRNAs and proteins) and cell activity in response to Pla-Exos. RNA cargo analysis was performed by RNA sequencing and RT-qPCR. Thy-1+ OFs were transfected with miR-144-3p mimics/inhibitors to evaluate its regulation of inflammation, fibrosis, and proliferation.

RESULTS

Pla-Exos derived from active TAO patients (Pla-ExosTAO-A) induced stronger production of inflammatory cytokines and hyaluronic acid (HA) in Thy-1+ OFs while inhibiting their proliferation. Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis and single sample gene set enrichment analysis (ssGSEA) suggested that the difference in mRNA expression levels between Pla-ExosTAO-A and Pla-ExosHC was closely related to immune cells. Differential expression analysis revealed that 62 upregulated and 45 downregulated miRNAs in Pla-ExosTAO-A, with the elevation of miR-144-3p in both Pla-Exos and PBMCs in active TAO group. KEGG analysis revealed that the target genes of differentially expressed miRNA and miR-144-3p enriched in immune-related signaling pathways. Overexpression of the miR-144-3p mimic significantly upregulated the secretion of inflammatory cytokines and HA in Thy-1+ OFs while inhibiting their proliferation.

CONCLUSION

Pla-Exos derived from patients with active TAO were immune-active, which may be a long-term stimulus casual for inflammatory and fibrotic progression of TAO. Our finding suggests that Pla-Exos could be used as biomarkers or treatment targets in TAO patients.

The changing landscape of thyroid eye disease: current clinical advances and future outlook

AIMS

This review aims to provide an overview of the current understanding of TED and its pathophysiology. To describe the evidence base for current consensus treatment recommendations and newer biological therapies available as well as to present future therapeutic research.

METHODS

We reviewed and assessed the peer-reviewed literature placing particular emphasis on recent studies evaluating the pathophysiology of TED, landmark trials forming the basis of current management and recent clinical trials informing future therapeutics. Searched were made in MEDLINE Ovid, Embase Ovid, US National Institutes of Health Ongoing Trials Register and EU Clinical Trials Register. Keywords included: "Thyroid Eye Disease", "Graves Orbitopathy", "Thyroid Orbitopathy" and "Graves' Ophthalmopathy".

RESULTS AND CONCLUSIONS

The pathophysiology of TED involves a complex array of cellular and humoral based autoimmune dysfunction. Previous therapies have been broad-based acting as a blunt instrument on this mechanism with varying efficacy but often accompanied with a significant side effect profile. The recent development of targeted therapy, spearheaded by Teprotumumab has led to an array of treatments focusing on specific components of the molecular pathway optimising their impact whilst possibly minimising their side effect profile. Future challenges involve identifying the most effective target for each patient rather than any single agent being a panacea. Long-term safety profiles will require clarification as unintended immunological consequence downstream may become manifest as seen in other diseases. Finally, future novel therapeutics will entail significant expenditure and may lead to a divergence of available treatment modalities between healthcare systems due to funding disparities.

Immune checkpoints: new insights into the pathogenesis of thyroid eye disease

Thyroid eye disease (TED) is a disfiguring autoimmune disease characterized by changes in the orbital tissues and is caused by abnormal thyroid function or thyroid-related antibodies. It is the ocular manifestation of Graves' disease. The expression of thyroid-stimulating hormone receptor (TSHR) and the insulin-like growth factor-1 receptor (IGF-1 R) on the cell membrane of orbital fibroblasts (OFs) is responsible for TED pathology. Excessive inflammation is caused when these receptors in the orbit are stimulated by autoantibodies. CD34+ fibrocytes, found in the peripheral blood and orbital tissues of patients with TED, express immune checkpoints (ICs) like MHC II, B7, and PD-L1, indicating their potential role in presenting antigens and regulating the immune response in TED pathogenesis. Immune checkpoint inhibitors (ICIs) have significantly transformed cancer treatment. However, it can also lead to the occurrence of TED in some instances, suggesting the abnormality of ICs in TED. This review will examine the overall pathogenic mechanism linked to the immune cells of TED and then discuss the latest research findings on the immunomodulatory role of ICs in the development and pathogenesis of TED. This will offer fresh perspectives on the study of pathogenesis and the identification of potential therapeutic targets.

The circulating IL-35+ regulatory B cells are associated with thyroid associated opthalmopathy

BACKGROUND

Thyroid-associated ophthalmopathy (TAO) is the most common orbital disease in adults, potentially leading to disfigurement and visual impairment. However, the causes of TAO are not fully understood. IL-35+B cells are a newly identified regulatory B cells (Bregs) in maintaining immune balance in various autoimmune diseases. Yet, the influence of IL-35+Bregs in TAO remains unexplored.

METHODS

This study enrolled 36 healthy individuals and 14 TAO patients. We isolated peripheral blood mononuclear cells and stimulated them with IL-35 and CpG for 48 h. Flow cytometry was used to measure the percentages of IL-35+Bregs.

RESULTS

The percentage of circulating IL-35+Bregs was higher in TAO patients, and this increase correlated positively with disease activity. IL-35 significantly increased the generation of IL-35+Bregs in healthy individuals. However, B cells from TAO patients exhibited potential impairment in transitioning into IL-35+Breg phenotype under IL-35 stimulation.

CONCLUSIONS

Our results suggest a potential role of IL-35+Bregs in the development of TAO, opening new avenues for understanding disease mechanisms and developing therapeutic approaches.

Peripheral CD3+CD4+ T cells as indicators of disease activity in thyroid eye disease: age-dependent significance

PURPOSE

To provide an in-depth analysis of the association of peripheral lymphocytes and the disease activity of thyroid eye disease (TED).

METHODS

This retrospective study enrolled 65 active TED patients and 46 inactive TED patients. Comparative analyses of peripheral lymphocyte subsets were conducted between active and inactive patients. Subgroup analyses were performed based on sex, age, disease duration, and severity. Correlation analyses explored the associations between lymphocyte subsets and TED activity indicators. Prediction models for TED activity were established using objective indicators.

RESULTS

Significantly elevated levels of CD3+CD4+ T cells were observed in active TED patients compared to inactive patients (P = 0.010). Subgroup analyses further revealed that this disparity was most prominent in females (P = 0.036), patients aged 50 years and younger (P = 0.003), those with long-term disease duration (P = 0.022), and individuals with moderate-to-severe disease (P = 0.021), with age exerting the most substantial impact. Subsequent correlation analysis confirmed the positive association between CD3+CD4+ T cells and the magnetic resonance imaging indicator of TED activity among patients aged 50 years and younger (P = 0.038). The combined prediction models for TED activity, established using objective indicators including CD3+CD4+ T cells, yielded areas under curve of 0.786 for all patients and 0.816 for patients aged 50 years and younger.

CONCLUSIONS

Peripheral CD3+CD4+ T cells are associated with disease activity of TED, especially in patients aged 50 years and younger. Our study has deepened the understanding of the peripheral T cell profiles in TED patients.

GSDMD mediated pyroptosis induced inflammation of Graves' orbitopathy via the NF-κB/ AIM2/ Caspase-1 pathway

Gasdermin D (GSDMD) is a key executor which triggers pyroptosis as well as an attractive checkpoint in various inflammatory and autoimmune diseases but it has yet to prove its function in Graves'orbitopathy (GO). Our aim was to investigate GSDMD levels in orbital connective tissue and serum of GO patients and then assess the association between serum levels and patients' clinical activity score (CAS). Further, GSDMD-mediated pyroptosis and the underlying mechanism in inflammatory pathogenesis in the cultured orbital fibroblasts (OFs) of GO patients were examined. OFs were collected after tumor necrosis factor (TNF)-α or interferon (IFN)-γ treatment or combination treatment at different times, and the expression of GSDMD and related molecular mechanisms were analyzed. Then, we constructed the GSDMD knockout system with siRNA and the system was further exposed to the medium with or without IFN-γ and TNF-α for a specified time. Finally, we evaluated the production of interleukin (IL)-1β and IL-18. We found that serum GSDMD levels were elevated and positively correlated with the CAS in GO patients. Meanwhile, the expression of GSDMD and N-terminal domain (NT-GSDMD) in orbital connective tissue of GO patients was augmented. Also, increased expression of GSDMD and related pyroptosis factors was observed in vitro model of GO. We further demonstrated that GSDMD-mediated pyroptosis induced inflammation via the nuclear factor kB (NF-κB)/absent in melanoma-2 (AIM-2)/caspase-1 pathway. In addition, blocking GSDMD suppressed proinflammatory cytokine production in GO. We concluded that GSDMD may be a biomarker as well as a potential target for the evaluation and treatment of inflammation related with GO.

Identification of immune-related regulatory networks and diagnostic biomarkers in thyroid eye disease

BACKGROUND

Thyroid eye disease (TED) is an orbit-associated autoimmune inflammatory disorder intricately linked to immune dysregulation. Complete pathogenesis of TED remains elusive. This work aimed to mine pathogenesis of TED from immunological perspective and identify diagnostic genes.

METHODS

Gene expression microarray data for TED patients were downloaded from Gene Expression Omnibus, immune-related genes (IRGs) were from ImmPort database, and TED-related transcription factors (TFs) were from Cirtrome Cancer database. Differential analysis, Gene Ontology (GO), and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses were performed. Regulatory networks of TFs and IRGs were constructed with Cytoscape. Diagnostic biomarkers in TED were identified through LASSO. Immune cell infiltration analysis was performed using CIBERSORT.

RESULTS

Twenty-three immune-related DEmRNAs were revealed and were primarily enriched in humoral immune response, positive regulation of inflammatory response, IL-17, and TNF pathways. Co-expression regulatory network included four TFs and 16 immune-related DEmRNAs. Seven diagnostic genes were identified, with Area Under the Curve (AUC) of 0.993 for training set and AUC value of 0.836 for validation set. TED patients exhibited elevated infiltration levels by macrophages M2, mast cells, and CD8 T cells among 22 immune cell types, whereas macrophages M2 and mast cells resting were significantly lower than normal group.

CONCLUSIONS

The seven feature genes had high diagnostic value for TED patients. Our work explored regulatory network and diagnostic biomarkers, laying theoretical basis for TED diagnosis and treatment.

Immunological Processes in the Orbit and Indications for Current and Potential Drug Targets

Thyroid eye disease (TED) is an extrathyroidal manifestation of Graves' disease (GD). Similar to GD, TED is caused by an autoimmune response. TED is an autoimmune inflammatory disorder of the orbit and periorbital tissues, characterized by upper eyelid retraction, swelling, redness, conjunctivitis, and bulging eyes. The pathophysiology of TED is complex, with the infiltration of activated T lymphocytes and activation of orbital fibroblasts (OFs) and autoantibodies against the common autoantigen of thyroid and orbital tissues. Better understanding of the multifactorial pathogenesis of TED contributes to the development of more effective therapies. In this review, we present current and potential drug targets. The ideal treatment should slow progression of the disease with as little interference with patient immunity as possible. In the future, TED treatment will target the immune mechanism involved in the disease and will be based on a strategy of restoring tolerance to autoantigens.

Thyroid Eye Disease and Its Association With Diabetes Mellitus: A Major Review

PURPOSE

Thyroid eye disease (TED) associated with diabetes mellitus (DM) presents unique challenges. DM is a risk factor for TED. Standard management of TED with glucocorticoids (GC), orbital radiation, or teprotumumab can cause adverse events in poor glycemic control. The authors reviewed the literature on the relationship between TED and DM and the management of co-existing diseases.

METHODS

The authors searched PubMed with keywords "thyroid eye disease," "diabetes mellitus," and similar terms from 2013 to 2022. The authors included relevant studies after screening the abstracts. Additional references to the selected studies were included where applicable. Data were extracted from the final articles according to the preplanned outline of the review.

RESULTS

The initial search yielded 279 abstracts. The final review included 93 articles. TED and DM interact at multiple levels-genetic, immunologic, cellular, nutritional, and metabolic. Both DM and thyroid dysfunction exacerbate the morbidity caused by the other. Metabolic factors also affect the inflammatory pathway for TED. Patients with DM develop TED with greater frequency and severity, necessitating interventions for vision salvage. Agents (GC, teprotumumab, or radiation) used for TED are often unsuitable for treatment with DM, especially if there is poor glycemic control or diabetic retinopathy. There were no studies on using steroid-sparing agents in TED with DM.

CONCLUSION

TED and DM co-exist because of multiple intersections in the pathophysiology. Challenges in the treatment include increased TED severity and risk of hyperglycemia and retinopathy. Multidisciplinary teams best undertake treatment of TED with DM.

Monoclonal Antibodies for the Treatment of Graves Orbitopathy: Precision Medicine?

PURPOSE

To summarize the development, nomenclature, and rationale of the reported use of monoclonal antibodies (Mabs) in Graves Orbitopathy (GO) and to undertake a systematic review of the management of GO with Mabs.

METHODS

The Pubmed and Embase databases and the Federal Brazilian searching site (Periódicos-CAPES) were screened. The authors searched all the keywords "monoclonal antibodies," "adalimumab," "belimumab," "infliximab," "rituximab," "teprotumumab," and "tocilizumab" combined with the terms "Graves Orbitopathy," "Graves eye disease" and "thyroid eye disease." All the articles published in English, French, and Spanish from 2000 to May 2022 were screened. Only publications with quantitative data on the activity of orbitopathy, proptosis, or both were included.

RESULTS

Seventy-six articles of the 954 screened records met the inclusion criteria. Seven Mabs were described for treating GO. The three most reported Mabs were Rituximab, Tocilizumab, and Teprotumumab. Only eight randomized clinical trials compared the effect of these three Mabs and Belimumab with the effect of steroids or placebos. Adalimumab, Infliximab, and K1-70 only appeared in a few case series and case reports. Frequent mild-to-moderate and few major side effects occurred with the three most used Mabs. Relapse rates ranged from 7.4% for Tocilizumab to at least 29.4% for Teprotumumab. No randomized clinical trials compared Mabs head-to-head.

CONCLUSION

Considering the lack of head-to-head comparisons between Mabs, the relapse rate, the possibility of severe collateral effects, and the cost of Mabs, it is not clear which Mab is the safest and most useful to treat GO.

Identification and validation of ferroptosis-related genes and immune cell infiltration in thyroid associated ophthalmopathy

Thyroid associated ophthalmopathy (TAO) is an orbital autoimmune inflammatory disease that is commonly associated with thyroid dysfunction. Although the etiology of TAO is unclear, ROS accumulation and oxidative stress have been closely linked to the pathogenesis of TAO. Ferroptosis is an iron-dependent programmed cell death characterized by intracellular labile iron levels, excessive accumulation of reactive oxygen species (ROS) and lipid peroxidation. Currently, there are few reports regarding the role of ferroptosis in TAO. This article aimed to identify ferroptosis-related genes (FRGs) with diagnostic and therapeutic potential in TAO and explore their relationship with immune cells and lncRNAs. GSE58331 was downloaded from Gene Expression Omnibus (GEO) database. A total of 162 DEGs were identified between 27 TAO samples and 22 health samples from GSE58331, among which six FRGs (CYBB, CTSB, SLC38A1, TLR4, PEX3, and ABCC1) were obtained. The AUC of SLC38A1, TLR4, PEX3 in lacrimal gland tissues was greater than 80 which suggested high diagnostic value in TAO. The result of immune cell infiltrate analysis indicated increased infiltration of monocytes (p < 0.001), macrophages M0(p = 0.039), mast cells activated (p = 0.008), and neutrophils (p = 0.045) in orbital tissues from TAO patients. Meanwhile, mast cells resting (p = 0.043) and macrophages M2 (p = 0.02) showed reduced infiltration in TAO samples. There were no gender differences in immune cell infiltration in the TAO patients. Two differentially expressed lncRNAs, LINC01140 and ZFHX4-AS1, in TAO groups were identified as ferroptosis-related lncRNAs. CYBB-LINC01140-TLR4, CYBB- LINC01140- SLC38A1, TLR4- LINC01140- SLC38A1, and CTSB- ZFHX4-AS1- CYBB may be potential RNA regulatory pathways in TAO. Targeted drugs and transcription factors for differential expressed FRGs were also screened out in our study. In vitro, experiments revealed that CTSB, PEX3, ABCC1 and ZFHX4-AS1(lncRNA) were differentially expressed in orbital fibroblasts (OFs) between TAO groups and healthy controls at the transcriptional level.

Pathophysiology of thyroid-associated orbitopathy

Thyroid-associated orbitopathy, the most common extrathyroidal manifestation of Graves' disease, is characterized by orbital inflammatory infiltration and activation of orbital fibroblasts, which mediates de novo adipogenesis, excessive production of hyaluronan, myofibroblast differentiation and ultimately tissue fibrosis. Interactions among T cells, B cells, and orbital fibroblasts result in their activation and perpetuation of orbital inflammation as well as tissue remodelling. T helper 17 cells belong to a newly identified pathogenic CD4+ T cell subset which possesses prominent pro-inflammatory and profibrotic capabilities. Thyroid stimulating hormone receptor/insulin-like growth factor-1 receptor crosstalk and the downstream signalling pathways of both receptors represent the major mechanisms leading to activation of orbital fibroblasts. Thyroid stimulating hormone receptor autoantibody is the disease specific biomarker of great clinical relevance and utility. There is growing evidence that oxidative stress, gut microbiome and epigenetics also play a role in the pathogenesis and their manipulation may represent novel therapeutic strategies.

M1-Like Macrophages Modulate Fibrosis and Inflammation of Orbital Fibroblasts in Graves' Orbitopathy: Potential Relevance to Soluble Interleukin-6 Receptor

Background: Graves' orbitopathy (GO) is a disfiguring and sight-threatening autoimmune disease. Previous studies have shown the infiltration of macrophages in GO orbital connective tissues. However, the immunophenotypes of macrophages and their modulatory effects on orbital fibroblasts (OFs) have not been examined so far. In this study, we sought to determine the pathophysiology of macrophages in GO. Methods: In this case-control study, orbital connective tissues collected from 40 GO patients and 20 healthy controls were immunohistochemically stained for cytokines and macrophage cell surface antigens. The polarization of orbital-infiltrating macrophages was investigated by flow cytometry and immunofluorescence. Effects of interleukin (IL)-6 combined with soluble IL-6 receptor (sIL-6R) on the proliferation, differentiation, and inflammation of different OF subsets were examined by CCK-8, Western blotting, and Luminex assays, respectively. The antigen-presenting abilities of different OF subsets under IL-6/sIL-6R signaling were studied by proteomics. Finally, the differentiation of CD8⁺ IL-17A-producing T cells by sIL-6R was tested. Results: GO orbital connective tissues displayed increased IL-6, sIL-6R, STAT3, and IL-17A levels. CD86⁺ M1-like macrophages were predominant in active GO patients, while stable GO patients tended to have more CD163⁺ M2-like macrophages. The expression of IL-6 was higher in M1-like macrophages, and the expression of transforming growth factor-β was higher in M2-like macrophages both in GO orbital connective tissues in situ in vivo and in cell culture system in vitro. The IL-6/sIL-6R stimulation promoted the fibrosis of both CD34⁺ and CD34^- OFs. Monocyte chemoattractant protein-1 expression was also induced by IL-6/sIL-6R stimulation in both OF subsets. IL-6/sIL-6R stimulation enhanced the antigen processing of CD34⁺ OFs through upregulating the intact major histocompatibility complex I and antigen transporters. However, the protein expressions of the thyrotropin receptor and insulin-like growth factor 1 receptor could not be directly increased by IL-6/sIL-6R stimulation in CD34⁺ OFs. Furthermore, sIL-6R was conducive to the differentiation of CD8⁺ IL-17A-producing T cells. Conclusions: Our study demonstrated the immunophenotypes of orbital-infiltrating macrophages that may activate OFs depending on the IL-6/sIL-6R signaling in GO. Our preclinical findings implicate, at least in part, the molecular rationale for blocking sIL-6R as a promising therapeutic agent for GO.

Chemokines in thyroid autoimmunity

The chemokine receptor CXCR3 and its chemokines CXCL9, CXCL10, and CXCL11 are involved in the pathogenesis of autoimmune diseases. Th1 lymphocytes are recruited by Th1 chemokines, secreted by damaged cells. In inflamed tissues, the attracted Th1 lymphocytes induce the IFN-gamma and TNF-alpha release, that stimulates the secretion of Th1 chemokines, initiating and reiterating an amplification feedback loop. Autoimmune thyroid disorders (AITD) are the most recurrent autoimmune diseases, including Graves' disease (GD) and autoimmune thyroiditis, clinically defined by thyrotoxicosis and hypothyroidism, respectively. Graves' ophthalmopathy is one of GD extrathyroidal manifestations, occurring in ~30-50% of GD patients. In the early phase of AITD, the Th1 immune response is prevalent, and a following switch to a Th2 immune response has been shown in the late, inactive, phase. The reviewed data underline the importance of chemokines in thyroid autoimmunity and suggest CXCR3-receptor and its chemokines as potential targets of novel drugs for these disorders.

Role of Peripheral Regulatory T Lymphocytes in Patients with Thyroid Associated Ophthalmopathy During Systemic Glucocorticoid Treatment: A Prospective Observational Study

OBJECTIVE

Thyroid-associated ophthalmopathy (TAO) is an autoimmune disorder involving the orbital tissue. This study aimed to understand the role of regulatory T cells (Tregs) in TAO during 12-week systemic glucocorticoid (GC) treatment.

METHODS

Thirty-two moderate-severe TAO patients with a clinical activity score (CAS) ≥3/7 or with prolonged T2 relaxation time (T2RT) on at least one side of extraocular muscle (EOM) were enrolled. The percentage of the peripheral CD4⁺CD25(high)CD127(-/low) Tregs was analyzed using flow cytometry before and after the GC treatment. The activity and severity of TAO, T2RT, and the clinical outcomes after the GC treatment were assessed. Their correlation with the peripheral Tregs was investigated.

RESULTS

There was no significant association between the baseline Treg fraction and the activity and severity of TAO or the treatment response. A significant reduction of Tregs was observed after the GC therapy merely in patients without any clinical improvement.

CONCLUSION

Treg reduction after systemic GC therapy is indicative of a poor therapeutic response. Accordingly, dynamic alterations of Tregs could help to evaluate the effectiveness of the GC treatment.

A review of TSHR- and IGF-1R-related pathogenesis and treatment of Graves' orbitopathy

Graves' orbitopathy (GO) is an organ-specific autoimmune disease, but its pathogenesis remains unclear. There are few review articles on GO research from the perspective of target cells and target antigens. A systematic search of PubMed was performed, focusing mainly on studies published after 2015 that involve the role of target cells, orbital fibroblasts (OFs) and orbital adipocytes (OAs), target antigens, thyrotropin receptor (TSHR) and insulin-like growth factor-1 receptor (IGF-1R), and their corresponding antibodies, TSHR antibodies (TRAbs) and IGF-1R antibodies (IGF-1R Abs), in GO pathogenesis and the potentially effective therapies that target TSHR and IGF-1R. Based on the results, OFs may be derived from bone marrow-derived CD34+ fibrocytes. In addition to CD34+ OFs, CD34- OFs are important in the pathogenesis of GO and may be involved in hyaluronan formation. CD34- OFs expressing Slit2 suppress the phenotype of CD34+ OFs. β-arrestin 1 can be involved in TSHR/IGF-1R crosstalk as a scaffold. Research on TRAbs has gradually shifted to TSAbs, TBAbs and the titre of TRAbs. However, the existence and role of IGF-1R Abs are still unknown and deserve further study. Basic and clinical trials of TSHR-inhibiting therapies are increasing, and TSHR is an expected therapeutic target. Teprotumumab has become the latest second-line treatment for GO. This review aims to effectively describe the pathogenesis of GO from the perspective of target cells and target antigens and provide ideas for its fundamental treatment.

TSG6 Plays a Role in Improving Orbital Inflammatory Infiltration and Extracellular Matrix Accumulation in TAO Model Mice

Introduction

TSG-6 plays a wide anti-inflammatory and therapeutic role in a variety of autoimmune diseases as the key mediator of mesenchymal stem cells (MSCs).

Purpose

We aimed to test whether TSG-6 could exert similar effects as MSCS in TAO via establishing TAO animal model immunized by hTSHR-A subunit plasmid.

Material and Methods

We tested the expression level of TSG-6 on intraconal orbital fat from controls and patients with TAO. We established a stable thyroid-associated ophthalmopathy animal model by immunizing 6-week-old female Balb/c mice with recombination hTSHR-A subunit plasmid. After four immunizations, TSG-6 or dexamethasone was injected through the tail vein. The effects of the drugs on body weight, thyroid function, orbital inflammation, fibrosis and lipogenesis were observed.

Results

The expression of TSG-6 in the orbital tissues of TAO patient is lower than that of normal people. In our animal model, mice showed weight loss, higher TT4 and TSHR antibody levels, and ocular symptoms such as inflammation and proptosis. TSG-6 can reduce ocular fibrosis and lipogenesis by inhibiting the infiltration of CD3+ T lymphocytes and macrophages in the mouse model of thyroid associated ophthalmopathy. Compared with dexamethasone, TSG-6 showed comparable anti-inflammatory effect, moreover, it has given a better performance in inhibiting adipogenesis.

Conclusion

It was demonstrated that TSG-6 has a considerable positive impact on improving eye symptoms of TAO mice, which could be a novel candidate for the early treatment of TAO.

Metformin Attenuates Inflammation and Fibrosis in Thyroid-Associated Ophthalmopathy

The pathogenesis of thyroid-associated ophthalmopathy (TAO) is still unclear, and therapeutic drugs have great limitations. As metformin has multiple therapeutic effects in many autoimmune diseases, we explored the effects of metformin on TAO in an in vitro fibroblast model. We used orbital connective tissues and fibroblasts that were obtained from TAO patients and normal controls. The activity of adenosine monophosphate-activated protein kinase (AMPK) and the levels of inflammatory or fibrotic factors were examined by immunofluorescence (IF) and immunohistochemistry (IHC). Quantitative real-time polymerase chain reaction (qPCR), cytokine quantification by enzyme-linked immunosorbent sssay (ELISA), IF, and western blotting (WB) were used to measure the expression of factors related to inflammation, fibrosis, and autophagy. To determine the anti-inflammatory and antifibrotic mechanisms of metformin, we pretreated cells with metformin, 5-aminoimidazole-4-carboxamide 1-β-D-ribofuranoside (AICAR, an AMPK activator) or compound C (CC, an AMPK inhibitor) for 24 h and used WB to verify the changes in protein levels in the AMPK/mammalian target of rapamycin (mTOR) pathway. We determined that the low activity of AMPK in the periorbital tissue of TAO patients may be closely related to the occurrence and development of inflammation and fibrosis, and metformin exerts multiple effects by activating AMPK in TAO. Furthermore, we suggest that AMPK may be a potential target of TAO therapy.

Current concepts regarding Graves' orbitopathy

Graves' orbitopathy (GO) is an orbital autoimmune disorder and the main extrathyroidal manifestation of Graves' disease, the most common cause of hyperthyroidism. GO affects about 30% of Graves' patients, although fewer than 10% have severe forms requiring immunosuppressive treatments. Management of GO requires a multidisciplinary approach. Medical therapies for active moderate-to-severe forms of GO (traditionally, high-dose glucocorticoids) often provide unsatisfactory results, and subsequently surgeries are often needed to cure residual manifestations. The aim of this review is to provide an updated overview of current concepts regarding the epidemiology, pathogenesis, assessment, and treatment of GO, and to present emerging targeted therapies and therapeutic perspectives. Original articles, clinical trials, systematic reviews, and meta-analyses from 1980 to 2021 were searched using the following terms: Graves' disease, Graves' orbitopathy, thyroid eye disease, glucocorticoids, orbital radiotherapy, rituximab, cyclosporine, azathioprine, teprotumumab, TSH-receptor antibody, smoking, hyperthyroidism, hypothyroidism, thyroidectomy, radioactive iodine, and antithyroid drugs. Recent studies suggest a secular trend toward a milder phenotype of GO. Standardized assessment at a thyroid eye clinic allows for a better general management plan. Treatment of active moderate-to-severe forms of GO still relies in most cases on high-dose systemic-mainly intravenous-glucocorticoids as monotherapy or in combination with other therapies-such as mycophenolate, cyclosporine, azathioprine, or orbital radiotherapy-but novel biological agents-including teprotumumab, rituximab, and tocilizumab-have achieved encouraging results.

Disulfiram Exerts Antiadipogenic, Anti-Inflammatory, and Antifibrotic Therapeutic Effects in an In Vitro Model of Graves' Orbitopathy

Background: Adipogenesis, glycosaminoglycan hyaluronan (HA) production, inflammation, and fibrosis are the main pathogenic mechanisms responsible for Graves' orbitopathy (GO). We hypothesized that disulfiram (DSF), an aldehyde dehydrogenase (ALDH) inhibitor used to treat alcoholism, would have therapeutic effects on orbital fibroblasts (OFs) in GO. This study aimed at determining the therapeutic effects and underlying mechanisms of DSF on these parameters. Methods: Primary cultures of OFs from six GO patients and six control subjects were established. The OFs were allowed to differentiate into adipocytes and treated with various concentrations of DSF. Lipid accumulation within the cells was evaluated by Oil Red O staining. Real-time polymerase chain reaction (RT-PCR) and Western blotting were used to measure the expression of key adipogenic transcription factors, ALDH1A1, ALDH2, and mitogen-activated protein kinase (MAPK) signaling proteins. Apoptosis assays and reactive oxygen species levels were evaluated by flow cytometry. HA production was measured by using an enzyme-linked immunosorbent assay (ELISA) kit. The mRNA levels of proinflammatory molecules were measured by using RT-PCR after interleukin (IL)-1β stimulation with or without DSF. The mRNA expression of markers associated with fibrosis was examined by using RT-PCR after transforming growth factor (TGF)-β1 stimulation with or without DSF. The wound-healing assay was assessed by phase-contrast microscopy. Results: Under identical adipogenesis conditions, GO OFs effectively differentiated, while normal control (NC) OFs did not. DSF dose dependently suppressed lipid accumulation during adipogenesis in GO OFs. The expression of key adipogenic transcription factors, such as perilipin-1 (PLIN1), PPARγ (PPARG), FABP4, and c/EBPα (CEBPA), was downregulated. Further, DSF inhibited the phosphorylation of ERK by inhibiting ALDH1A1. In addition, DSF attenuated HA production and suppressed inflammatory molecule expression induced by IL-1β in GO OFs and NC OFs. The antifibrotic effects of DSF on TGF-β1 were also observed in GO OFs. Conclusions: In the current study, we provide evidence of the inhibitory effect of DSF on GO OFs adipogenesis, HA production, inflammation, and fibrosis in vitro. The results of this study are noteworthy and indicate the potential use of DSF as a therapeutic agent for the treatment of GO.

Role of the mononuclear cell infiltrate in Graves' orbitopathy (GO): results of a large cohort study

OBJECTIVE

The extent to which mononuclear cells and TSH-receptor autoantibodies (TRAb) contribute to Graves' orbitopathy (GO) is not completely defined. Here we investigated the relationship between the immunohistochemical phenotype of orbital infiltrating cells and GO features in a large number of patients.

METHODS

We conducted an observational cohort study in 76 consecutive patients with GO (16 men and 60 women) who underwent orbital decompression over a period of 18 consecutive months. An ophthalmological evaluation was performed in all patients, as well as immunohistochemistry for CD3, CD4, CD8, CD56 (T-cell markers), CD25 (T and B-cell marker), CD20, CD19 (B-cell markers), and CD138 (plasmacell marker) in specimens collected at decompressive surgery.

RESULTS

Having established cutoff values for each marker, cell infiltrates were found in 60 patients (78.9%; CD3: 39.4%, CD4 55.2%, CD8 50%, CD56: 0%, CD25: 28.9%, CD20: 51.3%, CD19: 25%, CD138: 26.3%). Eleven (14.4%) stained exclusively for CD138 (plasmacells). Patients with CD4-positive mononuclear cells had a significantly greater GO clinical activity score (CAS) (mean difference 1.07, 95% CI - 0.33 to - 1.82, P = 0.004 by univariate, P = 0.05 by multivariate analysis). CAS as well as the remaining GO features were not affected significantly by the mononuclear cell subpopulations in multivariate analyses.

CONCLUSIONS

Mononuclear cell infiltrates are present in the majority of GO patients, with a small percentage represented exclusively by plasmacells. CD4 cells exert a major role on GO activity. These findings may represent a further advancement in the comprehension of GO pathogenesis.

An Early Wave of Macrophage Infiltration Intertwined with Antigen-Specific Proinflammatory T Cells and Browning of Adipose Tissue Characterizes the Onset of Orbital Inflammation in a Mouse Model of Graves' Orbitopathy

Background: Graves' orbitopathy (GO) is an autoimmune-driven manifestation of Graves' disease (GD) where pathogenic autoantibodies to the thyrotropin receptor (TSHR) activate orbital fibroblasts/preadipocytes in the orbital tissue to induce inflammation and extracellular matrix deposition. Since there are significant limitations to study immunological and proinflammatory mediator expression in early and during disease progression in GO patients, we used our experimental mouse model to elucidate early pathogenic processes. Methods: We have developed a robust mouse model of GD/GO induced by electroporation immunization of plasmid encoding human TSHR A-subunit, comprising multiple injections over a course of 15 weeks to fully recapitulate the orbital pathology. In this study, we investigated kinetics of GO development in the model by serial analyses of immunological and cellular parameters during course of orbital inflammation. Results: Pathogenic anti-TSHR antibodies with thyroid-stimulating properties developed early after the second immunization step with concomitant induction of hyperthyroidism. Examination of orbital tissue showed an early wave of macrophage infiltration followed subsequently by CD3⁺ T cells into the orbital tissue. Examination of antigen-specific T cell activity using recombinant human A-subunit protein showed high CD8⁺ T cell proliferation during this early phase of disease onset, whereas effector CD4⁺ T cells and CD25⁺FOXP3⁺ regulatory T cells (Tregs) were downregulated. The early phase of disease was also characterized by abundant presence of proinflammatory cytokines interferon-γ (IFN-γ) and tumor necrosis factor-α (TNF-α). Moreover, as the disease progressed, there was significant increase in browning of orbital fat tissue, which may be dependent on the proinflammatory milieu and/or the increased thyroid hormone levels during the established hyperthyroid status. Conclusions: This work revealed early infiltration of macrophages in the orbital region and induction of pathogenic anti-TSHR antibodies during disease onset in the model. This was followed subsequently by influx of CD8⁺ T cells specific for TSHR coupled with reduction in Tregs and substantial increase in brown adipose tissue. These new insights into the development of orbital inflammation in the model have implications for testing new therapeutic regimens by targeting macrophage function during early phases of orbital inflammation in the model.

2021 update on thyroid-associated ophthalmopathy

PURPOSE

Our understanding of thyroid-associated ophthalmopathy (TAO, A.K.A Graves' orbitopathy, thyroid eye disease) has advanced substantially, since one of us (TJS) wrote the 2010 update on TAO, appearing in this journal.

METHODS

PubMed was searched for relevant articles.

RESULTS

Recent insights have resulted from important studies conducted by many different laboratory groups around the World. A clearer understanding of autoimmune diseases in general and TAO specifically emerged from the use of improved research methodologies. Several key concepts have matured over the past decade. Among them, those arising from the refinement of mouse models of TAO, early stage investigation into restoring immune tolerance in Graves' disease, and a hard-won acknowledgement that the insulin-like growth factor-I receptor (IGF-IR) might play a critical role in the development of TAO, stand out as important. The therapeutic inhibition of IGF-IR has blossomed into an effective and safe medical treatment. Teprotumumab, a β-arrestin biased agonist monoclonal antibody inhibitor of IGF-IR has been studied in two multicenter, double-masked, placebo-controlled clinical trials demonstrated both effectiveness and a promising safety profile in moderate-to-severe, active TAO. Those studies led to the approval by the US FDA of teprotumumab, currently marketed as Tepezza for TAO. We have also learned far more about the putative role that CD34⁺ fibrocytes and their derivatives, CD34⁺ orbital fibroblasts, play in TAO.

CONCLUSION

The past decade has been filled with substantial scientific advances that should provide the necessary springboard for continually accelerating discovery over the next 10 years and beyond.

Correlation between Peripheral T Cell Subsets and the Activity of Thyroid-Associated Ophthalmopathy

INTRODUCTION

Thyroid-associated ophthalmopathy (TAO) is the most common orbital immunological disease in adults. T cells play an important role in the pathogenesis of TAO. However, our knowledge of the circulating T cell subsets in TAO is limited.

OBJECTIVE

To investigate the circulating T cell subsets in TAO and the correlations between them and the activity of TAO.

METHODS

Thirty-eight TAO patients (19 active and 19 nonactive) were enrolled. The absolute number and percentage of total lymphocytes, CD3+T cells, CD4+T cells, CD8+ T cells, CD3+CD4-CD8-T cells (DNT cells), and CD3+CD4+CD8+ T cells (DPT cells) in peripheral blood were measured by flow cytometer.

RESULTS

TAO patients were divided into the active group and the nonactive group by the clinical activity score (CAS). The mean CAS was 4 ± 1.11 in the active group and 1.47 ± 0.61 in the nonactive group. No statistical differences were found in gender, age, and the levels of FT3, FT4, TSH, and TRAb between the two groups. The percentage of DNT cells was lower in the active group than in the non-active group, and it was negatively correlated with CAS (r = -0.349, P=0.032), but not the absolute number. The CD4/CD8 ratio, the absolute number and percentage of CD3+ T cells, CD4+ T cells, CD8+ T cells, and DPT cells did not differ between the two groups.

CONCLUSION

In the present study, we found the percentage of DNT cells was significantly lesser in the active TAO than in the nonactive TAO, and it was negatively correlated with the activity of the TAO. It suggests that DNT cells may involve in the immunopathogenesis of TAO and can serve as a clinical biomarker of the disease activity.

Thyroid eye disease: From pathogenesis to targeted therapies

Thyroid eye disease (TED) is the most common extrathyroidal manifestation of autoimmune Graves’ hyperthyroidism. TED is a debilitating and potentially blinding disease with unclear pathogenesis. Autoreactive inflammatory reactions targeting orbital fibroblasts (OFs) lead to the expansion of orbital adipose tissues and extraocular muscle swelling within the fixed bony orbit. There are many recent advances in the understating of molecular pathogenesis of TED. The production of autoantibodies to cross-linked thyroid-stimulating hormone receptor and insulin-like growth factor-1 receptor (IGF-1R) activates OFs to produce significant cytokines and chemokines and hyaluronan production and to induce adipocyte differentiation. In moderately severe active TED patients, multicenter clinical trials showed that inhibition of IGF-1R with teprotumumab was unprecedentedly effective with minimal side effects. The emergence of novel biologics resulted in a paradigm shift in the treatment of TED. We here review the literature on advances of pathogenesis of TED and promising therapeutic targets and drugs.

Adipocytokines in Graves' orbitopathy and the effect of high-dose corticosteroids

Graves' orbitopathy (GO) is a serious, progressive eye condition seen in patients with autoimmune thyroid disease. GO is characterized by inflammation and swelling of soft orbital tissues. Adipose tissue produces cytokine mediators called adipokines. The present study focuses on the relationship between serum levels of selected adipokines in patients with GO, comparing them with the control group, and uniquely describes the effect of high-dose systemic corticosteroids (HDSC) on their levels. For the purposes of this study, we collected blood samples before and after the treatment with HDSC from 60 GO patients and 34 control subjects and measured serum levels of adiponectin, AIF-1, A-FABP and FGF-21. Levels of adiponectin significantly differed among the three study groups (ANOVA p = 0.03). AIF-1 levels were also significantly different among the study groups (ANOVA p < 0.0001). AIF-1 was significantly associated with the presence of GO after adjusting for clinical factors (age, sex, smoking and BMI) and level of TSH (odds ratio 1.003, p < 0.01). This finding could enforce targeting macrophages in treatment strategies for GO since AIF-1 is considered as a marker of their activation.

Signal transducer and activator of transcription 3 as a potential therapeutic target for Graves' orbitopathy

The roles of signal transducer and activator of transcription 3 (STAT3) in inflammation, oxidative stress, and adipogenesis during Graves' orbitopathy (GO) are incompletely understood. Here, STAT3 expression in orbital tissues (from individuals with GO and healthy control subjects) was studied, and the role of STAT3 in GO pathogenesis was examined through small-interfering RNA (siRNA)-mediated silencing in primary orbital fibroblasts. STAT3 mRNA expression was higher in GO orbital tissues than in non-GO tissues. Treatment with proinflammatory cytokines, thyroid-stimulating hormone, or insulin-like growth factor-1 induced STAT3 mRNA in GO orbital fibroblasts, but not in non-GO cells. STAT3 silencing inhibited interleukin-1β-induced inflammatory cytokines and oxidative stress-induced haem oxygenase-1 expression. STAT3 siRNA-transfected GO orbital fibroblasts showed decreased adipocyte differentiation. STAT3 affected proinflammatory cytokine production, oxidative stress responses, and adipogenesis in an in vitro model of GO, suggesting that STAT3 mediates GO pathology, and that modulating STAT3 expression may have therapeutic potential against GO.

In vivo confocal microscopy assessment of meibomian glands microstructure in patients with Graves' orbitopathy

BACKGROUND

To evaluate microstructural changes in the meibomian glands (MGs) in patients with active and inactive Graves' orbitopathy (GO), using in vivo confocal microscopy (IVCM), and to investigate the correlations between clinical and confocal findings.

METHODS

Forty patients (80 eyes) with GO (34 eyes with active GO, 46 eyes with inactive GO), and 31 age- and sex-matched control participants (62 eyes) were enrolled consecutively. A researcher recorded the clinical activity score (CAS) for each patient. A complete ophthalmic examination was then performed, including external eye, ocular surface and MGs. IVCM of the MGs was performed to determine the MG acinar density (MAD), MG longest and shortest diameters (MALD and MASD), MG orifice area (MOA), MG acinar irregularity (MAI), meibum secretion reflectivity (MSR), acinar wall inhomogeneity (AWI), acinar periglandular interstices inhomogeneity (API), and severity of MG fibrosis (MF).

RESULTS

All confocal microscopy assessments of MGs significantly differed among groups (all P = 0.000). Compared to controls, GO groups showed lower MOA (1985.82 ± 1325.30 μm2 in active GO and 2021.59 ± 1367.45 μm2 in inactive GO vs. 3896.63 ± 891.90 μm2 in controls, all P = 0.000) and MAD (87.21 ± 32.69 /mm2 in active GO and 80.72 ± 35.54 /mm2 in inactive GO vs. 114.69 ± 34.90 /mm2 in controls, P = 0.001 and 0.000, respectively); greater MALD (118.11 ± 30.23 μm in active GO and 120.58 ± 27.64 μm in inactive GO vs. 58.68 ± 20.28 μm in controls, all P = 0.000) and MASD (44.77 ± 19.16 μm in active GO and 46.02 ± 20.70 μm in inactive GO vs. 27.80 ± 9.90 μm in controls, all P = 0.000); and higher degrees of MAI, MSR, and MF (all P<0.05). Eyes with active GO had higher degrees of MAI (P = 0.015), AWI (P = 0.000), and API (P = 0.000), while eyes with inactive GO had higher degrees of MSR (P = 0.000) and MF (P = 0.017). In GO groups, AWI and API were positively correlated with CAS (r = 0.640, P = 0.000; r = 0.683, P = 0.000, respectively), and MF was negatively correlated with CAS (r = - 0.228, P = 0.042).

CONCLUSIONS

IVCM effectively revealed microstructural changes of MGs in eyes with GO and provided strong in vivo evidence for the roles of obstruction and inflammation in the ocular surface disease process. Furthermore, it revealed discernible patterns of MG abnormalities in eyes with active GO and inactive GO, which are not easily distinguishable by typical clinical examinations.

Leptin receptor is a key gene involved in the immunopathogenesis of thyroid-associated ophthalmopathy

Thyroid‐associated ophthalmopathy (TAO), the most common and severe manifestation of Graves' disease (GD), is a disfiguring and potentially blinding autoimmune disease. The high relapse rate (up to 20%) and substantial side effects of glucocorticoid treatment further decrease the life quality of TAO patients. To develop novel therapies, we amid to explore the immunopathogenesis of TAO. To identify the key immune‐related genes (IRGs) in TAO, we integrated the IRG expression profiles in thyrocytes from a GD patient set (GD vs healthy control) and a TAO patient set (TAO vs GD). Gene Ontology (GO), Kyoto Encyclopedia of Genes and Genomes (KEGG), protein‐protein interaction (PPI) and receiver operating characteristic (ROC) curve analyses identified the leptin receptor (LEPR) gene as the key IRG in TAO immunopathogenesis. Gene set enrichment analysis (GSEA) suggested enrichment of the antigen presentation pathway in TAO patients with higher LEPR. Increased LEPR expression was validated in TAO orbital tissues, and weighted gene co‐expression network analysis (WGCNA) showed that cell adhesion processes were positively correlated with LEPR. Our study revealed that LEPR is a key gene in TAO immunopathogenesis and plays different roles in thyrocytes and orbital tissues. Our findings provide new insights into diagnostic and therapeutic biomarkers for TAO.

Genetic Profiling of Orbital Fibroblasts from Patients with Graves' Orbitopathy

CONTEXT

Graves' orbitopathy (GO) is an autoimmune disease that persists when immunosuppression is achieved. Orbital fibroblasts from GO patients display peculiar phenotypes even if not exposed to autoimmunity, possibly reflecting genetic or epigenetic mechanisms, which we investigated here.

OBJECTIVE

We aimed to explore potential genetic or epigenetic differences using primary cultures of orbital fibroblasts from GO and control patients.

METHODS

Cell proliferation, hyaluronic acid (HA) secretion, and HA synthases (HAS) were measured. Next-generation sequencing and gene expression analysis of the whole genome were performed, as well as real-time-PCR of selected genes and global DNA methylation assay on orbital fibroblasts from 6 patients with GO and 6 control patients from a referral center.

RESULTS

Cell proliferation was higher in GO than in control fibroblasts. Likewise, HA in the cell medium was higher in GO fibroblasts. HAS-1 and HAS-2 did not differ between GO and control fibroblasts, whereas HAS-3 was more expressed in GO fibroblasts. No relevant gene variants were detected by whole-genome sequencing. However, 58 genes were found to be differentially expressed in GO compared with control fibroblasts, and RT-PCR confirmed the findings in 10 selected genes. We postulated that the differential gene expression was related to an epigenetic mechanism, reflecting diverse DNA methylation, which we therefore measured. In support of our hypothesis, global DNA methylation was significantly higher in GO fibroblasts.

CONCLUSIONS

We propose that, following an autoimmune insult, DNA methylation elicits differential gene expression and sustains the maintenance of GO.

Therapy With Different Dose Regimens of Rituximab in Patients With Active Moderate-To-Severe Graves' Orbitopathy

BACKGROUND

Immunosuppressive therapy of Graves' orbitopathy (GO) is indicated during the active phase of disease. Intravenous steroids (IVGC) are effective in about 70% of patients, although unresponsiveness or relapse are observed. In previous studies, rituximab (RTX) has been shown to be effective in inactivating moderate-to-severe GO when used early in the disease, but its optimal dosage has never been studied in randomized clinical trials. Aim of this study was to compare the efficacy and safety of different doses of RTX, based on a post-hoc analysis of two open label studies and one prospective trial randomized to IVGC.

METHODS

of 40 patients (35 women, 5 men), with active moderate-to-severe GO treated with RTX, 14 received a single dose of 100 mg (Group 1), 15 a single dose of 500 mg (Group 2) and 11 two 1000 mg doses, administered one week apart (Group 3). Thyroid function, TSH-receptor antibodies (TRAb) and peripheral CD19+ cells were measured. Primary endpoint was disease inactivation, measured as a decrease of the Clinical Activity Score (CAS) of at least two points. Secondary endpoints were improvement of proptosis, diplopia, quality of life and safety.

RESULTS

Baseline CAS decreased significantly in all groups (P<0.0001), independently of GO duration or whether patients had newly occurring or relapsing GO after IVGC. Proptosis did not significantly change. There was an inverse correlation between the Gorman score for diplopia and RTX dose (P<0.01). The appearance score of the GO-QoL improved in Group 1 (P=0.015), and the visual function score, in Group 2 (P=0.04). A reduction of serum TRAb was observed in Group 1 (P=0.002) and Group 2 (P<0.0002), but not in Group 3. CD19+ cell decreased in all groups (P<0.01), independently of the dose.

CONCLUSIONS

We studied the optimal dosage of RTX in the treatment of active moderate-to-severe GO. In this analysis, we considered the efficacy of RTX in inactivating GO, in changing its natural course, its effect on disease severity and on the patients' quality of life. Based on our clinical findings, and balancing the cost of therapy, a single 500 mg dose regimen is suggested in the majority of patients.

Cytokines as Targets of Novel Therapies for Graves' Ophthalmopathy

Graves' disease (GD) is an organ-specific autoimmune disorder of the thyroid, which is characterized by circulating TSH-receptor (TSH-R) stimulating antibodies (TSAb), leading to hyperthyroidism. Graves' ophthalmopathy (GO) is one of GD extra-thyroidal manifestations associated with the presence of TSAb, and insulin-like growth factor-1 receptor (IGF-1R) autoantibodies, that interact with orbital fibroblasts. Cytokines are elevated in autoimmune (i.e., IL-18, IL-6) and non-autoimmune hyperthyroidism (i.e., TNF-α, IL-8, IL-6), and this could be associated with the chronic effects of thyroid hormone increase. A prevalent Th1-immune response (not related to the hyperthyroidism per se, but to the autoimmune process) is reported in the immune-pathogenesis of GD and GO; Th1-chemokines (CXCL9, CXCL10, CXCL11) and the (C-X-C)R3 receptor are crucial in this process. In patients with active GO, corticosteroids, or intravenous immunoglobulins, decrease inflammation and orbital congestion, and are considered first-line therapies. The more deepened understanding of GO pathophysiology has led to different immune-modulant treatments. Cytokines, TSH-R, and IGF-1R (on the surface of B and T lymphocytes, and fibroblasts), and chemokines implicated in the autoimmune process, are possible targets of novel therapies. Drugs that target cytokines (etanercept, tocilizumab, infliximab, adalimumab) have been tested in GO, with encouraging results. The chimeric monoclonal antibody directed against CD20, RTX, reduces B lymphocytes, cytokines and the released autoantibodies. A multicenter, randomized, placebo-controlled, double-masked trial has investigated the human monoclonal blocking antibody directed against IGF-1R, teprotumumab, reporting its effectiveness in GO. In conclusion, large, controlled and randomized studies are needed to evaluate new possible targeted therapies for GO.

Mechanisms That Underly T Cell Immunity in Graves' Orbitopathy

Graves' orbitopathy (GO), also known as thyroid-associated ophthalmopathy, is the most common ocular abnormality of Graves' disease. It is a disfiguring, invalidating, and potentially blinding orbital disease mediated by an interlocking and complicated immune network. Self-reactive T cells directly against thyroid-stimulating hormone receptor-bearing orbital fibroblasts contribute to autoimmune inflammation and tissue remodeling in GO orbital connective tissues. To date, T helper (Th) 1 (cytotoxic leaning) and Th2 (antibody leaning) cell subsets and an emerging role of Th17 (fibrotic leaning) cells have been implicated in GO pathogenesis. The potential feedback loops between orbital native residential CD34^- fibroblasts, CD34⁺ infiltrating fibrocytes, and effector T cells may affect the T cell subset bias and the skewed pattern of cytokine production in the orbit, thereby determining the outcomes of GO autoimmune reactions. Characterization of the T cell subsets that drive GO and the cytokines they express may significantly advance our understanding of orbital autoimmunity and the development of promising therapeutic strategies against pathological T cells.

Clinical relevance of T lymphocyte subsets in pediatric Graves' disease

Objectives Graves' disease (GD) is an autoimmune disease involving intimate response of both T cells and B cells. Immunophenotyping of peripheral blood lymphocyte subsets in GD children with different clinical characteristics can provide further information of the pathogenesis of GD. Methods We studied the lymphocyte subsets in peripheral blood of 141 children with GD. We repeatedly divided the patients into two groups in accordance with different clinical characteristics (abnormal or normal alanine aminotransferase (ALT) levels, the presence or absence of Graves' orbitopathy (GO), and the presence or absence of hematuria. Then we compared the lymphocyte subsets measurements between two paired groups. Results We found that serum ALT levels correlated positively with CD3+CD8+ T cell percentages in children with GD. Moreover, we detected higher percentages of CD3-CD19+ cells and higher ratio of CD4/CD8 in patients with GO. However, no correlation was found between GO status and lymphocyte subsets after excluding confounding effect of TRAb. No difference of lymphocyte subset percentages was found between groups with or without hematuria. Conclusions Serum ALT levels correlate positively with cytotoxic T cell percentages in the peripheral blood of children with GD. The cytotoxic T cell may play a role in the pathogenesis of hepatic dysfunction in children with GD.

Altered Expression of CXCL13 and Its Chemokine Receptor CXCR5 on B Lymphocytes during Active Graves' Orbitopathy

PURPOSE

To characterize the phenotypic abnormalities of peripheral B cells in patients with Graves' orbitopathy (GO) and explore the role of chemokine CXC ligand 13 and its receptor type 5 (CXCL13/CXCR5) in relation to B-cell homeostasis using specific neutralizing antibodies.

METHODS

Adults with active GO (n = 22), inactive GO (n = 28), and healthy control subjects (n = 28) were included in the study. Peripheral B cells and B-cell subsets were quantified and analyzed for CXCR5 expression by flow cytometry. The serum CXCL13 concentration was measured by enzyme-linked immunosorbent assays. For chemotactic experiments, Transwell plates were used, and migrating B cells were further analyzed by flow cytometry.

RESULTS

Compared to healthy subjects, patients with active GO had a significantly higher number of CD19⁺ B cells and the CD19⁺CD27⁺ memory B-cell subset (P = .041 and P = .019, respectively), whereas a marginal increase in the number of these cells was found in patients with inactive GO (P = .062 and P = .087, respectively). Serum CXCL13 levels were significantly higher in patients with active GO (86.9 ± 30.4 pg/mL) than in those with inactive GO (41.7 ± 18.1 pg/mL; P < .001) and in healthy subjects (36.2 ± 7.8 pg/mL; P < .001). The increased CXCL13 concentration was positively and significantly correlated with the clinical activity score (r = 0.757, P < .001). Finally, serum from patients with active GO exerted a stronger chemotactic activity towards B cells and the CD19⁺CD27⁺ memory B-cell subset. Blocking CXCL13 or CXCR5 with neutralizing antibodies reduced B-cell migration by a mean of 20%.

CONCLUSIONS

Our data suggest that aberrant CXCL13/CXCR5 expression may contribute to the deficits in B-lymphocyte homeostasis observed in active GO.

Prevalence of thyroid eye disease in Graves' disease: A meta-analysis and systematic review

OBJECTIVE

Thyroid eye disease (TED) is a debilitating condition that frequently manifests in patients suffering from Graves' disease (GD). This study aims to analyse the prevalence of TED among GD patients, with a focus on geographical region-specific rates.

METHODS

Medline and Embase were searched for articles examining TED prevalence on April 2020, and articles were retrieved and sieved. Statistical analysis was performed after Freeman-Tukey double arcsine transformation. Thereafter, results were pooled with random effects by DerSimonian and Laird model.

RESULTS

Fifty-seven articles involving 26,804 patients were included in the review. The overall pooled prevalence of TED was 40% (CI: 0.32 to 0.48) and by continent was 38% (CI: 0.31 to 0.46) for Europe, 44% (CI: 0.32 to 0.56) for Asia, 27% (CI: 0.06 to 0.56) for North America and 58% (CI: 0.55 to 0.61) for Oceania. The prevalence of TED in Southeast Asia was 35% (CI: 0.24 to 0.47) and Middle East 48% (CI: 0.19 to 0.78). Subgroup analysis showed regions with predominantly Caucasians (37%; CI: 0.28 to 0.46) had a lower prevalence of TED compared to Asians (45%; CI: 0.33 to 0.58). The pooled prevalence of lid retraction was 57% (CI: 0.39 to 0.74), proptosis 57% (CI: 0.48 to 0.65), diplopia 36% (CI: 0.24 to 0.48) and ocular hypertension 13% (CI: 0.06 to 0.19).

CONCLUSION

A substantial proportion of patients with GD have TED and often manifest as lid retraction, proptosis and diplopia. Early detection through active screening might help to mitigate the progression of TED and its associated complications.

Evidence for Associations Between Th1/Th17 "Hybrid" Phenotype and Altered Lipometabolism in Very Severe Graves Orbitopathy

PURPOSE

The purpose of this article is to investigate the characteristics of Th1-cell and Th17-cell lineages for very severe Graves orbitopathy (GO) development.

METHODS

Flow cytometry was performed with blood samples from GO and Graves disease (GD) patients and healthy controls, to explore effector T-cell phenotypes. Lipidomics was conducted with serum from very severe GO patients before and after glucocorticoid (GC) therapy. Immunohistochemistry and Western blotting were used to examine orbital-infiltrating Th17 cells or in vitro models of Th17 polarization.

RESULTS

In GD, Th1 cells predominated in peripheral effector T-cell subsets, whereas in GO, Th17-cell lineage predominated. In moderate-to-severe GO, Th17.1 cells expressed retinoic acid receptor-related orphan receptor-γt (RORγt) independently and produced interleukin-17A (IL-17A), whereas in very severe GO, Th17.1 cells co-expressed RORγt and Tbet and produced interferon-γ (IFN-γ). Increased IFN-γ-producing Th17.1 cells positively correlated with GO activity and were associated with the development of very severe GO. Additionally, GC therapy inhibited both Th1-cell and Th17-cell lineages and modulated a lipid panel consisting of 79 serum metabolites. However, in GC-resistant, very severe GO, IFN-γ-producing Th17.1 cells remained at a high level, correlating with increased serum triglycerides. Further, retro-orbital tissues from GC-resistant, very severe GO were shown to be infiltrated by CXCR3+ Th17 cells expressing Tbet and STAT4 and rich in triglycerides that promoted Th1 phenotype in Th17 cells in vitro.

CONCLUSIONS

Our findings address the importance of Th17.1 cells in GO pathogenesis, possibly promoting our understanding of the association between Th17-cell plasticity and disease severity of GO.

Orbital diseases mimicking graves' orbitopathy: a long-standing challenge in differential diagnosis

Graves' orbitopathy (GO) is the most common cause of orbital tissue inflammation, accounting for ~ 60% of all orbital inflammatory conditions in the population aged 21-60 years, and for ~ 40% in the population aged > 60 year. GO is observed in 25-30% of patients with Graves' hyperthyroidism and more rarely in association with hypothyroid autoimmune thyroiditis. In addition, a small proportion of GO patients (1-2%) do not have a clinically overt thyroid dysfunction. Clinically, GO is characterized by proptosis, inflammation involving the eyelids and the conjunctiva, extraocular muscle hypertrophy, with consequent reduction of ocular motility and diplopia, and in the most severe cases, compression of the optic nerves at the orbital apex, with reduction of visual acuity. At CT scan or MRI, a muscle increase involving the superior, medial and inferior rectus is quite typical. In the most severe forms, compression of the optic nerves at the orbital apex can be observed. Euthyroid GO is usually an early sign of a full-blown Graves' disease; however, in some cases, the orbital disease can remain isolated. Moreover, euthyroid GO can rarely be unilateral, which makes the picture even more confusing. Under those circumstances, the diagnostic process becomes obviously quite difficult, having other conditions mimicking GO been excluded. A number of inflammatory conditions affecting orbital tissue can mimic GO, thereby requiring an accurate evaluation for a proper differential diagnosis. The majority of these conditions are immune mediated. Most of them are benign, but they can be rather aggressive and some can cause visual loss. The most common inflammatory condition affecting orbital tissues and mimicking GO is idiopathic orbital inflammation. Other, more rare, orbital diseases that should be considered in the differential diagnosis are infections, orbital manifestations of systemic diseases, primitive and secondary orbital neoplasms, and orbital vascular alterations. In most instances, when an orbitopathy occurs in the absence of hyperthyroidism, the diagnosis of the disease underlying the ocular symptoms and signs is based on exclusion of the other conditions. Here we review the conditions that can mimic GO and how to distinguish them from this obnoxious eye disease.

Fibrosis in dysthyroid eye disease

Dysthyroid eye disease is a rare condition, mainly found in people with Graves' hyperthyroidism. Autoimmune responses to thyroid/orbit shared antigens drive extensive tissue remodelling. This includes excess adipogenesis and over-production of extra-cellular matrix, which both tend to occur in the earlier 'active' inflammatory stages of disease. With time these give way to fibrosis, which has a profound impact on eye motility and may be life-long. Progress has been made in identifying the shared autoantigen(s) and the role of specific T cells and autoantibodies in remodelling, which have facilitated development of novel therapies. However relatively little is known of the autoimmune processes under-pinning fibrosis and currently there are no adequate medical treatments.

Immunohistochemical analysis of human orbital tissue in Graves' orbitopathy

PURPOSE

Immunohistochemistry of orbital tissues offers a correlation between the microscopic changes and macroscopic clinical manifestation of Graves' orbitopathy (GO). Summarizing the participation of different molecules will help us to understand the pathogenesis of GO.

METHODS

The pertinent and current literature on immunohistochemistry of human orbital tissue in GO was reviewed using the NCBI PubMed database.

RESULTS

33 articles comprising over 700 orbital tissue samples were included in this review. The earliest findings included the demonstration of HLA-DR and T cell (to a lesser extent B cell) markers in GO orbital tissues. Subsequent investigators further contributed by characterizing cellular infiltration, confirming the presence of HLA-DR and TSHR, as well as revealing the participation of cytokines, growth factors, adhesion molecules and miscellaneous substances. HLA-DR and TSHR are over-expressed in orbital tissues of GO patients. The inflammatory infiltration mainly comprises CD4 + T cells and macrophages. Cytokine profile suggests the importance of Th1 (especially in early active phase) and Th17 immunity in the pathogenesis of GO. Upregulation of proinflammatory/profibrotic cytokines, adhesion molecules and growth factors finally culminate in activation of orbital fibroblasts and perpetuation of orbital inflammation. The molecular status of selected parameters correlates with the clinical presentation of GO.

CONCLUSION

Further investigation is warranted to define precisely the role of different molecules and ongoing search for new players yet to be discovered is also important. Unfolding the molecular mechanisms behind GO will hopefully provide insights into the development of novel therapeutic strategies and optimize our clinical management of the disease.

New insights into the pathogenesis and nonsurgical management of Graves orbitopathy

Graves orbitopathy, also known as thyroid eye disease or thyroid-associated orbitopathy, is visually disabling, cosmetically disfiguring and has a substantial negative impact on a patient's quality of life. There is increasing awareness of the need for early diagnosis and rapid specialist input from endocrinologists and ophthalmologists. Glucocorticoids are the mainstay of treatment; however, recurrence occurs frequently once these are withdrawn. Furthermore, in >60% of cases, normal orbital anatomy is not restored, and skilled rehabilitative surgery is required. Clinical trials have shown that considerable benefit can be derived from the addition of antiproliferative agents (such as mycophenolate or azathioprine) in preventing deterioration after steroid cessation. In addition, targeted biologic therapies have shown promise, including teprotumumab, which reduces proptosis, rituximab (anti-CD20), which reduces inflammation, and tocilizumab, which potentially benefits both of these parameters. Other strategies such as orbital radiotherapy have had their widespread role in combination therapy called into question. The pathophysiology of Graves orbitopathy has also been revised with identification of new potential therapeutic targets. In this Review we provide an up-to-date overview of the field, outline the optimal management of Graves orbitopathy and summarize the research developments in this area to highlight future research questions and direct future clinical trials.

A Case of Unilateral Dermopathy Possibly Related to Graves' Disease

BACKGROUND

The pathogenesis of the extrathyroidal manifestations of Graves' disease (GD) is not fully clarified. According to the most common hypothesis, they would reflect an autoimmune reaction against antigens constitutively expressed by the thyroid and by the extrathyroidal affected tissues. According to another hypothesis, the so-called Kriss' hypothesis, soluble autoantigens released from the thyroid would reach the affected tissues, where they would become the target of the immune system. In this regard, a shift in gravity during sleep may favour antigen deposition.

CASE REPORT

A 59-year old man with GD came to our observation because of a dermopathy. He had been treated with radioactive iodine for Graves' hyperthyroidism and with glucocorticoids and orbital decompression for a bilateral Graves' orbitopathy (GO). The patient complained of a monolateral, untreated dermopathy, affecting the left leg and hand. At physical examination the skin of the left pretibial area and of the dorsal surface of the left hand appeared red and thickened, with an orange peel aspect. Interestingly, the patient reported that he usually slept laying on the left side of his body.

DISCUSSION

The observation of a patient with a monolateral dermopathy somehow reports to the Kriss' hypothesis, especially in view of the patient's habit of sleeping on the same side as dermopathy was present. Of course, this does not represent a proof that the Kriss' hypothesis is correct, but it carries an element in favour of it. The fact that GO was bilateral is somehow against it, but does not exclude this possibility.

Insights Into Local Orbital Immunity: Evidence for the Involvement of the Th17 Cell Pathway in Thyroid-Associated Ophthalmopathy

CONTEXT

Unique features of local immunity in thyroid-associated ophthalmopathy (TAO) may affect disease progression.

OBJECTIVE

To investigate the association between the orbital immune microenvironment and TAO development.

DESIGN/SETTING/PARTICIPANTS

TAO and control orbital connective tissues were collected.

MAIN OUTCOME MEASURES

Single-cell sequencing examined orbital lymphocytic infiltrates. Multicolor flow cytometry explored the phenotypes of different cell subsets and in vitro models for cell functional studies. Coculture experiment and western blotting assay were used to determine underlying mechanism of the enhanced T helper 17 (Th17) cell pathway.

RESULTS

The TAO orbital microenvironment was composed of natural killer cells, dendritic cells, macrophages, T cells, plasma cells, and CD34+ orbital fibroblasts, but few B cells. Increases in CD3+CD8- IL-17A-producing and RAR-related orphan receptor (ROR)γt-expressing T cells and in CD3+CD8- IL-13-producing and GATA3-expressing T cells suggested Th17 and Th2 cell responses in TAO orbits. Increased interferon-γ (IFN-γ)-producing and RORγt+Tbet+ T cells indicated a Th1-like phenotype of orbital-infiltrating Th17 cells. Higher IL-23R and IL-1R expression and lower IL-21R expression were also observed on Th17 cells in TAO orbits. Multivariate analyses revealed that the Th17 pathway [IL-17A (P = 0.001), IFN-γ (P = 0.009), RORγt (P = 0.003), IL-23R (P = 0.033), IL-21R (P = 0.019)], and Th2 pathway [IL-13 (P = 0.015), GATA3 (P = 0.012)] were associated with TAO. IL-17A, IL-23R, and IL-1R correlated with clinical activity score and visual acuity. CD34+ orbital fibroblasts exhibited distinct cell surface marker expression and promoted IL-23R and IL-1R expression on T cells to facilitate the Th17-cell phenotype through prostaglandin E2-EP2/EP4-cAMP signaling.

CONCLUSION

Our study addresses the importance of retroorbital immunity and suggests possible means of disrupting TAO pathogenesis.

Serum antibodies against the insulin-like growth factor-1 receptor (IGF-1R) in Graves' disease and Graves' orbitopathy

BACKGROUND

A role of the insulin-like growth factor-1 receptor (IGF-1R) in the pathogenesis of Graves' orbitopathy (GO) has been proposed, but the existence and function of anti-IGF-1R-antibodies (IGF-1R-Abs) are debated.

METHODS

We designed a cross-sectional investigation to measure serum IGF-1R-Abs by a commercial assay in consecutive patients with Graves' disease (GD) compared with healthy subjects and patients with autoimmune thyroiditis (AT). A total of 134 subjects were screened including 27 healthy subjects, 80 GD patients (54 of whom with GO), and 27 AT patients. The main outcome measure was the prevalence of positive serum IGF-1R-Abs in GO, compared with GD without GO and with the other study groups.

RESULTS

Having established a cut-off value at 55.2 ng/ml for positive tests, positive IGF-1R-Abs were more frequent in GD (25%), than in AT (3.7%, P = 0.003) and healthy subjects (0%, P = 0.006). Within GD, there was no difference between patients with or without GO. Serum levels of IGF-1R-Abs differed across the study population (P < 0.0001), reflecting their higher concentrations in GD (P < 0.0001 vs both AT and healthy subjects), but with no difference between patients with or without GO. In patients with GO, there was an inverse correlation between serum IGF-1R-Abs and CAS (R = - 0.376, 95% CI: from - 0.373 to - 0.631; P = 0.005), the significance of which remains to be investigated.

CONCLUSIONS

Serum autoantibodies against the IFG-1R are present in one-fourth of GD patients, regardless of the presence of GO. Further functional studies are needed to investigate the significance of their inverse correlation with GO activity.

Defective Regulatory B Cells Are Associated with Thyroid Associated Ophthalmopathy

PURPOSE

To investigate the change of IL-10 producing regulatory B cells (Bregs), which function to suppress peripheral immune responses, in patients with thyroid associated ophthalmopathy (TAO).

METHODS

Peripheral blood mononuclear cells (PBMCs) were isolated from healthy controls (N=54), patients with Grave's disease (N=26), and TAO patients (N=125), and stimulated with CpG/CD40L. The frequency of IL-10 producing Bregs and the expression of IL-10 in response to thyroid-stimulating hormone (TSH) stimulation were measured by flow cytometry. CD4+ T cells were cultured with Breg-depleted PBMCs to elucidate the function of Bregs in TAO patients. The potential immunoregulatory mechanism was also investigated by western blot and chromatin immunoprecipitation assays.

RESULTS

Active TAO patients had higher baseline levels of Bregs in their peripheral blood than both healthy controls and inactive patients. TSH promoted Bregs. Bregs from TAO patients were defective in suppressing the activation of IFN-γ+ and IL-17+ T cells in vitro.

CONCLUSIONS

We found that regulatory B cells in TAO patients are functionally defective, suggesting the defective Bregs might be responsible for the pathogenesis of TAO.

Altered Corneal Nerves in Chinese Thyroid-Associated Ophthalmopathy Patients Observed by In Vivo Confocal Microscopy

BACKGROUND Thyroid-associated ophthalmopathy (TAO) is a common endocrine autoimmune disease. The present study explored corneal nerve changes in TAO patients. MATERIAL AND METHODS Thirty-eight Chinese TAO patients and 20 healthy individuals were included in the study. Central corneal subbasal nerve density and morphology were evaluated with in vivo laser scanning confocal microscopy and quantified using automated CCmetrics software. RESULTS The values of the central corneal subbasal nerve plexus parameters of both active and inactive TAO patients were significantly decreased compared with those of controls, including corneal nerve fiber density (CNFD) (P<0.001 for both), corneal nerve branch density (CNBD) (P<0.001 for both), corneal nerve fiber length (CNFL) (P<0.001 for both), corneal nerve fiber total branch density (CTBD) (P<0.001 for both), corneal nerve fiber area (CNFA) (P<0.001 for both), corneal nerve fiber width (CNFW) (P=0.046, P=0.027, respectively), and corneal nerve fiber fractal dimension (ACNFrD) (P<0.001 for both). In addition, CNFD and ACNFrD values were significantly lower in the active TAO patients compared with those in the inactive TAO patients (P=0.020, P=0.002, respectively). There were significant correlations between CNFD, CNBD, CNFL, CTBD, CNFA, and ACNFrD and the ocular surface parameters and activity assessment items. CONCLUSIONS Abnormal corneal subbasal nerves were observed in both active and inactive Chinese TAO patients, suggesting that nerve degeneration is associated with the disease. However, the exact underlying mechanisms remain to be elucidated.

B cells in Graves' Orbitopathy: more than just a source of antibodies?

B cells have multiple actions on different phases of an immune reaction, mainly resulting in B and T cell-interaction (help), production of cytokines, regulation of dendritic cells and downregulation of regulatory B cells. The effectiveness of B cell depletion therapy is probably due to blockade of the antigen-presenting function of B cells, occurring very early in the setting of autoimmune reactions. B cells undergo a maturation process from stem cells during which the CD 20 antigen, which is the target of rituximab (RTX), is expressed from the stage of pre-B cells to mature and memory B cells, but not on plasma cells. During the maturation process, the cytokine B cell stimulating factor (BAFF) induces maturation of B cells and expansion of clones to produce plasma cells and eventually antibodies. The effect of RTX in GO is rather rapid, with significant improvement of the disease already 4-6 weeks after the first RTX infusion. Based on the evidence of significant lymphocytic infiltration in the orbits of patients with active GO, it is reasonable to postulate that RTX may cause depletion of B cells and block their antigen-presenting cell mechanism. Since it has been reported that serum BAFF concentrations are elevated in hyperthyroid GD patients and that BAFF is expressed on the thyrocytes of patients with either autoimmune disease or nodular goiter, the hypothesis that belimumab, an anti-BAFF monoclonal antibody, may be effective in patients with active GO his currently being tested in a randomized controlled trial.