Unmet needs in autoimmunity and potential new tools

The causal relationship between sarcoidosis and autoimmune diseases: a bidirectional Mendelian randomization study in FinnGen

Background

Sarcoidosis has been considered to be associated with many autoimmune diseases (ADs), but the cause-and-effect relationship between these two diseases has not been fully explored. Therefore, the objective of this study is to explore the possible genetic association between sarcoidosis and ADs.

Methods

We conducted a bidirectional Mendelian randomization (MR) study using genetic variants associated with ADs and sarcoidosis (4,041 cases and 371,255 controls) from the FinnGen study. The ADs dataset comprised 96,150 cases and 281,127 controls, encompassing 44 distinct types of autoimmune-related diseases. Subsequently, we identified seven diseases within the ADs dataset with a case size exceeding 3,500 and performed subgroup analyses on these specific diseases.

Results

The MR evidence supported the causal association of genetic predictors of ADs with an increased risk of sarcoidosis (OR = 1.79, 95% CI = 1.59 to 2.02, P IVW-FE = 1.01 × 10-21), and no reverse causation (OR = 1.05, 95% CI 0.99 to 1.12, P IVW-MRE = 9.88 × 10-2). Furthermore, subgroup analyses indicated that genetic predictors of type 1 diabetes mellitus (T1DM), celiac disease, and inflammatory bowel disease (IBD) were causally linked to an elevated risk of sarcoidosis (All P < 6.25 × 10-3). Conversely, genetic predictors of sarcoidosis showed causal associations with a higher risk of type 1 diabetes mellitus (P < 6.25 × 10-3).

Conclusion

The present study established a positive causal relationship between genetic predictors of ADs (e.g. T1DM, celiac disease, and IBD) and the risk of sarcoidosis, with no evidence of reverse causation.

The roles of PPARγ and its agonists in autoimmune diseases: A comprehensive review

Autoimmune diseases are common diseases of the immune system that are characterized by the loss of self-tolerance and the production of autoantibodies; the breakdown of immune tolerance and the prolonged inflammatory reaction are undisputedly core steps in the initiation and maintenance of autoimmunity. Peroxisome proliferator-activated receptors (PPARs) are ligand-dependent transcription factors that belong to the nuclear hormone receptor family and act as ligand-activated transcription factors. There are three different isotypes of PPARs: PPARα, PPARγ, and PPARβ/δ. PPARγ is an established regulator of glucose homeostasis and lipid metabolism. Recent studies have demonstrated that PPARγ exhibits anti-inflammatory and anti-fibrotic effects in multiple disease models. PPARγ can also modulate the activation and polarization of macrophages, regulate the function of dendritic cells and mediate T cell survival, activation, and differentiation. In this review, we summarize the signaling pathways and biological functions of PPARγ and focus on how PPARγ and its agonists play protective roles in autoimmune diseases, including autoimmune thyroid diseases, multiple sclerosis, rheumatoid arthritis, systemic sclerosis, systemic lupus erythematosus, primary Sjogren syndrome and primary biliary cirrhosis.

Role of CD226 Rs763361 Polymorphism in Susceptibility to Multiple Autoimmune Diseases

Background: Gly307Ser (rs763361) polymorphism in Cluster of Differentiation 226 (CD226) gene has been implicated in susceptibility to autoimmune diseases (ADs) with controversial results. This study aimed to conduct a meta-analysis for examining the relationship between CD226 rs763361 polymorphism and ADs risk. Methods: a literature search was performed to identify relevant studies published in Embase, PubMed, Wanfang, and China National Knowledge Infrastructure. In the most appropriate genetic models, pooled odds ratio (OR) with 95% confidence interval (CI) was calculated for evaluating the strength of the associations. Besides standard meta-analysis, cumulative meta-analysis was also conducted to assess the trend in OR over time. Also, we performed subgroup and sensitivity analysis, and checked for the heterogeneity and publication bias. Results: Twenty-nine reports with 51 independent studies, comprising 18157 cases and 29904 controls, were enrolled in this meta-analysis. Among overall and various ethnic populations (Europeans, Asians, Africans, and South Americans), CD226 rs763361 polymorphism was significantly associated with ADs susceptibility; in the subgroup analysis by disease type, rs763361 polymorphism revealed significant associations with the risk of RA, SLE, T1D, and MS. The sensitivity analysis and cumulative meta-analysis confirmed the stability and robustness of these significant results. However, no evidence of stable significant association emerged in the subgroup analysis of SSc. Conclusion: These findings demonstrate that CD226 rs763361 polymorphism confers susceptibility to ADs in the overall population, Europeans, Asians, Africans, and South Americans. rs763361 polymorphism in CD226 gene may be a potential susceptible predictor of ADs especially RA, SLE, T1D, and MS.

The Inflammatory Response in Psoriasis: a Comprehensive Review

Psoriasis is a chronic inflammatory autoimmune disease characterized by an excessively aberrant hyperproliferation of keratinocytes. The pathogenesis of psoriasis is complex and the exact mechanism remains elusive. However, psoriasis is thought to result from a combination of genetic, epigenetic, and environmental influences. Recent studies have identified that epigenetic factors including dysregulated DNA methylation levels, abnormal histone modification and microRNAs expressions are involved in the development of psoriasis. The interplay of immune cells and cytokines is another critical factor in the pathogenesis of psoriasis. These factors or pathways include Th1/Th2 homeostasis, the Th17/Treg balance and the IL-23/Th17 axis. Th17 is believed particularly important in psoriasis due to its pro-inflammatory effects and its involvement in an integrated inflammatory loop with dendritic cells and keratinocytes, contributing to an overproduction of antimicrobial peptides, inflammatory cytokines, and chemokines that leads to amplification of the immune response. In addition, other pathways and signaling molecules have been found to be involved, including Th9, Th22, regulatory T cells, γδ T cells, CD8(+) T cells, and their related cytokines. Understanding the pathogenesis of psoriasis will allow us to develop increasingly efficient targeted treatment by blocking relevant inflammatory signaling pathways and molecules. There is no cure for psoriasis at the present time, and much of the treatment involves managing the symptoms. The biologics, while lacking the adverse effects associated with some of the traditional medications such as corticosteroids and methotrexate, have their own set of side effects, which may include reactivation of latent infections. Significant challenges remain in developing safe and efficacious novel targeted therapies that depend on a better understanding of the immunological dysfunction in psoriasis.

Th9 cells and IL-9 in autoimmune disorders: Pathogenesis and therapeutic potentials

Naïve CD4⁺ T cells are pleiotropically divided into various T helper (Th) cell subsets, according to their pivotal roles in the regulation of immune responses. The differentiation of Th9 cells, an interleukin (IL)-9 producing subset, can be impacted by specific environmental cues, co-stimulation with transforming growth factor β (TGF-β) and IL-4, and other regulatory factors. Although IL-9 has been recognized as a classical Th2-related cytokine, recent studies have indicated that IL-9-producing cells contribute to a group of autoimmune disorders including systemic lupus erythematosus (SLE), multiple sclerosis (MS), inflammatory bowel diseases (IBD), rheumatoid arthritis (RA) and psoriasis. Studies of Th9 cells in autoimmune diseases, although in their infancy, are expected to be of growing interest in the study of potential mechanisms of cytokine regulatory pathways and autoimmune pathogenesis. Several in vitro and in vivo pre-clinical trials have been conducted to explore potential therapeutic strategies by targeting the IL-9 pathway. Specifically, anti-IL-9 monoclonal antibodies (mAbs) and IL-9 inhibitors may potentially be used for the clinical treatment of allergic diseases, autoimmune diseases or cancers. Here, we review recent research on Th9 cells and IL-9 pertaining to cell differentiation, biological characteristics and pivotal cellular inter-relationships implicated in the development of various diseases.

The epigenetics of PBC: The link between genetic susceptibility and environment

Primary biliary cholangitis (PBC) previously known as primary biliary cirrhosis is an autoimmune disease-associated with progressive cholestasis, the presence of autoreactive T cell and characteristic serological autoantibodies. Genetic and genome-wide association studies (GWAS) have recently shed light on the genetic background of PBC. Besides that some causal nucleotide changes and mechanisms remain largely unknown as suggested for example, by the observation that monozygotic twins have an identical DNA sequence even if presents some phenotypic differences that may be consequences of different exposures to environmental stressors. For this reason, it is believed that epigenetic mechanisms may be involved in PBC pathogenesis, as already demonstrated in many autoimmune diseases and can eventually provide an understanding that has been missed from genetics alone. This review will focus on the most commonly studied epigenetic modifications already demonstrated in PBC; special attention will be paid also to other epigenetic mechanisms so far not demonstrated in PBC patients, but that could increase our understanding in PBC pathogenesis.