Genetic and epigenetic influences on the loss of tolerance in autoimmunity

Genetic variants differentially associated with rheumatoid arthritis and systemic lupus erythematosus reveal the disease-specific biology

Two rheumatic autoimmune diseases, rheumatoid arthritis (RA) and systemic lupus erythematosus (SLE), have distinct clinical features despite their genetic similarities. We hypothesized that disease-specific variants exclusively associated with only one disease could contribute to disease-specific phenotypes. We calculated the strength of disease specificity for each variant in each disease against the other disease using summary association statistics reported in the largest genome-wide association studies of RA and SLE. Most of highly disease-specific associations were explained by non-coding variants that were significantly enriched within regulatory regions (enhancers or H3K4me3 histone modification marks) in specific cell or organ types. (e.g., In RA, regulatory T primary cells, CD4+ memory T primary cells, thymus and lung; In SLE, CD19+ B primary cells, mobilized CD34+ primary cells, regulatory T primary cells and monocytes). Consistently, genes in the disease-specific loci were significantly involved in T cell- and B cell-related gene sets in RA and SLE. In summary, this study identified disease-specific variants between RA and SLE, and provided statistical evidence for disease-specific cell types, organ and gene sets that may drive the disease-specific phenotypes.

Autoimmune Disease-Associated Hypertension

Purpose of Review

To highlight important new findings on the topic of autoimmune disease-associated hypertension.

Recent Findings

Autoimmune diseases including systemic lupus erythematosus and rheumatoid arthritis are associated with an increased risk for hypertension and cardiovascular disease. A complex interaction among genetic, environmental, hormonal, and metabolic factors contribute to autoimmune disease susceptibility while promoting chronic inflammation that can lead to alterations in blood pressure. Recent studies emphasize an important mechanistic role for autoantibodies in autoimmune disease-associated hypertension. Moving forward, understanding how sex hormones, neutrophils, and mitochondrial dysfunction contribute to hypertension in autoimmune disease will be important.

Summary

This review examines the prevalent hypertension in autoimmune disease with a focus on the impact of immune system dysfunction on vascular dysfunction and renal hemodynamics as primary mediators with oxidative stress as a main contributor.

Cluster analysis of autoimmune rheumatic diseases based on autoantibodies. New insights for polyautoimmunity

Autoimmune diseases (ADs) are a chronic and clinically heterogeneous group of diseases characterized by share common immunopathogenic mechanisms and risk factors (i.e., the autoimmune tautology), which explain the fact that one AD may coexist with others (i.e., polyautoimmunity - PolyA). In the present exploratory study, a mixed-cluster analysis of the most common autoimmune rheumatic diseases (ARDs) was done. A total of 187 consecutive women with established systemic lupus erythematosus (n = 70), rheumatoid arthritis (n = 51), systemic sclerosis (n = 35) and Sjögren's syndrome (n = 31) were included. A comprehensive clinical, autoantibody and cytokine assessment was simultaneously done. Total PolyA was registered in 142 (75.9%) patients. Six clusters were obtained, built mainly on autoantibodies: PolyA-I to -VI. The PolyA-III cluster showed the highest frequency of overt PolyA (p = 0.01), and the PolyA-I, -III, and -IV clusters exhibited the highest positivity for IL-12/23p40 (p = 0.015). These results provide new insights into the pathophysiology of PolyA and warrant prospective validation to enable development of a more accurate taxonomy of ARDs.

Mice Selected for Acute Inflammation Present Altered Immune Response during Pristane-Induced Arthritis Progression

Mouse lines selected for maximal (AIRmax) or minimal acute inflammatory reaction (AIRmin) were used to characterize the immune response and the influence of genetic background during pristane-induced arthritis (PIA). Susceptible AIRmax mice demonstrated exacerbated cellular profiles during PIA, with intense infiltration of lymphocytes, as well as monocytes/macrophages and neutrophils, producing higher levels of IL-1β, IFN-γ, TNF-α, IL-10, total IgG3, and chemokines. Resistant AIRmin mice controlled cell activation more efficiently than the AIRmax during arthritis progression. The weight alterations of the spleen and thymus in the course of PIA were observed. Our data suggest that selected AIRmax cellular and genetic immune mechanisms contribute to cartilage damage and arthritis severity, evidencing many targets for therapeutic actions.

Epigenetic Control of Pancreatic Regeneration in Diabetes

Both type 1 and type 2 diabetes are conditions that are associated with the loss of insulin-producing β-cells within the pancreas. An active research therefore aims at regenerating these β-cells with the hope that they could restore euglycemia. The approaches classically used consist in mimicking embryonic development, making use of diverse cell sources or converting pre-existing pancreatic cells. Despite impressive progresses and promising successes, it appears that we still need to gain further insight into the molecular mechanisms underlying β-cell development. This becomes even more obvious with the emergence of a relatively new field of research, epigenetics. The current review therefore focuses on the latest advances in this field in the context of β-cell (neo-)genesis research.

An altered CD8+ T cell epitope of insulin prevents type 1 diabetes in humanized NOD mice

Autoreactive CD8⁺ T cells, which play an indispensable role in β cell destruction, represent an emerging target for the prevention of type 1 diabetes (T1D). Altered peptide ligands (APLs) can efficiently induce antigen-specific T cells anergy, apoptosis or shifts in the immune response. Here, we found that HLA-A*0201-restricted CD8⁺ T cell responses against a primary β-cell autoantigen insulin epitope InsB1_5-14 were present in both NOD.β2m^null.HHD NOD mice and T1D patients. We generated several APL candidates for InsB1_5-14 by residue substitution at the p6 position. Only H6F exhibited an inhibitory effect on mInsB1_5-14-specific CD8⁺ T cell responses in vitro. H6F treatment significantly reduced the T1D incidence, which was accompanied by diminished autoreactive CD8⁺ T cell responses to mInsB1_5-14, inhibited infiltration of CD8⁺ and CD4⁺ T cells in the pancreas and reduced pro-inflammatory cytokine production in pancreatic and splenic T cells in NOD.β2m^null.HHD mice. Mechanistically, H6F treatment significantly augmented a tiny portion of CD8⁺CD25⁺Foxp3⁺ T cells in the spleen and especially in the pancreas. This subset exhibited typical Treg phenotypes and required peptide-specific restimulation to exert immunosuppressive activity. Therefore, this APL H6F may be a promising candidate with potential clinical application value for antigen-specific prevention of T1D.