MicroRNAs targeting TGF-ß signaling exacerbate central nervous system autoimmunity by disrupting regulatory T cell development and function.

Transforming growth factor beta (TGF-ß) signaling is essential for a balanced immune response by mediating the development and function of regulatory T cells (Tregs) and suppressing autoreactive T cells. Disruption of this balance can result in autoimmune diseases, including multiple sclerosis (MS). MicroRNAs (miRNAs) targeting TGF-ß signaling have been shown to be upregulated in naïve CD4 T cells in MS patients, resulting in a limited in vitro generation of human Tregs. Utilizing the murine model experimental autoimmune encephalomyelitis, we show that perinatal administration of miRNAs, which target the TGF-ß signaling pathway, enhanced susceptibility to central nervous system (CNS) autoimmunity. Neonatal mice administered with these miRNAs further exhibited reduced Treg frequencies with a loss in T cell receptor repertoire diversity following the induction of experimental autoimmune encephalomyelitis in adulthood. Exacerbated CNS autoimmunity as a result of miRNA overexpression in CD4 T cells was accompanied by enhanced Th1 and Th17 cell frequencies. These findings demonstrate that increased levels of TGF-ß-associated miRNAs impede the development of a diverse Treg population, leading to enhanced effector cell activity, and contributing to an increased susceptibility to CNS autoimmunity. Thus, TGF-ß-targeting miRNAs could be a risk factor for MS, and recovering optimal TGF-ß signaling may restore immune homeostasis in MS patients.

Dysregulated autotaxin expression by T cells in multiple sclerosis.

Multiple sclerosis (MS) is a demyelinating disease characterized by infiltration of autoreactive T cells into the central nervous system (CNS). In order to understand how activated, autoreactive T cells are able to cross the blood brain barrier, the unique molecular characteristics of pathogenic T cells need to be more thoroughly examined. In previous work, our laboratory found autotaxin (ATX) to be upregulated by activated autoreactive T cells in the mouse model of MS. ATX is a secreted glycoprotein that promotes T cell chemokinesis and transmigration through catalysis of lysophoshphatidic acid (LPA). ATX is elevated in the serum of MS patients during active disease phases, and we previously found that inhibiting ATX decreases severity of neurological deficits in the mouse model. In this study, ATX expression was found to be lower in MS patient immune cells during rest, but significantly increased during early activation in a manner not seen in healthy controls. The ribosomal binding protein HuR, which stabilizes ATX mRNA, was also increased in MS patients in a similar pattern to that of ATX, suggesting it may be helping regulate ATX levels after activation. The proinflammatory cytokine interleukin-23 (IL-23) was shown to induce prolonged ATX expression in MS patient Th1 and Th17 cells. Finally, through ChIP, re-ChIP analysis, we show that IL-23 may be signaling through pSTAT3/pSTAT4 heterodimers to induce expression of ATX. Taken together, these findings elucidate cell types that may be contributing to elevated serum ATX levels in MS patients and identify potential drivers of sustained expression in encephalitogenic T cells.

Autotaxin in encephalitogenic CD4 T cells as a therapeutic target for multiple sclerosis.

Multiple sclerosis (MS) is an immune-mediated inflammatory disease of the CNS. A defining characteristic of MS is the ability of autoreactive T lymphocytes to cross the blood-brain barrier and mediate inflammation within the CNS. Previous work from our lab found the gene Enpp2 to be highly upregulated in murine encephalitogenic T cells. Enpp2 encodes for the protein autotaxin, a secreted glycoprotein that catalyzes the production of lysophosphatidic acid and promotes transendothelial migration of T cells from the bloodstream into the lymphatic system. The present study sought to characterize autotaxin expression in T cells during CNS autoimmune disease and determine its potential therapeutic value. Myelin-activated CD4 T cells upregulated expression of autotaxin in vitro, and ex vivo analysis of CNS-infiltrating CD4 T cells showed significantly higher autotaxin expression compared with cells from healthy mice. In addition, inhibiting autotaxin in myelin-specific T cells reduced their encephalitogenicity in adoptive transfer studies and decreased in vitro cell motility. Importantly, using two mouse models of MS, treatment with an autotaxin inhibitor ameliorated EAE severity, decreased the number of CNS infiltrating T and B cells, and suppressed relapses, suggesting autotaxin may be a promising therapeutic target in the treatment of MS.

B-cell receptor physical properties affect relative IgG1 and IgE responses in mouse egg allergy.

Mutated and unmutated IgE and IgG play different and partly opposing roles in allergy development, but the mechanisms controlling their relative production are incompletely understood. Here, we analyzed the IgE-response in murine food allergy. Deep sequencing of the complementary-determining region (CDR) repertoires indicated that an ongoing unmutated extrafollicular IgE response coexists with a germinal center response, even after long-lasting allergen challenges. Despite overall IgG1-dominance, a significant proportion of clonotypes contained several-fold more IgE than IgG1. Clonotypes with differential bias to either IgE or IgG1 showed distinct hypermutation and clonal expansion. Hypermutation rates were associated with different physiochemical binding properties of individual B-cell receptors (BCR). Increasing BCR signaling strength inhibited class switching from IgG1 to IgE in vitro, preferentially constraining IgE formation. These data indicate that antigen-binding properties of individual BCRs determine differential IgE hypermutation and IgE versus IgG1 production on the level of single B-cell clones.

IgG Fc N-Glycosylation Translates MHCII Haplotype into Autoimmune Skin Disease.

The major histocompatibility complex haplotype represents the most prevalent genetic risk factor for the development of autoimmune diseases. However, the mechanisms by which major histocompatibility complex-associated genetic susceptibility translates into autoimmune disease are not fully understood. Epidermolysis bullosa acquisita is an autoimmune skin-blistering disease driven by autoantibodies to type VII collagen. Here, we investigated autoantigen-specific plasma cells, CD4+ T cells, and IgG fraction crystallizable glycosylation in murine epidermolysis bullosa acquisita in congenic mouse strains with the disease-permitting H2s or disease-nonpermitting H2b major histocompatibility complex II haplotypes. Mice with an H2s haplotype showed increased numbers of autoreactive CD4+ T cells and elevated IL-21 and IFN-γ production, associated with a higher frequency of IgG autoantibodies with an agalactosylated, proinflammatory N-glycan moiety. Mechanistically, we show that the altered antibody glycosylation leads to increased ROS release from neutrophils, the main drivers of autoimmune inflammation in this model. These results indicate that major histocompatibility complex II-associated susceptibility to autoimmune diseases acuminates in a proinflammatory IgG fraction crystallizable N-glycosylation pattern and provide a mechanistic link to increased ROS release by neutrophils.

IL-2-Agonist-Induced IFN-γ Exacerbates Systemic Anaphylaxis in Food Allergen-Sensitized Mice.

Food allergies are common, costly and potentially life-threatening disorders. They are driven by Th2, but inhibited by Th1 reactions. There is also evidence indicating that IL-2 agonist treatment inhibits allergic sensitization through expansion of regulatory T cells. Here, we tested the impact of an IL-2 agonist in a novel model for food allergy to hen´s egg in mice sensitized without artificial adjuvants. Prophylactic IL-2 agonist treatment expanded Treg populations and inhibited allergen-specific sensitization. However, IL-2 agonist treatment of already sensitized mice increased mast cell responses and allergic anaphylaxis upon allergen re-challenge. These effects depended on allergen-specific IgE and were mediated through IFN-γ, as shown by IgE transfer and blockade of IFN-γ with monoclonal antibodies. These results suggest that although shifting the allergic reaction toward a Treg/Th1 response inhibits allergic sensitization, the prototypic Th1 cytokine IFN-γ promotes mast cell activation and allergen-induced anaphylaxis in individuals that are already IgE-sensitized. Hence, while a Th1 response can prevent the development of food allergy, IFN-γ has the ability to exacerbate already established food allergy.