The mechanisms involved in the pathogenesis of autoimmune disorders, including systemic lupus erythematosus (SLE), have not been fully elucidated. Some of these mechanisms involve epigenetic ...regulation of gene expression. The histone methyltransferase Ezh2 contributes to epigenetic regulation of gene expression, is highly expressed in germinal center (GC) B cells and follicular T helper (T
) cells, and may be involved in lupus pathogenesis.
The murine bm12 model of lupus-like chronic graft versus host disease (cGVHD) was induced by intra-peritoneal injection of negatively isolated allogeneic CD4
T cells. Lupus-like disease development was monitored by ELISA determination of serum anti-dsDNA and anti-chromatin antibody titers. Immune cell activation and Ezh2 expression were evaluated by flow cytometry and Western blotting.
Decreased autoantibody production and GC formation are observed when Ezh2-deficient CD4
T cells are used instead of wild-type (WT) to induce cGVHD and when mice that receive allogeneic WT donor T cells to induce cGVHD are treated with GSK503, an Ezh2-specific inhibitor. In the bm12 cGVHD model, WT donor T cells are normally fully activated 1 week after infusion into an allogeneic host, exhibit a T
cell (PD-1
/CXCR5
) phenotype with upregulated Ezh2, and activate B cells to form germinal centers (GCs). In contrast, Ezh2-deficient donor T cells generate fewer T
cells that fail to activate B cells or promote GC formation. Despite similar T-independent, LPS-induced B cell responses, OVA-immunized CD4.Ezh2-KO mice had a skewed low-affinity IgM phenotype in comparison to similarly treated WT mice. In addition, early after OVA immunization, more CD4
T cells from B6.CD4.Ezh2-KO mice had a CD44
/CD62L
phenotype, which suggests arrested or delayed activation, than CD4
T cells from ovalbumin-immunized B6.WT mice.
Ezh2 gene deletion or pharmacological Ezh2 inhibition suppresses autoantibody production and GC formation in bm12 lupus-like cGVHD and decreases affinity maturation and isotype switching in response to immunization with a T cell-dependent antigen. Ezh2 inhibition may be useful for the treatment of lupus and other autoimmune disorders.
This review highlights some of the advances in mechanisms of allergic disease, particularly anaphylaxis, including food allergy, drug hypersensitivity, atopic dermatitis (AD), allergic ...conjunctivitis, and airway diseases. During the last year, a mechanistic advance in food allergy was achieved by focusing on mechanisms of allergen sensitization. Novel biomarkers and treatment for mastocytosis were presented in several studies. Novel therapeutic approaches in the treatment of atopic dermatitis and psoriasis showed that promising supplementation of the infant's diet in the first year of life with immunoactive prebiotics might have a preventive role against early development of AD and that therapeutic approaches to treat AD in children might be best directed to the correction of a TH 2/TH 1 imbalance. Several studies were published emphasizing the role of the epithelial barrier in patients with allergic diseases. An impaired skin barrier as a cause for sensitization to food allergens in children and its relationship to filaggrin mutations has been an important development. Numerous studies presented new approaches for improvement of epithelial barrier function and novel biologicals used in the treatment of inflammatory skin diseases. In addition, novel transcription factors and signaling molecules that can develop as new possible therapeutic targets have been reported.
Food allergy (FA) is an increasing problem that has no approved treatment. The pro-TH2 cytokines IL-25, IL-33, and thymic stromal lymphopoietin (TSLP) are associated with FA, and mAbs to these ...cytokines are reported to suppress murine FA development.
We sought to determine whether anti–pro-TH2 cytokine mAbs can block both FA maintenance and induction.
IgE-mediated FA was induced in BALB/c mice by oral gavage with medium-chain triglycerides (MCTs) plus egg white (EW) and was characterized by increased numbers of lamina propria TH2 cells, mast cells, and eosinophils, shock (hypothermia), mast cell degranulation (increased serum mouse mast cell protease 1), increased serum IgG1 anti-EW and IgE levels, and increased IL-4 and IL-13 secretion after MCT/EW challenge. Mice were injected with anti–IL-25, IL-33 receptor, and/or TSLP mAbs before initial oral gavage with MCT/EW to suppress FA development; treatment with the same mAbs was initiated after FA development to suppress established FA.
Injection of an mAb to IL-25, IL-33 receptor, or TSLP strongly inhibited FA development. No single mAb to a pro-TH2 cytokine could suppress established FA, and optimal FA suppression required treatment with a cocktail of all 3 anti–pro-TH2 mAbs. Treatment with the 3-mAb cocktail during initial MCT/EW immunization induced EW tolerance.
All of the pro-TH2 cytokines are required to induce our model of FA, whereas any pro-TH2 cytokine can maintain established FA. Pro-TH2 cytokines prevent oral tolerance. Combined treatment with antagonists to all 3 pro-TH2 cytokines or with an inhibitor of pro-TH2 cytokine production might be able to suppress established human FA.
Risk assessment of individuals with anaphylaxis is currently hampered by lack of (1) an optimal and readily available laboratory test to confirm the clinical diagnosis of an anaphylaxis episode and ...(2) an optimal method of distinguishing allergen-sensitized individuals who are clinically tolerant from those at risk for anaphylaxis episodes after exposure to the relevant allergen. Our objectives were to review the effector mechanisms involved in the pathophysiology of anaphylaxis; to explore the possibility of developing an optimal laboratory test to confirm the diagnosis of an anaphylaxis episode, and the possibility of improving methods to distinguish allergen sensitization from clinical reactivity; and to develop a research agenda for risk assessment in anaphylaxis. Researchers from the American Academy of Allergy, Asthma & Immunology and the European Academy of Allergology and Clinical Immunology held a PRACTALL (Practical Allergy) meeting to discuss these objectives. New approaches being investigated to support the clinical diagnosis of anaphylaxis include serial measurements of total tryptase in serum during an anaphylaxis episode, and measurement of baseline total tryptase levels after the episode. Greater availability of the test for mature β-tryptase, a more specific mast cell activation marker for anaphylaxis than total tryptase, is needed. Measurement of chymase, mast cell carboxypeptidase A3, platelet-activating factor, and other mast cell products may prove to be useful. Consideration should be given to measuring a panel of mediators from mast cells and basophils. New approaches being investigated to help distinguish sensitized individuals at minimum or no risk from those at increased risk of developing anaphylaxis include measurement of the ratio of allergen-specific IgE to total IgE, determination of IgE directed at specific allergenic epitopes, measurement of basophil activation markers by using flow cytometry, and assessment of allergen-specific cytokine responses. Algorithms have been developed for risk assessment of individuals with anaphylaxis, along with a research agenda for studies that could lead to an improved ability to confirm the clinical diagnosis of anaphylaxis and to identify allergen-sensitized individuals who are at increased risk of anaphylaxis.
Asthma is a common, disabling inflammatory respiratory disease that has increased in frequency and severity in developed nations. We review studies of murine allergic airway disease (MAAD) and human ...asthma that evaluate the importance of Th2 cytokines, Th2 response-promoting cytokines, IL-17, and proinflammatory and anti-inflammatory cytokines in MAAD and human asthma. We discuss murine studies that directly stimulate airways with specific cytokines or delete, inactivate, neutralize, or block specific cytokines or their receptors, as well as controversial issues including the roles of IL-5, IL-17, and IL-13Ralpha2 in MAAD and IL-4Ralpha expression by specific cell types. Studies of human asthmatic cytokine gene and protein expression, linkage of cytokine polymorphisms to asthma, cytokine responses to allergen stimulation, and clinical responses to cytokine antagonists are discussed as well. Results of these analyses establish the importance of specific cytokines in MAAD and human asthma and have therapeutic implications.
Histamine is a critical mediator of IgE/mast cell–mediated anaphylaxis. Histamine is synthesized by decarboxylating the amino acid histidine, a reaction catalyzed by the histidine decarboxylase (Hdc) ...gene–encoded enzyme HDC. However, regulation of the Hdc gene in mast cells is poorly understood.
We sought to investigate the in vivo regulation of IgE/mast cell–mediated anaphylaxis by the transcription factors GATA2 and microphthalmia-associated transcription factor (MITF) and the mechanisms by which GATA2 and MITF regulate Hdc gene expression in mouse and human mast cells.
Mice deficient in the transcription factors Gata2, aryl hydrocarbon receptor (Ahr), aryl hydrocarbon receptor repressor (Ahrr), or basic helix-loop-helix family member E40 (Bhlhe40) were assessed for anaphylactic reactions. Chromatin immunoprecipitation sequencing analysis identified putative Hdc enhancers. Luciferase reporter transcription assay confirmed enhancer activities of putative enhancers in the Hdc gene. The short hairpin RNA knockdown approach was used to determine the role of MITF in regulating mouse and human HDC gene expression.
Connective tissue mast cell–specific Gata2-deficient mice did not have IgE/mast cell-mediated anaphylaxis. GATA2 induced the expression of Mitf, Ahr, Ahrr, and Bhlhe40 in mast cells. MITF, but not AHR, AHRR, or BHLHE40, was required for anaphylaxis. MITF bound to an enhancer located 8.8 kb upstream of the transcription start site of the Hdc gene and directed enhancer activity. MITF overexpression largely restored Hdc gene expression in the Gata2-deficient mast cells. In the human mast cell line LAD2, MITF was required for the HDC gene expression and histamine synthesis.
The transcription factors GATA2 and MITF regulate Hdc gene expression in mast cells and are required for IgE/mast cell–mediated anaphylaxis.
Display omitted
IgG-mediated anaphylaxis occurs in mice and may contribute to human reactions to infused drugs. To distinguish IgE- from putative IgG-mediated human anaphylaxis, we developed blood markers for murine ...anaphylaxis and evaluated their human relevance. Both IgG- and IgE-mediated anaphylaxis were characterized by decreased basophil and monocyte percentages and an increased neutrophil percentage in mouse blood. IgE- but not IgG-mediated murine anaphylaxis was accompanied by large increases in IL-4 secretion, plasma soluble IL-4 receptor-α (IL-4Rα) concentration, and T-cell membrane IL-4Rα expression. T-cell IL-4Rα expression also increased when mice that express human Fcε receptor Iα were sensitized with IgG-depleted serum from a peanut-allergic individual and challenged with peanut extract. Increased T-cell IL-4Rα expression is likely to also be a marker for human IgE-mediated anaphylaxis, because IgE-activated human basophils secrete IL-4, and IL-4 increases human T-cell IL-4Rα expression in vitro. Murine IgG- but not IgE-mediated anaphylaxis was characterized by decreased neutrophil Fcγ receptor III (FcγRIII) expression that was observed even when the antigen dose was insufficient to induce shock. Human neutrophils cultured with IgG immune complexes also lost FcγRIII. These observations suggest that decreased blood neutrophil FcγRIII expression without increased IL-4Rα expression can be used to determine whether and when IgG-mediated anaphylaxis occurs in man.
Peanut allergy and anaphylaxis Finkelman, Fred D
Current opinion in immunology,
12/2010, Letnik:
22, Številka:
6
Journal Article
Recenzirano
Odprti dostop
Peanuts are a frequent cause of food allergy and the most common cause of fatal food-induced anaphylaxis in the U.S. Advances during the past two years have promoted our understanding of peanut ...allergens and peanut allergy prevalence, etiology, diagnosis, and therapy. The advances highlighted in this review include evidence that the peanut allergens most important in disease differ in different parts of the world, that early oral exposure to peanuts may decrease the frequency of peanut allergy, while early nonoral exposure may have the opposite effect, that complement activation by peanut constituents appears to promote peanut-induced anaphylaxis and that oral immunotherapy, anti-IgE antibody, and a herbal formulation are promising approaches for the treatment of this disorder.
The molecular mechanisms that drive mucosal T helper type 2 (T(H)2) responses against parasitic helminths and allergens remain unclear. In this study, we demonstrate in mice that TFF2 (trefoil factor ...2), an epithelial cell-derived repair molecule, is needed for the control of lung injury caused by the hookworm parasite Nippostrongylus brasiliensis and for type 2 immunity after infection. TFF2 is also necessary for the rapid production of IL-33, a T(H)2-promoting cytokine, by lung epithelia, alveolar macrophages, and inflammatory dendritic cells in infected mice. TFF2 also increases the severity of allergic lung disease caused by house dust mite antigens or IL-13. Moreover, TFF2 messenger RNA expression is significantly increased in nasal mucosal brushings during asthma exacerbations in children. These experiments extend the biological functions of TFF2 from tissue repair to the initiation and maintenance of mucosal T(H)2 responses.
Asparaginase is an important drug for the treatment of leukemias. However, anti-asparaginase antibodies often develop, which can decrease asparaginase drug levels and increase the risk of relapse. ...The aim of this study is to identify the immunoglobulin isotypes and receptors responsible for asparaginase hypersensitivities. Mice immunized with asparaginase developed anti-asparaginase IgG1 and IgE antibodies, and challenging the sensitized mice with asparaginase induced severe hypersensitivity reactions. Flow cytometry analysis indicated that macrophages/monocytes, neutrophils, and basophils bind asparaginase
through FcγRIII. In contrast, asparaginase binding to basophils was dependent on FcγRIII and IgE. Consistent with the asparaginase binding data, basophil activation by asparaginase occurred via both IgG/FcγRIII and IgE/FcεRI. Depleting >95% of B cells suppressed IgG but not IgE-dependent hypersensitivity, while depleting CD4
T cells provided complete protection. Combined treatment with either anti-IgE mAb plus a platelet-activating factor receptor antagonist or anti-FcγRIII mAb plus a H1 receptor antagonist suppressed asparaginase hypersensitivity. The observations indicate that asparaginase hypersensitivity is mediated by antigen-specific IgG and/or IgE through the immunoglobulin receptors FcγRIII and FcεRI, respectively. Provided that these results apply to humans, they emphasize the importance of monitoring both IgE- and IgG-mediated asparaginase hypersensitivities in patients receiving this agent.
PDF
