Immunoglobulin E

The role of IgE in allergic disease mechanisms is performed principally through its interactions with two receptors, FcεRI on mast cells and basophils, and CD23 (FcεRII) on B cells. The former mediates allergic hypersensitivity, the latter regulates IgE levels, and both receptors, also expressed on antigen-presenting cells, contribute to allergen uptake and presentation to the immune system. We have solved the crystal structure of the soluble lectin-like "head" domain of CD23 (derCD23) bound to a subfragment of IgE-Fc consisting of the dimer of Cε3 and Cε4 domains (Fcε3-4). One CD23 head binds to each heavy chain at the interface between the two domains, explaining the known 2:1 stoichiometry and suggesting mechanisms for cross-linking membrane-bound trimeric CD23 by IgE, or membrane IgE by soluble trimeric forms of CD23, both of which may contribute to the regulation of IgE synthesis by B cells. The two symmetrically located binding sites are distant from the single FcεRI binding site, which lies at the opposite ends of the Cε3 domains. Structural comparisons with both free IgE-Fc and its FcεRI complex reveal not only that the conformational changes in IgE-Fc required for CD23 binding are incompatible with FcεRI binding, but also that the converse is true. The two binding sites are allosterically linked. We demonstrate experimentally the reciprocal inhibition of CD23 and FcεRI binding in solution and suggest that the mutual exclusion of receptor binding allows IgE to function independently through its two receptors.

Kyungohkgo (KOG) is one of the most important formulas in traditional oriental medicine. We investigated the remedial effect of KOG on the development of atopic dermatitis (AD) in female NC/Nga mice. AD-like lesion was induced by the application of 2,4-Dinitrochlorobenzene on to the back skin repeatedly; KOG was administered orally (12.5 and 25.0 mg/kg) and topically (0.5 and 1.0 mg/mouse) to NC/Nga mice once a day for all through the period of this experiment and every mouse body weight was periodically taken. The effects of KOG on 2,4-Dinitrochlorobenzene-treated NC/Nga mice were determined by measuring AD-like skin lesions, the infiltration of mast cells and serum immunoglobulin E concentration. After the KOG applications are over, the KOG groups had less skin lesions than the atopy one, their immunoglobulin E levels were significantly downregulated and the infiltration of mast cells in the dorsal skin were reduced. Our results suggest that KOG may be effective in alleviating the development of AD. The inhibition of AD in NC/Nga mice may be influenced by the prevention of mast cell activation.

In patients given a diagnosis of chronic spontaneous urticaria (CSU), there are no obvious external triggers, and the factors that initiate the clinical symptoms of wheal, flare, and itch arise from within the patient. Most patients with CSU have an autoimmune cause: some patients produce IgE autoantibodies against autoantigens, such as thyroperoxidase or double-stranded DNA, whereas other patients make IgG autoantibodies against FcεRI, IgE, or both, which might chronically activate mast cells and basophils. In the remainder of patients with CSU, the nature of the abnormalities has not yet been identified. Accumulating evidence has shown that IgE, by binding to FcεRI on mast cells without FcεRI cross-linking, can promote the proliferation and survival of mast cells and thus maintain and expand the pool of mast cells. IgE and FcεRI engagement can also decrease the release threshold of mast cells and increase their sensitivity to various stimuli through either FcεRI or other receptors...

Atopic dermatitis (AD) is characterized by alterations in cellular and humoral immunity including elevated serum levels of IgE, IL-2 receptor (IL-2R) and eosinophil cationic protein (ECP). In order to evaluate the relevance of these serum parameters as indicators of disease activity, the concentrations of IgE, IL-2R and ECP were measured in serum samples of patients with an acute exacerbation of AD (n=19) on admission to hospital and every 6 days up to discharge, and compared with those from normal non-atopic controls (n= 15). The severity of the disease in the AD patients was examined using an established clinical scoring system. On admission, AD patients showed significantly elevated serum levels of IgE, IL-2R and ECP compared with normal controls (P≤0.0001). Clinical improvement was associated with a decrease of both the clinical score (P≤0.001) and serum ECP levels (P≤0.005). No significant changes in serum IgE and serum IL-2R were observed. In addition, there was a significant correlation between serum ECP and the clinical score (R=0.67, P≤0.001). These data indicate that serum ECP may be a helpful tool for monitoring disease activity in AD.

Allergy to crustacean shellfish is one of the most common IgE-mediated food allergies, and tropomyosin has been identified as the major allergen. However, not all subjects affected by this allergy are IgE-positive to tropomyosin. To evaluate whether sera of patients with shrimp allergy but negative for tropomyosin react to other allergen(s); and to evaluate the role such allergen(s) may play in cross-reactivity between crustaceans and house dust mites (HDMs). Three different pools of sera-one from subjects with shellfish allergy and HDMs positivity, but negative for recombinant and native tropomyosin (rPen a 1 and nPen m 1) (Pool 2); a second from subjects with tropomyosin and HDMs positivity (Pool 1); and the last from subjects allergic only to HDMs (Pool 3) were submitted to immunoblotting. Subsequently, a 20 kDa protein- enriched fraction of shrimp extract was used at two different concentrations (10 and 100 microg/mL) to pre-absorb the Pool 2 serum and to evaluate, by ELISA assa...

We investigated the expression of novel anti-inflammatory interleukin (IL)-38 and regulatory T (Treg) lymphocytes in childhood asthma patients. The protein and mRNA expression level of IL-38, periostin, peripheral CD4⁺CD25⁺CD134⁺ T lymphocytes as well as CD4⁺CD25(high)FoxP3⁺ and CD4⁺CD25(high)CD127(-) Treg lymphocytes from 40 asthmatic patients and 20 normal control (NC) subjects were studied using ELISA, qPCR and flow cytometry. Serum and supernatant cytokines/chemokines were determined by multiplex assay. Serum IL-38, IL-5, IL-17, IL-6, interferon-γ, periostin, IL-1β and IL-13 concentrations were significantly higher in asthmatic patients with or without steroid treatment than those in controls (all p < 0.05). The percentages of both CD4⁺CD25(high)FoxP3⁺ and CD4⁺CD25(high)CD127(-) Treg lymphocytes were markedly decreased in asthmatic patients with and without steroid treatment than those in controls (all p < 0.05). The elevated IL-38 concentration negatively correlated with ...