Bart R. Blokhuis

Antigen-specific, antibody-coated, exosome-like nanovesicles deliver suppressor T-cell microRNA-150 to effector T cells to inhibit contact sensitivity

BACKGROUND T-cell tolerance of allergic cutaneous contact sensitivity (CS) induced in mice by high doses of reactive hapten is mediated by suppressor cells that release antigen-specific suppressive nanovesicles. OBJECTIVE We sought to determine the mechanism or mechanisms of immune suppression mediated by the nanovesicles. METHODS T-cell tolerance was induced by means of intravenous injection of hapten conjugated to self-antigens of syngeneic erythrocytes and subsequent contact immunization with the same hapten. Lymph node and spleen cells from tolerized or control donors were harvested and cultured to produce a supernatant containing suppressive nanovesicles that were isolated from the tolerized mice for testing in active and adoptive cell-transfer models of CS. RESULTS Tolerance was shown due to exosome-like nanovesicles in the supernatants of CD8(+) suppressor T cells that were not regulatory T cells. Antigen specificity of the suppressive nanovesicles was conferred by a surface coat of antibody light chains or possibly whole antibody, allowing targeted delivery of selected inhibitory microRNA (miRNA)-150 to CS effector T cells. Nanovesicles also inhibited CS in actively sensitized mice after systemic injection at the peak of the responses. The role of antibody and miRNA-150 was established by tolerizing either panimmunoglobulin-deficient JH(-/-) or miRNA-150(-/-) mice that produced nonsuppressive nanovesicles. These nanovesicles could be made suppressive by adding antigen-specific antibody light chains or miRNA-150, respectively. CONCLUSIONS This is the first example of T-cell regulation through systemic transit of exosome-like nanovesicles delivering a chosen inhibitory miRNA to target effector T cells in an antigen-specific manner by a surface coating of antibody light chains.

Contribution of IgE and immunoglobulin free light chain in the allergic reaction to cow's milk proteins

BACKGROUND Cows milk allergy (CMA) affects 2.5% of young infants. In previous murine studies it was observed that allergic sensitization to the major cows milk allergens casein and whey led, respectively, to IgE-independent and IgE-dependent clinical responses. OBJECTIVES In this study the involvement of immunoglobulin free light chains (Ig-fLCs) in the hypersensitivity response to cows milk proteins was explored in mice, and Ig-fLC serum levels were determined in children affected by CMA or atopic dermatitis (AD). METHODS Mice were orally sham, casein, or whey sensitized. Acute allergen-specific skin responses were determined, and serum immunoglobulin and Ig-fLC concentrations were measured. Ig-fLC dependency was validated by using the Ig-fLC blocker F991 in actively and passively sensitized mice. Ig-fLC serum concentrations were measured in a cohort of infants with CMA and infants with AD. RESULTS After sensitization, no specific IgE was detectable in sera of casein-sensitized mice, whereas specific IgE levels were enhanced in whey-sensitized mice. Instead, Ig-fLC levels were increased in sera from casein-sensitized mice. Furthermore, blocking Ig-fLCs strongly diminished the allergic skin responses not only in casein-sensitized mice but also in mice transferred with splenocyte supernatants of casein-sensitized mice. In both patients with CMA and patients with AD, serum Ig-fLC concentrations were significantly enhanced. CONCLUSIONS This study indicates that sensitization with cows milk proteins can lead to both IgE-dependent and Ig-fLC-dependent allergic hypersensitivity responses. Also, in children affected with CMA or AD, serum Ig-fLC concentrations were increased, implying the relevance of Ig-fLC measurements in the diagnoses of human allergic disease.

Free immunoglobulin light chains: a novel target in the therapy of inflammatory diseases.

In recent years, novel therapeutic strategies have become available for the treatment of chronic inflammatory disease. Neutralizing proinflammatory mediators such as leukotrienes and TNF-alpha, in addition to anti-IgE therapies (Omaluzimab) that target higher in the inflammatory cascade, have shown success in the treatment of allergic or autoimmune disorders. Free immunoglobulin light chains, which are produced by B lymphocytes and secreted into serum, might play a crucial role in the pathogenesis of inflammatory disease. Concentrations of free light chains are significantly increased under diverse pathological conditions in humans, and have been linked to the progression and severity of immune diseases. Here we discuss the importance of free immunoglobulin light chains as a potential therapeutic target in the treatment of chronic inflammatory disease.

Non-IgE mediated mast cell activation.

Mast cells are crucial effector cells in allergic reactions, where IgE is the best known mechanism to trigger their degranulation and release of a vast array of allergic mediators. However, IgE is not the only component to stimulate these cells to degranulate, while mast cell activation can also result in differential release of mediators. There is a plethora of stimuli, such as IgG, complement components, TLR ligands, neuropeptides, cytokines, chemokines and other inflammatory products, that can directly trigger mast cell degranulation, cause selective release of mediators, and stimulate proliferation, differentiation and/or migration. Moreover, some of these stimuli have a synergic effect on the IgE-mediated mast cell activation. Because of the ability to respond to a large repertoire of stimuli, mast cells may act as a versatile cell in various physiological and pathological conditions. In this review, we discuss current knowledge on non-IgE stimuli for (human) mast cells.

Ig-Free Light Chains Play a Crucial Role in Murine Mast Cell-Dependent Colitis and Are Associated with Human Inflammatory Bowel Diseases

Traditionally, mast cells were regarded as key cells orchestrating type I hypersensitivity responses. However, it is now recognized that mast cells are widely involved in nonallergic (non-IgE) chronic diseases. Also, in inflammatory bowel disease (IBD), a disease not associated with increased IgE concentrations, clear signs of activation of mast cells have been found. In this study, we investigated if Ig-free L chain-induced hypersensitivity-like responses through activation of mast cells could contribute to the pathophysiology of IBD. As a mast cell-dependent model for IBD, mice were skin-sensitized with dinitrofluorobenzene followed by intrarectal application of the hapten. In this murine IBD model, F991 prevented mast cell activation and also abrogated the development of diarrhea, cellular infiltration, and colonic lymphoid follicle hyperplasia. Furthermore, passive immunization with Ag-specific Ig-free L chains (IgLCs) and subsequent rectal hapten challenge elicited local mast cell activation and increased vascular permeability in the colon of mice. Clinical support is provided by the observation that serum concentrations of IgLCs of patients suffering from Crohn’s disease are greatly increased. Moreover, increased presence of IgLCs was evident in tissue specimens from colon and ileum tissue of patients with IBD. Our data suggest that IgLCs may play a role in the pathogenesis of IBD, which provides novel therapeutic means to prevent or ameliorate the adverse gastrointestinal manifestations of IBD.

Atopic and non-atopic allergic disorders: current insights into the possible involvement of free immunoglobulin light chains.

Allergic diseases have become a serious global health problem in the developed world. IgE interacting with its high‐affinitiy receptor FcɛRI is considered a major contributing factor to most types of allergies, but depending on the type of allergy, however, a subgroup of patients displays common symptoms and yet lack elevated levels of total serum IgE and/or antigen‐specific IgE. Novel therapeutic strategies such as anti‐IgE therapy may therefore not be applicable to these patients. It is clear, however, that these patients do display activation of mast cells. In several patients suffering from immunological disorders, an increase in free immunoglobulin (IG) light chain levels can be detected. Previously, we have described the capability of free light chains to elicit immediate hypersensitivity responses. In this Opinion article, we will discuss the role of IgE‐ and non‐IgE‐mediated mechanisms in allergic disorders and point out a possible role of free IG light chains in the pathogenesis of the non‐atopic types of these allergies.

Immunoglobulin Free Light Chains Are Increased in Hypersensitivity Pneumonitis and Idiopathic Pulmonary Fibrosis

Background Idiopathic pulmonary fibrosis (IPF), a devastating lung disorder of unknown aetiology, and chronic hypersensitivity pneumonitis (HP), a disease provoked by an immunopathologic reaction to inhaled antigens, are two common interstitial lung diseases with uncertain pathogenic mechanisms. Previously, we have shown in other upper and lower airway diseases that immunoglobulin free light chains (FLCs) are increased and may be involved in initiating a local inflammation. In this study we explored if such a mechanism may also apply to HP and IPF. Methods In this study we examined the presence of FLC in serum and BAL fluid from 21 IPF and 22 HP patients and controls. IgG, IgE and tryptase concentrations were measured in BAL fluid only. The presence of FLCs, plasma cells, B cells and mast cells in lung tissue of 3 HP and 3 IPF patients and 1 control was analyzed using immunohistochemistry. Results FLC concentrations in serum and BAL fluid were increased in IPF and HP patients as compared to control subjects. IgG concentrations were only increased in HP patients, whereas IgE concentrations were comparable to controls in both patient groups. FLC-positive cells, B cells, plasma cells, and large numbers of activated mast cells were all detected in the lungs of HP and IPF patients, not in control lung. Conclusion These results show that FLC concentrations are increased in serum and BAL fluid of IPF and HP patients and that FLCs are present within affected lung tissue. This suggests that FLCs may be involved in mediating pathology in both diseases.

Depletion of CD4+CD25+ T cells switches the whey-allergic response from immunoglobulin E- to immunoglobulin free light chain-dependent

Background Symptoms of allergy are largely attributed to an IgE‐mediated hypersensitivity response. However, a considerable number of patients also exhibit clinical features of allergy without detectable systemic IgE. Previous work showed that Ig‐free light chains (IgLC) may act as an alternate mechanism to induce allergic responses. CD4+CD25+ T cells are crucial in the initiation and regulation of allergic responses and compromised function might affect the response to allergens.

Antigen Binding Characteristics of Immunoglobulin Free Light Chains: Crosslinking by Antigen is Essential to Induce Allergic Inflammation

Beside the production of complete immunoglobulins IgG, IgE, IgA, IgM and IgD, consisting of tetrameric heterodimers of immunoglobulin heavy and light chains, B cells also secrete immunoglobulin free light chains (Ig-fLC). Previous studies showed that Ig-fLCs are able to induce immediate hypersensitivity reactions. It is apparent that recognition and binding of antigen are crucial steps in the onset of these inflammatory responses. In this study, the binding characteristics of Ig-fLC to antigen were further investigated using various biochemical approaches. In addition, we investigated whether antigen-mediated crosslinking of Ig-fLC is required to initiate allergic skin inflammation in vivo. Our study shows that binding of Ig-fLCs to antigen can be measured with different experimental setups. Surface plasmon resonance analysis showed real-time antigen binding characteristics. Specific antigen binding by Ig-fLCs was further detected using immunoblotting and ELISA. Using the ELISA-based assay, a binding affinity of 76.9±3.8 nM was determined for TNP-specific Ig-fLC. Antigen-induced ear swelling in mice passively sensitized with trinitrophenol-specific Ig-fLC was inhibited when multivalent antigen was combined with excess of monovalent antigen during challenge. We conclude that Ig-fLCs are able to interact with antigen, a prerequisite for antigen-specific cellular activation. In analogy to antigen-specific Fc receptor-induced mast cell activation, crosslinking of Ig-fLCs is necessary to initiate a local allergic response.

Immunoglobulin-free light chains mediate antigen-specific responses of murine dorsal root ganglion neurons.

Immunoglobulin-free light chains (IgLC) secreted by B lymphocytes, have been shown to mediate hypersensitivity by inducing antigen-specific mast cell activation. Although both mast cells and sensory neurons contribute to the hypersensitivity response, the role of IgLC in relation to sensory neurons is unknown. We therefore aimed to investigate the effects of IgLC on cultures of murine dorsal root ganglion (DRG) neurons. Immunohistochemistry demonstrated that IgLC and IgE could specifically bind to DRG neurons, on which the presence of FcepsilonRI, the specific receptor for IgE, was demonstrated by western blotting. Further, optical recordings with Fluo-4 showed that application of the corresponding antigen to IgLC- or IgE-sensitized DRG neurons induces a sustained increase in intracellular Ca(2+) in about half of these neurons. These results show that IgLC and IgE can mediate antigen-specific responses in murine neurons. Our findings present a novel way of antigen-specific neuronal activation.