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.

New insights on the possible role of mast cells in aspirin-induced asthma

Nonsteroidal anti-inflammatory drugs (NSAIDs) are major drugs used in the treatment of inflammation and pain in a wide variety of disorders. The best-known mechanism of action of NSAIDs is the inhibition of prostaglandin synthesis as a result of their action on cyclooxygenase (COX) enzymes. However, data have been accumulating through the years indicating that NSAIDs also act on other targets in cell signaling. It has been established that NSAIDs induce anti-inflammatory effects independent of COX. Acetylsalicylic acid (ASA) and other inhibitors of COX induce severe bronchospasms and asthmatic attacks in a significant population of asthmatic patients. The etiology of ASA induced asthma is complex and not fully understood, but most evidence points towards an abnormality of arachidonic acid (AA) metabolism. Since doses of ASA necessary to treat chronic inflammatory diseases appeared much higher than those required to inhibit PG synthesis, COX-independent mechanisms of NSAIDs were postulated. Recently, we have shown that NSAIDs induced expression of heat shock proteins specially HSP70. Heat shock proteins (HSPs) are normal intracellular proteins that are produced in greater amounts when cells are subjected to stress or injury. Interestingly, a potential pathogenic role for heat shock proteins in diseases such as autoimmune disease, vascular disease has been reported. Because mast cells have been reported to play a role in the pathogenesis of ASA induced asthma, a link between heat shock proteins and this disease could postulated. In this review, an overview is given on aspirin-induced asthma and the cells and mediators that may play a role therein. Mast cell signaling with regard to interaction with NSAIDs and heat shock proteins (HSPs) and toll-like receptors (TLRs) is further highlighted.

Evidence for the involvement of free light chain immunoglobulins in allergic and nonallergic rhinitis

BACKGROUND

Allergic rhinitis is characterized by mast cell degranulation induced by antigen cross-linking of IgE. It has been proposed that some patients with rhinitis show nasal allergy in the absence of systemic markers of atopy, termed entopy. Recent murine studies suggest the existence of an IgE-independent hypersensitivity response involving antigen-induced mast cell activation, mediated by immunoglobulin free light chains (FLCs).

OBJECTIVES

To determine whether FLC is associated with mast cell-mediated nasal hypersensitivity and its relationship with eosinophilic activity in allergic and nonatopic rhinitis.

METHODS

Patients with allergy and nonallergic rhinitis with eosinophilia syndrome (NARES) had levels of soluble FLC measured in nasal secretions and serum. In addition, levels of the nasal inflammatory mediators mast cell tryptase and eosinophil cationic protein were quantified. Cellular expression of kappa and lambda FLC was characterized in the nasal mucosa of allergic and nonatopic idiopathic rhinitis and control subjects by using immunohistochemistry. Immunopositive cells were phenotyped by using laser microdissection and PCR.

RESULTS

Free light chain was significantly increased in nasal secretions of subjects with allergy and NARES, and in serum of patients with NARES. Nonatopic patients with allergy showed significantly increased nasal mast cell tryptase and eosinophil cationic protein. FLC-positive cells were significantly increased in allergic and nonatopic mucosa, and were shown to be mast cells and plasma cells.

CONCLUSION

Nasal FLC is significantly increased in allergic and nonatopic rhinitis nasal mucosa, suggesting a role in nasal hypersensitivity. Further studies are needed to identify which allergens trigger FLC-mediated responses in nonatopic rhinitis.

Mast cells as target in cancer therapy

A close interaction of cancer cells with their microenvironment is important for their growth and survival. In this respect, the involvement of inflammatory cells in the initiation, promotion and progression of cancer has pointed to new therapeutic opportunities in the treatment of cancer. The main immune cell types implicated in tumor-associated inflammation are macrophages, dendritic cells, lymphocytes, neutrophils, eosinophils and mast cells. Their precise role in intercellular communication, regulation of tumor inflammation, and to what respect this inflammation contributes to tumor development, are not completely understood. Mast cells are key effector cells in allergic diseases, but it has become apparent that they also contribute to other pathologies, including autoimmune diseases and cancer. Activated mast cells can release many pro-angiogenic and tumor growth stimulatory mediators. Increased numbers of mast cells are found in many tumors and it has been shown that the number of tumor infiltrating mast cells correlate with increased intratumoral microvessel density, enhanced tumor growth and tumor invasion, and poor clinical outcome. Therefore, modulating mast cell recruitment, viability, activity, or mediator release patterns at malignant sites can be of importance to control tumor growth. In this review, we will focus on the contribution of mast cells to tumor development and growth and the possibilities to interfere in mast cell activation and proliferation in the therapy of cancer.

Cigarette smoke suppresses in vitro allergic activation of mouse mast cells

BACKGROUND

Mast cells are important effector cells in innate or acquired immunity that contribute to host defence. Excessive activation of mast cells can result in the development of allergic diseases, including atopic asthma. Mast cell activation by IgE and specific antigen induces the cells to release spasmogenic, vasoactive and pro-inflammatory mediators, which enhance airway smooth muscle contraction, vascular permeability and inflammatory cell recruitment. Recently, we have demonstrated that exposure of mast cells to cigarette smoke medium (CSM) triggered mast cells to produce chemokines. On the other hand, smoking may decrease the risk of allergic sensitization, which could be explained by a reduced IgE production or a diminished response of mast cells to activation of the IgE receptor.

OBJECTIVE

In this study, we investigated the effect of CSM on the allergic activation of mast cells through IgE and antigen.

METHODS

Primary cultured murine mast cells were exposed to CSM and activated with IgE and antigen or lipopolysaccharide (LPS). The release of granules, production of leukotrienes, chemokines and cytokines was determined in the supernatants by ELISA. The effect of CSM exposure on intracellular signalling, especially the nuclear factor (NF)-kappaB and extracellular signal-regulated kinase (Erk)1/2 pathways, was analysed by Western blotting.

RESULTS

CSM suppressed IgE-mediated degranulation and cytokine release, but no effect was observed on leukotriene release. CSM induced phosphorylation of Erk1/2 in mast cells. In CSM-exposed mast cells, activating transcription factor (ATF)-1 was phosphorylated after stimulation with IgE/Ag. LPS-activated mast cells were not influenced by CSM.

CONCLUSION

Our study suggests that exposure to cigarette smoke may lead to a reduced allergic activation of mast cells without affecting their response to activation via e.g. bacterial-derived LPS.

Cigarette smoke suppresses in vitro allergic activation of mouse mast cells (80.1)

Abstract

Background: Mast cells are important effector cells in innate or acquired immunity that contribute to host defense. Excessive activation of mast cells can result in the development of allergic diseases, including atopic asthma. Mast cell activation by IgE and specific antigen induces the cells to release spasmogenic, vasoactive, and proinflammatory mediators, which enhance airway smooth muscle contraction, vascular permeability, and inflammatory cell recruitment. Recently, we have demonstrated that exposure of mast cells to cigarette smoke medium (CSM) triggered mast cells to produce chemokines. On the other hand, smoking may decrease the risk of allergic sensitization, which could be explained by a reduced IgE production or a diminished response of mast cells to activation of the IgE receptor.

Objective: In this study, we investigated the effect of CSM on allergic activation of mast cells through IgE and antigen.

Methods: Primary cultured murine mast cells were exposed to CSM and activated with IgE and antigen or lipopolysaccharide (LPS). The releases of granules, production of leukotrienes, chemokines and cytokines was determined in supernatants by ELISA. The effect of CSM exposure on intracellular signaling, especially the NF-κB and Erk1/2 pathways, was analyzed by Western blotting.

Results: CSM suppressed IgE-mediated degranulation and cytokine release, but no effect was observed on leukotriene release. CSM induced phosphorylation of Erk1/2 in mast cells. In CSM-exposed mast cells ATF-1 was phosphorylated after stimulation with IgE/Ag. LPS activated mast cells were not influenced by CSM.

Conclusion: Our study suggests that exposure to cigarette smoke may lead to a

reduced allergic activation of mast cells without affecting their response to activation via e.g. bacterial derived LPS.

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 FcepsilonRI 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.

IgE and immunoglobulin free light chains in allergic disease: new therapeutic opportunities

The prevalence of allergy and associated diseases has dramatically increased during the last few decades. These hypersensitivity reactions can be subdivided into IgE- and non-IgE-dependent diseases. Anti-IgE approaches, such as omalizumab, have provided a novel treatment for allergic diseases, and have demonstrated benefit in severe allergic asthma and seasonal allergies. Nevertheless, this approach does not eliminate disease and many patients do not respond to treatment. The newly described mechanism for allergic diseases based on mast cell sensitization by Ig free light chains is exciting and may provide another approach to the treatment of allergic diseases. The peptide inhibitor F-991 has demonstrated remarkable biological activity in a number of animal models of allergic diseases, and promise for the potential treatment of allergic diseases in humans.

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.

Mechanisms of allergy and asthma

Allergies are the result of an inappropriate reaction against innocuous environmental proteins. The prevalence and severity of allergic diseases has increased dramatically during the last decade in developed countries. Allergen-specific T helper (Th) cells play a pivotal role in the pathogenesis of allergic hypersensitivity reactions. These Th cells activate a complex immune reaction that triggers the release of potent mediators and enhances the recruitment of inflammatory cells, which in turn elicit an inflammatory response that leads to the clinical symptoms of allergic disease. The current therapies for allergic diseases focus primarily on control of symptoms and suppression of inflammation, without affecting the underlying cause. However, the knowledge about the pathophysiology of allergic diseases has substantially increased, offering new opportunities for therapeutic intervention. In this review, we will focus on current insights into the mechanism of allergic reactions.

Stimulation of cysteinyl leukotriene production in mast cells by heat shock and acetylsalicylic acid

Immunoglobulin (Ig) E-dependent activation of mast cells is central to the allergic response. The engagement of IgE-occupied receptors initiates a series of molecular events that causes the release of preformed, and de novo synthesis of, allergic mediators. Cysteinyl leukotrienes are able to contract airway smooth muscle and increase mucus secretion and vascular permeability and recruit eosinophils. Mast cells have also recently been recognized as active participants in innate immune responses. Heat stress can modulate innate immunity by inducing stress proteins such as heat-shock proteins (HSPs). We previously demonstrated that treatment of mast cells with heat shock or acetylsalicylic acid results in an increase of TNF-alpha and IL-6 release. This effect was paralleled by expression of HSP70. In the current study, we further investigated the effects of heat shock and acetylsalicylic acid on the activation of mast cells and the release of cysteinyl leukotrienes. In mouse mast cells, derived from a culture of bone marrow cells, responsiveness to heat shock, acetylsalicylic acid and exogenous or endogenous HSP70 was monitored by measuring leukotriene C4 release. We show that after heat shock treatment and exposure to acetylsalicylic acid leukotriene production was increased. Moreover, exogenous rHSP70 also induced leukotriene production. Because it has been reported that leukotriene production in mast cells may be mediated by Toll like receptor (TLR) activation, and HSP70 also activates TLRs signaling, we further explored these issues by using mast cells that are not able to produce HSP70, i.e. heat shock factor-1 (HSF-1) knockout cells. We found that in HSF-1 knockout bone marrow derived mast cells, heat shock and acetylsalicylic acid failed to induce release of leukotrienes. Moreover, in wild type cells the surface expression of TLR4 was attenuated, whereas the intracellular expression was up-regulated. We conclude that heat shock and acetylsalicylic acid induce the production and release of heat shock proteins from mast cells, which in turn stimulate leukotriene synthesis through activation of TLR4.

Topical application of F991, an immunoglobulin free light chain antagonist, prevents development of contact sensitivity in mice

BACKGROUND

Exposure to reactive chemicals or environmental allergens can lead to hypersensitivity reactions in the skin of predisposed people. Most of these reactions are of atopic origin, but a subgroup of patients exhibits skin hypersensitivity reactions without features of atopy.

OBJECTIVE

This study was undertaken to examine the effect of inhibiting the action of Ig-free light chains in a murine model for non-atopic skin hypersensitivity by dermal application of the free light chain antagonist F991.

METHODS

To study the efficacy of F991, BALB/c mice were either passively immunized with trinitrophenyl (TNP)-specific immunoglobulin light chains (IgLC) and challenged with the hapten picryl chloride (PCl) or actively skin-sensitized and challenged with dinitrofluorobenzene (DNFB). The effect of F991 or control treatment was investigated by measuring local edema formation and the production of pro-inflammatory cytokines.

RESULTS

Passive immunization with TNP-specific IgLC resulted in an increase in ear swelling 2 h after PCl challenge. F991 inhibited this enhanced ear swelling in a dose-dependent manner when applied 4 h before the sensitization with IgLC. F991 also inhibited DNFB-induced contact hypersensitivity reaction in the mouse skin 2 and 24 h after challenge when applied before challenge. Besides the prophylactic action, F991 when applied 2 h after DNFB-challenge, it was also able to attenuate symptoms of the DNFB-induced hypersensitivity reaction at 24 h after challenge. We showed that the beneficial effects of F991 are restricted to the side of application.

CONCLUSION

F991 is able to effectively alleviate symptoms of contact sensitivity in mice. Our study suggests that local interference with IgLC-induced allergic symptoms may be attractive in the treatment of hypersensitivity responses.

Aspirin induces the production of the inflammatory mediator 8-epi-PGF in mast cells

Recently it has been shown that mast cells, through release of their pro-inflammatory mediators, are involved in aspirin attacks in aspirin-sensitive patients. To date, little information is available concerning 8-isoprostane (8-epi-prostaglandin F) production by mast cells. Therefore, we examined whether exposure of mast cells to aspirin can lead to isoprostane production. In this study we show that in mast cells, IgE and antigen stimulates an intracellular oxidative burst inducing H(2)O(2) and 8-epi-PGF production. Moreover, we show that exposure of mast cells to aspirin directly induces the production of 8-epi-PGF. Our study suggests that production of 8-epi-PGF by mast cells could contribute to the inflammatory response in e.g. aspirin-sensitive asthma patients.

Induction of HSP70 is dispensable for anti-inflammatory action of heat shock or NSAIDs in mast cells

OBJECTIVE

It is well known that nonsteroidal anti-inflammatory drugs (NSAIDs), such as acetylsalicylic acid, ibuprofen, and indomethacin, induce anti-inflammatory effects through inhibition of cyclooxygenase enzyme activity. However, it has also been established that a variety of their anti-inflammatory effects are independent of cyclooxygenase. In the search for alternative modes of action, it was found that NSAIDs share some cellular effects with heat shock treatment. This prompted us to investigate whether NSAIDs modulate production of proinflammatory cytokines by mast cells through the heat shock response.

MATERIALS AND METHODS

In mouse mast cells, derived from a culture of bone marrow cells of male BALB/cBy and null HSF-1(-/-) mice, responsiveness to heat shock and NSAIDs was monitored by measuring tumor necrosis factor-alpha (TNF-alpha) and interleukin-6 (IL-6) production and signaling pathways.

RESULTS

In bone marrow-derived mast cells (BMMC), we found that heat shock and a number of NSAIDs induced heat shock protein 70 (HSP70), which was closely paralleled with inhibition of IL-6 and TNF-alpha production. Surprisingly, in BMMC from HSF-1(-/-)mice, heat shock and selected NSAIDs were still able to suppress cytokine production in the absence of HSP70 induction.

CONCLUSION

In this article, we provide evidence that inhibition of release of proinflammatory cytokines by NSAIDs and heat shock may be attributed to inhibition of the inhibitory nuclear factor kappaB (NF-kappaB) kinase activity, extracellular signal-regulated kinases 1/2, and p38 pathways, resulting in decreased transcriptional activity of the NF-kappaB pathway.

Acetylsalicylic acid-induced release of HSP70 from mast cells results in cell activation through TLR pathway

OBJECTIVE

Mast cells are considered major players in IgE-mediated allergic responses, but have also recently been recognized as active participants in innate as well as specific immune responses. Heat stress can modulate innate immunity by inducing stress proteins such as heat shock proteins (HSPs). It has been reported that HSPs are capable of inducing the production of pro-inflammatory cytokines by the monocyte-macrophage system. In the current study, we explored whether the stress response induces HSPs and affects the signaling pathways of mast cells.

METHODS

In mouse mast cells, derived from a culture of bone marrow cells of male BALB/cBy and null HSF-1(-/-) mice, responsiveness to exogenous and endogenous HSP70 was monitored by measuring cytokine release.

RESULTS

Using BMMC, we show that treatment with heat shock or acetylsalicylic acid results in a selective induction of HSPs, and leads to release of HSP70 into the extracellular environment. The release of HSP70 from mast cells may be of functional importance. We found that after induction of HSP70, the production of TNF-alpha and IL-6 was increased. In a number of experiments, we demonstrated that exogenous/secreted HSP70 is most likely responsible for the activation of mast cells to produce cytokines. Extracellular HSP70 induced production of TNF-alpha and IL-6 through the activation of the TLR4 receptor pathway, which was evidenced by an abrogation of the response in mast cells cultured from TLR4(null) or HSF-1(-/-) mice.

CONCLUSION

Our experiments suggest that stress conditions can induce pro-inflammatory cytokine production by mast cells through an autocrine or paracrine stimulation of TLR receptors after a heat shock response. The recognition that heat shock proteins induce mast cell activation suggests an involvement of these cells in the immunological processes induced by heat shock response.

Mast cell activation is differentially affected by heat shock

OBJECTIVE

Mast cells play pivotal roles in immediate-type and inflammatory allergic and nonallergic reactions. Cross-linking of the high-affinity receptor for IgE (FcepsilonRI) on mast cells activates a signaling pathway leading to Ca2+ mobilization and is followed by degranulation and the release of histamine and other preformed mediators, as well as de novo synthesis of arachidonic acid metabolites. In a previous study, we have demonstrated that heat shock activates heat shock transcription factor-1 (HSF-1), induces heat shock protein 70 (HSP70), and suppresses cytokine production in bone marrow-derived mast cells (BMMC). In this study, we further investigated the effects of heat shock on the activation of mast cells and the release of mast cell mediators.

METHODS

In mouse mast cells, derived from a culture of bone marrow cells of male BALB/cBy and null HSF-1(-/-)mice, responsiveness to heat shock was monitored by measuring beta-hexosaminidase and leukotriene C4 (LTC4) release.

RESULTS

Using BMMC, we found that heat shock inhibits degranulation of BMMC without affecting leukotriene production. To further elucidate the mechanism of suppression of degranulation, we studied the effects of heat shock on the regulation of signal transduction in more detail. We found that heat shock inhibits calcium mobilization and tyrosine phosphorylation of Syk and SHIP upon IgE receptor activation, but increases the phosphorylation of SHP-1 and -2. Moreover, our results revealed that suppression of tyrosine phosphorylation of Syk and SHIP coincided with an increased tyrosine phosphatase activity.

CONCLUSION

The inhibitory action of heat shock toward mast cell degranulation is likely due to shifting the balance between kinase and phosphatase activity.

Dual effects of acetylsalicylic acid on mast cell degranulation, expression of cyclooxygenase-2 and release of pro-inflammatory cytokines

Several studies have demonstrated that nonsteroidal anti-inflammatory drugs, such as acetylsalicylic acid (ASA), can have inhibitory or enhancing effects on inflammatory cell function. These effects seem independent of cyclooxygenase activity and prostaglandin synthesis inhibition. Here, we examined the effect of ASA on bone marrow-derived mast cells in more detail. ASA blocked the expression of cyclooxygenase-2, the production of tumor necrosis factor-alpha and interleukin-6, and the release of granule mediators from mast cells in a concentration-dependent fashion. Concomitantly, ASA inhibited nuclear factor (NF)-kappaB activity, as well as the phosphorylation and breakdown of the inhibitory protein IkappaB-alpha. We thus propose that the anti-inflammatory effects of ASA in mast cells are due to suppression of IkappaB kinase activity, thereby inhibiting subsequent phosphorylation and degradation of IkappaB-alpha, activation of NF-kappaB, and transcription of proinflammatory cytokines. The inhibition of BMMC degranulation was independent of NF-kappaB activation, however. Interestingly, the expression of cyclooxygenase-2 was not inhibited at 1mM ASA, but was even enhanced significantly. The latter might contribute to the adverse effects of ASA in ASA-sensitive asthmatics.

Elicitation of allergic asthma by immunoglobulin free light chains

The observation that only 50% of patients with adult asthma manifest atopy indicates that other inflammatory mechanisms are likely involved in producing the characteristic features of this disorder; namely reversible airway obstruction, hyperresponsiveness, and pulmonary inflammation. Our recent discovery that antigen-specific Ig free light chains (LCs) mediate hypersensitivity-like responses suggests that these molecules may be of import in the pathophysiology of asthma. Using a murine experimental model of nonatopic asthma, we now have shown that an LC antagonist, the 9-mer peptide F991, can abrogate the development of airway obstruction, hyperresponsiveness, and pulmonary inflammation. Further, passive immunization with antigen-specific LCs and subsequent airway challenge can elicit a mast cell-dependent reaction leading to acute bronchoconstriction. These findings, and the demonstration that the concentration of free kappa LCs in the sera of patients with adult asthma were significantly increased (as compared with age-matched nonasthmatic individuals), provide previously undescribed insight into the pathogenesis of asthma. In addition, the ability to inhibit pharmacologically LC-induced mast cell activation provides a therapeutic means to prevent or ameliorate the adverse bronchopulmonary manifestations of this incapacitating disorder.

Lung proteome alterations in a mouse model for nonallergic asthma

A mouse model for nonatopic asthma was employed to study the alterations of the lung proteome to gain insight into the underlying molecular mechanisms of disease pathophysiology post-challenge. Lung samples from asthmatic and control mice were used to generate 24 high quality two-dimensional electrophoresis gels wherein 2115 proteins were examined for disease relevance. In total, 23 proteins were significantly up- or down-regulated following hapten-challenge of dinitro-fluorobenzene-hypersensitive mice. Twenty proteins were identified by mass spectrometry, of which 18 could be linked to asthma related symptoms, such as stress and inflammation, lung detoxification, plasma exudation and/or tissue remodeling. As such, proteomics was clearly vindicated as a means of studying this complex disease phenomenon. The proteins found in this study may not necessarily play a role in the immunological mechanisms and/or pathophysiology of asthma development. However, they may prove useful as surrogate biomarkers for quantitatively monitoring disease state progression or response to therapy. The mathematics of achieving statistical confidence from low numbers of gel replicates containing large numbers of independent variables stress the need for high numbers of replicates to better sample the population of proteins revealed by two-dimensional gel electrophoresis.

Substance P can stimulate prostaglandin D2 and leukotriene C4 generation without granule exocytosis in murine mast cells

Mast cells play a central role in immediate type hypersensitivity and inflammatory events. Activation of mast cells not only can result in the release of preformed granule-associated mediators generally followed by de novo synthesis of lipid-derived substances. In the present study, we show that mast cell can be activated to release lipid mediators in absence of granule exocytosis. Primary cultured murine mast cells were stimulated with substance P and produced leukotriene C4, and prostaglandin D2 without the release of the granule-associated enzyme beta-hexosaminidase. Indomethacin and nordihydroguaiaretic acid caused complete inhibition of arachidonic metabolite generation. Leukotriene C4 and prostaglandin D2 production was blocked by genistein, a specific inhibitor of tyrosine kinases, and bisindolylmaleimide, a protein kinase C inhibitor, indicating a role for both phosphorylation pathways in the substance P-stimulated lipid mediator production. We suggest that the cytokine microenvironment of the mast cell determines whether mast cell stimulation leads to only lipid mediator release or full activation. Analysis of granule-associated mediators only might underestimate the role of mast cell activation under (patho)physiological conditions.

Immunoglobulin free light chains and mast cells: pivotal role in T-cell-mediated immune reactions?

Immunoglobulin (Ig) free light (L)-chains have long been considered as the meaningless remnants of a spillover in the regular Ig production by B cells. The recently discovered role for Ig free L-chains in mediating hypersensitivity-like responses sheds new light on their potential role in immune responses. Ig free L-chains can sensitize mast cells, such that a second encounter with the appropriate antigen results in mast-cell activation. The possible importance of this reaction for the induction of T-cell-mediated immune reactions, leading to contact sensitivity, multiple sclerosis and rheumatoid arthritis is discussed.