Histamine releasibility and expression of Lyn and Syk kinases in Indian subjects and role of less potent IL-3 in non-releaser basophils

BACKGROUND

Allergen-mediated activation of the IgE signal pathway in basophils and mast cells leads to release of mediators in-vitro and in-vivo systems. However, basophils from 10% to 20% of the population do not release histamine and other mediators on activation of the IgE signal transduction pathway and this has been attributed to the absence of tyrosine kinases Lyn and Syk. Interestingly, when these non-releaser basophils are incubated with the IL-3, it leads to the recovery of the histamine releasibility.

OBJECTIVE

To investigate histamine releasibility in the Indian population and to evaluate the role of IL-3 with reference to non-releaser phenotypes.

METHODS

Peripheral blood basophils from healthy adults were purified by density gradient centrifugation and negative immuno-selection. Histamine release assay was performed fluorometrically. Assessment of Lyn and Syk expression were carried out by flow-cytometry. SNP analysis in the IL-3 gene was carried by sequencing analysis.

RESULTS

Histamine release after ConA challenge varied greatly from 0% to 100% in Indian subjects. Eighteen percent subjects showed less than 5% histamine release (non-releasers). Flow-cytometric analysis revealed a significantly reduced expression of Lyn and Syk kinases in basophils (p<0.05). Histamine release also significantly correlated with expression of Lyn and Syk kinase (p<0.05). Non-releasers showed the presence of SNP at +79 (T-C), which leads to the one amino acid change at 8th position in the mature IL-3 from serine to proline.

CONCLUSIONS

About 18% of the Indian subjects studied showed non-releaser phenotype and also had reduced Lyn and Syk kinase expression. Non-releasers have also shown the presence of less potent isoform of IL-3/P8, which is suspected to be responsible for the non-releaser phenotype. This needs to be extended to a larger sample size and could be a potential target for the development of therapeutics for allergic patients.

Role of calcineurin in the regulation of human lung mast cell and basophil function by cyclosporine and FK506

BACKGROUND AND PURPOSE

Cyclosporine and FK506 are thought to act by targeting the Ca2+-dependent protein phosphatase, calcineurin. The aim of the present study was to determine whether cyclosporine and FK506 stabilize mast cells and basophils by interacting with calcineurin.

EXPERIMENTAL APPROACH

The effects of cyclosporine and FK506 on the IgE-mediated release of histamine from mast cells and basophils were evaluated. The presence of calcineurin in cells was determined by Western blotting. Ca2+-dependent protein phosphatase activities were assessed in cell extracts using a synthetic phosphorylated peptide that is known to serve as a substrate for calcineurin.

KEY RESULTS

FK506 was about 100-fold more potent than cyclosporine as an inhibitor of IgE-dependent histamine release from mast cells and basophils. Immunoblotting of solubilized preparations of purified cells demonstrated the presence of calcineurin in mast cells and basophils. In enzyme assays, mast cells expressed approximately 7-fold higher Ca2+-dependent protein phosphatase activity than basophils. Whereas cyclosporine effectively inhibited Ca2+-dependent protein phosphatase activity in cell extracts, FK506 was considerably less effective.

CONCLUSIONS AND IMPLICATIONS

FK506 and cyclosporine inhibit the stimulated release of histamine from mast cells and basophils. However, the ability of cyclosporine, but not FK506, to inhibit Ca2+-dependent protein phosphatase activity questions whether FK506 stabilizes mast cells and basophils by interacting with calcineurin.

Role of mast cells and basophils in chronic rhinosinusitis

Mast cells and basophils contribute to induction and/or maintenance of eosinophilic inflammation by a variety of mechanisms, including IgE-dependent and IgE-independent processes. The latter include a variety of stimuli that have only recently been elucidated, including mechanisms triggered by bacteria, virus, fungi, complement, or autoantibodies. MCs, and basophils contribute to inflammation both directly through the release of inflammatory mediators, cytokines and growth factors and indirectly through the activation of structural cells. Accumulating evidence places MCs (and most probably basophils) in a position of importance in the pathogenesis of CRS, particularly in the pathogenesis and progression of NP (Fig. 1). Mechanisms other than conventional IgE-dependent activation of MCs are intriguing as potential mechanisms of eosinophilic inflammation in non-allergic CRS/NP. Although it is not possible using current pharmacologic approaches to completely isolate the effects of MCs or basophils in CRS and NP pathogenesis, it seems most likely that such approaches will eventually be available. It might be expected that one or both of these cells will be shown to play important roles, particularly considering their potential for activation by IgE and non-IgE mechanisms, their production of a broad array of inflammatory mediators, cytokines and growth factors, and their unique assortment of proteases.

Agonist and antagonist effects of 15R-prostaglandin (PG) D2 and 11-methylene-PGD2 on human eosinophils and basophils

Prostaglandin (PG) D2 acts through both the DP(1) receptor, which is coupled to adenylyl cyclase, and the DP2 receptor (chemoattractant receptor-homologous molecule expressed on Th2 cells), which is present on eosinophils, basophils, and Th2 cells and results in cell activation and migration. The most potent prostanoid DP2 agonist so far reported is 15R-methyl-PGD2, in which the hydroxyl group has the unnatural R configuration. In contrast, the corresponding analog possessing the natural 15S configuration is approximately 75 times less potent. This raised the question of whether the isoprostane 15R-PGD2 might have potent DP2 receptor-mediated biological activity. We therefore chemically synthesized 15R-PGD2 and investigated its biological activity. This compound elicited DP2 receptor-mediated CD11b expression in human basophils and eosinophils and induced actin polymerization and migration in eosinophils with a potency about the same as that of PGD2. In contrast, it had only a weak effect on DP1 receptor-mediated adenylyl cyclase activity in human platelets. We also investigated the effects of modification of the 9-hydroxyl and 11-oxo groups of PGD2. Both PGK2, in which the 9-hydroxyl group is replaced by an oxo group, and 11-deoxy-11-methylene PGD2, in which the 11-oxo group is replaced by a CH2 group, have little or no DP1 or DP2 agonist activity. However, the 11-methylene analog is a DP2 antagonist (IC50, approximately 2 microM). We conclude that 15R-PGD2, which may be generated by oxidative stress, is a potent and selective DP2 agonist and that modification of the 11-oxo group of PGD2 can result in DP2 antagonist activity.

Trans-basement membrane migration of human basophils: role of matrix metalloproteinase-9

In allergic disorders, basophils migrate from the blood stream to inflamed tissue sites. Since trans-basement membrane migration is an important step for local basophil accumulation, we performed a human basophil transmigration assay using a model basement membrane, Matrigel. IL-3 in the upper chamber was critical for basophil trans-basement membrane migration over baseline levels, since none of the chemoattractants placed in the lower chambers induced migration. RANTES, IL-8, 5-oxo-6E,8Z,11Z,14Z-eicosatetraenoic acid (5-oxo-ETE) and platelet-activating factor (PAF) significantly up-regulated the transmigration of IL-3-treated basophils. Neutralizing experiments indicated the involvement of beta2 integrin and matrix metalloproteinase (MMP)-2/9 in basophil transmigration. Real-time quantitative PCR revealed that basophils constitutively expressed transcripts for MMP-9, and at lower levels, MMP-2, but cell-surface expression was only detected for MMP-9. MMP-9 was also detected in the cytoplasm and culture supernatant of the basophils. Treatment with IL-3 up-regulated the surface level of MMP-9 on the basophils. Our results suggest that basophils possess a unique regulatory mechanism for trans-basement membrane migration which is affected by cytokines, chemoattractants, beta2 integrin and MMPs, especially MMP-9. MMP-9 may be critically involved in the pathogenesis of local basophil influx in allergic diseases.

Effect of horse gram lectin (Dolichos biflorus agglutinin) on degranulation of mast cells and basophils of atopic subjects: identification as an allergen

Horse gram (Dolichos biflorus) is widely consumed in the tropical south Asian countries including rural areas of India. Since D. biflorus agglutinin (DBA) is an important dietary lectin in horse gram, we have studied its effect on the degranulation of mast cells and basophils of atopic subjects. Allergy to horse gram lectin has not been reported so far. Skin prick test (SPT) was performed with 100 microg/mL of DBA. DBA-specific IgE was detected by dot-blot, and ELISA. Histamine release (HR) assay was carried out using leukocytes from non-atopic and atopic subjects, and rat peritoneal exudate cells. Among the atopic group, 10 of 48 subjects (21%) were found to be positive for DBA by SPT, and none were positive in the non-atopic group (n=20). Two subjects out of the ten who tested positive for DBA by SPT were found to be sensitized to DBA as revealed by the presence of specific IgE by ELISA and dot-blot. The HR was found to be 2- to 3-fold higher in DBA-allergic subjects than in non-atopic and atopic subjects. Basophil HR by DBA was found to be similar in both non-atopic and atopic subjects. However, DBA induces activation of mast cells in vivo in a sub-population (21%) of atopic subjects. Two subjects have been identified as having food allergy to horse gram based on the presence of DBA-specific IgE with a positive correlation to basophil HR. This is the first report of food allergy to horse gram, and DBA has been identified as an allergen.

Effect of sodium sulfite on mast cell degranulation and oxidant stress

BACKGROUND

Sulfur dioxide is 1 of 6 environmental pollutants monitored by the Environmental Protection Agency. Its ability to induce bronchoconstriction is well documented. It is highly soluble, initially forming sulfite ions in solution. Sulfur oxides are important constituents of other pollutants, such as diesel exhaust and fine particulates.

OBJECTIVE

To investigate the cellular responses of sulfite on cultured mast cells (rat basophilic leukemia [RBL-2H3] cells) and human peripheral blood basophils.

METHODS

Sulfite-induced mast cell degranulation and intracellular production of reactive oxygen species were evaluated in the presence and absence of antioxidants and inhibitors of redox metabolism. Degranulation was determined using beta-hexosaminidase, serotonin, and histamine release assays. Induction of intracellular reactive oxygen species generation was determined using the redox-sensitive dye 2',7'-dichlorofluorescein diacetate.

RESULTS

Sodium sulfite induced degranulation and the generation of intracellular reactive oxygen species in RBL-2H3 cells. These responses were inhibited by the free radical scavenger tetramethylthiourea and the flavoenzyme inhibitor diphenyliodinium but not by depletion of extracellular calcium. Peripheral blood basophils also showed histamine release after exposure to sodium sulfite

CONCLUSIONS

Sulfite, the aqueous ion of sulfur dioxide, induces cellular activation, leading to degranulation in mast cells through a non-IgE-dependent pathway. The response also differs from IgE-mediated degranulation in that it is insensitive to the influx of extracellular calcium. The putative pathway seems to rely on activation of the reduced form of nicotinamide adenine dinucleotide phosphate oxidase complex, leading to intracellular oxidative stress.

Role of chemokines in severe asthma

The severe asthma phenotype is exhibited by a subset of asthma patients whose asthma symptom is poorly controlled by current therapies. Severe asthma represents a high unmet medical need and warrants research into the mechanisms driving the underlying pathophysiology. It is hypothesized that the underlying pathology associated with severe asthma is driving the symptoms experienced by these patients, which may share common features with mild to moderate asthma or may represent a unique pathological phenotype. For the purpose of this review, the pathophysiology associated with asthma in general are described and extended to incorporate severe asthma. Chemokines may contribute towards multiple features of asthma pathophysiology and this current review focuses on the biology of chemokines pertaining to asthma pathophysiology. Chemokines are important recruiters and activators of inflammatory cells and these infiltrating cells interact with resident cells, such as fibroblasts and it is through these pathways that chemokines appear to exert multiple biological actions. Clinical trials are underway with therapeutics targeting chemokine pathways for other inflammatory diseases. It is hoped that the information generated from these studies will contribute towards furthering our understanding of chemokine biology and be applied towards targeting severe asthma.

Evaluation of basophil activation in food allergy: present and future applications

PURPOSE OF REVIEW

The diagnosis of immediate hypersensitivity relies on specific IgE and history. Because of low specificity, however, provocation challenges are often necessary. Furthermore, IgE testing does not predict features such as reaction severity; nor can it discriminate cross-reactivity from multiple sensitizations. Direct and passive basophil activation tests may address these needs. In addition, measuring basophil activation ex vivo may be useful for monitoring patients with food allergies.

RECENT FINDINGS

Several papers using basophil activation tests demonstrate comparable sensitivity and specificity to current testing for food allergy. Flow-based basophil activation tests have also been used to assess functional characteristics of patient IgE. Finally, several activation phenotypes have been identified as markers of allergic inflammation in vivo; these phenotypes appear to correspond to earlier reports of spontaneous histamine-releasing basophils in patients with active allergic inflammation.

SUMMARY

Although in their early stages, direct basophil activation tests may prove to be useful in the clinic. Indirect basophil activation studies are useful when applied to compare functional aspects of IgE. Identification of basophil activation ex vivo is a promising approach for monitoring allergic inflammation.

Effects of Cellular Fine Structure on Scattered Light Pattern

Biological cells are complex in both morphological and biochemical structure. The effects of cellular fine structure on light scattered from cells are studied by employing a three-dimensional code named AETHER which solves the full set of Maxwell equations by using the finite-difference time-domain method. It is shown that changes in cellular fine structure can cause significant changes in the scattered light pattern over particular scattering angles. These changes potentially provide the possibility for distinguishability of cellular intrastructures. The effects that features of different intrastructure have on scattered light are discussed from the viewpoint of diagnosing cellular fine structure. Finally, we discuss scattered light patterns for lymphocyte-like cells and basophil-like cells.

Mechanisms of action of anti-immunoglobulin E therapy

The currently approved anti-immunoglobulin E (IgE) agent omalizumab is a humanized monoclonal antibody that recognizes human IgE in the vicinity of its binding sites for high- and low-affinity IgE receptors. Omalizumab binds free IgE and the complexes that are formed are removed by the hepatic reticuloendothelial system. Over time, IgE comes off its receptors on various cells (primarily basophils and mast cells), rendering these cells "nonfunctional," in that they lose their ability to respond to allergen. This process is enhanced by the fact that, as IgE receptors are freed, their numbers on cell surfaces decline. The kinetics of cellular defunctionalization may differ depending on the cell type (basophils are believed to lose IgE earlier), the number of cell-surface-specific IgE molecules before initiation of treatment, and the cellular sensitivity of individual patients. Inability to respond to allergen reduces acute allergic reactions and their inflammatory and physiological consequences such as late reductions in lung function and tissue eosinophilia. Chronic airway inflammation is suppressed also, but the effect on airway hyperresponsiveness is modest. A potential role of anti-IgE therapy to act as an immunomodulator by affecting antigen presentation through the removal of IgE from the surface of dendritic cells has not been explored. Also unknown is whether anti-IgE can bind to membrane-bound IgE on B lymphocytes and influence IgE production by these cells. Anti-IgE therapy has provided a strong proof of concept for the central role of the IgE system in asthma and other allergic diseases. (Allergy Asthma

Germin-like protein Cit s 1 and profilin Cit s 2 are major allergens in orange (Citrus sinensis) fruits

Oranges are clinically relevant allergenic foods. To date, orange allergens have not been characterized in detail. The study is aimed at analyzing the sensitization profile in orange-sensitized subjects with and without clinical allergy, and to identify orange allergens. Fifty-six sensitized subjects with self-reported reactions to orange were grouped into reactors (anaphylaxis or multiple episodes of immediate reactions and/or positive challenge tests) and non-reactors (negative open food challenge tests). Allergens were characterized by IgE immunoblotting, N-terminal sequencing, IgE-inhibition assays, and mediator release assays were performed to determine the allergenic potency of orange profilin. Of 56 subjects, 23 were classified as orange allergic showing mainly an oral allergy syndrome. Of 23 subjects classified as orange allergic, 22 were sensitized to profilin, Cit s 2. In patients with mono-sensitization to profilin in vitro histamine releases up to 75% from basophils were induced using orange extract and purified plant profilins. Of the allergic patients 78% were sensitized to germin-like protein, Cit s 1. Both allergens showed retained IgE reactivity in heat-processed orange juice. Interestingly, subjects with and without clinical allergy showed a comparable sensitization profile. Profilin and germin-like proteins are major orange allergens. The potential clinical relevance of orange profilin was indicated by its strong capacity to release histamine from basophils. However, a predominant sensitization to both allergens in subjects without symptoms also indicates a high frequency of clinically insignificant sensitization.

5. IgE, mast cells, basophils, and eosinophils

IgE, mast cells, basophils, and eosinophils constitute essential elements in allergic inflammation. Allergen-specific IgE, synthesized in response to allergens in the environment, becomes fixed to FcepsilonRI on the membranes of mast cells and basophils. Aggregation of receptor-bound IgE molecules on re-exposure to specific allergen results in the production of mediators that produce the allergic response. Principal among the cells drawn to sites of mediator release is the eosinophil.

Signaling transduction pathways involved in basophil adhesion and histamine release

BACKGROUND

Little is known about basophil with respect to the different signaling transduction pathways involved in spontaneous, cytokine or anti-IgE induced adhesion and how this compares to IgE-dependent and IgE-independent mediator secretion. The purpose of the present study was to investigate the roles of beta1 and beta2 integrins in basophil adhesion as well as hosphatidylinositol 3-kinase (PI3K), src-kinases and extracellular signal regulated kinase (ERK) 1/2 in basophil adhesion and histamine release (HR).

METHODS

Basophils (purity of 10% - 50%) were preincubated with anti-CD29 or anti-CD18 blocking antibodies before used for adhesion study. Basophils were preincubated with the pharmacological inhibitors wortmannin, PP1, PD98059 before used for adhesion and HR study. Cell adherence to bovine serum albumin (BSA) or fibronectin (Fn) was monitored using cell associated histamine as a basophil marker and the histamine was measured by the glass fiber assay.

RESULTS

Basophil spontaneous adhesion to Fn was inhibited by anti-CD29. Interleukin (IL)-3, granulocyte/macrophage colony stimulating factor (GM-CSF) induced adhesion to BSA was inhibited by anti-CD18. Wortmannin at 1 micromol/L and PP1 at 20 micromol/L strongly interfered with, whereas PD98059 at 50 micromol/L weakly inhibited basophil spontaneous adhesion to Fn. One micromol/L wortmannin strongly inhibited IL-3, IL-5, GM-CSF and anti-IgE induced adhesion to BSA. PP1 at 20 micromol/L partly inhibited anti-IgE induced adhesion. Fifty micromol/L PD98059 marginally inhibited IL-5, weakly inhibited anti-IgE, partly inhibited GM-CSF induced adhesion. Wortmannin, PP1 and PD98059 inhibited anti-IgE (1:100 or 1:1000) induced basophil HR in a dose dependent manner. They inhibited calcium ionophore A23187 (10 micromol/L, 5 micromol/L) induced basophil HR in a dose dependent manner, but to different extend with PP1 being the most efficient.

CONCLUSIONS

Basophil spontaneous adhesion to Fn is mediated by beta1-integrins whereas cytokine induced adhesion to BSA is mediated by beta2-integrins. PI3K, src-kinases and ERK1/2 play distinct signaling roles in basophil adhesion and HR. PI3K is the key player while ERK1/2 is the weakest participant.

Recent advances in the use of genetically engineered negative signaling molecules to treat allergic diseases

PURPOSE OF REVIEW

This review summarizes current knowledge regarding the control of human mast cell and basophil signaling and recent developments using a new therapeutic platform consisting of a human bifunctional gamma and epsilon heavy chain (Fcgamma-Fcepsilon) protein to inhibit allergic reactivity.

RECENT FINDINGS

Crosslinking of FcgammaRIIb to FcepsilonRI on human mast cells and basophils by a genetically engineered Fcgamma-Fcepsilon protein (GE2) leads to the inhibition of mediator release upon FcepsilonRI challenge. GE2 protein was shown to inhibit cord blood-derived mast cell and peripheral blood basophil mediator release in vitro in a dose dependent fashion including inhibition of human IgE reactivity to cat. In addition, IgE-mediated release from lung tissue was inhibited through GE2. The mechanism of inhibition in mast cells included alterations in IgE-mediated Ca2+ mobilization, Syk phosphorylation and the formation of Dok-Grb2-SHIP complex. Proallergic effects of Langerhans-like dendritic cells and B cell IgE switching were also inhibited by GE2. In vivo, GE2 was shown to block passive cutaneous anaphylaxis (PCA) driven by human IgE in mice expressing the human FcepsilonRI and inhibit skin test reactivity to dust mite antigen in a dose dependent manner in rhesus monkeys. The balance between positive and negative signaling controls mast cell and basophil reactivity that is critical in the expression of human allergic diseases. This approach using a human Fcgamma-Fcepsilon fusion protein to co-aggregate FcepsilonRI with the FcgammaRII holds promise as a new therapeutic platform for the immunomodulation of allergic diseases and potentially other mast cell/basophil-dependent disease states.

5-Oxo-6,8,11,14-eicosatetraenoic acid is a potent chemoattractant for human basophils

BACKGROUND

5-Oxo-6,8,11,14-eicosatetraenoic acid (5-oxo-ETE) is a chemoattractant for eosinophils and neutrophils, and the messenger RNA for its receptor, the oxo-eicosatetraenoic acid receptor (OXE), has been detected in several tissues.

OBJECTIVES

This study aimed at clarifying the role of 5-oxo-ETE in the regulation of basophil function.

METHODS

Basophil responses were determined in assays of flow-cytometric shape change, Ca(2+) flux, chemotaxis, and histamine release. Messenger RNA for OXE was detected by real-time PCR.

RESULTS

We observed that human eosinophils were 3 to 10 times more sensitive to 5-oxo-ETE than neutrophils in flow-cytometric shape change and Ca(2+) flux assays, as estimated from the half-maximal responses of the cells. Basophils responded to 5-oxo-ETE in the shape change assay with a sensitivity similar to that of eosinophils. 5-Oxo-ETE was a weak inducer of Ca(2+) flux in basophils and did not cause histamine release but was a highly effective chemoattractant for basophils in the low nanomolar concentration range in a pertussis toxin-sensitive manner. In agreement with these functional studies, the messenger RNA for the 5-oxo-ETE receptor, OXE, was detectable in basophils as in monocytes, eosinophils, and neutrophils, but not in fibroblasts. Specimens from sinus mucosa, tonsils, and adenoids also contained detectable levels of messenger RNA for OXE.

CONCLUSION

Our data suggest that 5-oxo-ETE is potentially involved in the regulation of basophil recruitment and might hence be a useful therapeutic target in atopic disease.

Stem cell factor stimulates the chemotaxis, integrin upregulation, and survival of human basophils

BACKGROUND

Little is known about the mechanisms that regulate the selective recruitment of basophils to sites of allergic inflammation.

OBJECTIVE

Here we examine the role of stem cell factor (SCF) in the regulation of basophil function.

METHODS

Human basophils were isolated from peripheral blood, and their migration was investigated in chemotaxis assays. Apoptosis was detected by means of annexin V and propidium iodide staining. The expression of cell-surface molecules was measured by means of flow cytometry.

RESULTS

SCF amplified the chemotactic responsiveness of human peripheral blood basophils to the chemoattractants eotaxin, monocyte chemotactic protein 2 and macrophage inflammatory protein 1alpha, and C5a, without being chemotactic or chemokinetic by itself. SCF synergized with chemoattractants in causing basophil upregulation of the integrin CD11b, and this effect was inhibited by a c-kit antibody, the tyrosine kinase inhibitor imatinib mesylate (STI-571), and a phosphatidylinositol 3 kinase inhibitor but not by inhibitors of p38 mitogen-activated protein kinase or mitogen-activated protein kinase/extracellular signal-regulated kinase kinase. Basophils bound fluorescence-labeled SCF and expressed its receptor, c-kit, which was markedly upregulated in culture for 24 to 48 hours in the presence of IL-3. Moreover, SCF prolonged basophil survival in concert with IL-3 by delaying apoptosis. These effects of SCF were selective for basophils because chemotaxis and CD11b upregulation of eosinophils or neutrophils were unchanged.

CONCLUSION

SCF might be an important selective modulator of basophil function through a phosphatidylinositol 3 kinase-dependent pathway.

Nerve growth factor influences IgE-mediated human basophil activation: functional properties and intracellular mechanisms compared with IL-3

NGF and IL-3 play a unique role in supporting human basophil differentiation and mediator secretion. Their importance in allergic disease is underlined further by studies showing elevated levels of these factors in asthmatics. Here, we compared the abilities of IL-3 and NGF to stimulate basophil histamine, IL-4 or IL-13 release, either directly or in conjunction with IgE-dependent stimulation and assessed the intracellular signals responsible. Our results show that the ability of IL-3 and NGF to enhance IgE-dependent histamine release are similar. Both factors also potentiated IgE-dependent IL-13 secretion to a greater degree than the release of histamine or IL-4. At high concentrations (100 ng/ml), IL-3 and NGF alone were capable of releasing cytokines but little histamine. These abilities of IL-3 and NGF to modulate basophil activation were sensitive to blockade by specific inhibitors of PI 3-kinase, p38 MAPK and PLC, but not PKC, suggesting that their effects are mediated considerably by pathways comparable to IgE-dependent signalling.

Saturation of immunoglobulin E (IgE) binding sites by polyclonal IgE does not explain the protective effect of helminth infections against atopy

One hypothesis for the decreased rates of atopy observed among helminth-infected individuals is that parasite-induced polyclonal immunoglobulin E (IgE) out-competes allergen-specific IgE for FcepsilonRI binding on basophils and mast cells. In experiments with fresh blood drawn from filaria-infected patients, we found no association between ratios of polyclonal to Brugia malayi antigen (BmAg)-specific IgE (range, 14:1 to 388:1) and basophil responses to BmAg as measured by histamine release. Using serum samples from a filaria-infected patient who also had dust mite (Dermatophagoides pteronyssinus)-specific IgE antibodies from time points with various ratios of polyclonal to D. pteronyssinus-specific IgE (16:1 to 86:1), we demonstrated that increased ratios of polyclonal to D. pteronyssinus-specific IgE did not attenuate basophil sensitization as measured by D. pteronyssinus-specific histamine release. Suppression of histamine release was likely not observed in either of these sets of experiments because polyclonal to antigen-specific IgE ratios were not sufficiently high, as concurrent passive sensitization of basophil experiments required ratios of polyclonal to antigen-specific IgE of greater than 500:1 to suppress basophil histamine release. Further, the intensity of IgE staining in basophil populations from 20 patients with active filaria infections correlated strongly with total serum IgE levels (rho = 0.698; P = 0.0024) with no plateau in intensity of IgE staining, even though some patients had total IgE levels of greater than 10,000 ng/ml. Our data therefore suggest that in helminth infections (and in filarial infections in particular), the ratios of polyclonal to allergen-specific IgE rarely reach those levels necessary to inhibit allergen-specific IgE-FcepsilonRI binding and to suppress allergen-induced degranulation of mast cells and basophils.

New chemokine targets for asthma therapy

Chemokines and chemokine receptors are part of a complex network of molecules that play a key role in leukocyte migration and activation. The chemokine family role is crucial in the immune system, orchestrating innate and acquired immune responses, but also in allergic inflammation. A subset of chemokines, including CCL11, CCL24, CCL26, CCL7, CCL13, CCL17, and CCL22 is highly expressed by the three main cell types involved in allergic inflammation: eosinophils, basophils, and Th2 lymphocytes. In vitro and in vivo experimental studies in murine models of asthma as well as evidence from patients with asthma confirm the role of these chemokines and their receptors, including CCR3, CCR4, and CCR8, establishing a subset of chemokine/chemokine receptor that is potentially important in allergic inflammation. Recent data support the concept that interfering with chemokines or chemokine receptors represents a new approach in allergy therapy. However, even if some of them have been shown to be effective in animal models, none is as yet used in human patients.

Allergy and asthma

Initiation and regulation of allergic inflammation is influenced by many factors, including cell type, membrane receptors, and mediators generated. Furthermore, the altered response of targeted tissues (ie, airway smooth muscle) becomes important to the eventual expression of asthma. Finally, the genetic regulation and association of genetic polymorphisms has enhanced our understanding of host susceptibility. In this review key findings published in 2004 issues of the Journal of Allergy and Clinical Immunology are highlighted to demonstrate recent advances in these areas.

Cutaneous basophil (Jones-Mote) hypersensitivity after "tolerogenic" doses of intravenous ovalbumin in the guinea pig

Cutaneous basophil hypersensitivity (CBH) was studied for tolerogenic requirements. Graded doses of intravenous ovalbumin (OA) were given to guinea pigs which were subsequently immunized appropriately to produce CBH, classic delayed hypersensitivity (classic DH), and/or antibodies of both passive cutaneous anaphylaxis (PCA) and hemolytic types. Results showed that doses of intravenous antigen sufficient to induce subsequent tolerance for classic DH and hemolytic antibody actually stimulate CBH reactivity and PCA antibody production. Other studies of dose-route relationships for CBH production demonstrated that optimal immunogenic dosage requirements for CBH varied widely with route of antigen employed. OA in incomplete Freund's adjuvant (IFA) injected into footpads had low dosage requirements, intravenous OA had high dose requirements, and intradermal soluble OA dosage requirements were intermediate. The observation that blatant immunogenic responses occur during the early period of tolerance induction amplifies the significant heterogeneity of the cellular immune response and may be of importance in understanding tolerogenesis. Similar immunogenic-tolerogenic requirements and the prime role played by the basophil suggest a developmental or functional relationship between CBH and PCA antibody response.

Anterior pituitary thyrotropes are multifunctional cells

Anterior pituitary (AP) contains some unorthodox multifunctional cells that store and secrete two different AP hormones (polyhormonal cells) and/or respond to several hypothalamic-releasing hormones (HRHs; multiresponsive cells). Multifunctional cells may be involved in paradoxical secretion (secretion of a given AP hormone evoked by a noncorresponding HRH) and transdifferentiation (phenotypic switch between different mature cell types without cell division). Here we combine calcium imaging (to assess responses to the four HRHs) and multiple sequential immunoassay of the six AP hormones to perform a single-cell phenotypic study of thyrotropes in normal male and female mice. Surprisingly, most of the thyrotropes were polyhormonal, containing, in addition to thyrotropin (TSH), luteinizing hormone (40-42%) and prolactin (19-21%). Thyrotropes costoring growth hormone and/or ACTH were found only in females (24% of each type). These results suggest that costorage of the different hormones does not happen at random and that gender favors certain hormone combinations. Our results indicate that thyrotropes are a mosaic of cell phenotypes rather than a single cell type. The striking promiscuity of TSH storage should originate considerable mix-up of AP hormone secretions on stimulation of thyrotropes. However, response to thyrotropin-releasing hormone was much weaker in the polyhormonal thyrotropes than in the monohormonal ones. This would limit the appearance of paradoxical secretion under physiological conditions and suggests that timing of hormone and HRH receptor expression during the transdifferentiation process is finely and differentially regulated.

Identification of Selective Basophil Chemoattractants in Human Nasal Polyps as Insulin-Like Growth Factor-1 and Insulin-Like Growth Factor-2

In a search for novel leukocyte chemoattractants at sites of allergic inflammation, we found basophil-selective chemoattractant activity in extracts of human nasal polyps. The extracts were fractionated by reverse phase HPLC, and the resulting fractions were tested for leukocyte-stimulating activity using sensitive shape change assays. The basophil-selective activity detected was not depleted by a poxvirus CC-chemokine-binding protein affinity column. This activity was further purified by HPLC, and proteins in the bioactive fractions were analyzed by tandem electrospray mass spectrometry. Insulin-like growth factor-2 (IGF-2) was identified in these HPLC fractions, and the basophil-stimulating activity was inhibited by an anti-IGF-2-neutralizing Ab. Recombinant IGF-2 induced a substantial shape change response in basophils, but not eosinophils, neutrophils, or monocytes. IGF-2 stimulated chemokinesis of basophils, but not eosinophils or neutrophils, and synergized with eotaxin-1/CCL11 in basophil chemotaxis. IGF-2 also caused up-regulation of basophil CD11b expression and inhibited apoptosis, but did not stimulate degranulation or Ca(2+) flux. Recombinant IGF-1 exhibited similar basophil-selective effects as IGF-2, and both growth factors were detected in nasal polyp extracts by ELISA. This is the first demonstration of chemokinetic factors that increase the motility of basophils, but do not act on other granulocytes or monocytes. IGF-1 and IGF-2 could play a role in the selective recruitment of basophils in vivo.

Transendothelial migration of human basophils

During allergic reactions, basophils migrate from the blood compartment to inflammatory sites, where they act as effector cells in concert with eosinophils. Because transendothelial migration (TEM) represents an essential step for extravasation of cells, for the first time we have studied basophil TEM using HUVEC. Treatment of HUVEC with IL-1beta significantly enhanced basophil TEM, which was further potentiated by the presence of a CCR3-specific ligand, eotaxin/CCL11. In addition to CCR3 ligands, MCP-1/CCL2 was also active on basophil TEM. Although stromal cell-derived factor-1/CXCL12, a CXCR4 ligand, failed to induce TEM in freshly isolated basophils, it caused strong TEM in 24-h cultured cells. IL-3 enhanced basophil TEM by increasing the chemokinetic response. Spontaneous TEM across activated HUVEC was inhibited by treatment of cells with anti-CD18 mAb, but not with anti-CD29 mAb, and also by treatment of HUVEC with anti-ICAM-1 mAb. Anti-VCAM-1 mAb alone failed to inhibit TEM, but showed an additive inhibitory effect in combination with anti-ICAM-1 mAb. In contrast, eotaxin- and IL-3-mediated TEM was significantly inhibited by anti-CD29 mAb as well as anti-CD18 mAb. These results indicate that beta2 integrins play the primary role in basophil TEM, but beta1 integrins are also involved, especially in TEM of cytokine/chemokine-stimulated basophils. In conclusion, the regulatory profile of basophil TEM is very similar to that reported for eosinophils. Our results thus support the previous argument for a close relationship between basophils and eosinophils and suggest that the in vivo kinetics of these two cell types are similar.

Basophils produce IL-4 and accumulate in tissues after infection with a Th2-inducing parasite

Using mice in which the eGfp gene replaced the first exon of the Il4 gene (G4 mice), we examined production of interleukin (IL)-4 during infection by the intestinal nematode Nippostrongylus brasiliensis (Nb). Nb infection induced green fluorescent protein (GFP)pos cells that were FcepsilonRIpos, CD49bbright, c-kitneg, and Gr1neg. These cells had lobulated nuclei and granules characteristic of basophils. They were found mainly in the liver and lung, to a lesser degree in the spleen, but not in the lymph nodes. Although some liver basophils from naive mice express GFP, Nb infection enhanced GFP expression and increased the number of tissue basophils. Similar basophil GFP expression was found in infected Stat6-/- mice. Basophils did not increase in number in infected Rag2-/- mice; Rag2-/- mice reconstituted with CD4 T cells allowed significant basophil accumulation, indicating that CD4 T cells can direct both tissue migration of basophils and enhanced IL-4 production. IL-4 production was immunoglobulin independent and only partially dependent on IL-3. Thus, infection with a parasite that induces a "Th2-type response" resulted in accumulation of tissue basophils, and these cells, stimulated by a non-FcR cross-linking mechanism, are a principal source of in vivo IL-4 production.

Inhibition of allergen-specific IgE reactivity by a human Ig Fcgamma-Fcepsilon bifunctional fusion protein

BACKGROUND

Coaggregating FcepsilonRI with FcgammaRII receptors holds great potential for treatment of IgE-mediated disease by inhibiting FcepsilonRI signaling. We have previously shown that an Fcgamma-Fcepsilon fusion protein, human IgG-IgE Fc fusion protein (GE2), could inhibit FcepsilonRI-mediated mediator releases in vitro and in vivo.

OBJECTIVE

We sought to test whether GE2 was capable of blocking mediator release from FcepsilonRI cells sensitized with IgE in vivo or in vitro before exposure to GE2, a critical feature for GE2 to be clinically applicable.

METHODS

GE2 was tested for its ability to inhibit Fel d 1-induced mediator release from human blood basophils from subjects with cat allergy, human lung-derived mast cells, human FcepsilonRIalpha transgenic mice sensitized with human cat allergic serum, and rhesus monkeys naturally allergic to the dust mite Dermatophagoides farinae.

RESULTS

Basophils from subjects with cat allergy and lung mast cells degranulate when challenged with Fel d 1 and anti-IgE, respectively. GE2 itself did not induce mediator release but strongly blocked this Fel d 1- and anti-IgE-driven mediator release. GE2 was able to block Fel d 1-driven passive cutaneous anaphylaxis at skin sites sensitized with human serum from subjects with cat allergy in human FcepsilonRIalpha transgenic mice, but by itself, GE2 did not induce a passive cutaneous anaphylaxis reaction. Finally, GE2 markedly inhibited skin test reactivity to D farinae in monkeys naturally allergic to this allergen, with complete inhibition being observed at 125 ng.

CONCLUSION

GE2 is able to successfully compete for FcepsilonRs and FcgammaRs on cells presensitized in vitro and in vivo and lead to inhibition of IgE-mediated reactivity through coaggregation of FcepsilonRI with FcgammaRII.

Differential modulation of human basophil functions through prostaglandin D2 receptors DP and chemoattractant receptor-homologous molecule expressed on Th2 cells/DP2

BACKGROUND

Both prostaglandin (PG) D receptor (DP) and CRTH2 (chemoattractant receptor-homologous molecule expressed on Th2 cells)/DP2 are high-affinity receptors for PGD2. Previous studies have demonstrated that PGD2 enhances releasability and induces CRTH2/DP2-mediated migration in human basophils, but the precise effects of PGD2 on basophils as well as receptor usage have not been fully clarified.

OBJECTIVE

We comprehensively explored the roles of DP and CRTH2/DP2 in basophil functions by using selective agonists and antagonists for each receptor.

METHODS

DP and CRTH2/DP2 transcripts were quantified by real-time PCR. We studied the effects of selective agonists (DP: BW245C; CRTH2/DP2: 13,14-dihydro-15-keto (DK)-PGD2) and/or antagonists (DP: BWA868C; CRTH2/DP2: ramatroban) on Ca2+ mobilization, migration, degranulation, CD11b expression and survival of human basophils.

RESULTS

Basophils expressed transcripts of both DP and CRTH2/DP2, but the levels of CRTH2/DP2 transcripts were ca. 100-fold higher compared with DP transcripts. Ca2+ influx was induced in basophils by either PGD2 or DK-PGD2/CRTH2 agonist but not by BW245C/DP agonist. Basophils treated with PGD2 were completely desensitized to subsequent stimulation with DK-PGD2, but not vice versa. DK-PGD2 as well as PGD2 up-regulated CD11b expression, induced migration and enhanced degranulation, and those effects were completely antagonized by ramatroban/CRTH2 antagonist. In contrast, BW245C/DP agonist exhibited an inhibitory effect on basophil migration and IgE-mediated degranulation, and the migration inhibitory effect was effectively antagonized by BWA868C/DP antagonist. On the other hand, while PGD2 significantly shortened the basophil life-span, neither DK-PGD2/CRTH2 agonist nor BW245C/DP agonist did.

CONCLUSION

CRTH2/DP2 is primarily responsible for the pro-inflammatory effects of PGD2 on human basophils, while DP introduces negative signals capable of antagonizing the effects of CRTH2/DP2 in these cells. The effects of PGD2 on longevity imply a mechanism(s) other than via DP or CRTH2/DP2. CRTH2/DP2 on basophils may afford opportunities for therapeutic targeting in allergic inflammation.

In vitro assays for the diagnosis of IgE-mediated disorders

Advances in technology have provided new laboratory tools for the quantitation of allergen-specific IgE antibodies in serum and on the surface of basophils. This review examines the evolution from qualitative IgE antibody assays of the late 1960s to the present-day, third-generation, automated and quantitative allergen-specific IgE assays. The latest technology trend is toward microarrays in which crude or purified native and recombinant allergens can be spotted in microdot arrays on silica chips to permit extensive panels of specific IgE measurements to be performed with small quantities of serum. Although these technologies hold promise, their diagnostic performance requires further assessment once their technical details have been optimized. Potential abuses of this newer IgE antibody technology include the use of allergosorbent specificities (eg, especially food and drugs) that lack validation, application of IgE antibody measurements in the diagnosis of non-IgE-dependent disorders (eg, aspirin sensitivity), and modification of IgE antibody assays to measure food-specific IgG antibody for which there is no clinical indication. Basophil mediator release assays have evolved to include flow cytometric methods that can quantitatively detect the presence of cell surface-bound allergen-specific IgE antibodies. Assays for histamine and leukotriene C 4 released after in vitro basophil activation are now more accurate and standardized. Current analytic methods for IgE antibodies provide more quantitative and reproducible measurements of IgE than ever before, although still with less sensitivity that traditional skin testing. The current challenge is to translate the quantitative IgE antibody results into a more accurate diagnosis of allergic disease.

A bispecific antibody against human IgE and human FcgammaRII that inhibits antigen-induced histamine release by human mast cells and basophils

BACKGROUND

FcgammaRIIB are low-affinity immunoglobulin (Ig)G receptors that we previously demonstrated to negatively regulate IgE-induced mast cell activation when coaggregated with FcepsilonRI. Here, we engineered and characterized a bispecific reagent capable of coaggregating FcgammaRIIB with FcepsilonRI on human mast cells and basophils.

METHODS

A bispecific antibody was constructed by chemically crosslinking one Fab' fragment against human IgE and one Fab' fragment against human FcgammaRII. This molecule was used to coaggregate FcepsilonRI with FcgammaRII on human mast cells and basophils sensitized with human IgE antibodies, and the effect of coaggregation was examined on mediator release upon challenge with specific antigen.

RESULTS

When used under these conditions, this bispecific antibody not only failed to trigger the release of histamine by IgE-sensitized cells, but it also prevented specific antigen from triggering histamine release. Comparable inhibitions were observed with mast cells and basophils derived in vitro from cord blood cells and with peripheral blood basophils.

CONCLUSIONS

The bispecific antibody described here is the prototype of similar molecules that could be used in new therapeutic approaches of allergic diseases based on the coaggregation of activating receptors, such as FcepsilonRI, with inhibitory receptors, such as FcgammaRIIB, that are constitutively expressed by mast cells and basophils.

Basophils Infiltrate Human Gastric Mucosa at Sites of Helicobacter pylori Infection, and Exhibit Chemotaxis in Response to H. pylori-derived Peptide Hp(2–20)

Basophils, which are normally confined to the circulation, can migrate to sites of allergic inflammation. Using the specific mAb, BB1, we detected basophil infiltration of the gastric mucosa of Helicobacter pylori-infected patients affected by moderate and severe gastritis. Basophils were not found in H. pylori-free individuals or in subjects with mild gastritis. The H. pylori-derived peptide, Hp(2-20), was a potent basophil chemoattractant in vitro, whereas the control peptide, Hp1, was ineffective. Basophils from peripheral blood of healthy volunteers expressed mRNA for the formyl peptide receptors, N-formyl-peptide receptor (FPR), FPR-like (FPRL)1, and FPRL2. Preincubation of basophils with FMLP or Hp(2-20) caused complete desensitization to a subsequent challenge with homologous stimulus. Incubation of basophils with a low concentration of FMLP, which binds with high affinity to FPR, but not to FPRL1 or FPRL2, did not affect the chemotactic response to Hp(2-20). In contrast, a high concentration of FMLP, which binds to FPRL1 and FPRL2, reduced the chemotactic response to Hp(2-20). The FPR antagonist, cyclosporin H, prevented chemotaxis induced by FMLP, but not by Hp(2-20). Hp(2-20) could be responsible, at least in part, for basophil infiltration of the gastric mucosa of H. pylori-infected patients presumably through the interaction with FPRL1 and FPRL2.

Sensitive Flow Cytometric Method to Test Basophil Activation Influenced by Homeopathic Histamine Dilutions

OBJECTIVE

In an experimental setting, human basophil degranulation was triggered by anti-IgE to measure the effects from homeopathic solutions in an in-vitro cell system. A 3-color flow cytometric method with enhanced accuracy was established. As an example we looked at the influence of histamine on anti-IgE activation of basophils.

METHODS

Basophils were identified in the flow cytometer by their physical properties in the forward and side scatter light depiction and by gating on CD2(-), CD14(-), CD16(-), CD19(-), HLA-DR(-) negative and CD123-positive cells. CD63 expression on the cell surface of the anti-IgE-activated basophils served as an activation marker.

RESULTS

With this method we were able to study basophil function of the 0.6-3.9% basophils out of the mononuclear blood cell fraction and to document their activation status upon anti-IgE activation. Optimal activation occurs at 0.6 microg/ml final anti-IgE concentration; not less than 10,000 basophils have to be counted per batch to reduce the variation of the measurement. The fixation method was able to stabilize activation for two days. After investigation and reduction of the source of measurement variability, an unequivocally inhibited basophil activation was documented in a partly optimized system with homeopathic dilutions of histamine (10(-22)M, 10(-23)M, 10(-24)M, and 10(-25)M histamine). Dilutions greater than 10(-20)M histamine (Avogadro's number 6.02 x 10(23)) account for less than 1.36 molecules of histamine in the test sample, indicating a true homeopathic effect.

CONCLUSIONS

This test system is adequate for studying the effects of highly diluted mediators on basophil activation by anti-IgE. The systematic application of this experimental arrangement is recommended to study the effects of homeopathic dilutions on basophils.

A novel optical assay system for the quantitative measurement of chemotaxis

We have developed an optically accessible, horizontal chemotaxis apparatus consisting of an etched silicon substrate and a flat glass plate, both of which form two compartments with a 5-microm-deep microchannel in between. The device is held together with a stainless steel holder with holes for injecting cells and a chemoattractant to the different compartments. Migration of cells in the channel is traced with time-lapse intervals using a CCD camera. By developing a method for aligning cells at the edge of the channel, we could successfully reduce the number of cells required for a chemotactic assay, depending on the experiment, to 100 or less. To prevent ceaseless flow of contents between the adjacent compartments via the communicating microchannel, a space at the top end of the holder was filled with medium after aligning the cells. By using a fluorescent probe, we demonstrated experimentally that a stable concentration gradient could be maintained. Furthermore, we determined theoretical details of the gradient established using a model chemokine and a computational fluid dynamics code. Reproducible kinetic results of cell migration were obtained using human neutrophils and IL-8 as a model. Migration of other cells such as eosinophils, basophils and Jurkat lymphocytes toward the appropriate chemokines were also demonstrated.

Basophil activation and sulfidoleukotriene production in patients with immediate allergy to betalactam antibiotics and negative skin tests

BACKGROUND

New in vitro diagnostic methods for IgE-mediated drug allergic reactions, such as basophil activation test and antigen specific sulfidoleukotriene test, have proven their usefulness in patients with positive skin tests.

OBJECTIVE

To assess the usefulness of basophil activation test and antigen specific sulfidoleukotriene test in the diagnosis of patients with IgE-mediated allergy to Betalactam antibiotics and negative skin tests.

METHODS

The 23 patients included in the study underwent basophil activation test, antigen specific sulfidoleukotriene test and specific IgE. The patients were classified into three groups.

GROUP A

patients with positive specific IgE.

GROUP B

patients with a unique immediate reaction to Betalactams, negative specific IgE and positive oral provocation tests. And Group C: patients with at least two immediate reactions induced by Betalactams and negative specific IgE.

RESULTS

The sensitivity/specificity of the different tests are: basophil activation test 39.1 %/93.3%, antigen specific sulfidoleukotriene test 22.7%/83.3%, specific IgE 21.7%/86.7%. The joint use of the three tests allows diagnosis of 60.9% of the patients.

CONCLUSION

In vitro diagnostic tests, especially basophil activation test, are very important tools in the diagnosis of patients with IgE-mediated allergy to Betalactams and negative skin tests, avoiding performance of potentially dangerous oral provocation tests in a high percentage of cases.

IFN-alpha inhibits IL-3 priming of human basophil cytokine secretion but not leukotriene C4 and histamine release

BACKGROUND

Innate immune responses play a critical role in determining the course of acquired immunity, including that associated with allergic disease. Type I interferons, which are generated early in these reactions, are important soluble factors that prime for TH1-like activity.

OBJECTIVE

Because human basophils secrete IL-4 and IL-13 in response to both IgE-dependent and IgE-independent stimuli, we tested whether IFN-alpha, a major type I IFN, affects the production of these TH2 cytokines and/or mediator release from these cells.

METHODS

Basophils isolated from blood were treated with IFN-alpha in the presence and absence of IL-3 priming before stimulating through the IgE receptor to release histamine, leukotriene C4, and IL-4. Effects of IFN-alpha on IL-3-mediated IL-13 secretion and basophil survival were also tested. IFN-alpha receptor expression was determined by RT-PCR.

RESULTS

IFN-alpha specifically inhibited the effects IL-3 has on basophil cytokine secretion. Enhanced secretion of IL-4 resulting from IL-3 priming was significantly inhibited in cells concurrently cultured with IFN-alpha. This effect was specific for cytokine generation, because histamine and leukotriene C4 were unaffected. Furthermore, IFN-alpha blocked IL-13 secretion directly induced by IL-3. Although IFN-beta also possessed some inhibitory activity, IFN-gamma (a type II IFN) had no effect on basophil cytokine secretion. Basophils constitutively expressed mRNA for the type I IFN receptor, and IFN-alpha did not affect basophil viability with regard to inhibition of cytokine secretion.

CONCLUSIONS

These results support the belief that early innate immune responses resulting in IFN-alpha production negatively regulate allergic responses by also inhibiting priming of basophil cytokine release.

11-Dehydro-thromboxane B2, a stable thromboxane metabolite, is a full agonist of chemoattractant receptor-homologous molecule expressed on TH2 cells (CRTH2) in human eosinophils and basophils

Thromboxane (TX) A(2), a cyclooxygenase-derived mediator involved in allergic responses, is rapidly converted in vivo to a stable metabolite, 11-dehydro-TXB(2), which is considered to be biologically inactive. In this study, we found that 11-dehydro-TXB(2), but not the TXA(2) analogue U46,619 or TXB(2), activated eosinophils and basophils, as assayed by flow cytometric shape change. 11-Dehydro-TXB(2) was also chemotactic for eosinophils but did not induce, nor inhibit, platelet aggregation. Chemoattractant receptor-homologous molecule expressed on TH2 cells (CRTH2) is an important chemoattractant receptor expressed by eosinophils, basophils, and TH2 lymphocytes, and prostaglandin (PG)D(2) has been shown to be its principal ligand. 11-Dehydro-TXB(2) induced calcium flux mainly from intracellular stores in eosinophils, and this response was desensitized after stimulation with PGD(2) but not other eosinophil chemoattractants. Shape change responses of eosinophils and basophils to 11-dehydro-TXB(2) were inhibited by the thromboxane (TP)/CRTH2 receptor antagonist ramatroban, but not the selective TP antagonist SQ29,548, and were insensitive to pertussis toxin. The phospholipase C inhibitor U73,122 attenuated both 11-dehydro-TXB(2)- and PGD(2)-induced shape change. 11-Dehydro-TXB(2) also induced the chemotaxis of BaF/3 cells transfected with hCRTH2 but not naive BaF/3 cells. At a threshold concentration, 11-dehydro-TXB(2) had no antagonistic effect on CRTH2-mediated responses as induced by PGD2. These data show that 11-dehydro-TXB(2) is a full agonist of the CRTH2 receptor and hence might cause CRTH2 activation in cellular contexts where PGD-synthase is not present. Given its production in the allergic lung, antagonism of the 11-dehydro-TXB(2)/CRTH2axis may be of therapeutic relevance.

Hemopoietic Cells with Features of the Mast Cell and Basophil Lineages and their Potential Role in Allergy

Human mast cells (MCs) and basophils play a key role in the pathogenesis of allergic disorders, not only by producing inflammatory and fibrogenic mediators, but also by directly and indirectly secreting various cytokines and chemokines. Although mast cells and basophils have differences in many properties, recent evidence suggests that human MCs and basophils may be derived from a common progenitor, and their contents and phenotypes may be reversibly altered in a variety of allergic disorders. The study of FcetaRI signalling of mast cell and basophils offers new opportunities for therapeutic interventions based on the specific inhibition of the earliest events in allergic diseases. This article reviews the origin, differentiation, morphology and phenotypic properties of MCs and basophils, focussing particularly on the possible pathogenic role of MCs and basophils in allergy and biochemical targets for therapeutic interventions in allergic diseases.

Structural, cytochemical, immunocytochemical and ultrastructural characterization of blood granulocytes of the roadside hawk Buteo magnirostris (Gmelin, 1788) (Avian, Falconiform)

In the peripheral blood of the roadside hawk, Buteo magnirostris, the following types of granulocytic leucocytes were identified: heterophil, eosinophil and basophil. The heterophils presented acidophilic and spindle shaped granules, the eosinophils possess spherical eosinophilic granules and the basophils showed spherical and basophilic granules. The heterophils and eosinophils presented positive cytochemical reaction to glycogen and basic polyaminoacid, while the eosinophils presented sudanophilic granules, which were also positive for myeloperoxidase. The heterophils, alone, presented positivity for acid phosphatase in some granules and immunoreactivity to TGF-beta1 was observed only in the cytoplasm of the eosinophils. Electron microscopy demonstrated the heterophil granules as predominantly spindle shaped, being strongly electron-dense, while the eosinophils had numerous uniformly electron-dense spherical granules and the basophils presented three different types of granules identified according to their electron-density and the aspect of their matrix.

Piecemeal degranulation as a general secretory mechanism?

In this article we review the ultrastructural findings, functional aspects, and biological significance of piecemeal degranulation (PMD), a unique secretory pathway that has been described in basophils, mast cells, and eosinophils. Recent ultrastructural data suggestive of PMD in enteroendocrine cells of the gastrointestinal tract and chromaffin cells of the adrenal medulla are also presented and discussed. Further research on PMD in secretory cells of the endocrine and exocrine glands, as well as in neurons, is recommended, since the current data indicate that PMD has a broader spectrum of expression than was hitherto reported. The identification of the PMD phenotype in different cell types (e.g., basophils, mast cells, eosinophils, enteroendocrine cells, and adrenal chromaffin cells) suggests that PMD is a unique degranulation model for paracrine and endocrine secretion. Further investigation will clarify whether PMD can be considered as a general mechanism for the slow release of bioactive stored materials by granulated secretory cells.

Biologic activity of RANTES in apheresis PLT concentrates and its involvement in nonhemolytic transfusion reactions

BACKGROUND

RANTES, one of the PLT-derived biologic response modifiers, accumulates in PLT concentrates (PCs) during storage and may play a causative role in nonhemolytic transfusion reactions (NHTRs) after PC transfusion.

STUDY DESIGN AND METHODS

To investigate the association of RANTES with NHTRs, the biologic activity of RANTES in the supernatant of stored PC at the intravascular concentration expected after PC transfusion was assessed by examining chemotaxis and histamine release in human basophils. In addition, the levels of RANTES in PCs involved in NHTRs were compared with those in PCs causing no transfusion reactions.

RESULTS

The supernatant of PC diluted to contain 1 nM RANTES significantly increased the migration of and release of histamine from basophils. Neutralizing antibody to RANTES suppressed the PC-triggered migration, but not histamine release. The levels of RANTES in PCs involved in NHTRs after PC transfusion were comparable to those in PCs that did not cause any transfusion reactions.

CONCLUSION

RANTES that accumulated in PCs during storage was biologically active in a basophil chemotaxis assay at the intravascular concentration expected after PC transfusion. However, the NHTRs after PC transfusion were not simply related to the RANTES level in PCs.

Flow cytometric basophil activation test: a review

Flow cytometry is a technique enabling the analysis of physical and biological characteristics of cells or other biological particles when labeled with antibodies coupled to fluorochromes or other dyes. The basophil activation test (BAT), also called flow-cytometric allergen stimulation test (FAST) [commercially available under the name of Flow CAST (Bühlmann Laboratories) or BASOTEST (Beckton-Dickinson)] is based on the in vitro allergen-induced specific activation of basophils. This assay rests on the demonstration of some membrane protein markers that appear after exposure to the allergen. This paper reviews some of the literature about the use of this technique in the investigation of immediate-type allergies to inhalant allergens, drugs, and foods, as well as our own experience with this diagnostic technique. Flow cytometry is a reliable method for the quantification of basophil activation after allergenic stimulus in vitro and in vivo. It also enables us to detect allergic and pseudoallergic reactions because of other mechanisms than allergen-specific IgE antibodies. Further clinical evaluation of this technique will allow validation and better establishment of its diagnostic value in allergy.