Expression and modulation of FcepsilonRIalpha and FcepsilonRIbeta in human blood basophils

The Humanised NPY-mRFP RBL Reporter Cell Line Is a Fast and Inexpensive Tool for Detection of Allergen-Specific IgE in Human Sera

Rat basophilic leukaemia (RBL) cells have been used for decades as a model of high-affinity Immunoglobulin E (IgE) receptor (FcεRI) signalling. Here, we describe the generation and use of huNPY-mRFP, a new humanised fluorescent IgE reporter cell line. Fusion of Neuropeptide Y (NPY) with monomeric red fluorescent protein (mRFP) results in targeting of fluorescence to the granules and its fast release into the supernatant upon IgE-dependent stimulation. Following overnight sensitisation with serum, optimal release of fluorescence upon dose-dependent stimulation with allergen-containing extracts could be measured after 45 min, without cell lysis or addition of any reagents. Five substitutions (D194A, K212A, K216A, K226A, and K230A) were introduced into the FcεRIα cDNA used for transfection, which resulted in the removal of known endoplasmic reticulum retention signals and high surface expression of human FcεRIα* in huNPY-mRFP cells (where * denotes the penta-substituted variant), comparable to the ~500,000 FcεRIα molecules per cell in the RS-ATL8 humanised luciferase reporter, which is a human FcεRIα/FcεRIγ double transfectant. The huNPY-mRFP reporter was used to demonstrate engagement of specific IgE in sera of Echinococcus granulosus-infected individuals by E. granulosus elongation factor EgEF-1β and, to a lesser extent, by EgEF-1δ, which had been previously described as IgE-immunoreactive EgEF-1β/δ.

The role of allergen-specific IgE, IgG and IgA in allergic disease

Immunoglobulin E (IgE)‐mediated allergy is the most common hypersensitivity disease affecting more than 30% of the population. Exposure to even minute quantities of allergens can lead to the production of IgE antibodies in atopic individuals. This is termed allergic sensitization, which occurs mainly in early childhood. Allergen‐specific IgE then binds to the high (FcεRI) and low‐affinity receptors (FcεRII, also called CD23) for IgE on effector cells and antigen‐presenting cells. Subsequent and repeated allergen exposure increases allergen‐specific IgE levels and, by receptor cross‐linking, triggers immediate release of inflammatory mediators from mast cells and basophils whereas IgE‐facilitated allergen presentation perpetuates T cell–mediated allergic inflammation. Due to engagement of receptors which are highly selective for IgE, even tiny amounts of allergens can induce massive inflammation. Naturally occurring allergen‐specific IgG and IgA antibodies usually recognize different epitopes on allergens compared with IgE and do not efficiently interfere with allergen‐induced inflammation. However, IgG and IgA antibodies to these important IgE epitopes can be induced by allergen‐specific immunotherapy or by passive immunization. These will lead to competition with IgE for binding with the allergen and prevent allergic responses. Similarly, anti‐IgE treatment does the same by preventing IgE from binding to its receptor on mast cells and basophils. Here, we review the complex interplay of allergen‐specific IgE, IgG and IgA and the corresponding cell receptors in allergic diseases and its relevance for diagnosis, treatment and prevention of allergy.

Treatment of urticaria: a clinical and mechanistic approach

PURPOSE OF REVIEW

This manuscript describes the recommended therapy of chronic spontaneous urticaria based on our understanding of the pathogenesis of hive formation. Thus, the mechanism of action of each medication is elaborated in addition to a discussion of clinical utility.

RECENT FINDINGS

The main drugs are antihistamines, omalizumab, and cyclosporine with a success rate of 40-55, 65-80, and 70-80%, respectively. Used in sequence, over 90% of patients can be successfully treated. The addition of omalizumab represents a major advance because of its efficacy, easy utility, and favorable side-effect profile. The interaction with IgE eliminates any reaction with antigens to which it might be directed, down regulates IgE receptors on mast cells and basophils, and leads to down-regulation of mast cell functions with amelioration of hives.

SUMMARY

The use of antihistamines in high dosage (at least four times a day) is effective in close to half the patients with CSU. For antihistamine resistance, the use of omalizumab has revolutionized therapy of antihistamine-resistant cases because of its efficacy and excellent side-effect profile. If the response is insufficient, cyclosporine is the next choice. Patients should be monitored regarding any adverse effects on blood pressure or renal function. All these are far safer than extended use of corticosteroid.

IL-3 but not monomeric IgE regulates FcεRI levels and cell survival in primary human basophils

Binding of allergen-specific IgE to its primary receptor FcεRI on basophils and mast cells represents a central event in the development of allergic diseases. The high-affinity interaction between IgE and FcεRI results in permanent sensitization of these allergic effector cells and critically regulates their release of pro-inflammatory mediators upon IgE cross-linking by allergens. In addition, binding of monomeric IgE has been reported to actively regulate FcεRI surface levels and promote survival of mast cells in the absence of allergen through the induction of autocrine cytokine secretion including interleukin-3 (IL-3). As basophils and mast cells share many biological commonalities we sought to assess the role of monomeric IgE binding and IL-3 signaling in FcεRI regulation and cell survival of primary human basophils. FcεRI cell surface levels and survival of isolated blood basophils were assessed upon addition of monomeric IgE or physiologic removal of endogenous cell-bound IgE with a disruptive IgE inhibitor by flow cytometry. We further determined basophil cell numbers in both low and high serum IgE blood donors and mice that are either sufficient or deficient for FcεRI. Ultimately, we investigated the effect of IL-3 on basophil surface FcεRI levels by protein and gene expression analysis. Surface levels of FcεRI were passively stabilized but not actively upregulated in the presence of monomeric IgE. In contrast to previous observations with mast cells, monomeric IgE binding did not enhance basophil survival. Interestingly, we found that IL-3 transcriptionally regulates surface levels of FcεRI in human primary basophils. Our data suggest that IL-3 but not monomeric IgE regulates FcεRI expression and cell survival in primary human basophils. Thus, blocking of IL-3 signaling in allergic effector cells might represent an interesting approach to diminish surface FcεRI levels and to prevent prolonged cell survival in allergic inflammation.

The impacts of pretreatment circulating eosinophils and basophils on prognosis of stage Ⅰ-Ⅲ colorectal cancer

AIM

The effects of circulating eosinophils and basophils on cancer survival are unclear. Here, we aimed to explore the impacts of eosinophils and basophils on prognosis of stage I-III colorectal cancer (CRC) patients.

METHODS

From February 2003 to March 2013, 569 stage I-III CRC patients were enrolled in this retrospective study. The associations between pretreatment circulating eosinophils, basophils and CRC overall survival (OS), disease-free survival (DFS) were investigated. Moreover, the prognostic value of combined eosinophils/basophils and neutrophil to lymphocyte ratio (NLR)/platelet to lymphocyte ratio (PLR) was investigated.

RESULTS

Kaplan-Meier methods showed the associations of eosinophils < 0.095 × 10⁹ /L and shorter OS (P < 0.0001), eosinophils < 0.055 × 10⁹ /L and shorter DFS (P < 0.0001), basophils < 0.015 × 10⁹ /L and shorter OS (P = 0.001), basophils < 0.015 × 10⁹ /L and shorter DFS (P = 0.005). Cox regression model showed that eosinophils < 0.095 × 10⁹ /L (hazard ratio [HR], 1.723; 95% confidence intervals [CI] = 1.177-2.523) and basophils < 0.015 × 10⁹ /L (HR, 1.714; 95% CI = 1.152-2.548) were independent prognostic factors for OS, and eosinophils < 0.055 × 10⁹ /L (HR, 2.309; 95% CI = 1.587-3.361) and basophils < 0.015 × 10⁹ /L (HR, 1.397; 95% CI = 1.003-1.945) were independent prognostic factors for DFS, respectively. The combined eosinophil-PLR (HR, 2.611; 95% CI = 1.328-5.130) and basophil-PLR (HR, 2.520; 95% CI = 1.240-5.123) were the independent prognostic factors for OS. The combined eosinophil-NLR (HR, 2.770; 95% CI = 1.528-5.019) and eosinophil-PLR (HR, 4.788; 95% CI = 2.458-9.329) were the independent prognostic factors for DFS.

CONCLUSION

Pretreatment circulating eosinophils < 0.095 × 10⁹ /L/0.055 × 10⁹ /L and circulating basophils < 0.015 × 10⁹ /L have significant impacts on prognosis of stage I-III CRC patients.

The role of basophils as innate immune regulatory cells in allergy and immunotherapy

Basophils are circulating cells that are associated quite exclusively with allergy response and hypersensitivity reactions but their role in the immune network might be much more intriguing and complex than previously expected. The feasibility of testing their biology in vitro for allergy research and diagnosis, due fundamentally to their quite easy availability in the peripheral blood, made them the major source for assessing allergy in the laboratory assay, when yet many further cells such as mast cells and eosinophils are much more involved as effector cells in allergy than circulating basophils. Interestingly, basophil numbers change rarely in peripheral blood during an atopic response, while we might yet observe an increase in eosinophils and modification in the biology of mast cells in the tissue during an hypersensitivity response. Furthermore, the fact that basophils are very scanty in numbers suggests that they should mainly serve as regulatory cells in immunity, rather than effector leukocytes, as still believed by the majority of physicians. In this review we will try to describe and elucidate the possible role of these cells, known as "innate IL4-producing cells" in the immune regulation of allergy and their function in allergen immunotherapy.

IgE Inhibits Toll-like Receptor 7- and Toll-like Receptor 9-Mediated Expression of Interferon-α by Plasmacytoid Dendritic Cells in Patients With Systemic Lupus Erythematosus

OBJECTIVE

Plasmacytoid dendritic cells (PDCs) play a central role in pathogenesis of systemic lupus erythematosus (SLE) through their unique ability to produce large amounts of type I interferon (IFN) upon Toll-like receptor 7 (TLR-7) and TLR-9 triggering. PDCs express specific surface regulatory receptors involved in negative regulation of IFNα secretion. These receptors use the γ-chain of high-affinity Fc receptor (FcR) for IgE, FcɛRI. We undertook this study to test our hypothesis that IgE engagement of FcɛRI on PDCs may impact IFNα production in SLE patients.

METHODS

Serum levels of total IgE were measured in healthy volunteers, SLE patients, and patients with IgE-dependent allergic disorders. FcɛRI expression on PDCs from SLE patients was evaluated by flow cytometry. Purified PDCs were incubated with monoclonal IgE for 24 hours, then stimulated for 18 hours with TLR agonists or immune complexes (ICs). IFNα production by PDCs was detected by quantitative real-time polymerase chain reaction (PCR) and enzyme-linked immunosorbent assay. Expression of TLR-7, TLR-9, and IFN regulatory factor 7 (IRF-7) in PDCs was quantified by quantitative real-time PCR.

RESULTS

We observed significantly higher IgE levels in SLE patients with quiescent disease than in those with active disease. In SLE patients, IgE levels correlated inversely with disease activity. IgE levels were not associated with the presence of antinuclear IgE. Purified PDCs treated for 24 hours with monoclonal IgE up-regulated FcɛRI expression in an IgE dose-dependent manner. IgE-treated PDCs significantly decreased IFNα secretion and down-regulated CCR7 expression upon stimulation with TLR-7 and TLR-9 ligands and ICs from lupus patients. IgE treatment down-regulated expression of TLR-9 and IRF-7.

CONCLUSION

Our results support the notion that IgE plays a protective role in SLE pathogenesis through the modulation of inflammatory response by PDCs.

Distinct Contributory Factors Determine Basophil-Allergen Sensitivity in Grass Pollen Rhinitis and in Anaphylactic Wasp Venom Allergy

BACKGROUND

We sought to determine whether basophil-allergen sensitivity could be transferred to donor basophils by passive IgE sensitisation in allergic rhinitis and anaphylactic Hymenoptera venom hypersensitivity.

METHODS

We studied 15 wasp venom-, 19 grass pollen- and 2 house dust mite-allergic patients, 2 healthy donors, and 8 wasp venom-allergic donors. In all subjects, we first evaluated the initial basophil response to wasp venom, grass pollen, or house dust mite allergen. Donor basophils were then stripped, sensitised with the different patients' serum IgE, and challenged with the corresponding allergen. The CD63 response of donor basophils was then compared with initial basophil responses.

RESULTS

In wasp venom-allergic subjects, the IgE transfer did not reflect the initial basophil-allergen sensitivity, because the venom IgE of subjects with high or low basophil sensitivity induced comparable responsiveness in healthy donor basophils. Furthermore, vice versa, when we sensitised the donor basophils of wasp venom-allergic individuals with different wasp venom or house dust mite IgE, we demonstrated that their response was predictable by their initial basophil allergen sensitivity. In the rhinitis allergy model, the IgE transfer correlated with the patients' initial basophil responsiveness because the grass pollen IgE of the subjects with high basophil allergen sensitivity induced significantly higher responsiveness of donor basophils than the IgE of subjects with initially low basophil allergen sensitivity.

CONCLUSIONS

Our results suggest that basophil allergen sensitivity evaluated by flow-cytometric CD63 analysis depends on two distinct contribution factors. In anaphylactic Hymenoptera allergy, the major factor was intrinsic cellular sensitivity, whereas in pollen allergy, the major factor was allergen-specific IgE on the cell surface.

Stability of Syk protein and mRNA in human peripheral blood basophils

In human basophils, Syk expression is 10-fold lower than most other types of leukocytes. There are indirect studies that suggest that Syk protein is highly unstable (a calculated half-life less than 15 min) in human peripheral blood basophils. Therefore, in these studies, Syk stability was directly examined. Purified basophils were metabolically labeled and a pulse-chase experimental design showed Syk protein to be stable in the time frame of 12 h (95% likelihood that half-life is more than 12 h). However, its synthetic rate was very slow (∼10-fold slower) compared with CD34-derived basophils, which have been shown to express levels of Syk consistent with other mature circulating leukocytes. Syk mRNA expression was found to be 5-30-fold lower than other cell types (CD34-derived basophils, peripheral blood eosinophils, and plasmacytoid dendritic cells). Syk protein and mRNA levels, across cell types, were relatively concordant. Syk mRNA in basophils showed a half-life of 3.5 h, which was greater than that of interleukin-4 or Fc epsilon receptor I-α mRNA (∼2 h), but somewhat shorter than Fc epsilon receptor I-β mRNA (8 h). A comparison of miR expression between CD34-derived and peripheral blood basophils demonstrated only 1 significant increase, in miR-150 (77-fold). Transfection in human embryonic kidney cells of a stabilized form of miR-150 showed that it modified expression of c-Myb mRNA but not of Syk mRNA or protein. These results suggest that low Syk expression in basophils results, not from protein instability and perhaps not from mRNA stability. Instead, the results point to the transcriptional nature of an important point of regulation.

The role of FcεRI expressed in dendritic cells and monocytes

Early studies regarding the function of FcεRI in dendritic cells (DCs) and monocytes have focused on its role in mediating inflammatory signaling and enhancing T cell immunity. It has been the case in part because FcεRI is the major receptor that mediates allergic inflammatory signaling in mast cells and basophils and because DCs and monocytes are antigen presenting cells capable of activating naïve and/or effector T cells. These studies have led to the general belief that FcεRI-mediated DC signaling and antigen presentation promote development and activation of Th2 cells and contribute to allergic inflammatory diseases. However, this belief has long suffered from a lack of evidence. Recently, studies have emerged that provide evidence supporting an opposing role: that FcεRI on DCs instead promotes immune homeostasis and regulation. In this review, we will update the current status of our understanding of FcεRI biology and function, with a specific focus on DCs and monocytes.

Serum IgE clearance is facilitated by human FcεRI internalization

The high-affinity IgE receptor FcεRI is constitutively expressed in mast cells and basophils and is required for transmitting stimulatory signals upon engagement of IgE-bound allergens. FcεRI is also constitutively expressed in dendritic cells (DCs) and monocytes in humans; however, the specific functions of the FcεRI expressed by these cells are not completely understood. Here, we found that FcεRI expressed by human blood DC antigen 1-positive (BDCA1+) DCs and monocytes, but not basophils, traffics to endolysosomal compartments under steady-state conditions. Furthermore, IgE bound to FcεRI on BDCA1+ DCs was rapidly endocytosed, transported to the lysosomes, and degraded in vitro. IgE injected into mice expressing human FcεRIα (FCER1A-Tg mice) was endocytosed by conventional DCs and monocytes, and endocytosis was associated with rapid clearance of circulating IgE from these mice. Importantly, this rapid IgE clearance was dependent on monocytes or DCs but not basophils. These findings strongly suggest that constitutive internalization of human FcεRI by DCs and monocytes distinctively contributes to serum IgE clearance.

Kinetics of mast cell, basophil, and oral food challenge responses in omalizumab-treated adults with peanut allergy

BACKGROUND

Monoclonal antibodies directed at IgE demonstrate clinical efficacy in subjects with peanut allergy, but previous studies have not addressed the kinetics of the clinical response or the role of mast cells and basophils in the food-induced allergic response.

OBJECTIVE

We sought to determine the kinetics of the clinical response to omalizumab and whether clinical improvement is associated with either mast cell or basophil suppression.

METHODS

Subjects with peanut allergy were treated with omalizumab for 6 months and assessed for clinical and cellular responses. At baseline, subjects had a double-blind, placebo-controlled oral food challenge (OFC), skin prick test titration (SPTT), and basophil histamine release (BHR) to peanut. BHR was repeated at week 2 and then weekly until it decreased to less than 20% of baseline values. The OFCs and SPTTs were repeated after the BHR reduction (or at week 8 if BHR did not decrease) and again at 6 months.

RESULTS

Fourteen subjects enrolled in the study. At the second food challenge, there was a significant increase in the threshold dose of peanut inducing allergic symptoms (80 to 6500 mg, P < .01). Peanut-induced BHR was either completely suppressed (n = 5) or 10-fold more allergen was required to induce maximal BHR (n = 9), and SPTT responses were not significantly changed from baseline. After 6 months of omalizumab, further changes in the OFC threshold dose or BHR were not observed, but a significant suppression in SPTTs was identified.

CONCLUSIONS

The clinical response to omalizumab occurs early in treatment when the basophil, but not the mast cell, is suppressed, supporting a role for the basophil in acute food reactions.

FCεRI gene promoter polymorphisms and total IgE levels in susceptibility to atopic dermatitis in Korea

IgE-dependent activation of mast cells and basophils through the high-affinity IgE receptor (FcεRI) is involved in the pathogenesis of allergen-induced immune responsiveness in atopic diseases like atopic dermatitis (AD). We sought to determine FcεRI gene polymorphisms are associated with AD in Korean patients, and analyzed the relevance of FcεRI gene polymorphisms and serum IgE levels. We conducted a case-control association analysis (175 patients and 56 controls) of Korean subjects. Genotyping was performed using the TaqMan fluorogenic 5' nuclease assay, and serum levels of IgE were measured using a fluorescence enzyme immunoassay. We found that there were no significant relationships between FcεRI and AD, although there were trends towards an association between the 66T>C (rs2251746) polymorphism and total serum IgE levels in the Korean AD patients. In conclusion, while the 66T>C (rs2251746) of the FcεRIα polymorphism may be linked to AD and higher serum IgE levels, polymorphisms in the FcεRIβ gene did not confer susceptibility to AD in our patient sample.

Cat allergen-induced blood basophil reactivity in vitro predicts acute human nasal allergen challenge responses in vivo

BACKGROUND

Basophil histamine release (BHR) to allergen has been used as a confirmatory test to support the clinical diagnosis of allergic disease.

OBJECTIVE

Among subjects reporting respiratory cat allergy, we hypothesized that cat-induced BHR in vitro would predict nasal allergen challenge (NAC) response in that same individual. We therefore compared the magnitude of cat allergen-induced BHR to NAC outcome and serological measures of cat-specific IgE and the ratio of cat-specific IgE to total IgE.

METHODS

Forty-two subjects with a history of cat allergy, positive cat puncture skin test (PST) and detectable cat-specific IgE (> 0.1 kAU/L, ImmunoCap) participated with consent. Subjects were grouped as positive or negative cat allergen-induced BHR, with a positive result defined as the release of ≥ 20% of the total cellular histamine content. The majority of subjects also underwent a NAC with a positive result defined as ≥ 5 total sneezes.

RESULTS

Subjects with a positive compared with a negative cat allergen BHR had higher cat-specific IgE levels at 5.40 ± 1.24 kAU/L (n=25) vs. 1.55 ± 0.73 kAU/L (n=17, P=0.01) as well as a higher cat-specific IgE/total IgE ratio [6.1 ± 1.4% (n=25) vs. 1.6 ± 0.9% (n=17, P=0.01)]. Of the 31 subjects who underwent a NAC, a positive NAC was observed in 78% (18/23) with a positive cat allergen BHR compared with 37% (3/8) with a negative cat allergen BHR, giving a positive predictive value of 78% and a negative predictive value of 63%. The diagnostic sensitivity and specificity of a positive BHR to predict a positive NAC was 86% and 50%, respectively.

CONCLUSIONS AND CLINICAL RELEVANCE

A positive cat allergen-induced BHR is associated with higher cat-specific IgE levels, a higher cat-specific to total IgE ratio and is predictive of a positive cat-induced NAC [ClinicalTrials.gov NCT00604786].

Regulation of Syk kinase and FcRbeta expression in human basophils during treatment with omalizumab

BACKGROUND

In human basophils from different subjects, maximum IgE-mediated histamine release and the level of Syk protein expression correlate well. Recent studies suggest that in some patients treated with omalizumab, the response to stimulation with anti-IgE antibody increases. In unrelated studies there is also evidence that the composition of FcepsilonRI in basophils differs among subjects. This observation raised the possibility that the stoichiometry of FcRbeta/FcepsilonRIalpha is not fixed to a 1:1 ratio and might be modifiable during changes in the basophil's environment.

OBJECTIVE

We sought to determine whether treatment with omalizumab results in increases in Syk expression and anti-IgE-mediated histamine release and disproportionately alters the relative presence of FcRbeta and FcepsilonRIalpha.

METHOD

Syk, FcepsilonRIalpha, and FcRbeta expression was monitored during the treatment of subjects with omalizumab.

RESULTS

Treatment with omalizumab reduced histamine release from peripheral blood leukocytes stimulated with cat allergen in vitro, but histamine release stimulated with anti-IgE antibody increased 2-fold. Expression of Syk increased 1.86-fold. There was no change in the expression of c-Cbl, a signaling element that is sensitive to the presence of IL-3, and no increase in response to formyl-met-leu-phe (tripeptide), a response that also increases in the presence of IL-3. There was a 60% decrease in the FcRbeta/FcepsilonRIalpha ratio in patients treated with omalizumab.

CONCLUSIONS

In the context of previous studies, these studies provide support for a proposal that Syk expression is modulated in vivo through an IgE-dependent mechanism and that the ratio of FcepsilonRI alpha and beta subunits in basophils is influenced by factors extrinsic to the cell.

Effects of omalizumab on basophil and mast cell responses using an intranasal cat allergen challenge

BACKGROUND

Omalizumab treatment suppresses FcepsilonRI expression faster on blood basophils than skin mast cells.

OBJECTIVE

We used omalizumab to elucidate the relative contributions of basophil versus mast cell FcepsilonRI activation in a nasal allergen challenge (NAC) model.

METHODS

Eighteen subjects with cat allergy were enrolled in a 3.5-month, double-blind, randomized (3.5:1), placebo-controlled trial of omalizumab using standard dosing. At baseline, subjects underwent NAC with lavage for prostaglandin D(2) measurement, skin prick test titration (SPTT), and blood sampling for basophil histamine release (BHR) and basophil IgE/FcepsilonRI measurements. Basophil studies were repeated at day 3 and then weekly until cat allergen-induced BHR was <20% of baseline or until day 45. Baseline visit procedures were repeated after the BHR reduction (midstudy NAC) and at the treatment period's completion (final NAC).

RESULTS

Subjects treated with omalizumab who completed all NACs (n = 12) demonstrated significant mean reduction in BHR to an optimal dose of cat allergen by midstudy NAC compared with baseline (74% decrease; P = .001). In addition, these subjects demonstrated significant decreases in mean combined nasal symptom scores (50% decrease; P = .007) and total sneeze counts (59% decrease; P = .01) by midstudy NAC relative to baseline NAC. In contrast, measures of mast cell response (SPTT and nasal lavage prostaglandin D(2)) were only significantly reduced by the final NAC. Subjects on placebo (n = 4) did not experience a shift in basophil, NAC symptom, or mast cell measures.

CONCLUSION

Reduction in nasal symptom scores occurred when the basophil, but not mast cell, response was reduced on omalizumab, implicating a role for basophils in the acute NAC response.

Specific post-transcriptional inhibition of mRNA for ligand binding chain of IgE high affinity receptor

IgE high affinity receptor (FcεRI) plays an important role in triggering type I allergic reactions. In this study, we have investigated the ability of four synthetic and sequence-specific RNA interfering antisense oligodeoxynucleotides (AS-ODNs) to reduce the expression of FcεRIα gene in granulocytes of allergy sufferers in vitro. Only AS1 out of four AS-ODNs specifically inhibited the FcεRIα gene expression and the dose response assay revealed that AS1 was capable of specific inhibition of target mRNA expression over a linear concentration range without affecting the expression of house keeping genes such as glyceraldehyde-3-phosphate dehydrogenase (GAPDH). Together, these results indicate that sequence-specific RNA interfering ODNs can be effectively used to silence the expression of key genes like IgE high affinity receptor that are involved in chronic inflammatory diseases.

Expression of the high affinity IgE receptor by neutrophils of individuals with allergic asthma is both minimal and insensitive to regulation by serum IgE

We evaluated the hypothesis that serum IgE regulates neutrophil FcepsilonRI expression in the same manner as described for other FcepsilonRI+ cells. FcepsilonRI expression by neutrophils of 40 asthma subjects and 20 control subjects did not correlate with serum IgE levels, whereas FcepsilonRI expression by basophils of the same subjects showed a highly significant correlation. The level of FcepsilonRI expression by neutrophils of both asthma and control subjects was approximately 1% of that for basophil FcepsilonRI expression. IgE+ neutrophils were minimally detectable, and FcepsilonRI alpha-subunit was not detected in Western blots of neutrophil membranes and cytosol. The neutrophil FcepsilonRI did not support anti-IgE stimulated superoxide release or IgE-induced increase in neutrophil survival. We conclude that FcepsilonRI expression by neutrophils of both asthma patients and control individuals is minimal at best and that, if present, neutrophil FcepsilonRI expression, unlike that of other human FcepsilonRI+ cells, is not regulated by serum IgE.

IgE receptor and signal transduction in mast cells and basophils

There are many aspects of mast cell and basophil biology that are being explored today. Notably, there is a wide variety of studies of the roles these two cell types play in the development of a multitude of diseases and the role they play in the general immune response. But the original reasons for studying these two cells types--because they are considered crucial to immediate hypersensitivity reactions--remain a driving force for research. These two cell types express the complete high affinity IgE receptor and aggregation of this receptor results in the secretion of multiple potent mediators that cause many of the signs and symptoms of an allergic reaction. Understanding more about the biology of the receptor and the signaling that it initiates remains important to the development of new therapeutic approaches to inhibit this reaction.

Basophil histamine release activity and disease severity in chronic idiopathic urticaria

BACKGROUND

Altered basophil degranulation phenotypes are found in patients with chronic idiopathic urticaria (CIU).

OBJECTIVE

To evaluate CIU disease severity in relation to basophil histamine release (HR) characteristics.

METHODS

Patients with CIU were recruited from allergy and dermatology clinics. Patients with recent use of systemic corticosteroids or immunosuppressants were excluded. Patients completed disease severity surveys and had blood basophils isolated and stimulated for HR using polyclonal goat anti-human IgE and N-formyl-met-leu-phe. The HR was measured using automated fluorometry. Multivariate linear regression analyses were used to investigate relationships between HR data and CIU disease measures.

RESULTS

Fifty patients completed surveys, of which 34 were further categorized into 2 subgroups based on basophil HR response to anti-IgE stimulation: responders (> or = 10% HR) and nonresponders (< 10% HR). Responders and nonresponders reported similar use of oral corticosteroids, work absences, and quality-of-life impairment but differed in their patterns of medications used for CIU. Basophil responders had a trend of higher use of the emergency department for CIU management. Multivariate regression revealed that patients with the basophil responder phenotype experienced significantly higher current itch scores (P = .02) compared with nonresponders.

CONCLUSIONS

Quality-of-life impairment is similar in CIU basophil subsets. Patients with CIU with a basophil responder phenotype report longer disease duration, a higher frequency of emergency department use, and significantly higher itch severity.

Genetic variability of the high-affinity IgE receptor alpha subunit (Fc epsilon RI alpha) is related to total serum IgE levels in allergic subjects

Known susceptibility genes to atopy and asthma have been identified by linkage or associations with clinical phenotypes, including total serum IgE levels. IgE-mediated sensitivity reactions require a high-affinity IgE receptor (FcepsilonRI), which immobilizes the immunoglobulin on the surface of the effector cells, mostly mast cells and basophils. In this mini-review, recent findings are presented on genetic variation of this receptor, as related to atopy. Transcription of FCER1A gene encoding the receptor alpha subunit can be initiated from two separate promoters, the proximal one and the distal one, which results in a transcript containing two novel untranslated exons (1A, 2A). Our knowledge on the role of this mechanism in allergic diseases is still at an infancy stage. Within regulatory elements of FCER1A some common single nucleotide polymorphisms have functional associations, which were recently reported and replicated in different ethnical groups. Interestingly, these associations do not confer susceptibility to allergic diseases, but rather modulate serum concentrations of IgE. Similarly to the previously investigated beta subunit of the receptor, FCER1A is a good candidate for a quantitative trait locus (QTL) in allergic diseases, and appears to participate in the systemic regulation of IgE levels.

Endocytosis, recycling, and degradation of unoccupied FcepsilonRI in human basophils

Previous studies about basophils and mast cells identified the ability of IgE to up-regulate FcepsilonRI expression by a process that depends on stabilization of the surface receptor by IgE. However, the mechanism of loss from the cell surface, when unoccupied, is not known. The current studies have examined whether unoccupied FcepsilonRI on basophils is lost by shedding or endocytosis. IgE was dissociated partially from purified human basophils to augment loss of the unoccupied receptor, and comparisons were made between basophils +/- IgE resensitization prior to 1-day culture. Incubation did not result in a detectable receptor in culture supernatants. However, in the presence of IL-3, although total cell surface expression decreased by 30% (relative to resensitized cells), FcepsilonRI from whole cell lysates was not statistically different between the two conditions. Incubation for 18 h without IL-3 resulted in the same loss from the cell surface but equivalent loss in whole cell lysates. This degradation process was reversible with Bafilomycin A. There was also evidence that the internalized receptor could be recycled. After the initial 18-h down-regulation, the receptor could be found partially restored to the cell surface if IgE were added back to the culture +/- cycloheximide. Loss of the unoccupied receptor, as well as accumulation of the receptor under the influence of IgE, was found to be insensitive to the presence of a src-family kinase inhibitor, PP1. These studies establish that the unoccupied receptor is lost by a process of endocytosis, partially recycled to the cell surface, and ultimately degraded by a lysosomal mechanism.

Basophil FcepsilonRI histamine release parallels expression of Src-homology 2-containing inositol phosphatases in chronic idiopathic urticaria

BACKGROUND

Basophils are implicated in the pathogenesis of chronic idiopathic urticaria (CIU). Autoantibodies to the IgE receptor (FcepsilonRI) and serum histamine releasing activity have been detected in some subjects with CIU, although their role in vivo is unclear. Basophils of patients with CIU have altered FcepsilonRI-mediated histamine release (HR); however, the mechanism is unknown. In the basophil FcepsilonRI signaling pathway, protein levels of Src-homology 2-containing-5'-inositol phosphatase (SHIP)-1 are inversely correlated with the release of mediators or releasability. A related phosphatase, SHIP-2, is a negative regulator of monocyte IgG receptor (FcgammaR) signaling . We hypothesized that SHIP levels are altered in CIU basophils.

METHODS

Blood basophils were isolated from cold urticaria, CIU, or normal donors, and FcepsilonRI-dependent and independent HR were quantified. Protein levels of SHIP-1, SHIP-2, spleen tyrosine kinase, and phosphorylated Akt were determined by Western blotting. Subjects' serum was tested for serum histamine releasing activity and anti-FcepsilonRIalpha antibodies.

RESULTS

CIU basophils displayed a bimodal response to anti-IgE activation. One half of CIU subjects' basophils had reductions in anti-IgE-induced HR and were designated nonresponders (CIU NR). CIU NR basophil HR remained diminished at 10-fold to 30-fold higher doses of anti-IgE. CIU anti-IgE responder basophils had HR similar to normal subjects. SHIP-1 and SHIP-2 proteins were increased in CIU NR basophils and were linked to reduced phosphoAkt after anti-IgE stimulation. CIU basophil anti-IgE response was not related to the presence of serologic factors.

CONCLUSION

In CIU basophils, the observed changes in FcepsilonRI signaling pathway molecule expression may underlie changes in releasability.

CLINICAL IMPLICATIONS

Patients with CIU can be segregated on the basis of basophil functional phenotype.

Comparision of two-flow cytometry methods for basophil degranulation in patients sensitized to grass pollen

BACKGROUND

Two-flow cytometry methods for quantification of degranulated basophil after allergen-specific activation were discussed. The methods are discerned by used membrane receptors--FcepsilonRI or IL-3Ralpha Our goal was to evaluate the diagnostic potential of the methods and to correlate them to allergen-specific IgE detection and skin prick test (SPT).

METHODS

Patient's and control's groups were studied with Bulgarian grass pollen allergen B1 simultaneously by flow cytometry kits: Basotest and BD FastImmune test. Allergy diagnosis was based on clinical history and SPT. The determination of specific IgE was performed by ELISA--RIDASCREEN.

RESULTS

There were no significant differences between the patient's results from Basotest and FastImmune (P>0.05). A significant correlation between values, analyzed by Basotest and by FastImmune was found (r=0.88). The sensitivity and specificity of the Basotest, FastImmune, specific IgE and SPT were 85%, 72%, 92% and 92% sensitivity and 100%, 92%, 100% and 85% specificity respectively. The efficiency was between 82% and 97%. There were a significant correlation between the specific IgE and flow cytometry tests: tau=0.92 (Basotest) and tau=0.71 (FastImmune) and a moderate significant correlation between the SPT and the in vitro tests: tau=0.26 (Basotest) and tau=0.31 (FastImmune).

CONCLUSION

The successful use of the Bulgarian grass pollen allergen B1 and both flow cytometry tests was presented. These methods could be as specific tools for IgE-mediated diagnosis especially FastImmune in the case of low IgE receptor expression.

Stimulation of human endothelium with IL-3 induces selective basophil accumulation in vitro

Basophils have been shown to accumulate in allergic airways and other extravascular sites. Mechanisms responsible for the selective recruitment of basophils from the blood into tissue sites remain poorly characterized. In this study, we characterized human basophil rolling and adhesion on HUVECs under physiological shear flow conditions. Interestingly, treatment of endothelial cells with the basophil-specific cytokine IL-3 (0.01-10 ng/ml) promoted basophil and eosinophil, but not neutrophil, rolling and exclusively promoted basophil adhesion. Preincubation of HUVECs with an IL-3R-blocking Ab (CD123) before the addition of IL-3 inhibited basophil rolling and adhesion, implicating IL-3R activation on endothelial cells. Incubation of basophils with neuraminidase completely abolished both rolling and adhesion, indicating the involvement of sialylated structures in the process. Abs to the beta(1) integrins, CD49d and CD49e, as well as to P-selectin and P-selectin glycoprotein ligand 1, inhibited basophil rolling and adhesion. Furthermore, blocking chemokine receptors expressed by basophils, such as CCR2, CCR3, and CCR7, demonstrated that CCR7 was involved in the observed recruitment of basophils. These data provide novel insights into how IL-3, acting directly on endothelium, can cause basophils to preferentially interact with blood vessels under physiological flow conditions and be selectively recruited to sites of inflammation.

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.

Evidence of in vivo basophil activation in chronic idiopathic urticaria

BACKGROUND

Approximately 40% of chronic idiopathic urticaria (CIU) subjects have autoantibodies to either FcepsilonRIalpha or IgE. The effect of such autoantibodies on circulating basophil activation status is unknown.

OBJECTIVE

The expression of cell surface activation markers on basophils from CIU, non-allergic, and allergic subjects were compared. Further, the relationship between marker expression and serum factors reported in CIU, such as histamine-releasing activity (HRA) and immunoreactivity to FcepsilonRIalpha were examined.

METHODS

Peripheral blood was obtained from CIU, allergic, and non-allergic donors and fractionated by density gradients. Enriched basophils (1-12%) were analysed by flow cytometry for expression of activation markers including CD63, CD69, and CD203c. Dilutions of serum (5-50%) were analysed for HRA on basophils from a normal donor. Serum was tested for immunoreactivity by western blotting to a standard cell lysate prepared from an RBL-SX38 cell line transfected with human FcepsilonRIalpha.

RESULTS

CIU subjects (n=9) and allergic subjects (n=8) exhibited enhanced expression of CD63 and CD69, as compared with non-allergic subjects (n=7); however, no difference was seen among groups for CD203c expression. Five CIU and two non-allergic subjects had evidence of significant serum HRA (>20%), whereas two CIU, two allergic, and three non-allergic subjects had evidence of serum immunoreactivity to FcepsilonRIalpha. Serum HRA and serum immunoreactivity to FcepsilonRIalpha were not associated with enhanced surface marker expression.

CONCLUSION

Basophil activation marker expression is increased in CIU subjects and is not associated with serum factors. In addition, serum HRA and FcepsilonRIalpha immunoreactivity are not unique to CIU, or related to enhanced circulating basophil marker expression.

Correlation between eosinophils and protection against reinfection with Schistosoma mansoni and the effect of human immunodeficiency virus type 1 coinfection in humans

Longitudinal investigations of an adult male population of Kenyan car washers who have heavy and quantifiable occupational exposure to Schistosoma mansoni cercariae revealed that some individuals develop resistance to reinfection while others remain highly susceptible. We sought to characterize immune correlates associated with host protection in this population. Previous studies have demonstrated an association of peripheral eosinophilia with resistance to reinfection with schistosomes. Thus, we investigated the relationship between the percentage of circulating eosinophils and the effect of human immunodeficiency virus type 1 (HIV-1) coinfection on the susceptibility of the car washers to reinfection with schistosomes. Elevated percentages of circulating eosinophils were associated with resistance to reinfection by S. mansoni in HIV-1-seronegative persons. In the HIV-1-seropositive cohort, low CD4+-T-cell counts were associated with a less intense eosinophilia. Moreover, eosinophils from the car washers expressed high levels of FcepsilonRI beta chain, a molecule important in immunoglobulin E (IgE)-mediated immunity. Levels of FcepsilonRI beta chain expression correlated with serum levels of total and antigen-specific IgE for HIV-1-negative car washers, but this was not the case for individuals coinfected with HIV-1. Overall, these data further implicate eosinophils as having a potential role in development of protective immunity against schistosomes and suggest that changes associated with HIV-1 coinfection increase susceptibility to reinfection.

IgE and FcepsilonRI regulation

The high-affinity immunoglobulin (Ig)E receptor, FcepsilonRI, regulates the action of mast cells and basophils and therefore, regulates the expression of atopic disease. There have been several recent observations that demonstrate new behaviors for this receptor. The control of FcepsilonRI expression, control of cell function by FcepsilonRI, and expression of FcepsilonRI on other cell types are important new areas of understanding currently being explored.

Are basophil histamine release and high affinity IgE receptor expression involved in asymptomatic skin sensitization?

BACKGROUND

Immunoglobulin (Ig)E-sensitized persons with positive skin prick test, but no allergy symptoms, are classified as being asymptomatic skin sensitized (AS). The allergic type 1 disease is dependant on IgE binding to the high affinity IgE-receptor (FcepsilonRI) expressed on basophils and mast cells. However, a relationship between the AS status and FcepsilonRI has not been investigated. We aimed to characterize basophils from AS by looking at histamine release (HR) (sensitivity and reactivity) and the FcepsilonRI molecule, and compare it with nonatopic (NA) or allergic (A) persons.

METHODS

Blood was obtained from NA (n = 14), grass and/or birch A persons (n = 17) and mono-sensitized grass or birch pollen AS (n = 12). The basophil sensitivity and reactivity were examined by anti-IgE triggered HR. Surface expression of FcepsilonRI and IgE were measured by flow cytometry, FcepsilonRIalpha protein was identified using a radioimmunoassay and Western blot. mRNA coding for the classic FcepsilonRIbeta-chain and the truncated form (FcepsilonRIbetaT) were determined by real-time PCR.

RESULTS

The AS group was less reactive than NA or A persons when triggered by anti-IgE and had a significant higher number of nonresponders. However, there was no difference in sensitivity among the three groups and furthermore; the groups did not vary in FcepsilonRI- and IgE-surface expression, FcepsilonRIalpha-protein level or beta/betaT ratio.

CONCLUSION

Basophils from AS persons are less reactive and include more nonresponders than basophils from NA and A persons, but do not differ regarding the FcepsilonRI molecule.

Transport of the IgE receptor alpha-chain is controlled by a multicomponent intracellular retention signal

The human high affinity IgE receptor (FcepsilonRI) is a central component of the allergic response and is expressed as either a trimeric alphagamma2 or tetrameric alphabetagamma2 complex. It has been previously described that the cytoplasmic domain (CD) of the alpha-chain carries a dilysine motif at positions -3/-7 from the C terminus that functions in intracellular retention prior to assembly with other FcepsilonRI subunits. In this report we have further explored the role of the -3/-7 dilysine signal in controlling steady-state alpha-chain transport by mutational analysis and found little surface expression of a -3/-7 dialanine alpha-chain mutant but significant Golgi localization. We compared the transport properties of a series of alpha-chain cytoplasmic domain truncation mutants and observed that truncation mutants lacking 23 or more C-terminal residues showed a dramatic increase in steady-state transport suggesting a role for the membrane-proximal CD sequence in alpha-chain retention. By performing alanine-scanning mutagenesis we identified a dilysine sequence (Lys(212)-Lys(216)) proximal to the transmembrane domain (TMD) that is important for both alpha-chain cell-surface expression and intracellular stability. Furthermore, co-mutation of the Lys(212)-Lys(216) residues with the -3/-7 dilysine signal produced a dramatic increase in alpha-chain surface expression that was further increased by co-mutation of the lone charged residue (Asp(192)) in the TMD thereby defining three regions that function to regulate alpha-chain transport and in a highly synergistic manner.

Basophils and mast cells in chronic idiopathic urticaria

Chronic idiopathic urticaria (CIU) is diagnosed in patients when urticarial eruptions recur for more than 6 weeks, and no specific cause is determined. Given that urticaria resembles the lesions induced by injection of histamine or allergen into the skin, a role for mast cells or basophils has been proposed in the generation of localized urticarial lesions. However, currently, the exact mechanisms governing regional mast cell or basophil activation are unknown. In the past decade, there has been mounting interest in viewing CIU as an autoimmune disease, given the presence of circulating autoantibodies to IgE or the alpha subunit of the high-affinity IgE receptor (FceRI) in a subset of patients. In this review, we propose that in addition to autoantibodies, specific differences in the expression of FceRI-signaling molecules in the basophils or mast cells of CIU patients may contribute to the generation of urticarial eruptions.

TLR9- and FcεRI-Mediated Responses Oppose One Another in Plasmacytoid Dendritic Cells by Down-Regulating Receptor Expression

Plasmacytoid dendritic cells (pDC) express not only TLR9 molecules through which ligation with CpG DNA favors Th1 responses but also possess IgE receptors (FcepsilonRI) implicated in allergen presentation and induction of Th2 responses. This dichotomy prompted an investigation to determine whether TLR9- and IgE receptor-mediated responses oppose one another in pDC by affecting receptor expression and associated functional responses. Results showed that IgE cross-linking reduced TLR9 in pDC and inhibited the capacity of these cells to secrete IFN-alpha when stimulated with the CpG oligodeoxynucleotide (ODN)-2216. In contrast, an approximately 15-fold reduction in FcepsilonRIalpha mRNA and a loss in surface protein were seen in pDC first exposed to TLR9 ligation with ODN-2216. Results indicated that type I IFNs partly mediated this effect, as rIFN-alpha also caused a significant approximately 4-fold reduction in FcepsilonRIalpha mRNA. Finally, this reduction in FcepsilonRIalpha mediated by ODN-2216 correlated with a selective suppression of allergen-induced CD4+ T cell proliferation, but not of responses resulting from tetanus toxoid. Overall, these results imply mechanisms by which specific innate and IgE-dependent immune responses counterregulate one another at the dendritic cell level and may have significant impact on whether an ensuing response is either of Th1 or Th2 in nature.

IgE and Fc{epsilon}RI regulation

A central feature of allergic reactions is the aggregation of the high-affinity IgE receptor, FcepsilonRI, to initiate a change in the behavior of the cell expressing the receptor. It is now clear that a number of cell types can express this receptor, which broadens the biology that revolves around IgE antibody. It is also quite clear that the presence of monomeric IgE antibody alters the expression of FcepsilonRI. There remains considerable uncertainty about the importance of independent regulation of the FcepsilonRIbeta subunit or its splice variant beta(T), in terms of regulating both expression and function of FcepsilonRI. There is also only primitive understanding of the role of various polymorphisms in the subunit genes on the atopic phenotype. There are, however, many efforts being made to resolve these issues and to discover other factors that regulate expression of this receptor. Of particular interest for understanding the variation in expression in atopy among patients, the role of this receptor on non-mast cell/basophils will be important to elucidate.

The immunoglobulin E receptor: expression and regulation

The interaction of immunoglobulin E (IgE) and its receptors is critical for the manifestation of allergic disease. Currently, IgE receptors include the high-affinity Fc epsilonRI and the low-affinity Fc epsilonRII. Fc epsilonRI is a tetrameric or trimeric complex, and each has distinct expression patterns and unique functional consequences. In general, serum levels of IgE regulate Fc epsilonRI expression, and novel therapies that lower the concentration of IgE have provided insights into the contribution of this receptor in allergic disease. Newer therapies targeting Fc epsilonRI-signaling elements and the low-affinity IgE receptor, Fc epsilonRII (CD23), are being developed.

FHL3 negatively regulates human high-affinity IgE receptor beta-chain gene expression by acting as a transcriptional co-repressor of MZF-1

The high-affinity IgE receptor FcepsilonRI plays a key role in triggering allergic reactions. We recently reported that human FcepsilonRI beta-chain gene expression was down-regulated by a transcription factor, MZF-1, through an element in the fourth intron. In the present study, we found that this transcriptional repression by MZF-1 required FHL3 (four and a half LIM domain protein 3) as a cofactor. Yeast two-hybrid and immunoprecipitation assays demonstrated that FHL3 bound MZF-1 in vitro and in vivo. Overexpression of FHL3 in KU812 cells suppressed the beta-chain promoter activity through the element in the fourth intron in an MZF-1-dependent manner. Furthermore, results from pull-down assays and gel-filtration chromatography employing nuclear extracts indicated that MZF-1 and FHL3 formed a complex of high molecular mass with some additional proteins in the nucleus. Granulocyte-macrophage colony-stimulating factor, which was reported to decrease FcepsilonRI expression, induced the accumulation of FHL3 in the nucleus, in accordance with the repressive role of FHL3 in beta-chain gene expression.

Mutations in the high-affinity IgE receptor beta-chain are not associated with nonresponder status

BACKGROUND

Basophils of some individuals do not release histamine upon activation of their high-affinity immunoglobulin E (IgE) receptor (Fc(epsilon)RI), but do so if this receptor is circumvented for cell activation. This so-called nonresponder phenomenon is clinically relevant, because in various studies atopy was less frequent or absent in nonresponder individuals. So far, it is unknown if this phenomenon is acquired during adulthood or exists from birth on.

METHODS

Histamine release was determined from isolated leucocytes stimulated with anti-IgE or calciumionophor. Also, random primed cDNA was synthesized and the open reading frame (ORF) of the Fc(epsilon)RI beta-subunit amplified and sequenced.

RESULTS

In the first part of our study, we examined the role of atopic status, type of atopy, and age in a random population of 95 children of whom we found 22% to be nonresponder. None of these parameters correlated with the nonresponder status. Except for food allergy, no specific type of atopy correlated with histamine release. The mechanism underlying the nonresponder phenomenon is assumed to occur early in the signalling cascade. We hypothesized that mutations in the Fc(epsilon)RI beta-chain may be associated with the nonresponder status, and in the second part of our study sequenced the beta-subunit in 20 responders and 20 nonresponders. Two conservative and two nonconservative heterozygous one base mutations (Thr179Thr, Asp216Asp, Ile147Leu and Glu237Gly) were found in two nonresponders and one responder. Three of these mutations have not been described so far.

CONCLUSION

The nonresponder phenomenon is present from birth on and genetically determined. In our population, it was not associated with age or the presence of atopy, and appeared not to be caused by mutations in the Fc(epsilon)RI beta-chain.

A comparative study of the FcepsilonRI molecule on human mast cell and basophil cell lines

BACKGROUND

Mast cells and basophils express the high-affinity IgE receptor FcepsilonRI. We have analysed the human mast cell line LAD2 and four subclones of the basophil cell line KU812 in order to reveal possible differences concerning the FcepsilonRI surface regulation, anti-IgE-triggered activation, FcepsilonRIalpha protein stability and the mRNA level of FcepsilonRIalpha-, beta- and the truncated beta-chain (beta(T)), and thereby determine the utility of these cell lines in investigations of the FcepsilonRI biology.

METHODS

The surface expression of FcepsilonRI was assessed by flow cytometry, using the monoclonal antibody CRA1. The FcepsilonRI-induced cellular activation (i.e. cross-linking of FcepsilonRI) was determined by changes in the intracellular level of Ca2+, which was measured by fluorescence of Fura-2. The level of the FcepsilonRIalpha protein was determined by a Western blot technique and by a radioimmunoassay. The mRNA level of FcepsilonRIalpha, beta- and beta(T)-chain was analysed using real-time PCR.

RESULTS

Two KU812 subclones and especially LAD2 had FcepsilonRI surface expression which was capable of inducing cellular activation. Both the FcepsilonRI expression and stability of the FcepsilonRIalpha protein were increased when IgE was present. All the cell lines expressed mRNA of FcepsilonRIalpha-, beta- and beta(T), with LAD2 tending to have the highest expression. However, a determination of the beta/beta(T) ratio demonstrated no difference between any of the cell clones.

CONCLUSION

These cell lines are important tools in the investigation of both the FcepsilonRI molecule and the effects induced by its activation.

Polymorphisms in the FcεRIβ Promoter Region Affecting Transcription Activity: A Possible Promoter-Dependent Mechanism for Association between FcεRIβ and Atopy

The beta subunit of the high-affinity IgE receptor (FcepsilonRI) plays an important role in IgE-mediated allergic reactions as an amplifier for cell surface expression and signal transduction of FcepsilonRI. FcepsilonRIbeta is presumed to be one of the genes linked with atopic diseases. However, the validity of the associations previously found between single nucleotide polymorphisms (SNPs) in FcepsilonRIbeta and atopic diseases is questionable. In the present study, we found correlation between the SNP of FcepsilonRIbeta at +6960A/G, resulting in a Glu237Gly amino acid substitution, and the cell surface expression level of FcepsilonRI on blood basophils, although it has been shown that the Glu237Gly mutation itself does not affect the surface expression or function of FcepsilonRI. We additionally found four SNPs in the promoter region of FcepsilonRIbeta, among which -426T/C and -654C/T were tightly linked with +6960A/G. Reporter plasmids carrying the -426C and -654T promoter displayed higher transcriptional activity than those carrying the -426T and -654C promoter. We found that transcription factor YY1 preferentially bound and transactivated the -654T promoter. Furthermore, expression of FcepsilonRI beta-chain mRNA in basophils from individuals who have the minor heterozygous genotype was significantly higher than that of the major homozygous genotype. These results suggest that the SNPs in the FcepsilonRIbeta promoter are causally linked with atopy via regulation of FcepsilonRI expression.

The role of the FcepsilonRI beta-chain in allergic diseases

The high affinity receptor for IgE, FcepsilonRI, is a multimeric surface receptor that is expressed exclusively as a tetramer on rodent cells, but exists as a tetramer or trimer on human cells. The tetrameric form is expressed on effector cells of allergic responses such as mast cells and basophils and is composed of an IgE-binding alpha-subunit, a beta-subunit and a gamma-subunit dimer. Complexes lacking the beta-subunit are found on human antigen-presenting cells. On mast cells and basophils, FcepsilonRI is essential for IgE-mediated acute allergic reactions. Crosslinking of FcepsilonRI by IgE and multivalent antigen induces a signaling cascade that culminates in the release of preformed mediators and the synthesis of lipid mediators and cytokines. The beta-subunit functions as an amplifier of FcepsilonRI expression and signaling. As a consequence, strongly enhanced mast cell effector functions and in vivo allergic reactions can be observed in the presence of FcepsilonRIbeta. In contrast, a truncated beta-isoform (betaT) that is produced by alternative splicing acts as an inhibitor of FcepsilonRI surface expression. Thus, by producing two proteins with antagonistic functions, the FcepsilonRIbeta gene could serve as a potent regulator of allergic responses. In addition, the genomic region encompassing the beta-chain has been linked to atopy and a number of polymorphisms within the FcepsilonRIbeta gene are associated with various atopic diseases. It remains to be elucidated how these polymorphisms might affect the allergic phenotype. These functions of the beta-chain together with the described genetic linkages to atopy make it a candidate for a role in the pathophysiology of allergic diseases.

Expression of actin and tubulins in purified human basophil leukocytes upon stimulation with IL-3

BACKGROUND

Pharmacological and morphological results indicate that the cytoskeleton proteins tubulins and actin play a role in the histamine release process in basophil leukocytes and mast cells. In this report, we investigate the expression of these cytoskeleton proteins in purified human basophils upon stimulation with anti-IgE and IL-3.

METHODS

Human basophils were purified using a negative selection procedure. They were incubated for 6 h with anti-IgE and/or IL-3 in radiolabeling media. Proteins in the cells were analyzed by two-dimensional gel electrophoresis and autoradiography. Actin and alpha- and beta-tubulin were identified by amino acid sequence analysis or matrix assisted laser desorption/ionisation time-of-flight mass spectrometry. The synthesis of these proteins under different experimental conditions was evaluated by densitometry.

RESULTS

Actin is regulated dose dependently by IL-3 with an optimum concentration of 100 ng/ml, corresponding to the optimal IL-3 concentration for enhancement of histamine release. The synthesis of tubulins was not significantly upregulated by IL-3 or anti-IgE alone, but there was a slight and significant upregulation of tubulins upon stimulation with both IL-3 and anti-IgE in doses optimal for maximal histamine release.

CONCLUSIONS

The de novo synthesis of actin is regulated dose dependently by IL-3 in purified human basophils in short-term culture. The optimum IL-3 concentration is the same as for enhancement of histamine release, suggesting that the same processes that regulate IL-3-induced enhancement of histamine release also regulate the expression of actin. The finding that the expression of the tubulins is not upregulated by IL-3 alone suggests that regulation of tubulin synthesis is not a pathway by which IL-3 in itself primes basophil histamine release.

A novel -66T/C polymorphism in Fc epsilon RI alpha-chain promoter affecting the transcription activity: possible relationship to allergic diseases

We found a novel polymorphism, -66T/C, in the promoter region of human FcepsilonRIalpha, the specific component of the high affinity receptor for IgE (FcepsilonRI), which is essential for the cell surface expression of FcepsilonRI and the binding of IgE Ab. When the effect of the single nucleotide replacement on the promoter function was analyzed, the transcription activity of the T allele promoter was found to be higher than that of the C allele promoter, and was markedly up-regulated by the overexpression of GATA-1 when compared with the C allele promoter. This is probably because the promoter with T at -66 has an additional GATA-1-binding motif in the region, which may assure higher affinity of the transcription factor to the promoter. In accordance with this, EMSA actually indicated that GATA-1 bound to the T allele probe (-80/-59) with the affinity higher than that to the C allele probe. Statistical analysis suggested that a significant portion of nonallergic individuals has heterozygous -66T/C genotype, while most of allergic individuals have homozygous -66T/T genotype in Japanese population. Our findings for the first time demonstrate the presence of FcepsilonRIalpha polymorphism related to the allergic diseases.

Competing functions encoded in the allergy-associated F(c)epsilonRIbeta gene

Allergic reactions are triggered via crosslinking of the high-affinity receptor for immunoglobulin E, F(c)epsilonRI. In humans, F(c)epsilonRI is expressed as a tetramer (alphabetagamma(2)) and a trimer (alphagamma(2)). The beta subunit is an amplifier of F(c)epsilonRI surface expression and signaling. Here, we show that as a consequence of alternative splicing, the F(c)epsilonRIbeta gene encodes two proteins with opposing and competing functions. One isoform is the full-length classical beta, the other a novel truncated form, beta(T). In contrast to beta, beta(T) prevents F(c)epsilonRI surface expression by inhibiting alpha chain maturation. Moreover, beta(T) competes with beta to control F(c)epsilonRI surface expression in vitro. We propose that the relative abundance of the products of the beta gene may control the level of F(c)epsilonRI surface expression and thereby influence susceptibility to allergic diseases.

Evidence for a differential expression of the FcepsilonRIgamma chain in dendritic cells of atopic and nonatopic donors

While mast cells and basophils constitutively express the high-affinity IgE receptor (Fc epsilon RI), it is absent or weakly expressed on APCs from normal donors. Fc epsilon RI is strongly upregulated on APCs from atopic donors and involved in the pathophysiology of atopic diseases. Despite its clinical relevance, data about Fc epsilon RI regulation on APCs are scarce. We show that in all donors intracellular alpha chain of the Fc epsilon RI (Fc epsilon RI alpha) accumulates during DC differentiation from monocytes. However, expression of gamma chains of the Fc epsilon RI (Fc epsilon RI gamma), mandatory for surface expression, is downregulated. It is low or negative in DCs from normal donors lacking surface Fc epsilon RI (Fc epsilon RI(neg) DCs). In contrast, DCs from atopics express surface Fc epsilon RI (Fc epsilon RI(pos) DCs) and show significant Fc epsilon RI gamma expression, which can be coprecipitated with Fc epsilon RI alpha. In Fc epsilon RI(neg) DCs lacking Fc epsilon RI gamma, immature and core glycosylated Fc epsilon RI alpha accumulates in the endoplasmic reticulum. In Fc epsilon RI(pos) DCs expressing Fc epsilon RI gamma, an additional mature form of Fc epsilon RI alpha exhibiting complex glycosylation colocalizes with Fc epsilon RI gamma in the Golgi compartment. IgE binding sustains surface-expressed Fc epsilon RI on DCs from atopic donors dependent on baseline protein synthesis and transport and enhances their IgE-dependent APC function. We propose that enhanced Fc epsilon RI on DCs from atopic donors is driven by enhanced expression of otherwise limiting amounts of Fc epsilon RI gamma and is preserved by increased IgE levels.

How IgE upregulates the allergic response

For several decades it has been known that IgE is central to the allergic response. In recent years, however, IgE has been described as having several actions in addition to passively arming the mast cell or basophil by binding to their high affinity IgE receptors. Recent studies have revealed roles for IgE in the regulation of its own receptor expression and in contributing to cell survival. Furthermore, the presence of trimeric high-affinity IgE receptors on leukocytes other than mast cells and basophils, together with the discovery of previously unknown functions of the beta subunit of the complex, has added to the complexity of IgE modulation of the allergic response.

Differences in functional consequences and signal transduction induced by IL-3, IL-5, and nerve growth factor in human basophils

Previous studies have indicated a redundancy in the effects of the cytokines, IL-3, IL-5, and nerve growth factor (NGF) on acute priming of human basophils. In the current study, we have examined the effects of these three cytokines on 18-h priming for leukotriene C4 generation, their ability to induce Fc(epsilon)RIbeta mRNA expression, or their ability to sustain basophil viability in culture. We also examine a variety of the signaling steps that accompany activation with these cytokines. In contrast with the ability of IL-3 to alter secretagogue-mediated cytosolic calcium responses following 18-h cultures, 18-h treatment with IL-5 or NGF did not affect C5a-induced leukotriene C4 generation or alter C5a-induced intracellular Ca2+ concentration elevations. IL-3 and IL-5, but not NGF, induced Fc(epsilon)RIbeta mRNA expression and all three improved basophil viability in culture with a ranking of IL-3 > IL-5 > or = NGF. All three cytokines acutely activated the extracellular signal-regulated kinase pathway and the signaling elements that preceded extracellular signal-regulated kinase and cytosolic phospholipase A2 phosphorylation, consistent with their redundant ability to acutely prime basophils. However, only IL-3 and IL-5 induced Janus kinase 2 and STAT5 phosphorylation. This pattern of signal element activation among the three cytokines most closely matched their ability to induce expression of Fc(epsilon)RIbeta mRNA. Induction of the sustained calcium signaling that follows overnight priming with IL-3 appeared to be related to the strength of the early signals activated by these cytokines but the relevant pathway required was not identified. None of the signaling patterns matched the ability of the cytokines to promote basophil survival.