Omalizumab treatment downregulates dendritic cell FcepsilonRI expression

BACKGROUND: Dendritic cells (DCs) are potent antigen-presenting cells that express FcepsilonRI, the high-affinity IgE receptor. Although the downregulation of basophil FcepsilonRI during anti-IgE therapy with omalizumab is well documented, its effect on FcepsilonRI expression by DCs has not been reported. OBJECTIVE: We hypothesized that IgE regulates surface FcepsilonRI expression by DCs in vivo and that, consequently, anti-IgE therapy decreases FcepsilonRI expression by DCs. METHODS: In a randomized, double-blind, placebo-controlled clinical trial 24 subjects (16 receiving omalizumab and 8 receiving placebo) with seasonal allergic rhinitis received the study drug on days 0 and 28. Serial blood samples drawn on days 0, 7, 14, 28, and 42 were analyzed for precursor DC1 (pDC1) and pDC2 surface expression of FcepsilonRIalpha by using flow cytometry. RESULTS: Omalizumab caused a significant decrease in surface FcepsilonRI expression at all time points examined in both the pDC1 and pDC2 subsets. No significant change was seen with placebo. The maximum decrease in FcepsilonRI expression in the omalizumab group was 52% and 83%, respectively, for the pDC1 and pDC2 subsets. The decrease in FcepsilonRI expression by both pDC subsets correlated with the decrease in serum-free IgE and was of a similar magnitude to that found in basophils. A 10-fold decrease in IgE corresponded to a 42% and 54% decrease in surface FcepsilonRI expression by the pDC1 and pDC2 subsets, respectively. CONCLUSION: These results demonstrate that anti-IgE therapy causes a rapid decrease in DC surface FcepsilonRI expression and establish that IgE is an important regulator of FcepsilonRI expression by DCs.     

Omalizumab rapidly decreases nasal allergic response and FcepsilonRI on basophils

BACKGROUND: Omalizumab is a monoclonal anti-IgE antibody that is effective for the treatment of allergic respiratory disorders; however, its onset of action is unknown. OBJECTIVE: This study was designed to determine the onset of action of omalizumab through the use of a challenge model to determine time-dependent inhibition of ragweed-induced changes in nasal volume as well as correlate the kinetics of omalizumab-induced decreases in serum free IgE and FcepsilonRI receptors on basophils. METHODS: We conducted a 6-week, randomized, double-blind, placebo-controlled study of 24 rhinitic patients with ragweed allergy. After PD(30) ragweed nasal allergen challenge, patients received either omalizumab, approximately 0.016 mg/kg per IgE (IU/mL), or placebo at days 0 and 28 and were rechallenged with ragweed PD(30) dose biweekly. FcepsilonRI expression on blood basophils was determined by flow cytometry at baseline and 7, 14, 28, and 42 days after treatment. IgE levels were measured at baseline and on days 3, 28, and 42. RESULTS: Mean IgE levels decreased by 96% (P <.001) from baseline within 3 days in the omalizumab group. Baseline 30% ragweed-induced nasal volume response was decreased to 20.4% at 7 to 14 days (P <.001) and 12.2% at 35 to 42 days (P <.001) for the omalizumab group. There was a median decrease in basophil FcepsilonRI expression of 73% (P <.001) in the omalizumab group, with maximum inhibition occurring within 14 days of treatment. No significant changes in IgE levels, nasal allergen challenge responses, or basophil FcepsilonRI expression were observed throughout the study in the placebo group. CONCLUSIONS: Our study showed that the onset of action by omalizumab in blunting ragweed-induced nasal responses is within 2 weeks, and this response was associated with 2 putative mechanisms of action: decreased serum free IgE and decreased FcepsilonRI receptor expression on immune effector cells.     

哮喘青春期缓解者外周血IgE、嗜酸和嗜碱性细胞的变化

儿童哮喘青春期缓解已停发3年以上者16例,静脉取血检测外周血IgE、嗜酸性细胞、嗜碱性细胞值以及分别以粉尘螨浸液（5×10~4g/ml）、扰人IgE（0.1μg/ml）,高渗甘露醇作为刺激剂的人嗜碱性细胞释放能力,并以无过敏史、家族史的正常人30例和本院哮喘患者25例进行比较,可观察到青春期缓解组:（1）嗜酸性细胞值增高者为3/16（18.75％）明显低于哮喘组的15/25（60％）（P<0.05）,与正常组的1/30（3.33％）无明显差异;（2）IgE值增高者为2/16（12.5％）,与正常组的1/30（3.33％）无明显差异,虽低于哮喘组的9/25（36％）,但仍无显著性差异;（3）嗜碱性细胞值为9/16（56.25％）与哮喘组的15/25（60％）相仿;明显高于正常组的1/30（3.33％）（p<0.001）;（4）以粉尘螨和抗人IgE为刺激剂的HBDT其阳性数均为1/16（6.25％）与正常组的1/30（3.33％）和0/30（0％）相接近,均明显低于哮喘组的15/25（60％）和14/25（56％）（P<0.001）,而以甘露醇为刺激剂的HBDT阳性数在青春期缓解组为9/16（56.25％）与哮喘组的19/25（76％）无差异,明显高于正常组的4/30（13.33％）（P<0.001）。表明哮喘在青春期缓解者嗜酸性细胞明显降低,IgE有一定程度下降,而嗜碱性细胞在量和质方面仍存在着异常。     

Regulation of surface FcepsilonRI expression on human eosinophils by IL-4 and IgE

BACKGROUND: Recent studies have demonstrated that eosinophils from allergic patients express low levels of FcepsilonRI on their surface, but the regulatory mechanisms of eosinophil surface FcepsilonRI expression are not fully understood. We investigated whether IL-4 and IgE, which are reported to regulate surface FcepsilonRI expression on human mast cells, are able to affect surface FcepsilonRI expression in normal human eosinophils. METHODS: Eosinophils purified from peripheral blood were cultured with IL-5 and with or without IL-4 and/or IgE, and surface FcepsilonRI expression was analyzed by flow cytometry using an anti-FcepsilonRI mAb, CRA-1. RESULTS: Apparent FcepsilonRI expression (approximately 1% of mast cell FcepsilonRI levels) was observed in eosinophils cultured with both IL-4 and IgE. A combination of IL-4 (>or=1 ng/ml) and IgE (>or= 0.5 microg/ml) was necessary for the maximal induction of surface FcepsilonRI expression. In the presence of IL-4 and IgE, eosinophils cultured for 2 days demonstrated low but statistically significant levels of surface FcepsilonRI, which reached a plateau after 7 days of culture. However, cross-linkage of surface FcepsilonRI molecules by CRA-1 or anti-IgE did not induce any eosinophil activation. CONCLUSIONS: IL-4 and IgE can affect the levels of surface FcepsilonRI on normal human eosinophils. FcepsilonRI expression on eosinophils may be regulated by a mechanism similar to that in mast cells.     

Omalizumab Protects against Allergen- Induced Bronchoconstriction in Allergic (Immunoglobulin E-Mediated) Asthma

Background: Omalizumab has been shown to suppress responses to inhaled allergens in allergic asthma patients with pretreatment immunoglobulin E (IgE) ≤700 IU/ml. To extend current dosing tables, we evaluated the potential of high omalizumab doses to block allergen-induced bronchoconstriction in patients with higher IgE levels. Methods: Asthmatic adults (18-65 years; body weight 40-150 kg) were divided into groups according to screening IgE (group 1: 30-300 IU/ml; group 2: 700-2,000 IU/ml) and randomized 2:1 to omalizumab/placebo every 2 or 4 weeks for 12-14 weeks. Allergen bronchoprovocation (ABP) testing was performed before treatment and at weeks 8 and 16. The primary efficacy endpoint, the early-phase allergic response (EAR), was defined as the maximum percentage drop in forced expiratory volume in 1 s during the first 30 min after ABP. Serum free IgE was determined as a pharmacodynamic endpoint, and the exhaled fractional concentration of nitric oxide (FE(NO)) was an exploratory endpoint. Results: Fifty patients were included in the study. Omalizumab improved EAR; at week 8, EAR was 23.1% for placebo, 9.3% in group 1 (p = 0.018 versus placebo) and 5.6% in group 2 (p < 0.001). At week 16, EAR was 20%, 11.8% (p = 0.087) and 5.1% (p < 0.001), respectively. Free IgE decreased in groups 1 and 2 and remained <50 ng/ml in all patients during weeks 6-16. Omalizumab completely suppressed FE(NO) increases after ABP in both groups. Conclusions: Omalizumab blocked early asthmatic responses over a broad range of IgE/body weight combinations. Extending the dosing tables enables omalizumab to benefit a wider range of patients.     

Anti-IgE as a mast cell-stabilizing therapeutic agent

After nearly 20 years of development, humanized monoclonal anti-IgE antibodies have been shown in about 20 phase II and III clinical trials to be effective and safe in treating allergic asthma, perennial and seasonal allergic rhinitis, and allergic reactions to peanuts. Omalizumab has been approved in the United States, European Union, and several other countries for treating patients 12 years and older with moderate-to-severe allergic asthma. Although anti-IgE is often referred to as an IgE-neutralizing antibody and can block IgE's binding to high-affinity IgE Fc receptors (FcepsilonRI) on mast cells and basophils, it has multiple immunoregulatory effects. One such effect is that as the result of depleting free IgE, FcepsilonRI on mast cells and basophils is downregulated to less than 5% within a few weeks to a few months of anti-IgE treatment. This renders the mediator-packed inflammatory cells insensitive to allergen stimulation. Hence this therapeutic anti-IgE represents a new class of mast cell-stabilizing agents, reducing FcepsilonRI density on mast cells and basophils and causing them to be insensitive to allergens. This mechanism contrasts with that of cromones, mast cell-stabilizing agents that retard Ca++ mobilization and the degranulation process, thus deflating the intracellular activation signal triggered by IgE-FcepsilonRI aggregation.     

Autoantibodies to the high-affinity IgE receptor in children with chronic urticaria.

BACKGROUND: Chronic urticaria (CU) in childhood remains a challenge for investigation, and its etiology is largely unknown. Autoantibodies to the high-affinity IgE receptor (FcepsilonRI) are believed to play a role in the pathogenesis of this disease in adults. OBJECTIVE: To determine the prevalence of autoantibodies to FcepsilonRIalpha on basophils in children with CU vs atopic eczema dermatitis syndrome (AEDS). METHODS: Eighty children with CU were compared with 38 children with AEDS. In addition to complete blood cell counts and total IgE measurements, CAP-RASTs to egg, codfish, soy, milk, and peanut were performed. Stool samples were examined for parasites, and autologous serum skin testing and a functional anti-FcepsilonRIalpha assay were conducted to detect autoantibodies. RESULTS: No significant differences were observed between children with CU and controls in mean basophil or eosinophil counts. Twenty (26%) of 77 children with CU and 31 (82%) of 38 with AEDS had positive CAP-RAST results (P < .001). Only 2.5% of the children with CU and 0% with AEDS had stool samples positive for parasites (P = .005). Anti-FcepsilonRIalpha autoantibodies were positive in 37 (47%) of 78 children with CU and in none of 33 with AEDS. Non-IgG histamine-releasing factors were found in 10 (13%) of 78 children with CU. CONCLUSIONS: Children have a similar prevalence of autoantibodies to the FcepsilonRIalpha as has been previously published for adults. Few have type I allergies, and parasite infestation is also uncommon. Further studies are required to investigate the predictive value of the autoantibodies in these children with respect to clinical profile, requirements for medications other than antihistamines, and remission rates.     

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.     

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.     

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.     

Effect of omalizumab on patients with chronic urticaria.

BACKGROUND: Chronic urticaria (CU) is often difficult to treat. Approximately 40% to 50% of patients with no apparent cause are believed to have an associated autoimmune profile that may play a pathogenetic role. OBJECTIVES: To describe 3 patients with CU refractory to conventional treatment who responded to omalizumab therapy. METHODS: Treatment was maximized with antihistamines, antileukotrienes, and histamine2 blockers with no improvement. Systemic steroids provided only temporary relief. Laboratory workup revealed 1 patient with a low IgE level and elevated anti-IgE receptor antibody level, 1 patient with an elevated IgE level but a normal anti-IgE receptor antibody level, and 1 patient with a very elevated IgE level and an elevated anti-IgE receptor antibody level. All 3 patients were prescribed omalizumab therapy every 2 weeks. RESULTS: Two patients had total clearing of urticaria within 1 week and 1 patient within 6 weeks of starting omalizumab therapy. The patient with the elevated anti-IgE receptor antibody level had normalization of the level after starting treatment. CONCLUSIONS: Omalizumab may have a beneficial effect in the treatment of CU. Further studies are needed to confirm this effect and better elucidate the mechanism for the observed improvement.     

Efficacy and safety of a recombinant anti-immunoglobulin E antibody (omalizumab) in severe allergic asthma

BACKGROUND: Patients with severe asthma are often inadequately controlled on existing anti-asthma therapy, constituting an unmet clinical need. OBJECTIVE: This randomized, double-blind, placebo-controlled trial evaluated the ability of omalizumab, a humanized monoclonal anti-IgE antibody, to improve disease control sufficiently to enable inhaled corticosteroid reduction in patients with severe allergic asthma. METHODS: After a run-in period when an optimized fluticasone dose (> or =1000 microg/day) was received for 4 weeks, patients were randomized to receive subcutaneous omalizumab [minimum 0.016 mg/kg/IgE (IU/mL) per 4 weeks; n=126] or matching placebo (n=120) at intervals of 2 or 4 weeks. The study comprised a 16-week add-on phase of treatment followed by a 16-week fluticasone-reduction phase. Short-/long-acting beta(2)-agonists were allowed as needed. RESULTS: Median reductions in fluticasone dose were significantly greater with omalizumab than placebo: 60% vs. 50% (P=0.003). Some 73.8% and 50.8% of patients, respectively, achieved a > or =50% dose reduction (P=0.001). Fluticasone dose reduction to < or =500 microg/day occurred in 60.3% of omalizumab recipients vs. 45.8% of placebo-treated patients (P=0.026). Through both phases, omalizumab reduced rescue medication requirements, improved asthma symptoms and asthma-related quality of life compared to placebo. CONCLUSION: Omalizumab treatment improves asthma control in severely allergic asthmatics, reducing inhaled corticosteroid requirements without worsening of symptom control or increase in rescue medication use.     

Omalizumab, an anti-IgE antibody, in the treatment of adults and adolescents with perennial allergic rhinitis.

BACKGROUND: Treatment with omalizumab, an anti-IgE antibody, improves symptoms and quality of life in patients with seasonal allergic rhinitis but has not previously been investigated in patients with perennial symptoms. OBJECTIVE: To investigate the efficacy, safety, and tolerability of omalizumab in the treatment of perennial allergic rhinitis (PAR). METHODS: Two hundred eighty-nine patients (aged 12 to 70 years) with moderate-to-severe symptomatic PAR were randomized to 16 weeks' double-blind subcutaneous treatment with either placebo (n = 145) or omalizumab (at least 0.016 mg/kg/IgE [IU/mL] per 4 weeks; n = 144). The primary efficacy variable was the mean daily nasal severity score, as determined from patient daily diary cards. Secondary efficacy variables included use of rescue antihistamine, rhinoconjunctivitis-specific quality of life (RQoL), and patients' evaluation of treatment efficacy. Safety and tolerability were evaluated from adverse event reports and laboratory safety parameters. RESULTS: Throughout 16 weeks of treatment, the mean daily nasal severity score was significantly lower in omalizumab-treated patients than with placebo (P < 0.001). The improvement in symptoms when taking omalizumab was paralleled by a reduction in use of rescue antihistamine (P < or = 0.005 overall) and improved RQoL relative to placebo. Patients' evaluation of treatment efficacy significantly favored omalizumab over placebo (P = 0.001). Omalizumab therapy was well tolerated. There were no safety concerns. CONCLUSIONS: Omalizumab was safe and well tolerated in the treatment of patients with PAR, providing effective control of symptoms and improved RQoL while simultaneously minimizing reliance on rescue antihistamines.     

The effect of omalizumab on nasal allergic inflammation

BACKGROUND: In sensitized patients, coupling between IgE and FcepsilonRI receptors on mast cells leads to release of proinflammatory mediators and a subsequent influx of inflammatory cells to the affected organ. Omalizumab (Xolair; formerly rhuMAb-E25) binds to circulating IgE, thus preventing induction of the allergic process. OBJECTIVE: We investigated the effect of treatment with omalizumab on seasonal allergic rhinitis and related changes in inflammatory cell numbers in nasal biopsy specimens. METHODS: Patients were randomized to treatment with omalizumab or placebo before the pollen season; the treatment was started and continued during season. Symptoms and use of medication were recorded, and blood samples and nasal biopsy specimens were obtained before and during season. Immunocytochemistry was performed on biopsy sections through use of the following antibodies: anti-CD4, CD8 (T lymphocytes), EG2, and anti-eosinophil peroxidase (eosinophils), anti-tryptase (mast cells), human neutrophil lipocalin (neutrophils), and antibodies against IgE and FcepsilonRI. RESULTS: During the season, blood eosinophils increased in placebo-treated patients but not in omalizumab-treated patients (P =.01); the difference between the treatment groups was significant (P =.04). Free IgE in serum decreased significantly (P =.0002) in omalizumab-treated patients but not in placebo-treated patients; the difference between the groups was significant (P =.0001). In nasal biopsy specimens, the number of eosinophil peroxidase-positive staining cells increased in the placebo-treated patients (P =.003) but not in the actively treated patients during the season; the difference between the groups was significant (P =.0001). The number of IgE(+) staining cells decreased significantly in the omalizumab group during the season in comparison with the placebo group (P =.04). CONCLUSION: The clinical benefit of treatment with omalizumab is associated with an anti-inflammatory effect on cellular markers in blood and nasal tissue.     

Omalizumab, anti-IgE recombinant humanized monoclonal antibody, for the treatment of severe allergic asthma

BACKGROUND: A recombinant humanized anti-IgE mAb, omalizumab, forms complexes with free IgE, blocking its interaction with mast cells and basophils; as a consequence, it might be effective in the treatment of asthma. OBJECTIVE: The purpose of this study was to evaluate the efficacy and safety of omalizumab in the treatment of inhaled corticosteroid-dependent asthma. METHODS: In this phase III, double-blinded, placebo-controlled trial, 525 subjects with severe allergic asthma requiring daily inhaled corticosteroids were randomized to receive placebo or omalizumab subcutaneously every 2 or 4 weeks, depending on baseline IgE level and body weight. Inhaled corticosteroid doses were kept stable over the initial 16 weeks of treatment and tapered during a further 12-week treatment period. RESULTS: Omalizumab treatment resulted in significantly fewer asthma exacerbations per subject and in lower percentages of subjects experiencing an exacerbation than placebo treatment during the stable steroid phase (0.28 vs 0.54 [P =.006] and 14.6% vs 23.3% [P =.009], respectively) and during the steroid reduction phase (0.39 vs 0.66 [P =.003] and 21.3% vs 32.3% [P =.004], respectively). Beclomethasone dipropionate reduction was significantly greater with omalizumab treatment than with placebo (median 75% vs 50% [P <.001]), and beclomethasone dipropionate discontinuation was more likely with omalizumab (39.6% vs 19.1% [P <.001]). Improvements in asthma symptoms and pulmonary function occurred along with a reduction in rescue beta-agonist use. Omalizumab was well tolerated, with an adverse-events profile similar to that of placebo. CONCLUSION: The addition of omalizumab to standard asthma therapy reduces asthma exacerbations and decreases inhaled corticosteroid and rescue medication use.     

Mast cells express IL-13R alpha 1: IL-13 promotes human lung mast cell proliferation and Fc epsilon RI expression

BACKGROUND: The Th2 cytokine interleukin (IL)-13 is implicated in the development of various allergic diseases including asthma. The IL-13 receptor, IL-13Ralpha1, is expressed on most leukocytes, except T-cells. Evidence to support IL-13Ralpha1 expression on mast cells is limited. METHODS: We investigated: (i) IL-13Ralpha1 expression by human lung mast cells (HLMC); (ii) the number of IL-13Ralpha1+ bronchial submucosal mast cells in subjects with asthma and normal controls and (iii) the effect of IL-13 priming on HLMC expression of high-affinity IgE receptor (FcepsilonRI), stem cell factor receptor (CD117), histamine release, proliferation, and survival. RESULTS: Human lung mast cell expressed IL-13Ralpha1 mRNA. IL-13Ralpha1 was highly expressed on the surface HLMC (82+/-9%). Bronchial submucosal mast cell IL-13Ralpha1 expression was higher in asthmatics (86+/-2%) than normal controls (78+/-2%; P=0.015). IL-13 priming for 30 min did not increase HLMC histamine release, in the presence or absence of SCF or in response to IgE/anti-IgE activation. IL-13 priming for 5 days upregulated HLMC FcepsilonRI expression (22% increase in fluorescent intensity; P=0.003), increased histamine release following IgE/anti-IgE activation by 56% (P=0.03) and increased proliferation by 50% (P=0.003) without affecting cell survival or CD117 expression. The IL-13 specific neutralizing antibody CAT-354 inhibited all IL-13 mediated effects. CONCLUSION: Human lung mast cell express IL-13Ralpha1 and activation by IL-13 for 5 days increased FcepsilonRI expression and proliferation. Histamine release was not affected by short-term priming with IL-13, but was upregulated by priming for 5 days suggesting that this effect was mediated by the increased FcepsilonRI expression. These data support the view that targeting IL-13 may be beneficial in the treatment of asthma.     

Human dendritic cell 1 and dendritic cell 2 subsets express FcepsilonRI: correlation with serum IgE and allergic asthma

BACKGROUND: Type 1 dendritic cells (DC1) express the high-affinity IgE receptor (FcepsilonRI); however, the regulation of FcepsilonRI expression by DCs is not well understood. Type 2 DC (DC2) expression of FcepsilonRI has not been demonstrated. OBJECTIVE: We hypothesized that DC2 cellsalso express FcepsilonRI and that expression of FcepsilonRI by the DC1 and DC2 subsets correlates with serum IgE and allergic asthma disease status. METHODS: To test these hypotheses, we quantitated FcepsilonRI alpha chain expression by the peripheral blood precursor DC1 (pDC1) and pDC2 subsets by using flow cytometry. RESULTS: FcepsilonRI was expressed by the pDC1 and pDC2 subsets, as well as tissue DCs from tonsils. Relative FcepsilonRI expression by basophil, pDC1, and pDC2 subsets was 12:6.5:1, respectively. In both pDC subsets, FcepsilonRI expression was significantly greater in allergic asthmatic subjects than in nonatopic control subjects. pDC1 and pDC2 expression of FcepsilonRI was highly correlated to serum IgE concentration. The pDC1, pDC2, and basophil subsets demonstrated a similar magnitude of increase in FcepsilonRI expression relative to changes in serum IgE. CONCLUSIONS: FcepsilonRI expression is characteristic of both the DC1 and DC2 subsets. Furthermore, FcepsilonRI expression by these cells is highly correlated to serum IgE and to basophil FcepsilonRI expression and is greater in subjects with allergic asthma. These data support the concept that novel therapeutic approaches directly targeted at FcepsilonRI expression would affect both the sensitization and the effector phases of the allergen-specific immune response.     

Decrease in reactivity of basophils by immunotherapy with housedust extract

Changes of basophil reactivity to housedust extract and anti-IgE during immunotherapy was examined in thirteen patients with bronchial asthma sensitive to housedust. (i) A significant decrease in the morphological reactivity of basophils to housedust extract was observed 6 months after the beginning of immunotherapy with the antigen, and a significant decrease after 12 and 18 months’ therapy, accompanied with the decrease of histamine release from the cells. The percent reactive basophils to the antigen decreased from 59.2 ± 2.9% before the therapy to 40.0 ± 1.8% after 18 months’immunotherapy. (ii) A decrease in the morphological reactivity of basophils to anti-IgE was also shown during immunotherapy. The basophil reactivity to anti-IgE decreased significantly at the late stage (18 months) of immunotherapy. (iii) A significant reduction of specific IgE antibody to housedust was observed 12 and 18 months after the beginning of immunotherapy. It was suggested from these results that immunotherapy causes some changes on the surface of basophils and decreased reactivity of the cells, and that a decrease of reactive basophils to anti-IgE in the process of immunotherapy might be due to a decrease in number of IgE receptors essentially or functionally.     

CD‐sens: a biological measure of immunological changes stimulated by ASIT

Background: Allergen‐specific immunotherapy (ASIT) in allergic rhinitis and asthma is the only treatment that effects the long‐term development of these diseases. Basophil allergen threshold sensitivity, CD‐sens, which is a valuable complement to resource‐demanding clinical challenge tests, was used to monitor the initiation of ASIT induced allergen ‘blocking activity’. Methods: Patients IgE‐sensitized to timothy (n = 14) or birch (n = 19) pollen were started on conventional (8–16 weeks) or ultra rush ASIT, respectively, and followed by measurements of CD‐sens, allergen binding activity (ABA) and serum IgG4‐ and IgE‐antibody concentrations. Results: CD‐sens decreased during the early phase of ASIT‐treatment. In parallel, ABA increased and correlated significantly with the increasing levels of IgG4 antibody concentrations. High dosages of allergen were more effective while mode of dosing up did not seem to matter. No change was seen in basophil reactivity. Conclusion: CD‐sens and ABA, in contrast to basophil reactivity, seem to be promising tools to monitor protective immune responses initiated by ASIT.     

Rat monoclonal anti-murine IgE antibody removes IgE molecules already bound to mast cells or basophilic leukemia cells,resulting in the inhibition of systemic anaphylaxis and passive cutaneous anaphylaxis

IgE plays a central role in allergic reactions. Some anti-IgE antibodies (HMK-12, 6HD5) inhibit the binding of IgE to the FcepsilonRI of mast cells/basophilic leukemia cells (PT-18, RBL/2H3), but less inhibition is seen with the anti-allotypic JKS-6 and the anti-idiotypic Eb-1. Anti-IgE HMK-12 can detach bound IgE molecules from the FcepsilonRI. When mast cells or basophils were incubated with monoclonal anti-DNP-IgE SPE-7, washed and treated with anti-IgE HMK-12, anti-IgE/IgE complexes were found in the supernatant. Similar results were obtained with the Fab fragment of HMK-12. Mice injected with anti-DNP-IgE SPE-7 and later with DNP-BSA had the typical systemic anaphylactic shock. However, if they were injected with the anti-IgE antibody (HMK-12) before the challenge, they did not get an anaphylactic shock. In the sera of mice injected with monoclonal IgE SPE-7 and anti-IgE antibody (HMK-12), IgE/anti-IgE complexes were detected. No passive cutaneous anaphylaxis occurred if the rats were injected with anti-IgE antibodies before the challenge. In summary, anti-IgE antibodies can remove IgE antibodies from the FcepsilonRI; anti-IgE/IgE complexes can be detected in vitro and in vivo, and anti-IgE antibodies can inhibit IgE-mediated systemic or local anaphylactic reactions.