Cross-linking of IgE-receptor complexes at the cell surface: synthesis and characterization of a long bivalent hapten that is capable of triggering mast cells and rat basophilic leukemia cells

The ability of a series of bivalent haptens to bind and cross-link immunoglobulin E (IgE) in solution and on the surface of cells was examined. Several short (less than 30 A) dinitrophenyl (DNP) haptens were found to bind tightly to and cross-link a monoclonal anti-DNP IgE in solution, but these failed to trigger substantial release of 3H-serotonin from sensitized rat basophilic leukemia (RBL) cells or rat peritoneal mast cells. A longer bivalent hapten, approximately 50 A in length, consisting of two DNP-aminocaproyl-L-tyrosine (DCT) groups coupled to the alpha-amino groups of L-cystine was synthesized and characterized. This bivalent hapten [(DCT)2-cystine], binds very tightly to the same monoclonal anti-DNP IgE in solution and cross-links these antibodies to form higher mol. wt aggregates as judged by gel filtration and binding studies. It also stimulates degranulation of both RBL and mast cells sensitized with two different monoclonal anti-DNP IgE antibodies, with the mast cells exhibiting generally greater responsiveness to this ligand. The (DCT)2-cystine bivalent hapten appears to have the structural features necessary for carrying out detailed binding studies with receptor-bound IgE on the cell surface.     

Monomer hapten and hapten‐specific IgG inhibit mast cell activation evoked by multivalent hapten with different mechanisms

Aggregation of IgE bound to high affinity IgE receptor (FcεRI) by multivalent antigen induces mast cell activation. Reportedly, disaggregation of aggregated FcεRI immediately terminated degranulation, and formation of co‐ligated FcεRI and low affinity IgG receptor FcγRIIB blocked degranulation by inhibitory signal via SH2‐containing inositol 5’‐phosphatase 1 (SHIP1) phosphorylation. However, their molecular mechanisms to inhibit mast cell activation have been unclear in detail. Herein, we found that addition of excess monomeric hapten (TNP‐alanine) to multivalent antigen (TNP‐OVA)‐activated rat basophilic leukemia cells and mouse bone marrow‐derived mast cells induced immediate and transient Syk dephosphorylation, which was previously phosphorylated by TNP‐OVA addition. Syk dephosphorylation correlated to rapidly decreased intracellular Ca²⁺ concentrations ([Ca²⁺]_i), terminated degranulation, and suppressed cytokine production through inhibition of Akt and ERK phosphorylation. Addition of hapten‐specific IgG monoclonal antibody (anti‐TNP IgG1) to activated mast cells induced translocation of SHIP1 to the plasma membrane and its phosphorylation, indicating that co‐ligation of FcεRI and FcγRIIB after FcεRI aggregation can lead to SHIP1 activation. SHIP1 phosphorylation led to gradually decreased [Ca²⁺]_i, weak inhibition of degranulation, and strong inhibition of cytokine production. Our findings clearly show the inhibitory mechanism of cell function in activated mast cells by operating Fc receptor crosslinking.     

RBL cells expressing human Fc epsilon RI are a sensitive tool for exploring functional IgE-allergen interactions: studies with sera from peanut-sensitive patients

Rat basophilic leukemia cells (RBL SX-38) express the alpha, beta, and gamma chains of human Fc epsilon RI. Following sensitization with IgE from a subset of allergic human donors, these cells can be triggered by exposure to anti-IgE or to very low concentrations of specific allergens. We examined 18 sera from patients who were highly sensitive to peanuts by history and had anti-peanut IgE by in vitro testing. The ability of these sera to sensitize the RBL SX-38 cells for degranulation with peanut allergens correlates very well with the absolute amount of anti-peanut IgE (r=0.95; p<0.001). The most effective sera contained at least 50 kU/l of total IgE and at least 15 kU/l of peanut-specific IgE. RBL SX-38 cells sensitized with these sera degranulated optimally upon exposure to anti-IgE (net degranulation of 40+/-8%, means+/-S.D.; n=8) and to a 10(5)-10(6) dilution of crude peanut extract (CPE) (37+/-7% net degranulation; 93+/-13% of that seen with anti-IgE). This assay is quite sensitive. Cells sensitized with selected sera are activated by exposure to a 1:10(7) dilution of the CPE containing picogram amounts of peanut allergens. This assay is also quite specific. Cells sensitized with sera from patients with anti-peanut IgE and no detectable IgE against soybean, walnut or grass pollen did not degranulate following exposure to these latter antigens. The converse was also true; cells sensitized with sera from patients without anti-peanut IgE did not react to peanut. These data demonstrate that RBL cells expressing human Fc epsilon RI form the basis of a useful model system for the detection of allergens and for the study of IgE-allergen interactions.     

Aspergillus oryzae lectin induces anaphylactoid oedema and mast cell activation through its interaction with fucose of mast cell-bound non-specific IgE

We investigated whether Aspergillus oryzae lectin (AOL), a fucose-specific lectin, induces anaphylactoid reactions and mast cell activation. The injection of AOL into footpads of mice produced a dose-related acute paw oedema. The AOL-induced oedema was attenuated by predose of histamine H1 receptor blocker or pretreatment of the lectin with fucose before injection and was not observed in SCID and mast cell-deficient WBB6F1-W/Wv mice. These results suggested that the AOL-induced anaphylactoid reaction was mediated by histamine released from mast cells. In addition, the activation of mast cells was seemed to be induced by the crosslinking of IgE on the cell surface following the binding of AOL to fucose residues in IgE. Consistent with the in vivo results, AOL induced the degranulation of the rat mast cell line RBL2H3 sensitized with monoclonal IgE. As AOL induced the increase in intracellular Ca(2+) concentration of IgE-sensitized RBL2H3 cells as well as antigen stimulation, AOL could input signals from FcεRI. The degranulation of IgE-sensitized RBL2H3 cells by AOL was diminished by pretreatment of AOL with fucose. Defucosylated IgE did not induce degranulation of RBL2H3 cells in response to AOL stimulation, in spite of its ability to induce degranulation by antigen stimulation as intact IgE. These results indicated that AOL bound to fucose residue of IgE causing antigen-independent IgE-mediated mast cell activation and anaphylactoid reactions in vitro and in vivo, respectively. AOL bound to human IgE as well as to mouse IgE, suggesting the possible implication of AOL in the allergic response to Aspergillus oryzae in humans.     

A novel in vitro assay for mouse IgE

A simple and sensitive assay for screening mouse IgE-producing hybridomas is described. Rat basophil leukemia (RBL) cells (either live or glutaraldehyde fixed) were sensitized by mouse monoclonal IgE and then rosetted with antigen-coated sheep red blood cells. The assay is established using a mouse monoclonal IgE anti-DNP and was able to detect as little as 5 ng/ml IgE. The rosette assay is also a useful technique for studying the binding of mouse IgG monoclonal (MC) antibodies to RBL cells.     

Activation and hapten inhibition of mast cells sensitized with monoclonal IgE anti-penicillin antibodies: evidence for two-site recognition of the penicillin derived determinant

We utilized an in vitro mast cell activation assay and hapten inhibition of mediator release to characterize the fine specificity of two IgE anti-penicillin monoclonal antibodies (mAb). Cultured mouse mast cells were passively sensitized with IgE mAb anti-benzylpenicillin (BP) or anti-amoxicillin (AX) and challenged with a range of penicillin-human serum albumin (HSA) conjugates. Mast cells sensitized with IgE anti-BP degranulated in response to BP-HSA, but not to AX-HSA or ampicillin(AMP)-HSA, whereas mast cells sensitized with IgE anti-AX responded to AX-HSA but not to BP-HSA or AMP-HSA. Because BP, AX and AMP differ chemically only in the structure of their side chain, these results show that this part of the drug molecule is essential for recognition by IgE antibody. Unexpectedly, although IgE-sensitized mast cells responded to only one penicillin in protein-conjugated form, antigen-induced degranulation was inhibited by the monomeric derivative of more than one penicillin. Furthermore, antigen activation of IgE-sensitized cells was inhibited, although less potently, by haptens representative of the specific penicillin side chain or the binuclear portion of the drug molecule. These patterns of recognition and hapten inhibition were also seen in solid-phase enzyme-linked immunosorbent assay (ELISA), although all haptenic inhibitors were approximately 100 times less potent in the ELISA compared to the mast cell assay. To explain these findings we propose a model in which IgE binding to penicillin-protein antigen is dependent on recognition of two distinct epitopes on the drug molecule: the first comprising the side chain, and the second comprising the binuclear portion plus the proximal region of the side chain. This two-site hypothesis provides a generally applicable model of antibody recognition of penicillins and provides a rational basis for understanding the specificity and cross-reactivity of IgE-mediated allergic reactions to penicillins.     

Differential induction of anti-trinitrophenyl plaque-forming cell responses to lightly and heavily conjugated trinitrophenylated heterologous and autologous erythrocytes in mice

Various anti-TNP PFC (2,4,6-trinitrophenyl plaque-forming cell) responses were obtained by injecting C3H mice with different conjugates of trinitrophenylated sheep red cells (TNP-SRC). Mice which were injected with lightly conjugated TNP-SRC (TNP_0.14SRC) produced indirect anti-TNP PFC 4 days after injection, while mice which were injected with heavily conjugated TNP-SRC (TNP₁₄SRC) produced both direct and indirect anti-TNP PFC or direct anti TNP PFC only. Heavily conjugated trinitrophenylated autologous mouse red cells elicited a low direct anti-TNP PFC response 4 days after injection. The system is another example of the capacity to modify antibody responses by modification of the antigen.     

Interleukin-2-inducible T cell kinase regulates mast cell degranulation and acute allergic responses

Bruton's tyrosine kinase (Btk) is thought to positively regulate mast cell activation, implying a role in allergic responses. We have compared acute and late phase allergic airway reactions in mice lacking either Btk or interleukin-2-inducible T cell kinase (Itk), another Tec kinase expressed in mast cells. Btk(-/-) mice showed minor protection against allergic symptoms when challenged with allergen via the airways. In sharp contrast, both acute and late phase inflammatory allergic responses were markedly reduced in Itk(-/-) mice. Notably, airway mast cell degranulation in Itk(-/-) mice was severely impaired, despite wild-type levels of allergen-specific IgE and IgG1. The degranulation defect was confirmed in DNP-conjugated human serum albumin-challenged mice passively sensitized with anti-DNP IgE antibodies, and was also observed after direct G-protein stimulation with the mast cell secretagogue c48/80. Moreover, late phase inflammatory changes, including eosinophilia, lymphocyte infiltration, and Th2 cytokine production in the lungs, was eliminated in Itk(-/-) mice. Collectively, our data suggest a critical role of Itk in airway mast cell degranulation in vivo that together with an impaired T cell response prevents the development of both acute and late phase inflammatory allergic reactions.     

Anti-anti-IgE idiotypic antibodies mimic IgE in their binding to the Fc epsilon receptor

The binding site of some anti-idiotypic antibodies (anti-Id) can appear as a structural image of the antigen and as such may mimic its biologic activity. We raised anti-anti-IgE antibodies in an attempt to obtain anti-Id capable of interacting with the Fc epsilon receptor (Fc epsilon R). Guinea pigs were immunized with purified murine monoclonal antibodies (mAb) that had been found to react with epitopes closely related to the site on the IgE molecule which is recognized by the Fc epsilon R. After only two injections, we could detect in the immune sera anti-Id that inhibited the binding of IgE to the anti-IgE mAb used as immunogens. However, only after 10 immunizations over a period of about 6 months could we detect antibodies that competed efficiently with the binding of IgE to rat basophilic leukemia (RBL) cells. The "IgE-like" anti-Id could be affinity purified from immunosorbents made of the anti-IgE mAb. F(ab')2 and Fab' fragments were as effective inhibitors of IgE binding as the intact anti-anti-Id antibodies. Some of the anti-Id caused RBL degranulation and all of them, like IgE, inhibited the binding of specific anti-Fc epsilon R mAb to RBL cells. In summary, by hyperimmunization with anti-IgE mAb we could obtain anti-Id whose antigen-binding site is recognized by the mast cell receptor specific to the Fc portion of IgE.     

In vitro assessment of the allergenicity of novel MF59-adjuvanted pandemic H1N1 influenza vaccine produced in dog kidney cells

A licensed inactivated MF59-adjuvanted seasonal influenza vaccine (Optaflu) produced in canine kidney cells (MDCK 33016-PF) contained no egg proteins and did not trigger degranulation in rat basophilic leukemia (RBL) cells passively sensitized with human anti-dog IgE, supporting its safe use in dog-allergic individuals. The cell-derived pandemic H1N1 influenza vaccine was also adjuvanted with the emulsion adjuvant MF59, and support for its similar safe use was sought. We sought to evaluate in vitro allergenicity of the MF59-adjuvanted cell-derived pandemic H1N1 influenza vaccine in subjects with dog allergy, with a mediator release assay. RBL-2H3 cells transfected with human Fcε receptor type 1 were sensitized with sera from adult dog-allergic subjects and stimulated with serial dilutions of pandemic H1N1 influenza vaccine and dog dander extract. β-N-hexosaminidase release (NHR) was used as a marker of RBL degranulation.. Median dog dander-specific IgE in 30 dog-allergic subjects was 27.7 kUA/L (range 10.1; > 100); and in 5 dog non-allergic subjects was < 0.35 kUA/L (UniCAP system). Median (range) maximum NHR in dog-allergic subjects was: pandemic H1N1 influenza vaccine 1.1% (0; 4.4) and dog dander 6.9% (0.7; 37.3), P < 0.001. In conclusion, MF59-adjuvanted pandemic H1N1 influenza vaccine produced in continuous canine kidney cells did not trigger degranulation in RBL cells passively sensitized with human anti-dog IgE, supporting its safe use in dog-allergic individuals.     

Inhibition of IgE binding to mast cells and basophils by monoclonal antibodies to murine IgE

In an attempt to identify the site on IgE which binds with high affinity to the Fc? receptor (Fc?R) on mast cells, we established monoclonal anti-IgE antibodies (mAb) by fusion of myeloma cells with rat splenocytes immunized with purified murine IgE mAb. Six individual mAb were found to react with various IgE mAb of different specificities and not with immunoglobulins of other classes. Three different clusters of epitopes on the Fc? portion could be detected by antibody competition studies. These antigenic determinants were expressed on the Fc? portion and required the two heavy chains in their native conformation. Two groups of mAb and their Fab′ fragments completely inhibited the binding of ¹²⁵I-labeled IgE to rat basophilic leukemia cells (RBL), and one mAb inhibited the specific IgE binding only partially (55–65%). Likewise, the Fab′ fragments of the purified mAb inhibited the antigen-mediated, IgE-dependent, serotonin release of RBL cells. These in vitro findings were confirmed by in vivo experiments, which demonstrated that the anti-IgE mAb could specifically block passive cutaneous anaphylaxis reaction when injected i.d., before challenging with the antigen. The differences in blocking reactivity of the various anti-IgE mAb are discussed in view of heterogeneity in the IgE-Fc?R interaction.     

The Effect of Disodium Cromoglycate on In Vitro Mast Cell Degranulation in Human Jejunal Mucosa

The in vitro effect of disodium cromoglycate (DSCG) on IgE antigen-induced mast cell degranulation is described. Serum from an egg white allergic patient was used to sensitize jejunal mucosa from nine individuals. Egg white was used to challenge the IgE sensitized mast cells. DSCG in concentrations 3 x 10(-7) M to 3 x 10(-4) M was added to the mucosal specimens before antigen challenge. Mast cell degranulation in the sensitized specimens challenged with egg white was 38%. Mast cell degranulation in sensitized specimens treated with DSCG before and during antigen challenge was reduced to 2% at a concentration of 3 x 10(-5) M of DSCG (P=0.006) and to 28% at a concentration of 3 x 10(-6) M (P=0.027). No significant reduction of mast cell degranulation was seen at concentrations of 3 x 10(-7) M and 3 x 10(-4) M. The results support a role for DSCG in the treatment of gastrointestinal allergy.     

Ligation of IgE receptors causes an anaphylactic response and neutrophil infiltration but does not induce eosinophilic inflammation in mice

Background: Eosinophils are selectively recruited into the tissues during chronic allergic inflammation. IgE is considered an initiator of the allergic reaction; however, the roles of IgE in allergic inflammation are not fully understood. Objective: We tested the hypothesis that antigen interaction with specific IgE antibody provokes eosinophilic inflammation. Methods: BALB/c mice were actively sensitized with ragweed extract and passively sensitized with anti-dinitrophenyl (anti-DNP) mouse IgE and challenged intraperitoneally by injecting either ragweed extract or DNP-ovalbumin (OVA). Immediate anaphylactic responses were examined by monitoring vascular permeability and by measuring histamine content in peritoneal lavage fluids. Late-phase allergic responses were examined by total cell counts and cell differentials. Results: Mice sensitized and challenged with ragweed showed immediate anaphylactic responses followed by temporal increases in neutrophils at 3 to 12 hours and sustained ncreases in eosinophils in their peritoneal cavities after 24 hours. Double-sensitized mice (ie, sensitized actively for ragweed and passively for DNP-OVA) challenged with ragweed showed immediate anaphylactic responses and peritoneal eosinophilia at 48 hours. Double-sensitized mice challenged with DNP-OVA showed comparable immediate anaphylactic responses but no peritoneal eosinophilia. Furthermore, at 8 hours, ragweed-challenged animals recruited both eosinophils and neutrophils, but DNP-OVA–challenged animals recruited only neutrophils. Finally, after active sensitization and challenge with ragweed, mast cell–deficient mice (WBB6F1-W/W^v) lacked the immediate response but showed comparable eosinophil accumulation as their litter mate controls (WBB6F1-+/+). Conclusion: Interaction of antigen with IgE antibody is insufficient to provoke eosinophilic inflammation in mice. (J Allergy Clin Immunol 2000;105:1202-10.)     

The stimuli releasing histamine from murine bone marrow-derived mast cells. 1. The presence of P2-purinoceptors

We have examined the histamine-releasing effects of 4 different stimuli on murine bone marrow-derived mast cells (BMMC). We obtained 10(9) BMMC from one femur of a CBA/J mouse when it was cultured in the presence of conditioned medium from WEHI-3 cells for 4 weeks. When these cells were sensitized with monoclonal anti-DNP IgE antibodies, DNP35HSA antigen, ionomycin, thrombin and ATP induced 70%, 70%, 40% and 60% histamine release from BMMC, respectively. Thrombin induced rapid degranulation, whereas the kinetics of histamine release by other stimuli reached a plateau after 5 min. ADP, AMP and GTP as well as ATP but not adenosine caused histamine release from BMMC, suggesting the presence of P2-purinoceptors on these cells.     

Detection of human IgE antibody by a modified rat mast cell degranulation technique

A rat mast cell degranulation (R.M.C.D.) technique is described in detail. This method is shown to detect specific antibodies to rye grass pollen and purified factors thereof (rye Group I antigen). The antibody detected belongs to the IgE immunoglobulin class as evidenced by specific degranulation when the rat mast cells are passively sensitized with the sensitive subject''s serum and challenged with a monospecific rabbit antimyeloma IgE antiserum. No significant mast cell degranulation is observed with serum alone, antigen alone, or when anti-IgG, IgA or IgM are used in this system in an appropriate set of controlled experiments.     

A canine model for reaginic hypersensitivity and allergic bronchoconstriction

Immunization of neonatal dogs with a conjugate of 2,4-dinitrobenzene and ovalbumin (DNP₂-OA), using aluminum hydroxide as the adjuvant, elicited long-lasting (over 30 wk) anti-DNP and anti-OA IgE antibody responses of high titers as determined by homologous passive cutaneous anaphylaxis. Low antigen doses of 10 or 50 μg were more effective than the higher doses of 250 or 1,250 μg in inducing high IgE antibody levels. However, this method of immunization failed to elicit any detectable IgE antibody response in adult dogs. Bronchoprovocation with antigen of sensitized animals having IgE antibody titers in excess of 64 resulted in a marked increase in airflow resistance, which could be corrected by the administration of nebulized isoproterenol. On the other hand, sensitized animals with IgE antibody titers in the order of 64 did not manifest significant bronchoconstriction on inhalation challenge but developed anaphylaxis following intravenous injection of the antigen.     

Lactobacillus buchneri S-layer as carrier for an Ara h 2-derived peptide for peanut allergen-specific immunotherapy

Peanut allergy is an IgE-mediated severe hypersensitivity disorder. The lack of a treatment of this potentially fatal allergy has led to intensive research on vaccine development. Here, we describe the design and initial characterization of a carrier-bound peptide derived from the most potent peanut allergen, Ara h 2, as a candidate vaccine. Based on the adjuvant capability of bacterial surface (S-) layers, a fusion protein of the S-layer protein SlpB from Lactobacillus buchneri CD034 and the Ara h 2-derived peptide AH3a42 was produced. This peptide comprised immunodominant B-cell epitopes as well as one T cell epitope. The fusion protein SlpB-AH3a42 was expressed in E. coli, purified, and tested for its IgE binding capacity as well as for its ability to activate sensitized rat basophil leukemia (RBL) cells. The capacity of Ara h 2-specific IgG rabbit-antibodies raised against SlpB-AH3a42 or Ara h 2 to inhibit IgE-binding was determined by ELISA inhibition assays using sera of peanut allergic patients sensitized to Ara h 2. IgE specific to the SlpB-AH3a42 fusion protein was detected in 69% (25 of 36) of the sera. Despite the recognition by IgE, the SlpB-AH3a42 fusion protein was unable to induce β-hexosaminidase release from sensitized RBL cells at concentrations up to 100 ng per ml. The inhibition of IgE-binding to the natural allergen observed after pre-incubation of the 20 sera with rabbit anti-SlpB-AH3a42 IgG was more than 30% for four sera, more than 20% for eight sera, and below 10% for eight sera. In comparison, anti-Ara h 2 rabbit IgG antibodies inhibited binding to Ara h 2 by 48% ±13.5%. Our data provide evidence for the feasibility of this novel approach towards the development of a peanut allergen peptide-based carrier-bound vaccine. Our experiments further indicate that more than one allergen-peptide will be needed to induce a broader protection of patients allergic to Ara h 2.     

Challenge of mast cells with increasing amounts of antigen induces desensitization

Background In vivo rush desensitization is a procedure widely employed to quickly desensitizo allergic patients by administering increasing doses of the offending antigen at short intervals. The mechanism(s) underlying this process and the possible role of mast cells in it have not been well delineated. Objective To define an ex vivo model for rush desensitization utilizing the mast cell-fibroblast coculture system. Methods Rat peritoneal mast cells were cultured on 3T3 fibroblasls and were pre-incubated with saturating or suboptimal concentrations of IgE anti-DNP antibodies. Mast cells were then repeatedly challenged at 30 min intervals, with increasing amounts (0.001 100ng/mL) of the antigen DNP-HSA, in the presence of calcium ions. Parallel control cultures were stimulated only once by each antigen concentration. In another set of experiments, mast cells were repeatedly activated with increasing concentrations (0.1-1000 ng/mL) of compound 48/80. Supernatants and cell sonicates were assessed for histamine content and the percentage of histamine released was calculated. Results When saturating concentrations of IgE anti-DNP antibodies were used, mast cells challenged repeatedly with DNP-HSA did not release significant amounts of histamine up to an antigen concentration of I ng/mL. At this stage they were partially desensitized, releasing only 108.3 . 17.1 ng histamine/plate (7.9±0.8%). A marked desensitization was observed at optimal antigen concentration (100 ng/mL). where experimental mast cells released only 45.6±10.9ng/plate, compared with 661.9±48.2ng/plate in firstly challenged cultures. Desensitization was probably not due to mast cells histamine depletion, since the cells still contained large amounts of histamine (579.5±108.6ng/plate) at the end of the procedure. A similar pattern of desensitization was observed when mast cell were preincubated with a subotimal concentration of IgE antibodies. Activation of mast cells with increasing amounts of the IgE-independent secretagogue, compound 48/80. did not cause desensitization since at each concentration both repetitively challenged and control cultures released similar amounts of histamine. Furthermore, challenge of antigen-desensitized mast cells with compound 48/80 caused the release of 75.9±4.9% histamine comparable to the percentage of histamine released from controls (79.5±6.7). Conclusion Repeated exposure of mast cells to gradually increasing amounts of antigen induces their refractoriness. This observation would suggest a role for mast cells in rush desensitization procedure in vivo. Our coculture system may serve as a useful model for studying this process.     

Vitamin E, γ‐tocopherol,diminishes ex vivo basophil response to dust mite allergen

Epidemiologic studies suggest that dietary vitamin E is a candidate intervention for atopic disease. We used in vitro and ex vivo exposures to test the hypothesis that the most common dietary isoform of vitamin E, γ‐tocopherol (γT), could suppress FcεRI‐mediated basophil activation. Rat basophilic leukemia (RBL)‐SX38 cells that express human FcεRI were treated with or without γT, followed by stimulation with α‐IgE. In the ex vivo study, 20 Der f 1‐allergic volunteers consumed a γT‐enriched supplement for 7 days. Their basophils were challenged ex vivo with α‐IgE and graded doses of Der f 1 before and after the supplementation period. γt treatment of RBL‐SX38 cells significantly reduced basophil degranulation and de novo TH2 cytokine production. Daily consumption of a γT‐rich supplement by dust mite‐allergic volunteers reduced basophil activation after ex vivo dust mite challenge. Vitamin E supplements rich in γT may be useful adjuncts in decreasing atopic disease.     

Therapeutic potential of anti-IgE antibodies

Anti-IgE antibodies directed against the FcRI-binding region on IgE inhibit binding of IgE to IgE receptors without inducing mediator release from IgE sensitized cells. In mice these antibodies selectively reduce serum IgE, inhibit antigen induced skin reactions, cytokine production by lung Th2 cells, and pulmonary eosinophil infiltration. Clinical trials in humans reveal that such antibodies are well tolerated and reduce rhinitis symptoms and early and late phase bronchoconstriction responses. Thus interruption of the allergic cascade at the IgE antibody level with non-anaphylactogenic anti-IgE antibodies is effective and represents an attractive intervention for the treatment of allergic diseases.