Arg16Gly β2-adrenergic receptor gene polymorphism in Japanese patients with aspirin-exacerbated respiratory disease

BACKGROUND

There has been no report that investigated β(2)-adrenergic receptor (ADRB2) gene polymorphism in patients with aspirin-exacerbated respiratory disease (AERD).

METHODS

DNA in the specimens in three groups of study subjects classified patients with AERD, patients with aspirin-tolerant asthma (ATA) and normal controls was extracted, and the target DNA sequence of the ADRB2 was amplified using a set of primers to generate an amplicon of 219 bp in length. Allelic discrimination assay for single nucleotide polymorphisms relating to the ADRB2 gene expression was carried out by using a previously described single nucleotide polymorphism detective system, sequence-specific thermal-elution chromatography.

RESULTS

The frequency of the Gly variant allele in patients with AERD was significantly lower than that in patients with ATA (p = 0.007), and the odds ratio (OR) of AERD to ATA associated with wild-type ArgArg homozygote was 3.300. Frequencies of wild-type ArgArg homozygote are significantly higher than those of variant-type ArgGly/GlyGly genotype in patients with AERD compared with those with ATA (p < 0.001, OR = 3.153). In patients with AERD, frequencies of wild-type ArgArg homozygote in both female and male patients are significantly higher than those of variant-type ArgGly/GlyGly genotype in male patients compared with those with ATA (p < 0.001, OR = 5.128 and p = 0.007, OR = 4.367, respectively). Also, in patients with AERD, frequencies of wild-type ArgArg homozygote in female patients are significantly higher than those of variant-type ArgGly/GlyGly genotype in female patients compared with those with ATA (p = 0.002, OR = 2.825).

CONCLUSIONS

We were the first to analyze Arg16Gly ADRB2 gene polymorphism in Japanese patients with AERD, and showed that Arg16Gly ADRB2 gene polymorphism in Japanese patients with AERD is different from that in the patients with ATA.

Processing of human protryptase in mast cells involves cathepsins L, B, and C

Human β-tryptase is stored in secretory granules of human mast cells as a heparin-stabilized tetramer. β-Protryptase in solution can be directly processed to the mature enzyme by cathepsin (CTS) L and CTSB, and sequentially processed by autocatalysis at R(-3), followed by CTSC proteolysis. However, it is uncertain which CTS is involved in protryptase processing inside human mast cells, because murine bone marrow-derived mast cells from CTSC-deficient mice convert protryptase (pro-mouse mast cell protease-6) to mature mouse mast cell protease-6. This finding suggests that other proteases are important for processing human β-protryptase. In the current study, reduction of either CTSB or CTSL activity inside HMC-1 cells by short hairpin RNA silencing or CTS-specific pharmacologic inhibitors substantially reduced mature β-tryptase formation. Similar reductions of tryptase levels in primary skin-derived mast cells were observed with these pharmacologic inhibitors. In contrast, protryptase processing was minimally reduced by short hairpin RNA silencing of CTSC. A putative pharmacologic inhibitor of CTSC markedly reduced tryptase levels, suggesting an off-target effect. Skin mast cells contain substantially greater amounts of CTSL and CTSB than do HMC-1 cells, the opposite being found for CTSC. Both CTSL and CTSB colocalize to the secretory granule compartment of skin mast cells. Thus, CTSL and CTSB are central to the processing of protryptase(s) in human mast cells and are potential targets for attenuating production of mature tryptase in vivo.

Promiscuous processing of human alphabeta-protryptases by cathepsins L, B, and C

Human α- and β-protryptase zymogens are abundantly and selectively produced by mast cells, but the mechanism(s) by which they are processed is uncertain. β-Protryptase is sequentially processed in vitro by autocatalysis at R(-3) followed by cathepsin (CTS) C proteolysis to the mature enzyme. However, mast cells from CTSC-deficient mice successfully convert protryptase (pro-murine mast cell protease-6) to mature murine mast cell protease-6. α-Protryptase processing cannot occur by trypsin-like enzymes due to an R(-3)Q substitution. Thus, biological mechanisms for processing these zymogens are uncertain. β-Tryptase processing activity(ies) distinct from CTSC were partially purified from human HMC-1 cells and identified by mass spectroscopy to include CTSB and CTSL. Importantly, CTSB and CTSL also directly process α-protryptase (Q(-3)) and mutated β-protryptase (R(-3)Q) as well as wild-type β-protryptase to maturity, indicating no need for autocatalysis, unlike the CTSC pathway. Heparin promoted tryptase tetramer formation and protected tryptase from degradation by CTSB and CTSL. Thus, CTSL and CTSB are capable of directly processing both α- and β-protryptases from human mast cells to their mature enzymatically active products.

Disparity in FcεRI-induced degranulation of primary human lung and skin mast cells exposed to adenosine

Inhaled and intravenously administered adenosine induces mast cell-mediated (histamine-dependent) bronchospasm in asthmatics without causing urticaria. A differential response to adenosine by human lung and skin mast cells is shown: low concentrations potentiate FcεRI-induced degranulation of human lung mast cells but not that of skin mast cells. Human lung mast cells were found to express ∼ 3-fold more A3AR messenger RNA (mRNA) than skin mast cells, suggesting the involvement of the G(i)-linked A3AR. Indeed, the adenosine-induced potentiation was sensitive to inhibition by pertussis toxin and, furthermore, could be induced with an A3AR-specific agonist. This study reveals a previously unrecognized disparity in the response to adenosine by primary human mast cells from lung and skin that might explain why adenosine induces a pulmonary but not dermatologic allergy-like response in vivo. In addition, we identify the A3AR as a potentiating receptor of FcεRI-induced degranulation, thereby implicating it in the in vivo bronchoconstrictive response to adenosine in asthmatics.

Mast cell phenotype, location, and activation in severe asthma. Data from the Severe Asthma Research Program

RATIONALE

Severe asthma (SA) remains poorly understood. Mast cells (MC) are implicated in asthma pathogenesis, but it remains unknown how their phenotype, location, and activation relate to asthma severity.

OBJECTIVES

To compare MC-related markers measured in bronchoscopically obtained samples with clinically relevant parameters between normal subjects and subjects with asthma to clarify their pathobiologic importance.

METHODS

Endobronchial biopsies, epithelial brushings, and bronchoalveolar lavage were obtained from subjects with asthma and normal subjects from the Severe Asthma Research Program (N = 199). Tryptase, chymase, and carboxypeptidase A (CPA)3 were used to identify total MC (MC(Tot)) and the MC(TC) subset (MCs positive for both tryptase and chymase) using immunostaining and quantitative real-time polymerase chain reaction. Lavage was analyzed for tryptase and prostaglandin D2 (PGD2) by ELISA.

MEASUREMENTS AND MAIN RESULTS

Submucosal MC(Tot) (tryptase-positive by immunostaining) numbers were highest in "mild asthma/no inhaled corticosteroid (ICS) therapy" subjects and decreased with greater asthma severity (P = 0.002). In contrast, MC(TC) (chymase-positive by immunostaining) were the predominant (MC(TC)/MC(Tot) > 50%) MC phenotype in SA (overall P = 0.005). Epithelial MC(Tot) were also highest in mild asthma/no ICS, but were not lower in SA. Instead, they persisted and were predominantly MC(TC). Epithelial CPA3 and tryptase mRNA supported the immunostaining data (overall P = 0.008 and P = 0.02, respectively). Lavage PGD2 was higher in SA than in other steroid-treated groups (overall P = 0.02), whereas tryptase did not differentiate the groups. In statistical models, PGD2 and MC(TC)/MC(Tot) predicted SA.

CONCLUSIONS

Severe asthma is associated with a predominance of MC(TC) in the airway submucosa and epithelium. Activation of those MC(TC) may contribute to the increases in PGD2 levels. The data suggest an altered and active MC population contributes to SA pathology.

Current strategies in the management of hypereosinophilic syndrome, including mepolizumab

BACKGROUND

Patients with hypereosinophilic syndrome (HES) vary considerably in their clinical presentation with regard to the severity and pattern of end-organ involvement. Clinical manifestations range from nonspecific symptoms to life-threatening, multisystem damage caused by eosinophil infiltration and local release of proinflammatory mediators and toxic granule products from these invading cells. The primary objective of treatment is to reduce blood and tissue eosinophilia and prevent eosinophil-mediated tissue damage as safely as possible. Systemic corticosteroids, such as prednisone, are first-line therapy for the management of patients with symptomatic HES who lack the Fip1-like 1-platelet-derived growth factor receptor-alpha (FIP1L1-PDGFRA) gene fusion mutation. The tyrosine kinase inhibitor, imatinib, is first-line treatment for FIP1L1-PDGFRA-positive patients). Because of the toxicity and serious side-effects that can occur with oral corticosteroids, alternative therapies may need to be introduced to reduce the cumulative corticosteroid exposure while maintaining disease control.

SCOPE

Among corticosteroid-sparing agents are cytotoxic drugs and interferon-alpha; anti-interleukin-5 (IL-5) monoclonal antibodies are also currently under investigation for the treatment of HES. This manuscript reviews the available treatments for HES and the range of side-effects associated with long-term corticosteroid use, and then focuses on the anti-IL-5 monoclonal antibodies, mepolizumab and reslizumab. Of these, only mepolizumab has been studied in a randomized, placebo-controlled trial. Literature search methodology utilized www.pubmed.gov and www.clinicaltrials.gov with search terms including hypereosinophilic syndrome and corticosteroid side-effects coupled with search terms including eosinophils, mepolizumab and reslizumab through March 2010.

FINDINGS

Three case studies are presented that demonstrate the limitations of corticosteroid therapy in terms of tolerability and quality of life, and the subsequent use of mepolizumab as a corticosteroid-sparing agent in these individuals.

CONCLUSION

Targeted eosinophil-directed therapy with an anti-IL-5 neutralizing monoclonal antibody reduced the need for corticosteroids in these three HES patients without disease exacerbations.

Mast cells from different molecular and prognostic subtypes of systemic mastocytosis display distinct immunophenotypes

BACKGROUND

Systemic mastocytosis (SM) is a heterogeneous group of disorders with distinct clinical and biological behavior. Despite this, little is known about the immunophenotypic features of the distinct diagnostic categories of SM.

OBJECTIVE

To analyze the immunophenotypic characteristics of bone marrow (BM) mast cells (MCs) of different subtypes of SM.

METHODS

Bone marrow samples from 123 patients with different subtypes of SM and 92 controls were analyzed for a broad panel of immunophenotypic markers by flow cytometry.

RESULTS

Three clearly different maturation-associated immunophenotypic profiles were found for BMMCs in SM. These different profiles were associated with both genetic markers of the disease and its clinical behavior. BMMCs from poor-prognosis categories of SM (aggressive SM and MC leukemia) typically showed an immature phenotype with clonal involvement of all myeloid lineages by the D816V stem cell growth factor receptor gene (KIT) mutation. In turn, a mature activated versus resting BMMC immunophenotype was commonly found among patients with good-prognosis subtypes of SM depending on whether they carried (indolent SM and clonal MC activation disorders) or not (well differentiated SM) the D816V KIT mutation.

CONCLUSION

Bone marrow MCs from SM show 3 different maturation-related immunophenotypic profiles that are associated with both the genetic markers of the disease and its clinical behavior.

Tryptase is not cleared by the kidneys into the urine

BACKGROUND

Patients with chronic kidney disease have been reported to have increased concentrations of blood tryptase. Detection of tryptase in the urine of healthy subjects has been reported.

OBJECTIVE

The objective is to determine whether tryptase is indeed cleared by the kidneys.

METHODS

Blood and urine collections were performed in healthy and systemic mastocytosis subjects. Total and mature tryptase concentrations in blood and total tryptase concentrations in urine were determined.

RESULTS

Total tryptase levels in urine were below the limit of detection in both healthy subjects and those with systemic mastocytosis, even after concentrating the urine 10-fold. Thus, both mature and protryptase levels in urine are <0.2 ng/ml.

CONCLUSION

Tryptase is not cleared by the kidneys into the urine.

Safety of binodenoson, a selective adenosine A2A receptor agonist vasodilator pharmacological stress agent, in healthy subjects with mild intermittent asthma

BACKGROUND

The pharmacological stress agents adenosine and dipyridamole are contraindicated in asthma patients because of the risk of adenosine receptor-mediated bronchospasm. Binodenoson, a selective adenosine A(2A) receptor agonist, produces maximal coronary hyperemia during pharmacological stress testing yet has a low affinity for the adenosine A(1), A(2B), and A(3) receptors that are probably responsible for bronchospasm. This study was conducted to assess the safety of binodenoson in 87 healthy young adult volunteers with documented mild, intermittent asthma.

METHODS AND RESULTS

This study consisted of a dose-escalating, single-blinded phase and a placebo-controlled, double-blinded phase conducted in healthy, young adults with documented mild, intermittent, asthma. In the single-blinded phase, 3 sequential cohorts of 8 subjects received intravenous binodenoson (0.5, 1.0, and 1.5 microg/kg). In the double-blinded phase, commenced after medical review of results from the single-blinded phase, subjects were randomly assigned 2:1 to either binodenoson 1.5 microg/kg (n=41) or placebo (n=22). The primary end point was clinically significant bronchoconstriction, defined as a decrease in forced expiratory volume in 1 second of >/=20% from the preinjection measure. Secondary safety end points were changes from preinjection measure in forced expiratory volume in 1 second, forced vital capacity, and forced expiratory flow during the middle 50% of the forced vital capacity; vital signs; pulse oximetry; and adverse events. Binodenoson caused no clinically significant bronchoconstriction or alterations in pulmonary function parameters and transiently increased heart rate and systolic blood pressure. The most common treatment-emergent adverse events were tachycardia, dizziness, and flushing.

CONCLUSIONS

Binodenoson was safe, well tolerated, and caused no clinically significant bronchoconstriction or pulmonary responses in a small population of healthy subjects with mild, intermittent asthma.

TGF-beta1 attenuates mediator release and de novo Kit expression by human skin mast cells through a Smad-dependent pathway

TGF-beta has pleiotropic effects on many cell types at different stages of their development, including mast cells. The present study examines the effects of TGF-beta on human skin mast cells of the MC(TC) type. The expression of TGF-beta receptors (TGF-R) was verified at the mRNA and protein levels for TGF-RI and TGF-RII, and at the mRNA level for accessory molecules beta-glycan and endoglin. TGF-beta did not affect mast cell viability after 1 wk at concentrations < or = 10 ng/ml, but at 50 ng/ml caused significant cell death. TGF-beta inhibited surface and total expression of Kit in a dose-dependent manner, whereas the surface expression of Fc epsilonRI, Fc gammaRI, and Fc gammaRII was not affected. TGF-beta inhibited degranulation and cytokine production, but not PGD(2) production. TGF-beta diminished surface Kit expression through a TGF-RI kinase/Smad-dependent pathway by inhibiting new synthesis of Kit protein, which became evident following internalization and degradation of Kit after mast cells were exposed to the Kit ligand, stem cell factor. In contrast, addition of TGF-beta had no discernible effect on surface Kit expression when administered 3 days after stem cell factor, by which time surface Kit levels had returned to baseline. Although both transcription and translation are important for de novo expression of Kit, Kit mRNA levels were not affected by TGF-beta. Therefore, transcription of a gene other than Kit might be involved in Kit expression. Finally, activation of mast cells increased their susceptibility to TGF-beta-mediated apoptosis, a process that might regulate the survival of activated mast cells in vivo.

Exercise-induced hypersensitivity syndromes in recreational and competitive athletes: a PRACTALL consensus report (what the general practitioner should know about sports and allergy)

Exercise-induced (EI) hypersensitivity disorders are significant problems for both recreational and competitive athletes. These include EI-asthma, EI-bronchoconstriction, EI-rhinitis, EI-anaphylaxis and EI-urticaria. A group of experts from the European Academy of Allergology and Clinical Immunology and the American Academy of Allergy Asthma and Immunology met to discuss the pathogenesis of these disorders and how to diagnose and treat them, and then to develop a consensus report. Key words (exercise with asthma, bronchoconstriction, rhinitis, urticaria or anaphylaxis) were used to search Medline, the Cochrane database and related websites through February 2008 to obtain pertinent information which, along with personal reference databases and institutional experience with these disorders, were used to develop this report. The goal is to provide physicians with guidance in the diagnosis, understanding and management of EI-hypersensitivity disorders to enable their patients to safely return to exercise-related activities.

A simple and rapid genotyping assay for simultaneous detection of two ADRB2 allelic variants using fluorescence resonance energy transfer probes and melting curve analysis

Allelic variants at codons 16 and 27 of the beta(2)-adrenergic receptor gene (ADRB2) have shown clinical and pharmacological implications in asthma, hypertension, ischemic heart failure, diabetes, obesity, and cystic fibrosis. We have developed a simultaneous genotyping assay for the c.46A>G and c.79C>G allelic variants using hybridization probes and melting curve analysis. The assay was optimized on a panel of 30 DNA samples of known ADRB2 genotype as determined by sequencing with 100% concordance between the two techniques. Melting temperature (Tm) ranges for the different genotypes were obtained using data from three independent experiments. Single peaks for p.Arg16Arg (Tm = 57.76 degrees C +/- 0.10 degrees C) and p.Gly16Gly (Tm = 66.73 degrees C +/- 0.18 degrees C) and two melting peaks for p.Arg16Gly were obtained. Similarly, single peaks for p.Gln27Gln (Tm = 53.98 degrees C +/- 0.19 degrees C) and p.Glu27Glu (Tm = 64.93 degrees C +/- 0.16 degrees C) and two peaks for p.Gln27Glu were detected. Independent operators easily assigned genotypes in a sample set of 385 asthmatic patients. Haplotype and allele frequencies were in concordance with previously published data: Arg allele frequencies in children/adults were 0.34/0.30 in Caucasians and 0.45/0.52 in African Americans, and Gln allele frequencies were 0.58/0.52 in Caucasians and 0.82/0.84 in African Americans. Thus, the ADRB2 genotyping assay represents a highly reliable and rapid technique for routine clinical use in the simultaneous detection of ADRB2 variants.

Generation of anaphylatoxins by human beta-tryptase from C3, C4, and C5

Both mast cells and complement participate in innate and acquired immunity. The current study examines whether beta-tryptase, the major protease of human mast cells, can directly generate bioactive complement anaphylatoxins. Important variables included pH, monomeric vs tetrameric forms of beta-tryptase, and the beta-tryptase-activating polyanion. The B12 mAb was used to stabilize beta-tryptase in its monomeric form. C3a and C4a were best generated from C3 and C4, respectively, by monomeric beta-tryptase in the presence of low molecular weight dextran sulfate or heparin at acidic pH. High molecular weight polyanions increased degradation of these anaphylatoxins. C5a was optimally generated from C5 at acidic pH by beta-tryptase monomers in the presence of high molecular weight dextran sulfate and heparin polyanions, but also was produced by beta-tryptase tetramers under these conditions. Mass spectrometry verified that the molecular mass of each anaphylatoxin was correct. Both beta-tryptase-generated C5a and C3a (but not C4a) were potent activators of human skin mast cells. These complement anaphylatoxins also could be generated by beta-tryptase in releasates of activated skin mast cells. Of further biologic interest, beta-tryptase also generated C3a from C3 in human plasma at acidic pH. These results suggest beta-tryptase might generate complement anaphylatoxins in vivo at sites of inflammation, such as the airway of active asthma patients where the pH is acidic and where elevated levels of beta-tryptase and complement anaphylatoxins are detected.

Treatment of patients with the hypereosinophilic syndrome with mepolizumab

BACKGROUND

The hypereosinophilic syndrome is a group of diseases characterized by persistent blood eosinophilia, defined as more than 1500 cells per microliter with end-organ involvement and no recognized secondary cause. Although most patients have a response to corticosteroids, side effects are common and can lead to considerable morbidity.

METHODS

We conducted an international, randomized, double-blind, placebo-controlled trial evaluating the safety and efficacy of an anti-interleukin-5 monoclonal antibody, mepolizumab, in patients with the hypereosinophilic syndrome. Patients were negative for the FIP1L1-PDGFRA fusion gene and required prednisone monotherapy, 20 to 60 mg per day, to maintain a stable clinical status and a blood eosinophil count of less than 1000 per microliter. Patients received either intravenous mepolizumab or placebo while the prednisone dose was tapered. The primary end point was the reduction of the prednisone dose to 10 mg or less per day for 8 or more consecutive weeks.

RESULTS

The primary end point was reached in 84% of patients in the mepolizumab group, as compared with 43% of patients in the placebo group (hazard ratio, 2.90; 95% confidence interval [CI], 1.59 to 5.26; P<0.001) with no increase in clinical activity of the hypereosinophilic syndrome. A blood eosinophil count of less than 600 per microliter for 8 or more consecutive weeks was achieved in 95% of patients receiving mepolizumab, as compared with 45% of patients receiving placebo (hazard ratio, 3.53; 95% CI, 1.94 to 6.45; P<0.001). Serious adverse events occurred in seven patients receiving mepolizumab (14 events, including one death; mean [+/-SD] duration of exposure, 6.7+/-1.9 months) and in five patients receiving placebo (7 events; mean duration of exposure, 4.3+/-2.6 months).

CONCLUSIONS

Our study shows that treatment with mepolizumab, an agent designed to target eosinophils, can result in corticosteroid-sparing for patients negative for FIP1L1-PDGFRA who have the hypereosinophilic syndrome. (ClinicalTrials.gov number, NCT00086658 [ClinicalTrials.gov].).

Practical allergy (PRACTALL) report: risk assessment in anaphylaxis

Effector mechanisms in anaphylaxis were reviewed. Current approaches to confirmation of the clinical diagnosis were discussed. Improved methods for distinguishing between allergen sensitization (which is common in the general population) and clinical risk of anaphylaxis (which is uncommon) were deliberated. Innovative techniques that will improve risk assessment in anaphylaxis in the future were described.

American Academy of Allergy, Asthma & Immunology/American College of Allergy, Asthma and Immunology Joint Task Force Report on omalizumab-associated anaphylaxis

The American Academy of Allergy, Asthma & Immunology and the American College of Allergy, Asthma and Immunology Executive Committees formed the Omalizumab Joint Task Force with the purpose of reviewing the Genentech Xolair (omalizumab) clinical trials and postmarketing surveillance data on anaphylaxis and anaphylactoid reactions. Using the definition of anaphylaxis proposed at a 2005 multidisciplinary symposia, the Omalizumab Joint Task Force concluded that 35 patients had 41 episodes of anaphylaxis associated with Xolair (omalizumab) administration between June 1, 2003, and December 31, 2005. With 39,510 patients receiving Xolair (omalizumab) during the same period of time, this would correspond to an anaphylaxis-reporting rate of 0.09% of patients. Of those 36 events for which the time of reaction was known, 22 (61%) reactions occurred in the first 2 hours after one of the first 3 doses. Five (14%) of the events after the fourth or later doses occurred within 30 minutes. Considering the timing of these 36 events, an observation period of 2 hours for the first 3 injections and 30 minutes for subsequent injections would have captured 75% of the anaphylactic reactions. The OJTF report provides recommendations for physicians who prescribe Xolair (omalizumab) on (1) the suggested wait periods after administration and (2) patient education regarding anaphylaxis.

Omalizumab reverses the phenotypic and functional effects of IgE-enhanced Fc epsilonRI on human skin mast cells

The dramatic effects of the anti-IgE mAb omalizumab to lower free IgE levels and Fc epsilonRI levels on basophils contrast with more modest clinical effects. Accordingly, whether IgE modulates Fc epsilonRI levels and Fc epsilonRI-dependent mediator release in vitro on human skin mast cells (MC(TC) type) that had matured in vivo is of interest. IgE reversibly enhanced Fc epsilonRI levels on MC(TC) cells in a dose- and time-dependent manner (up-regulation t(1/2) of 4-5 days with 1-3 microg/ml IgE), without affecting cell proliferation. A molar ratio of omalizumab to IgE of 0.9 at baseline prevented receptor up-regulation by 50%, whereas adding omalizumab to MC(TC) cells already with IgE-enhanced Fc epsilonRI levels at molar ratios of 5, 12.5, and 31 reduced Fc epsilonRI levels to baseline with respective t(1/2) values of 8.7, 6.3, and 4.8 days. MC(TC) cells with IgE-enhanced Fc epsilonRI levels were more sensitive to stimulation with a low dose of anti-Fc epsilonRI mAb in terms of degranulation and production of PGD(2), GM-CSF, IL-6, IL-13, and TNF-alpha. Reducing up-regulated Fc epsilonRI levels with omalizumab also reduced mediator release to a low dose of anti-Fc epsilonRI mAb to baseline by 3-4 wk. Thus, reducing free IgE should decrease the hypersensitivity of allergic individuals to low naturally occurring concentrations of allergens.

Risk assessment in anaphylaxis: current and future approaches

Risk assessment of individuals with anaphylaxis is currently hampered by lack of (1) an optimal and readily available laboratory test to confirm the clinical diagnosis of an anaphylaxis episode and (2) an optimal method of distinguishing allergen-sensitized individuals who are clinically tolerant from those at risk for anaphylaxis episodes after exposure to the relevant allergen. Our objectives were to review the effector mechanisms involved in the pathophysiology of anaphylaxis; to explore the possibility of developing an optimal laboratory test to confirm the diagnosis of an anaphylaxis episode, and the possibility of improving methods to distinguish allergen sensitization from clinical reactivity; and to develop a research agenda for risk assessment in anaphylaxis. Researchers from the American Academy of Allergy, Asthma & Immunology and the European Academy of Allergology and Clinical Immunology held a PRACTALL (Practical Allergy) meeting to discuss these objectives. New approaches being investigated to support the clinical diagnosis of anaphylaxis include serial measurements of total tryptase in serum during an anaphylaxis episode, and measurement of baseline total tryptase levels after the episode. Greater availability of the test for mature beta-tryptase, a more specific mast cell activation marker for anaphylaxis than total tryptase, is needed. Measurement of chymase, mast cell carboxypeptidase A3, platelet-activating factor, and other mast cell products may prove to be useful. Consideration should be given to measuring a panel of mediators from mast cells and basophils. New approaches being investigated to help distinguish sensitized individuals at minimum or no risk from those at increased risk of developing anaphylaxis include measurement of the ratio of allergen-specific IgE to total IgE, determination of IgE directed at specific allergenic epitopes, measurement of basophil activation markers by using flow cytometry, and assessment of allergen-specific cytokine responses. Algorithms have been developed for risk assessment of individuals with anaphylaxis, along with a research agenda for studies that could lead to an improved ability to confirm the clinical diagnosis of anaphylaxis and to identify allergen-sensitized individuals who are at increased risk of anaphylaxis.

Fullerene nanomaterials inhibit the allergic response

Fullerenes are a class of novel carbon allotropes that may have practical applications in biotechnology and medicine. Human mast cells (MC) and peripheral blood basophils are critical cells involved in the initiation and propagation of several inflammatory conditions, mainly type I hypersensitivity. We report an unanticipated role of fullerenes as a negative regulator of allergic mediator release that suppresses Ag-driven type I hypersensitivity. Human MC and peripheral blood basophils exhibited a significant inhibition of IgE dependent mediator release when preincubated with C(60) fullerenes. Protein microarray demonstrated that inhibition of mediator release involves profound reductions in the activation of signaling molecules involved in mediator release and oxidative stress. Follow-up studies demonstrated that the tyrosine phosphorylation of Syk was dramatically inhibited in Ag-challenged cells first incubated with fullerenes. In addition, fullerene preincubation significantly inhibited IgE-induced elevation in cytoplasmic reactive oxygen species levels. Furthermore, fullerenes prevented the in vivo release of histamine and drop in core body temperature in vivo using a MC-dependent model of anaphylaxis. These findings identify a new biological function for fullerenes and may represent a novel way to control MC-dependent diseases including asthma, inflammatory arthritis, heart disease, and multiple sclerosis.

Standards and standardization in mastocytosis: consensus statements on diagnostics, treatment recommendations and response criteria

Although a classification for mastocytosis and diagnostic criteria are available, there remains a need to define standards for the application of diagnostic tests, clinical evaluations, and treatment responses. To address these demands, leading experts discussed current issues and standards in mastocytosis in a Working Conference. The present article provides the resulting outcome with consensus statements, which focus on the appropriate application of clinical and laboratory tests, patient selection for interventional therapy, and the selection of appropriate drugs. In addition, treatment response criteria for the various clinical conditions, disease-specific symptoms, and specific pathologies are provided. Resulting recommendations and algorithms should greatly facilitate the management of patients with mastocytosis in clinical practice, selection of patients for therapies, and the conduct of clinical trials.

Human mast cells produce and release the cytotoxic lymphocyte associated protease granzyme B upon activation

Mast cells are widely distributed throughout the body and express effector functions in allergic reactions, inflammatory diseases, and host defense. Activation of mast cells results in exocytosis of preformed chemical mediators and leads to novel synthesis and secretion of lipid mediators and cytokines. Here, we show that human mast cells also express and release the cytotoxic lymphocyte-associated protease, granzyme B. Granzyme B was active and localized in cytoplasmic granules, morphologically resembling those present in cytotoxic lymphocytes. Expression and release of granzyme B by mast cell-lines HMC-1 and LAD 2 and by cord blood- and mature skin-derived human mast cells depended on the mode of activation of these cells. In mast cell lines and cord blood-derived mast cells, granzyme B expression was mainly induced by non-physiological stimuli (A23187/PMA, Compound 48/80) and substance P. In contrast, mature skin-derived mast cells only produced granzyme B upon IgE-dependent stimulation. We conclude that granzyme B is expressed and released by human mast cells upon physiologic stimulation. This suggests a role for granzyme B as a novel mediator in mast cell biology.

Tryptase haplotype in mastocytosis: relationship to disease variant and diagnostic utility of total tryptase levels

Serum mast cell tryptase levels are used as a diagnostic criterion and surrogate marker of disease severity in mastocytosis. Approximately 29% of the healthy population lacks alpha tryptase genes; however, it is not known whether lack of alpha tryptase genes leads to variability in tryptase levels or impacts on disease severity in mastocytosis. We have thus analyzed tryptase haplotype in patients with mastocytosis, computing correlations between haplotype and plasma total and mature tryptase levels; and disease category. We found: (1) the distribution of tryptase haplotype in patients with mastocytosis appeared consistent with Hardy-Weinberg equilibrium and the distribution in the general population; (2) the disease severity and plasma tryptase levels were not affected by the number of alpha or beta tryptase alleles in this study; and (3) information about the tryptase haplotype did not provide any prognostic value about the severity of disease. Total and mature tryptase levels positively correlated with disease severity, as well as prothrombin time and partial thromboplastin time, and negatively correlated with the hemoglobin concentration.