Pathophysiology of human basophils and mast cells in allergic disorders

The role of mast cells in human skin cancers

Mast cells (MCs) are immune cells derived from myeloid lineage present in all classes of vertebrates and have emerged preceding much time the development of adaptive immunity. MCs are involved in inflammatory processes, allergic reactions, and host responses to parasites and bacteria infectious diseases. MCs are located at the host-environment interface, at many sites of initial antigen entry, including skin, lung and gastrointestinal tract, and have part of a protective mechanism. Skin has an important role in protecting the host from invasion both as physical barriers and by employing an intricate network of resident immune and non-immune cells include macrophages, T and B lymphocytes, MCs, neutrophils, eosinophils, and Langerhans cells. In this review we discussed the role of MCs in human skin cancers.

Tryptase Positivity in Chronic Myeloid Leukemia With Marked Basophilia

Chronic myeloid leukemia (CML) is the most common chronic myeloproliferative disorder, which was the first to be described and understood at a molecular level. Marked basophilia can be seen in CML and other neoplastic and reactive processes. Tryptase is a serine protease that is mainly expressed in mast cells, whereas basophils express only trace amounts of the enzyme. Therefore, it has always been regarded as a specific marker for mast cells.

We report a case of a 41-year-old male who had been diagnosed with CML eight years ago, and, interestingly, his most recent bone marrow biopsy demonstrated an accelerated phase of the disease with a significant increase of basophils count. These basophils were immunoreactive with tryptase along with CD123.

In the literature, this phenomenon of tryptase immunoreactivity by basophils has been described in association with CML, primary myelofibrosis, and myelodysplastic syndrome. Therefore, our finding supports these data and suggests that tryptase should not be regarded as a specific marker for mast cells when approaching various myeloid neoplasms including CML.

Clinical and biochemical effects of a combination botanical product (ClearGuard) for allergy: a pilot randomized double-blind placebo-controlled trial

Background

Botanical products are frequently used for treatment of nasal allergy. Three of these substances, Cinnamomum zeylanicum, Malpighia glabra, and Bidens pilosa, have been shown to have a number of anti-allergic properties in-vitro. The current study was conducted to determine the effects of these combined ingredients upon the nasal response to allergen challenge in patients with seasonal allergic rhinitis.

Methods

Twenty subjects were randomized to receive the combination botanical product, (CBP) 2 tablets three times a day, loratadine, 10 mg once a day in the morning, or placebo, using a randomized, double-blinded crossover design. Following 2 days of each treatment and during the third day of treatment, subjects underwent a nasal allergen challenge (NAC), in which nasal symptoms were assessed after each challenge dose and every 2 hours for 8 hours. Nasal lavage fluid was assessed for tryptase, prostaglandin D2, and leukotriene E4 concentrations and inflammatory cells.

Results

Loratadine significantly reduced the total nasal symptom score during the NAC compared with placebo (P = 0.04) while the CBP did not. During the 8 hour period following NAC, loratadine and the CBP both reduced NSS compared with placebo (P = 0.034 and P = 0.029, respectively). Analysis of nasal lavage fluid demonstrated that the CBP prevented the increase in prostaglandin D2 release following NAC, while neither loratadine nor placebo had this effect. None of the treatments significantly affected tryptase or leukotriene E4 release or inflammatory cell infiltration.

Conclusion

The CBP significantly reduced NSS during the 8 hours following NAC and marginally inhibited the release of prostaglandin D2 into nasal lavage fluid, suggesting potential clinical utility in patients with allergic rhinitis.

Norepinephrine-induced cardiac hypertrophy and fibrosis are not due to mast cell degranulation

The norepinephrine (NE)-induced hypertrophy of the left ventricle (LV) in the rat is preceded by increased interleukin (IL)-6 expression and associated with LV fibrosis. We have examined whether the elevated level of IL-6 may be due to mast cell degranulation. Therefore we tested the effect of cromoglycate sodium salt (cromolyn), an inhibitor of mast cell degranulation with anti-inflammatory and membrane-stabilizing activity, on the increased expression of IL-6 mRNA and of mRNAs of proteins involved in the remodelling of the extracellular matrix (ECM) which is induced by NE (0.1 mg/kg x h). After 4 h, the NE-induced increase in IL-6 mRNA expression was not influenced by cromolyn (20 mg/kg x h). Cromolyn-infusion for 3 days did not affect the extent of LV hypertrophy induced by NE, as measured by the LV weight/body weight (LVW/BW) ratio and by atrial natriuretic peptide (ANP) expression. Cromolyn induced a slight depression of the NE-induced elevation of the matrix metalloproteinase (MMP)-2. However, it did not affect the NE-induced elevated levels of mRNAs of collagen I and III and the tissue inhibitor of matrix metalloproteinase (TIMP)-2. Since cromolyn did not reduce the NE-effects in rat hearts in vivo we conclude that mast cell degranulation seems not to be involved in them.

Association of the Src homology 2 domain-containing inositol 5' phosphatase (SHIP) to releasability in human basophils

During the study of the biology of the Human recombinant Histamine Releasing Factor (HrHRF), we uncovered a hyperreleasable phenotype of basophils from HrHRF-responder donors. Basophils from these donors released histamne to HrHRF, IL-3 and D(2)O. While there has been a significant amount of work elucidating signal transduction events in human basophils, the reason for this hyperreleasable phenotype remained illusive. A clue to the releasability of these highly allergic, asthmatic HrHRF-responder donor basophils was demonstrated in studies using SHIP knockout mice. Bone marrow-derived mast cells from the SHIP knockout mice demonstrated hyperreleasability to stimuli through the IgE receptor and alteration of subsequent signal transduction events. We have demonstrated a highly significant negative correlation between the amount of SHIP protein per cell equivalent and maximum histamine release to HrHRF. These results provide a clue to the hyperreleasable phenotype and implicate SHIP as an additional regulator of secretion in human basophils.

A comparison of mediators released or generated by IFN-gamma-treated human mast cells following aggregation of Fc gamma RI or Fc epsilon RI

The high affinity receptor for IgG (Fc gamma RI, CD64) is expressed on human mast cells, where it is up-regulated by IFN-gamma and, thus, may allow mast cells to be recruited through IgG-dependent mechanisms in IFN-gamma-rich tissue inflammation. However, the mediators produced by human mast cells after aggregation of Fc gamma RI are incompletely described, and it is unknown whether these mediators are distinct from those produced after activation of human mast cells via Fc epsilon RI. Thus, we investigated the release of histamine and arachidonic acid metabolites and examined the chemokine and cytokine mRNA profiles of IFN-gamma-treated cultured human mast cells after Fc gamma RI or Fc epsilon RI aggregation. Aggregation of Fc gamma RI resulted in histamine release and PGD(2) and LTC(4) generation. These responses were qualitatively indistinguishable from responses stimulated via Fc epsilon RI. Aggregation of Fc epsilon RI or Fc gamma RI led to an induction or accumulation of 22 cytokine and chemokine mRNAs. Among them, seven cytokines (TNF-alpha, IL-1beta, IL-5, IL-6, IL-13, IL-1R antagonist, and GM-CSF) were significantly up-regulated via aggregation of Fc gamma RI compared with Fc epsilon RI. TNF-alpha mRNA data were confirmed by quantitative RT-PCR and ELISA. Furthermore, we confirmed histamine and TNF-alpha data using IFN-gamma-treated purified human lung mast cells. Thus, aggregation of Fc gamma RI on mast cells led to up-regulation and/or release of three important classes of mediators: biogenic amines, lipid mediators, and cytokines. Some cytokines, such as TNF-alpha, were released and generated to a greater degree after Fc gamma RI aggregation, suggesting that selected biologic responses of mast cells may be preferentially generated through Fc gamma RI in an IFN-gamma-rich environment.

Linkage between IgE receptor-mediated histamine releasability from basophils and gene marker of chromosome 11q13

BACKGROUND

The genetics of the regulation of the release of mediators involving the interaction of IgE with cells and their ability to release mediators have not been extensively investigated. With use of the candidate gene approach, it was reported that the gene regulating the beta chain of the high-affinity receptor for IgE is on chromosome 11q13.

OBJECTIVE

To determine whether gene(s) in chromosome 11q13 may control the expression of maximal histamine release from basophil to anti-IgE stimuli, linkage analysis between this phenotype and the gene marker of chromosome 11q13 was performed.

METHODS

Maximal histamine release to anti-IgE and calcium ionophore A23187 and genotyping chromosome 11q13 with use of microsatellite marker (D11S97) were performed in 56 probands with asthma and 59 of their siblings. The linkage was analyzed by affected sib-pair analysis and the quantitative trait locus approach.

RESULTS

Maximal histamine release (mean +/- SE) to anti-IgE and A23187 was 43.3% +/- 3.5% and 30.9 +/- 3.4% in probands and 29.5% +/- 2.6% and 22.2% +/- 2.7 in siblings, respectively. Of 20 sib-pairs with the maximal histamine release to anti-IgE more than 33% (mean plus 1 SD of nonasthmatic controls), 11 (55%) shared 2 D11S97 alleles, 9 (45%) shared 1 allele, and neither sib-pair shared identical alleles, which indicates a significant linkage of maximal histamine to anti-IgE and gene marker of chromosome 11q13 (P =.02). The difference (mean +/- SE) of the maximal histamine release to anti-IgE between each proband and sibling was smaller in sib-pairs with 2 identical alleles than in those with 1 identical allele and with no identical allele (14.1% +/- 2.6% vs 25.8% +/- 3.1% vs 41.0% +/- 4.9%). However, the difference (mean +/- SE) to A23187 between each proband and sibling was not different among the 3 groups (9.7% +/- 1.8% vs 17.9% +/- 3.6% vs 10.4% +/- 4.8%).

CONCLUSION

Maximal histamine release from basophils to anti-IgE stimuli was linked to the gene marker of chromosome 11q13.

Immunological modulation of human cardiac mast cells

Human mast cells, by elaborating various cytokines, chemokines and proinflammatory mediators play a complex role in several allergic and inflammatory disorders. Mast cells have been identified in human heart tissue in close proximity to the sarcolemma, in perivascular and adventitial locations and in the shoulder region of coronary atheroma. Human heart mast cells (HHMC) can be isolated from patients undergoing heart transplantation and can be immunologically activated in vitro to induce the release of tryptase, chymase, cysteinyl leukotriene C4 and prostaglandin D2. Several cytokines (e.g., stem cell factor and TNF-alpha) reside in secretory granules of HHMC. Mast cell density is increased in the hearts of patients with ischemic and idiopathic dilated cardiomyopathy. Cardiac mast cells might contribute to the evolution of atherosclerosis, dilated cardiomyopathy, cardiac and systemic anaphylaxis through the release of cytokines and vasoactive and proinflammatory mediators.

Immunopharmacology of human mast cells and basophils

Human mast cells and basophils play a key role in the pathogenesis of several immunological and inflammatory disorders, not only by producing inflammatory and fibrogenic mediators, but also by directly (CD40 ligand) and indirectly secreting various cytokines and chemokines. Studies carried out to evaluate the effects of drugs that modulate the release of mediators and cytokines from these cells have contributed to clarifying the biochemical mechanism by which immunological and non-immunological stimuli activate these cells. Significant differences have been documented between human mast cells and basophils as regard the pharmacological agents that modulate the release of mediators, between mast cells isolated from different anatomical sites, and between compounds of the same class of drugs. Efforts to gain insight into the biochemical events occurring during immunological activation of mast cells and basophils could lead to the identification of new biochemical targets for therapeutic interventions in several immunological disorders.

The mast cell: origin, morphology, distribution, and function

The mast cell remains an enigmatic cell more than 100 years after its discovery by Paul Ehrlich at the turn of the century. It is a cell that is found widely distributed in the body particularly associated with connective tissues. It can be recognised by its content of metachromatic granules when appropriately fixed and stained with metachromatic dyes such as toulidine blue. The metachromatic granules of the mast cell remain an important differentiating characteristic from other cells although it is by no means absolute. In the early days of its discovery it was thought to originate from primitive mesenchyme, thymocyte or lymphocyte. More recent evidence suggests that it may have originated from the monocyte. Current evidence points to an origin from haemopoietic tissue in the bone marrow, the progenitors differentiate from primitive cells under the influence of cytokines (IL3), migrate to other body sites and then undergo differentiation and maturation under the influence of growth and other factors. The mast cell has many functions exerted through its ability to produce a host of biologically active substances the most notable being heparin, serotonin, dopamine, tryptase and chymase. These substances may be released in response to immunological and neural stimuli. Mast cells are found to be functionally heterogeneous, possibly site specific and have the ability to adapt to their environment, producing secretions commensurate with the needs of any situation. The mast cell is involved in immunological, neoplastic, inflammatory and other conditions. Much about its function has been unravelled but there remains more to be uncovered.

Nimesulide in the treatment of patients intolerant of aspirin and other NSAIDs

Aspirin (acetylsalicylic acid) and other NSAIDs are responsible for many adverse effects. Among them, pseudo-allergic reactions (urticaria/angioedema, asthma, anaphylaxis) affect up to 9% of the population and up to 30% of asthmatic patients. The mechanisms provoking these reactions have not been fully elucidated, but it appears that inhibition of cyclo-oxygenase (COX) plays a central role. The anti-inflammatory action of nimesulide differs from that of other NSAIDs, possibly because of its chemical structure. In particular, nimesulide is selective for COX-2 and displays additional properties in terms of its effects on inflammatory mediator synthesis and release. For these reasons, nimesulide is generally well tolerated by NSAID-intolerant patients and patients with NSAID-induced asthma. The good tolerability of nimesulide as an alternative drug for use in patients with NSAID intolerance has been demonstrated in a large number of clinical studies.

Transmural changes in mast cell density in rat heart after infarct induction in vivo

The cardiac distribution of mast cells was investigated after the induction of acute myocardial infarction in the rat. The left anterior descending coronary artery (LAD) was occluded by ligation in the infarct group, whereas in sham rats only a superficial ligature was placed beside the LAD. Rats of both groups were killed at 4, 7, 14, 21, 35, and 85 days following surgery. Hearts were excised and formalin-fixed. Mast cell densities were monitored in subepicardial and subendocardial layers of the left ventricle (LV) in 6 microns thick toluidine blue-stained cross-sections. In control (non-operated) animals, mast cell densities were comparable in the LV subepicardial and subendocardial layers (1.5-2.0 cells per mm2). Following infarction, the mast cell density at the subepicardial site of the infarction gradually increased, reaching a maximum of 25 cells per mm2 on day 21, while a non-significant increase was observed at the subendocardial site. In the non-infarcted regions, the mast cell density increased transiently to reach a maximum of 7 cells per mm2 on day 35 in the subepicardial layer. Again, changes in mast cell density in the subendocardial layer were non-significant. In the sham group, a gradual increase to 9 cells per mm2 on day 21 and a subsequent decrease to 5 cells per mm2 on day 85 were observed in the subepicardial layers. These findings indicate a massive accumulation of mast cells in the subepicardial layers of the infarcted region and a small but significant effect of the surgical procedure on cardiac mast cell deposition, especially in the outer layers of the left ventricle.

Immunological characterization and functional importance of human heart mast cells

Mast cells are present in normal and even more abundant in diseased human heart tissue and their localization is of particular relevance to their function. Within heart tissue mast cells lie between myocytes and in close contact with blood vessels. They are also found in the coronary adventitia and in the shoulder regions of a coronary atheroma. The density of cardiac mast cells is markedly higher in some patients with myocarditis and dilated cardiomyopathy than in accident victims without cardiovascular diseases. More importantly, in some of these conditions there is in situ evidence of mast cell activation. We have described an original technique to isolate and purify HHMC for in vitro study. This procedure gives viable cells and after stimulation with immunological or non-immunological stimuli they release performed (histamine and tryptase) and newly generated mediators (PGD2 and LTC4). We have demonstrated that HHMC differ from those in other anatomical districts in that they are activated by specific immunological and non-immunological stimuli, and in their relation to the arachidonic acid metabolism, suggesting that the local microenvironment can influence their phenotypic and biochemical characteristics. Our own and other findings suggest that HHMC have complex and significant roles in different pathophysiological conditions involving the cardiovascular system. Direct activation of HHMC by therapeutic and diagnostic substances injected intravenously explains some of the anaphylactoid reactions caused by these agents. HHMC possess Fc epsilon RI and IgE bound to the surface and C5a receptors, which could explain how cardiac mast cells are involved in systemic and cardiac anaphylaxis. Cardiac mast cells and those in human coronary arteries also play a role in the early and late stages of atherogenesis and during ischemic myocardial injury. In conclusion, although studies of HHMC are in their infancy, their in vitro isolation may be useful in identifying additional mediators synthesized and released, stimuli relevant to human pathophysiology, and pharmacological agents selectively modulating the activation of these cells and their mediators. Drugs specifically acting on HHMC or on their mediators may eventually be useful in treating different cardiovascular diseases.

Demonstration of specific high-affinity Fc epsilon-receptors on the human basophil-like leukemia cell line KU812 by flow cytometry

The specificity of IgE binding to a human basophil-like cell line (KU812) was studied by flow cytometry. Four IgE myeloma proteins, representing both light-chain types, one chimeric IgE protein, and polyclonal serum IgE blocked the direct binding of FITC-labeled IgE(DES) myeloma protein to KU812 cells in a dose-dependent and nearly equimolar way. Although not as efficiently as human IgE (from five to eight times less on a molar basis), both rat and mouse IgE blocked IgE(DES)-FITC binding to KU812 cells. In sharp contrast, all four human IgG subclasses, both IgA subclasses, and IgM myeloma proteins, as well as monomeric and heat-aggregated polyclonal human IgG, were unable to block significantly IgE(DES)-FITC binding to KU812 cells (< 0.5% on a molar basis). The cytophilic epitope on IgE was heat-susceptible (56 degrees C, 2 h), lost after reduction alkylation, and resident in the papain-derived Fc epsilon-fragment, but not in the papain-derived Fab epsilon- and Fc'epsilon-fragments nor in the pepsin-derived F(ab')2 epsilon- and Fc"epsilon-fragments. Washing and displacement experiments indicated that a major part of IgE reacted with high affinity to KU812 cells. The results indicate that the binding of IgE to KU812 cells is highly specific and involves the classical high-affinity Fc epsilon RI-receptor. Although the density of receptors is low, this human cell line offers a unique model to study IgE/Fc epsilon RI interactions.

Markers of eosinophilic inflammation in allergic diseases

The paper reviews personal studies aimed at identifying clinical markers of eosinophil inflammation in allergic diseases. Preliminary data on the use of flow cytometry as a method to detect eosinophil activation through phenotypic activation markers are reported. The concept of eosinophil releasibility is introduced on the basis of in vitro eosinophil activation and mediator release by different stimuli. Data showing an increase of serum levels of ECP mainly in subjects with sensitivity to perennial allergens and related to histamine bronchial reactivity are discussed in view of their practical impact in diagnosing and monitoring of allergic diseases and asthma.

Comparative analysis of biological activities of Der p I-derived peptides on Fc epsilon receptor-bearing cells from Dermatophagoides pteronyssinus-sensitive patients

The ability of four uncoupled synthetic peptides (p52-71, p117-133, p176-187, p188-199) derived from Der p I, a major allergen from the house dust mite Dermatophagoides pteronyssinus (Dpt) to stimulate Fc epsilon R+ cells from Dpt-sensitive patients was comparatively analysed. Each free peptide may specifically stimulate basophils (Fc epsilon RI+ cells) and platelets (Fc epsilon RII+ cells) from patients with significant levels of anti-Der p I IgE antibodies; p52-71 and p117-133 appear the best cell stimulation inducers. Both concentration-dependent biological activities of Der p I-peptide on Fc epsilon R+ cells are enhanced by coupling peptide to a carrier (as human serum albumin). Interestingly each Der p I-sensitive patient tested presents an individual pattern of response to peptide. Thus, from our results it appears that different Der p I sequences could be involved in the immune response to Der p I.

Mast cell activation enhances airway responsiveness to methacholine in the mouse

Mast cell-deficient mutant mice and their normal littermates were used to determine whether activation of mast cells by anti-IgE enhances airway responsiveness to bronchoactive agonists in vivo. Pulmonary conductance was used as an index of airway response as the mice were challenged with increasing intravenous doses of methacholine (Mch) or 5-hydroxytryptamine (5-HT). Mast cell activation with anti-IgE enhanced pulmonary responsiveness to Mch in both types of normal mice (P < 0.0001 by analysis of variance) but not in either genotype of mast cell-deficient mouse. Additionally, anti-IgE pretreatment of genetically mast cell-deficient W/Wv mice whose mast cell deficiency had been repaired by infusion of freshly obtained bone marrow cells or bone marrow-derived cultured mast cells from congenic normal mice led to significant (P < 0.0001) enhancement of Mch responsiveness. 5-HT responsiveness was not significantly influenced by anti-IgE pretreatment in any of the mice studied. The data support the hypothesis that IgE-mediated activation of mast cells enhances pulmonary responsiveness to cholinergic stimulation.

Effects of inhibitors of arachidonic acid metabolism on serotonin release from rat basophilic leukemia cells

Mast cells can release arachidonic acid (AA) metabolites as well as preformed mediators with IgE mediated stimulation, and these mediators are considered to play an important role in allergic reactions. The coincident release of preformed mediators and AA metabolites suggests that AA metabolism is related to mast cell degranulation. To clarify the relationship between mast cell degranulation and AA metabolism, the effects of various A cascade inhibitors on rat basophilic leukemia cell (RBL) mediator release induced by either anti-IgE or A23187 were examined. 5,8,11,14-eicosatetraynoic acid (ETYA) inhibited both PGD2 and LTC4/D4 generation, and partially inhibited serotonin release. Nordihydroguaiaretic acid (NDGA) caused complete inhibition of LTC4/D4 generation, and partial inhibition of PGD2 generation and serotonin release. The cyclooxygenase inhibitor, indomethacin, and the specific 5-lipoxygenase inhibitor, L-651,392 completely inhibited PGD2 and LTC4/D4 generation, respectively, without affecting release of other mediators. Both PGD2 and LTC4/D4 generation were abolished by the combination of indomethacin and L-651,392, however, serotonin release remained intact. HPLC analysis showed that no shift to other AA metabolites occurred after the treatment with these inhibitors. Mepacrine, a phospholipase A2 inhibitor, completely inhibited PGD2 and LTC4/D4 generation, as well as AA release itself, without affecting serotonin release. Therefore, neither AA metabolism nor AA release is necessary for RBL degranulation.

Mechanisms of activation of human mast cells and basophils by general anesthetic drugs

A study was performed about the effects of increasing concentrations of muscle relaxants (suxamethonium, d-tubocurarine, vecuronium, and atracurium), hypnotics (propofol, ketamine, and thiopental), opioids (morphine, buprenorphine, and fentanyl), and benzodiazepines (diazepam, flunitrazepam, and midazolam) on the release of preformed (histamine and tryptase) and de novo synthesized (prostaglandin D2: PGD2 and peptide-leukotriene C4: LTC4) chemical mediators from human basophils and mast cells isolated from skin (HSMC), lung parenchyma (HLMC) and heart tissue (HHMC). None of the drugs tested induced the release of histamine or LTC4 from basophils of normal donors. Suxamethonium did not induce mediator release from any type of human mast cell tested. Only the highest concentration of d-tubocurarine used caused histamine release from HSMC and HLMC. Atracurium, more than vecuronium, induced concentration-dependent histamine release from HSMC and HLMC. Propofol induced a concentration-dependent histamine release from HLMC, but not from HHMC. Only the highest concentrations of ketamine and thiopental used caused a significant release of histamine from HLMC. The muscle relaxants and hypnotics examined did not induce any de novo synthesis of PGD2 or LTC4 in mast cells. Morphine only induced histamine and tryptase release from HSMC, but not the de novo synthesis of PGD2. In contrast, buprenorphine caused histamine and tryptase release from HLMC, and not from HSMC, whilst it also induced de novo synthesis of PGD2 and LTC4 in HLMC. Fentanyl did not give any histamine and tryptase release from mast cells. Diazepam and flunitrazepam only induced a small release of histamine from mast cells, whereas midazolam caused the release of histamine from HLMC. The biochemical pathways underlying the release of mediators from human mast cells induced by drugs used during general anaesthesia are different from those underlying the immune release of histamine. From the results obtained with the in vitro model described here, it is clear that new drugs promising for the anesthesiologic arena should be tested in vitro before their potential histamine-releasing activity is experienced in vivo.

Anti-inflammatory effect of FK-506 on human skin mast cells

FK-506 and the structurally related macrolide rapamycin are high-affinity ligands for a specific binding protein (FK-506 binding protein). We examined the effects of FK-506 and rapamycin on the release of pre-formed (histamine) and de novo synthesized inflammatory mediators (prostaglandin D2) from mast cells isolated from human skin tissue. FK-506 (0.1 to 100 nM) concentration-dependently inhibited (5 to 65%) histamine release from skin mast cells activated by anti-IgE. FK-506 was more potent in skin mast cells than in basophils (IC40 = 2.15 +/- 0.78 nM versus 5.12 +/- 1.34 nM; p < 0.001), whereas the maximal inhibitory effect was higher in basophils than in skin mast cells (88.77 +/- 2.44% versus 67.30 +/- 3.98%; p < 0.01). FK-506 had little or no inhibitory effect on histamine release from skin mast cells challenged with compound A23187 and substance P, respectively, whereas it completely suppressed A23187-induced histamine release from basophils. FK-506 (0.1 to 100 nM) also inhibited (up to 65%) the de novo synthesis of prostaglandin D2 from skin mast cells challenged with anti-IgE. Despite its structural similarity to FK-506, rapamycin (10 to 300 nM) had little or no effect on the release of histamine from skin mast cells induced by anti-IgE, A23187, and substance P. However, rapamycin competitively antagonized the inhibitory effect of FK-506 on anti-IgE-induced histamine release from skin mast cells with a dissociation constant of about 14 nM. These data indicate that FK-506, but not rapamycin, is a potent anti-inflammatory agent acting on skin mast cells presumably by binding to the FK-506 binding protein. It thus appears that binding to the FK-506 binding protein is necessary, but not sufficient, to deliver an inhibitory signal to skin mast cells.

Specific histamine release capacity of peptides selected from the modelized Der p I protein, a major allergen of Dermatophagoides pteronyssinus

Dust mite allergens are considered as a major cause of allergic disease and as a risk factor for asthma. Der p I, a 222 amino-acid residue globular glycoprotein, is one of the major allergens from Dermatophagoides pteronyssinus (Dpt) mites. In this study, we have used predictive conventional algorithms (i.e. hydrophilicity, mobility, accessibility) and a three-dimensional model of Der p I derived from comparison to actinidin and papain to select continuous amino acid sequences as potential B cell epitopes. Four peptides, 52-71, 117-133, 176-187, 188-199 were synthesized. Their antigenic reactivity was investigated, mainly by measuring their capacity to induce in vitro histamine release. Results indicated that only Dpt-sensitive patients react specifically to Der p I-derived peptides and more frequently to 52-71 and 117-133. For each peptide, the intensity of response was dependent on the patient tested and on the peptide concn. The capacity of peptides to induce histamine release was demonstrated to be correlated with the serum level of anti-Der p I IgE (r = 0.86; p less than 10(-2)). Taken together these data emphasize, in Dpt-sensitive patients, the heterogeneity of the specific response to synthetic Der p I-derived peptides and underline the possible variety of epitopes belonging to the allergen Der p I.

Human basophil releasability. VIII. Increased basophil releasability in patients with scleroderma

We evaluated basophil releasability in 16 female patients with scleroderma (systemic sclerosis) and in 16 normal age- and sex-matched donors. Basophils from patients with scleroderma released significantly more histamine "spontaneously" than did those from normal donors (12.9 +/- 2.1% versus 4.5 +/- 0.7%; P less than 0.0005). Basophil reactivity (maximal percentage histamine release) to anti-IgE was higher in patients with scleroderma than in controls (57.0 +/- 7.5% versus 35.4 +/- 7.8%; P less than 0.05). Basophil sensitivity (the concentration of anti-IgE that causes 40% of maximal percentage histamine release) to anti-IgE in scleroderma patients was similar to that found in controls (4.6 +/- 2.8 x 10(-2) micrograms/ml versus 2.3 +/- 1.0 x 10(-1) micrograms/ml; P not significant). Scleroderma patients also showed enhanced releasability compared with that of the controls when challenged in vitro with interleukin-3 (8.3 +/- 1.7% versus 3.2 +/- 0.6%; P less than 0.01). Releasability induced by the formyl-containing tripeptide, f-met peptide, was significantly higher in the scleroderma patients than in the controls at the 2 lower concentrations used. No differences in basophil reactivity and sensitivity to f-met peptide and calcium ionophore A23187 were found between patients and normal donors. These results show that spontaneous basophil releasability and releasability in response to IgE cross-linking and activation of interleukin-3 receptors are increased in patients with scleroderma.

Human basophil/mast cell releasability. VII. Heterogeneity of the effect of adenosine on mediator secretion

5'-N-ethylcarboxamideadenosine (NECA) greater than 2-chloroadenosine greater than adenosine greater than N6-(R-phenyl-isopropyl)-adenosine (R-PIA) inhibited in vitro anti-IgE-induced histamine and peptide leukotriene C4 (LTC4) release from human basophils in a concentration-dependent fashion. Micromolar concentrations of adenosine, NECA and R-PIA potentiated the anti-IgE-stimulated release of histamine and LTC4 from human lung parenchymal mast cells. Submillimolar concentrations of adenosine, NECA and R-PIA inhibited in a concentration dependent manner the release of histamine and prostaglandin D2 (PGD2) from skin mast cells challenged with anti-IgE. These results demonstrate marked heterogeneity of the modulatory effect exerted by adenosine on mediator release from human basophils and mast cells.