Chymase-positive mast cells in small sized adenocarcinoma of the lung

Mast cells accumulate in angiogenesis-dependent situations of lung adenocarcinoma. Human mast cells are divided into two major subsets: MCT (mast cells with immunoreactivity for tryptase but not chymase) and MCTC (reactive for tryptase and chymase). Chymase is an important mediator of tissue remodeling, but research into chymase-containing mast cell subpopulations has been hampered by the lack of reagents suitable for use with formalin-fixed tissue. We stained chymase using CC1 antibody in 66 cases of small sized lung adenocarcinoma as well as CD34 and tryptase. There were significant positive correlations of microvessel counts with MCT-type and MCTC-type mast cell counts in lung adenocarcinomas. When analyzed according to Noguchi's classification, MCT-type and MCTC-type mast cells were significantly increased in Noguchi type-C tumors [localized bronchioloalveolar carcinoma (LBAC) with active fibroblastic proliferation] compared with in Noguchi type-A (LBAC) plus type-B tumors (LBAC with alveolar collapse). Members in the high-count group of MCTC-type but not MCT-type mast cells showed a significantly worse outcome than those in the low-count group in LBACs. Counting chymase-positive (MCTC-type) mast cells in tumor stroma may be a good prognosis predictor for LBACs, especially Noguchi type-C tumors.

Tryptase-stimulated human airway smooth muscle cells induce cytokine synthesis and mast cell chemotaxis

Asthmatic patients have higher numbers of mast cells in the smooth muscle layer of airways than normal subjects. Human airway smooth muscle cells (HASMCs) are a source of various cytokines including transforming growth factor beta1 (TGF-beta1), which is chemotactic for mast cells. We have thus examined the potential for interaction between HASMCs and mast cells and have investigated, in particular, the hypothesis that after stimulation, HASMCs can induce mast cell chemotaxis through the production of cytokines. Supernatants of HASMCs treated with the major mast cell product tryptase had increased chemotactic activity for the HMC-1 mast cell line. The effect depended on an intact catalytic site for tryptase and could be induced by a peptide agonist for protease activated receptor 2. Chemotactic activity was related to the synthesis of TGF-beta1 by HASMCs and, to a lesser extent, to stem cell factor. The number of mast cells within the smooth muscle layer of asthmatic patients was closely related to TGF-beta1 expression by smooth muscle. HASMCs may thus be able to stimulate the accumulation of mast cells, and these cells may, in turn, stimulate the secretion of chemotactic factors by HASMCs.

The release of basogranulin in response to IgE-dependent and IgE-independent stimuli: validity of basogranulin measurement as an indicator of basophil activation

BACKGROUND

Basogranulin, the novel basophil granule protein recognized by the monoclonal antibody BB1, can be released by stimulation with anti-IgE antibody or calcium ionophore. However, the kinetics and regulation of its secretion are unknown.

OBJECTIVE

We quantified basogranulin and histamine release in response to a range of stimuli to assess whether basogranulin secretion is a reliable marker of basophil activation.

METHODS

Isolated peripheral blood basophils were stimulated with anti-IgE antibody, calcium ionophore, N -formyl-Met-Leu-Phe, and complement C5a. The released basogranulin and histamine were quantified by dot blotting with BB1 and a fluorometric method, respectively. Basogranulin localization was confirmed by flow cytometry.

RESULTS

Both basogranulin and histamine displayed a bell-shaped response curve when basophils were challenged with anti-IgE. Half-maximal release occurred within 30 seconds. Basogranulin levels were maximal by 15 minutes, whereas those for histamine continued increasing to 30 minutes. Wortmannin, a PI3-K inhibitor, suppressed the release of both mediators. Basophils from donors with the "nonreleaser" phenotype secreted neither mediator in response to anti-IgE. Non-IgE-dependent stimuli released both mediators in parallel in a concentration-dependent manner. The correlation between the relative amounts of each mediator released was highly significant (r =.901, P <.0001, n = 87). Flow cytometry revealed that some of the secreted basogranulin adhered to the cell surface.

CONCLUSIONS

Basogranulin is secreted along with histamine in response to both FcepsilonR I-related and unrelated stimuli. It is therefore a valid marker of basophil activation and could provide the basis for an immunoassay that distinguishes between basophil and mast cell activation.

The inhibition of mast cell activation by neutrophil lactoferrin: uptake by mast cells and interaction with tryptase, chymase and cathepsin G

Inhibitors of mast cell tryptase and chymase can be effective as mast cell stabilising compounds. Lactoferrin has been reported to inhibit tryptase activity, but its actions on other serine proteases of mast cells and its potential to alter mast cell function are not known. We have examined the ability of lactoferrin to inhibit mast cell tryptase, chymase and cathepsin G, and investigated its potential to modulate the activation of human mast cells. Enzymatically dispersed cells from human skin, lung and tonsil were challenged with anti-IgE or calcium ionophore A23187, following incubation with recombinant human lactoferrin, and histamine release determined. IgE-dependent histamine release from skin mast cells was inhibited by up to 50% following incubation with lactoferrin (50 or 500 nM). Tonsil mast cells were also stabilised by lactoferrin, but not those from lung. Calcium ionophore A23187-induced histamine release was not altered by lactoferrin. A double-labelling immunocytochemical procedure revealed the presence of lactoferrin in 4-6% of mast cells, and this proportion increased to 40% following incubation with lactoferrin. Lactoferrin did not inhibit cleavage of synthetic substrates by tryptase and chymase directly, though it was able to diminish the ability of heparin to stabilise tryptase. Cathepsin G activity was inhibited by lactoferrin. The ability of lactoferrin to inhibit IgE-dependent activation of human mast cells and modulate protease activity suggests that the release of this neutrophil product may have a role in the downregulation of allergic inflammation.

The heterogeneity of mast cell tryptase from human lung and skin

There has long been conjecture over the degree to which there may be structural and functional heterogeneity in the tetrameric serine protease tryptase (EC 3.4.21.59), a major mediator of allergic inflammation. We have applied 2D gel electrophoresis to analyze the extent, nature, and variability of this heterogeneity in lysates of mast cells isolated from lung and skin, and in preparations of purified tryptase. Gels were silver stained, or the proteins transferred to nitrocellulose blots and probed with either tryptase-specific monoclonal antibodies or various lectins. Tryptase was the major protein constituent in mast cell lysates, and presented as an array of 9-12 diffuse immunoreactive spots with molecular masses ranging from 29 to 40 kDa, and pI values from 5.1 to 6.3. Although the patterns obtained for lung and skin tryptase were broadly similar, differences were observed between tissues and between individual donors. Lectin binding studies indicated the presence of mono-antennary or bi-antennary complex-type oligosaccharide with varying degrees of sialylation. Deglycosylation with protein-N-glycosidase F (PNGase F) reduced the size of both lung and skin tryptase, while incubation with PNGase F or neuraminidase narrowed the pI range, indicating variable degrees of glycosylation as a major contributor to the size and charge heterogeneity. Comparison of different purified preparations of lung and skin tryptase revealed no significant difference in pH profiles, but differences were seen in reactivity towards a range of chromogenic substrates, with substantial differences in Km, kcat and degree of cooperativity. Mathematical modeling indicated that the variety in kinetics parameters could not result solely from the sum of varying amounts of isoforms obeying Michaelis-Menten kinetics but with different values of Km and kcat. The heterogeneity demonstrated for tryptase in these studies suggests that there are important differences in tryptase function in different tissues.

Evidence of mast-cell activation in a subset of patients with eosinophilic chronic obstructive pulmonary disease

Although asthma has been viewed mainly as an eosinophilic disease, and chronic obstructive pulmonary disease (COPD) as a neutrophilic disease, recent studies have shown increased neutrophil counts in severe asthma and sputum eosinophilia in some COPD patients. In an attempt to further characterise these two syndromes according to pathology, the current authors have conducted a study of induced sputum in 15 subjects with COPD, 17 asthmatics, and 17 nonatopic healthy individuals. Sputum was analysed for cytology and levels of eosinophil cationic protein (ECP), albumin, tryptase and soluble intercellular adhesion molecule-1. The COPD subjects differed from the asthmatics as they had higher sputum neutrophil and lower columnar epithelial cell counts, but there were no differences in any soluble marker studied. When compared to control subjects, both the asthmatic and COPD subjects had raised eosinophil counts and ECP levels. In a subset of COPD subjects with sputum eosinophilia (>3% of total cells), significantly increased levels of tryptase were detected. In conclusion, although chronic obstructive pulmonary disease is a more neutrophilic disease than asthma, the two diseases are difficult to distinguish on the basis of sputum levels of the soluble markers traditionally associated with asthma. However, a subset of patients with chronic obstructive pulmonary disease with airway eosinophilia and mast-cell activation might represent a distinct pathological phenotype.

CCR3-blocking antibody inhibits allergen-induced eosinophil recruitment in human skin xenografts from allergic patients

Eosinophil, basophil, and T helper 2 (TH2) cell recruitment into tissues is a characteristic feature of allergic diseases. These cells have in common the expression of the chemokine receptor CCR3, which may represent a specific pathway for their accumulation in vivo. Although animal models of allergic reactions are available, findings cannot always be extrapolated to man. To overcome these limitations, we have developed a humanized mouse model of allergic cutaneous reaction using severe combined immunodeficiency mice engrafted with skin and autologous peripheral blood mononuclear cells from allergic donors. Intradermal injection of the relevant allergen into human skin xenografts from allergic individuals induced a significant recruitment of human CD4(+) T cells, basophils, and TH2-type cytokine mRNA-expressing cells, as well as murine eosinophils. Human skin xenografts, atopic status, and autologous peripheral blood mononuclear cell reconstitution were all mandatory to induce the allergic reaction. Next, we addressed the role of CCR3 in the endogenous mechanisms involved in the inflammatory cell recruitment in this experimental model of allergic cutaneous reaction. In vivo administration of an anti-human CCR3-blocking antibody selectively reduced accumulation of eosinophils but not that of CD4(+) cells, basophils, or cells expressing mRNA for TH2-type cytokines. These findings establish a new in vivo model of humanized allergic reaction and suggest that eosinophil migration is mediated mainly through CCR3. Finally, these results suggest that this model might be useful to test human-specific antiallergic modulators.

Activation markers of human basophils: CD69 expression is strongly and preferentially induced by IL-3

BACKGROUND

The biological functions of basophils are precisely regulated by various cytokines in vitro, but little is known about surface markers that are upregulated during the cytokine-mediated activation process.

OBJECTIVE

It has been well established that CD69, CD44, and CD54 represent "activation markers" for cytokine-mediated eosinophil activation. The objective of this study was to elucidate the expression and regulation of these molecules in human basophils in vitro as well as in vivo.

METHODS

Basophils were purified from venous blood by means of density gradient centrifugation followed by negative selection. Surface expression was analyzed by means of flow cytometry. We also studied the expression of CD69, CD44, and CD54 on basophils in bronchoalveolar lavage fluid and blood specimens from patients with asthma.

RESULTS

CD44 and CD54 were constitutively expressed on basophils and moderately upregulated by IL-3. On the other hand, CD69 expression was only weakly observed in freshly isolated basophils, but IL-3 induced extremely high levels of expression. Surface CD69 appeared rather slowly in comparison with CD63 and CD11b, and the induction of expression was completed within 24 hours. Basophil CD69 had no functional relevance, but it did have biological relevance. Whole blood basophils from asthmatic individuals expressed significantly higher levels of CD69 than did those from normal individuals. Furthermore, bronchoalveolar lavage fluid basophils showed higher levels of CD69 expression than did blood basophils from the same donors.

CONCLUSION

CD69 expression on basophils was preferentially and strongly upregulated by IL-3. CD69 on basophils might be useful as an in vitro as well as in vivo marker of activation of these cells by IL-3.

Elevated serum concentrations of beta-tryptase, but not alpha-tryptase, in Sudden Infant Death Syndrome (SIDS). An investigation of anaphylactic mechanisms

BACKGROUND

Sudden Infant Death Syndrome, (SIDS) or cot death, remains the most common category of post-perinatal death in the UK. By definition, the cause of death is unknown, but a long-standing theory is that some of these deaths could be the result of anaphylaxis.

OBJECTIVE

To investigate the potential contribution of anaphylactic mechanisms to deaths in infancy by determining relative levels of alpha- and beta-tryptases and both total and allergen-specific IgE in sera from groups of infants whose deaths were attributed to SIDS or to other causes.

METHODS

Serum samples were collected at the time of post-mortem examination from infants whose death was classed as SIDS (n = 40) and from a comparison group in which cause of death had been established (n = 32). Serum tryptase concentrations were measured with a radioimmunoassay with monoclonal antibody G5 which detects primarily beta-tryptase or an ELISA with antibody AA5 which has equal sensitivity for alpha- and beta-tryptases. Levels of total IgE and IgE specific for casein, beta-lactoglobulin, house dust mite and moulds were determined.

RESULTS

Analysis of the results of the two assays for tryptase indicated that levels of the beta-like tryptase (the form secreted on anaphylactic degranulation) were significantly higher in serum from infants with SIDS compared with those whose death was explained. There was no evidence for an increase in serum levels of alpha-tryptase (the variant secreted constitutively from mast cells). Total levels of serum IgE did not differ between the two groups and, reflecting the low circulating IgE concentrations in infancy, an elevation in IgE specific for the panel of allergens was not detected.

CONCLUSIONS

In a proportion of SIDS victims there may be increased serum levels of beta-like tryptase, a marker for anaphylaxis. The failure to detect an increase in alpha-tryptase would suggest that mast cell hyperplasia is not a feature of cot death. The nature of the inciting agents remains unclear, but anaphylaxis deserves serious consideration as a possible cause of sudden death in infancy.

Tryptase and agonists of PAR-2 induce the proliferation of human airway smooth muscle cells

Airway remodeling with smooth muscle cell (SMC) hyperplasia is a feature of chronic asthma. We investigated the potential for tryptase, the major secretory product of human mast cells, to act as a growth factor for human airway SMCs. Because this serine protease can activate proteinase-activated receptor-2 (PAR-2), we also examined the actions of SLIGKV, a peptide agonist of PAR-2. Incubation with lung tryptase provoked a twofold increase in [(3)H]thymidine incorporation; a similar increase in cell numbers was found when we used the MTS assay. The effect was catalytic site dependent, being abolished by the protease inhibitors leupeptin and benzamidine and by heat inactivation of the enzyme. Tryptase-induced DNA synthesis was inhibited by preincubation of the cells with pertussis toxin, calphostin C, or genistein. Transduction mechanisms are thus likely to involve a pertussis toxin-sensitive G protein, protein kinase C, and tyrosine kinase. SLIGKV elicited a response on SMCs similar to that of tryptase. Tryptase could provide an important stimulus for SMC proliferation in asthmatic airways, by acting on PAR-2.

Segmental bronchoprovocation in allergic rhinitis patients affects mast cell and basophil numbers in nasal and bronchial mucosa

Mast cells and basophils are cells that play an important role in the initiation and control of allergic inflammation in asthma and rhinitis. This study was undertaken to determine the presence and dynamics of mast cells and basophils in the nasal and bronchial mucosa of allergic rhinitis patients after segmental bronchial provocation (SBP). Eight nonasthmatic, grass pollen-allergic rhinitis patients and eight healthy controls were included. Bronchial and nasal biopsies, as well as blood samples, were taken before (T(0)) and 24 h (T(24)) after SBP. Immunohistochemical staining was performed for mast cells (tryptase and chymase; phenotypes MC(T), MC(TC), MC(C)) and basophils (BB1). In the bronchial mucosa, the number of BB1(+) cells increased significantly (p < 0.05) in allergic rhinitis patients after SBP. In the nasal mucosa, the numbers of MC(C) and MC(TC) cells decreased significantly, whereas the numbers of [BB1(+)] cells increased significantly in allergic rhinitis patients after SBP (p < 0.05). In blood, the number of basophils decreased (p < 0.05) and the level of interleukin (IL)-5 increased (p < 0.05) in atopic patients after SBP. No significant changes could be observed in healthy controls. This study shows that SBP in nonasthmatic allergic rhinitis patients reduces numbers of mast cells in the nose as a result of enhanced degranulation. At the same time, there is evidence for an influx of basophils from the blood into the nasal and bronchial mucosae.

Mass, charge, and subcellular localization of a unique secretory product identified by the basophil-specific antibody BB1

BACKGROUND

BB1 is a basophil-specific mAb (Lab Invest 1999;79:27-38). The identity of the corresponding antigen has not been determined, but it gives a granular appearance on staining and is secreted on activation of basophils.

OBJECTIVE

We sought to further characterize the basophilspecific antigen identified by BB1.

METHODS

Intracellular localization was determined by flow cytometry and by immunogold labeling and electron microscopy. Physical chemical properties were investigated by gel filtration chromatography and preparative isoelectric focusing.

RESULTS

In flow cytometry, permeabilization of cells increased immunofluorescence 100-fold, confirming the predominantly intracellular localization of the antigen. It was further localized to the secretory granules by immunoelectron microscopy. Double labeling with a CD63-specific antibody demonstrated selective binding of BB1 to the granule matrix. Gel filtration chromatography indicated that the antigen is secreted as a complex of approximately 5 x 10(6) d, which was well resolved from the 210-kd supramolecular complex containing tryptase. The antigen was degraded by pronase. Isoelectric focusing indicated a highly basic protein with an isoelectric point of 9.6.

CONCLUSION

With its granule localization, release on cell activation, and unique properties, the antigen identified by BB1 could be a novel mediator of allergic disease. We propose the name basogranulin for this novel basophil-specific protein.

Chemokine-induced cutaneous inflammatory cell infiltration in a model of Hu-PBMC-SCID mice grafted with human skin

Recently, certain chemokines and chemokine receptors have been preferentially associated with the selective recruitment in vitro of type 1 T cells, such as IP-10 and its receptor CXCR3, or type 2 T cells such as monocyte-derived chemokine (MDC) and eotaxin and their receptors CCR4 and CCR3. Very few models have provided confirmation of these findings in vivo. Taking advantage of the humanized SCID mouse model grafted with autologous human skin, the ability of the chemokines IP-10, MDC, eotaxin, and RANTES to stimulate cell recruitment was investigated. Intradermal IP-10 injection resulted in an influx of CD4+ T lymphocytes but also surprisingly in the recruitment of dendritic cells. MDC recruited mainly CD8+ T lymphocytes, and had little effect on eosinophils. As predicted, eotaxin was a potent inducer of eosinophil and basophil migration, also recruiting CD4+ T cells. RANTES, a ubiquitous chemokine associated with both type 1 and type 2 profiles, was able to recruit all cell types. CXCR3-positive cells were preferentially recruited by IP-10, whereas CCR3- and CCR4-positive cells were predominantly found after injection of eotaxin and MDC. Thus, in a human environment in vivo, some chemokines have the ability to recruit cells expressing chemokine receptors preferentially expressed on type 1 or type 2 cells. Further investigations revealed that MDC and eotaxin induced the recruitment of type 2, but not type 1, cytokine-producing cells. RANTES, on the other hand, induced the migration of both type 1 and type 2 cytokine-secreting cells, whereas IP-10 did not induce the recruitment of either subtype. These studies provide detailed information on the properties of MDC, eotaxin, IP-10, and RANTES as chemotactic molecules in skin in vivo. The use of the humanized SCID mouse model grafted with human skin is validated as a useful model for the evaluation of chemokine function in the inflammatory reaction, and suggests that therapeutic targeting of certain chemokines might be of interest in diseases associated preferentially with a type 1 or type 2 profile.

The activation of synovial mast cells: modulation of histamine release by tryptase and chymase and their inhibitors

Mast cells have been implicated as having pivotal roles in arthritis, but little is known of the processes leading to the activation of synovial mast cells or their potential for pharmacological control. We have investigated the ability of tryptase and chymase, and inhibitors of these major mast cell proteases to modulate the activation of mast cells from human synovial tissue. The tryptase inhibitor drug N-(1-hydroxy-2-naphthoyl)-L-arginyl-L-prolinamide hydrochloride (APC366) inhibited immunoglobulin E (IgE)-dependent histamine release in a dose-dependent manner, with about 70% inhibition being achieved at a dose of 300 microM. Histamine release stimulated by calcium ionophore A23187 was also inhibited by this compound. The chymase inhibitor chymostatin inhibited IgE-dependent histamine release by approximately 60% at 1 microg/ml. Tryptase at concentrations of 3.0 microg/ml and greater stimulated histamine release from synovial cells, which was dependent on catalytic activity, whereas chymase had little effect on these cells. The activation of mast cells by tryptase may represent an amplification process in the synovium. The mast cell stabilising properties of inhibitors of tryptase and chymase could be of therapeutic value in arthritis.

A polymorphic protease-activated receptor 2 (PAR2) displaying reduced sensitivity to trypsin and differential responses to PAR agonists

Protease-activated receptor 2 (PAR2) is a trypsin-activated member of a family of G-protein-coupled PARs. We have identified a polymorphic form of human PAR2 (PAR(2)F240S) characterized by a phenylalanine to serine mutation at residue 240 within extracellular loop 2, with allelic frequencies of 0.916 (Phe(240)) and 0.084 (Ser(240)) for the wild-type and mutant alleles, respectively. Elevations in intracellular calcium were measured in permanently transfected cell lines expressing the receptors. PAR(2)F240S displayed a significant reduction in sensitivity toward trypsin ( approximately 3.7-fold) and the PAR2-activating peptides, SLIGKV-NH(2) ( approximately 2.5-fold) and SLIGRL-NH(2) ( approximately 2.8-fold), but an increased sensitivity toward the selective PAR2 agonist, trans-cinnamoyl-LIGRLO-NH(2) ( approximately 4-fold). Increased sensitivity was also observed toward the selective PAR-1 agonist, TFLLR-NH(2) ( approximately 7-fold), but not to other PAR-1 agonists tested. Furthermore, we found that TLIGRL-NH(2) and a PAR4-derived peptide, trans-cinnamoyl-YPGKF-NH(2), were selective PAR(2)F240S agonists. By introducing the F240S mutation into rat PAR2, we observed shifts in agonist potencies that mirrored the human PAR(2)F240S, suggesting that Phe(240) is involved in determining agonist specificity of PAR2. Finally, differences in receptor signaling were paralleled in a cell growth assay. We suggest that the distinct pharmacological profile induced by this polymorphism will have important implications for the design of PAR-targeted agonists/antagonists and may contribute to, or be predictive of, an inflammatory disease.

Persistent airway T-lymphocyte activation in chronic corticosteroid-treated symptomatic asthma

BACKGROUND

A small proportion of patients with asthma have persistent symptoms despite regular treatment with high-dose inhaled and/or oral corticosteroids. There is little information regarding immunopathology in such patients.

OBJECTIVE

To compare airway inflammatory changes in subjects with chronic corticosteroid-dependent symptomatic asthma (n = 5) and subjects with asthma that was clinically well controlled on inhaled corticosteroid therapy (n = 9). Subjects in the corticosteroid-dependent group were receiving long-term treatment with oral prednisolone and high-dose inhaled corticosteroids.

METHODS

Subjects underwent fiberoptic bronchoscopy with bronchoalveolar lavage (BAL) and bronchial biopsy. T-lymphocytes subsets and activation markers in BAL fluid and peripheral blood were determined by FACS analysis. Bronchial biopsies were stained immunohistochemically, and numbers of inflammatory cells quantitated. Inflammatory mediators in BAL fluid were measured by immunoassay.

RESULTS

There was significantly greater expression of CD25 (P = .02) and HLA-DR (P = .04) by BAL fluid T-lymphocytes in corticosteroid-treated symptomatic asthmatics. In bronchial biopsies there were no significant differences between the two groups in the numbers of AA1+ cells (mast cells), EG2+ cells (eosinophils) or MT1+ T-lymphocytes. Levels of albumin, histamine, tryptase, and eosinophil cationic protein in BAL fluid did not differ significantly between groups.

CONCLUSIONS

Chronic corticosteroid-treated symptomatic asthma is associated with persistent airway T-lymphocyte activation. This, however, is not necessarily accompanied by the recruitment and activation of inflammatory cells within the airways.

Basophil and eosinophil accumulation and mast cell degranulation in the nasal mucosa of patients with hay fever after local allergen provocation

BACKGROUND

Basophils and mast cells have certain similarities and are believed to be important in upper and lower respiratory allergy.

OBJECTIVE

We sought to apply immunohistology to investigate the distribution and numbers of mast cells and basophils in the nasal mucosa after allergen provocation.

METHODS

Allergen challenge with grass pollen was performed in 9 patients with seasonal allergic rhinitis out of the hay fever season. Nasal biopsy specimens were taken before and approximately 1 hour, 24 hours, and 1 week after intranasal allergen provocation. We determined relative numbers and their phenotypic characteristics by using mAbs specific for tryptase, chymase, IgE, eosinophils (BMK-13), and a new mAb against basophils (BB1) by using immunohistochemistry in frozen sections.

RESULTS

In the nasal mucosa at baseline, practically no basophils were found in the epithelium. A significant increase in numbers was found in the epithelium and lamina propria of the nasal mucosa in the early phase as early as 1 hour after allergen provocation. At 24 hours and 1 week after allergen provocation, a significant increase in basophil numbers was found in the lamina propria only. The proportion of mast cells staining for chymase in the lamina propria decreased from a median of 38% (range, 0%-82%) to 14% (range, 0%-78%) within 1 hour of allergen provocation. The proportion of mast cells staining for chymase increased from 1% (range, 0%-86%) at baseline to 21% (range, 3%-85%) within 1 hour of allergen provocation. One week after provocation, mast cells returned to baseline numbers. A definite tissue eosinophilia was observed after allergen provocation.

CONCLUSION

Basophil numbers are increased in the epithelium and lamina propria of the nasal mucosa of subjects with rhinitis after allergen challenge, with influx already apparent at 1 hour. Moreover, changes in mast cell percentages and numbers were observed within 1 hour of allergen provocation.

Human mast cell tryptase stimulates the release of an IL-8-dependent neutrophil chemotactic activity from human umbilical vein endothelial cells (HUVEC)

Tryptase, the major product of human mast cell activation, is a potent stimulus of vascular leakage and neutrophil accumulation in vivo in animal studies, but the mechanisms of action remain unclear. Using HUVEC cultures we have sought to investigate the potential of tryptase to alter monolayer permeability or induce the release of neutrophil chemotactic activity. Tryptase (1-100 mU/ml) failed to alter the permeability of endothelial cell monolayers as assessed by albumin flux over 1 h. However, supernatants from endothelial cells treated with tryptase (1-50 mU/ml) for a 24-h period induced neutrophil migration across Transwell filters, with maximal migration observed at 10 mU/ml tryptase. Pretreatment of tryptase with the protease inhibitor leupeptin abolished the chemotactic activity, indicating a dependence on the catalytic site. Moreover, this effect was abolished by addition of an IL-8 neutralizing antibody, suggesting that IL-8 release makes an important contribution to the chemotactic activity. The interaction of mast cell tryptase with endothelial cells could be important in stimulating the ingress of neutrophils following mast cell activation in inflammatory disease.