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PubMed1993

Time course of plasma histamine and tryptase following food challenges in children with suspected food allergy.

This study was undertaken to investigate the kinetics of histamine and tryptase in the circulation of patients with food allergy and to determine whether the measurements of plasma histamine and tryptase concentrations after food challenges provided additional predictive markers for the diagnosis and evaluation of food allergy. Twenty-one open food challenges were performed on 13 patients with suspected food allergy. Plasma histamine and tryptase concentrations were measured during 4 hours after challenge. In the group of patients with immediate reactions after challenges, the mean plasma histamine concentration rose significantly at 120 and 240 minutes after the challenge, and the mean plasma tryptase concentration was increased significantly at 240 minutes after challenge. Plasma histamine and tryptase concentrations were measured during 24 hours after 8 open food challenges in 7 other patients with suspected food allergy. In each patient with a nonimmediate reaction, plasma histamine concentrations were increased at the onset of symptoms after challenge, but no plasma tryptase concentrations increased. The elevation of plasma histamine and tryptase in patients with immediate reactions following food challenge indicates mast cell activation. On the other hand, the elevation of plasma histamine without elevated plasma tryptase in the patients with nonimmediate reactions following food challenge may indicate basophil activation rather than mast cell activation. Plasma histamine and tryptase measurements after food challenge may be useful in the detection and evaluation of food allergy.

Adolescent↗
PubMed1996

Mast cell tryptase is a mitogen for epithelial cells. Stimulation of IL-8 production and intercellular adhesion molecule-1 expression.

Tryptase, a protease unique to the mast cell secretory granule, is released in substantial quantities into the respiratory tract of patients with inflammatory disease of the airways. We have investigated the potential of tryptase to act as a mitogen for bronchial epithelial cells and to stimulate release of IL-8 and expression of ICAM-1. Tryptase was isolated from extracts of human lung tissue using ammonium sulphate precipitation, octyl agarose, and heparin agarose chromatography. Purified tryptase stimulated DNA synthesis in the human epithelial cell line H292, as measured by [3H] thymidine incorporation. Maximal growth was observed after 24 h using 25 mU/ml of tryptase (where 1 micron is defined as that which can hydrolyze 1 mumol of the peptide substrate N-alpha-benzoyl-DL-arginine p-nitroanilide hydrochloride per minute at 25 degrees C), a concentration that is likely to be achieved in vivo. Inhibitors of tryptase activity, including leupeptin and benzamidine hydrochloride, significantly decreased tryptase-induced stimulation of DNA synthesis, indicating the requirement for an active catalytic site. Tryptase stimulated a catalytic site-dependent release of IL-8 from epithelial cells after 24 h, and this was associated with up-regulation of ICAM-1 expression, as revealed by FACS analysis. Tryptase may play a critical role in epithelial repair and in the recruitment of granulocytes following mast cell activation.

Carcinoma, Mucoepidermoid↗
PubMed1997

Potent induction of a neutrophil and eosinophil-rich infiltrate in vivo by human mast cell tryptase: selective enhancement of eosinophil recruitment by histamine.

Tryptase is the most abundant protein constituent of the secretory granules of human mast cells, but little is known of the contribution of this serine proteinase in acute allergic reactions. We have purified tryptase from human lung tissue by immunoaffinity procedures, and have investigated its potential to provoke an inflammatory infiltrate in vivo. Within 6 h of injection into the skin of guinea pigs, the accumulation of large numbers of neutrophils and eosinophils was observed, and those eosinophils closest to the injection site were partially degranulated. Similarly, injection of tryptase into the peritoneum of mice, even in quantities as low as 5 ng, stimulated the ingress of neutrophils. The response was dose dependent at 3, 6, and 16 h, with increases in median numbers of up to 400-fold. At the later time points eosinophil numbers were increased by up to 10-fold, and there were elevations also in the numbers of lymphocytes and macrophages. In both models, the actions of tryptase appeared to be dependent on an intact catalytic site. Coinjection of heparin with tryptase had relatively little effect on tryptase-induced responses. On the other hand, although histamine did not itself stimulate cell accumulation, over a range of concentrations it altered the cellular composition of the infiltrate induced by tryptase. Addition of histamine to tryptase provoked selective increases in eosinophil numbers of up to fivefold in the mouse peritoneum. Tryptase may provide an important stimulus for granulocyte recruitment in allergic disease.

Adjuvants, Immunologic↗
PubMed1986

Immunoassay of tryptase from human mast cells.

A sandwich ELISA was developed for the measurement of tryptase. The assay utilizes the mouse monoclonal anti-tryptase antibody, termed G5 (IgG2b kappa) in the solid phase and monospecific goat IgG anti-tryptase antibody together with tryptase in the fluid phase. The immunoassay will quantify 0.1 ng-5.6 ng of tryptase per 100 microliters of sample solution to within 0.1 ng. Intra-assay coefficients of variation were determined at 0.3 ng, 1.0 ng and 3.0 ng of tryptase per assay, respectively, to be 19%, 7% and 4% with buffer and 10%, 4%, and 4% in the presence of 20% plasma. Inter-assay coefficients of variation at the same respective levels of tryptase were 22%, 18% and 15% with buffer and 18%, 11% and 14% with 20% plasma. Net absorbance values obtained with a standard amount of tryptase in buffer alone and up to 50% (v/v) normal human citrate-treated plasma were within 10% of one another, indicating nearly complete detection of tryptase added to plasma. This represents the first sensitive immunoassay for a preformed mediator specific for human mast cells.

Antibodies, Monoclonal↗
PubMed1997

Quantitative analysis of tryptase and chymase containing mast cells in benign and malignant breast lesions.

The aim of our work was to study the number and distribution of tryptase- and chymase-containing mast cells in benign and malignant breast lesions. Tryptase positivity reflects the total number of mast cells, whereas chymase is not present in all mast cells. Active forms of tryptase and chymase were demonstrated enzymo-histochemically in 30 benign and 98 malignant fresh frozen breast lesions, which were graded and analysed morphometrically and statistically. The exclusive presence of tryptase and chymase in mast cells was confirmed in 5 cases by a sequential double-staining method. In benign lesions, the number of mast cells exhibiting tryptase activity was similar to that of chymase-active mast cells. Malignant tumours, however, had 2 to 3 times more tryptase-containing than chymase-containing mast cells, while the number of mast cells with tryptase activity was significantly higher (p < 0.02) than in benign lesions. In malignant lesions, tryptase-containing mast cells were concentrated at the tumour edge, i.e., the "invasion zone," whereas chymase-containing mast cells were not increased in this area.

Adult↗
PubMed2004

Mast cell tryptase, a still enigmatic enzyme.

Tryptases constitute a subfamily of trypsin-like proteinases, stored in the mast cell secretory granules of all mammalian organisms. These enzymes are released along with other mediators into the extracellular medium upon mast cell activation/degranulation. Among the trypsin-like enzymes, tryptases are unique: they are present as active enzymes in the mast cell granules, but display activity only extracellularly, and have a specificity which is much more restricted than trypsin. Tryptases are mostly tetrameric, and in only few organisms (not in humans) are they inhibited by endogenous inhibitors in vitro. The enzymatic and molecular properties of tryptases are far better characterized that any of their plausible biological functions. On the basis of its structural and functional features it could be predicted that tryptase would not degrade a large number of proteins in vivo due to low accessibility to the tetramer central pore where the active sites face inwards. Although their biological function has not yet been clarified, tryptases seem to be involved in a number of mast cell-mediated allergic and inflammatory diseases. In particular, the involvement of tryptase in asthma, an inflammatory disease of the airways often caused by allergy, has been proposed. Here we review the present knowledge on the structure-function relationship of tryptases from different organisms, with special emphasis on human enzymes, and on their role in a variety of pathophysiological processes.

Animals↗
PubMed2005

Mast cell tryptase: a new biomarker in patients with stable coronary artery disease.

Mast cells may participate actively in the inflammatory process of atherosclerotic plaques by releasing proteolytic enzymes and various other pro-inflammatory substances. We hypothesized that increased levels of mast cell tryptase, could be an important biomarker in patients with stable coronary artery disease (CAD). We measured tryptase in 102 patients without acute coronary syndromes undergoing cardiac catheterization. Patients with significant CAD [> or =50% stenosis in > or =1 artery (n=66)] had significantly higher serum tryptase than patients with normal angiography (n=13) or non-significant CAD [<50% stenosis (n=23)]. The median, 25th and 75th percentiles for tryptase in these two groups were 8.38 (6.4 and 10.7)mug/L versus 6.78 (5.61 and 9.72) microg/L, p=0.014. Patients in the highest quartile of tryptase levels had a 4.3-fold risk for CAD [Odds ratio (OR): 4.3; 95% confidence interval (CI): 1.08-17.19; p=0.04]. In a multivariate regression analysis, tryptase remained an independent predictor for CAD along with age (OR: 1.178; 95% CI: 1.021-1.359, p=0.025). High circulating tryptase levels may be a result of chronic low-grade inflammatory activity present in atherosclerotic plaques. Tryptase measurements may emerge as a novel way of identifying asymptomatic patients with CAD, and represent a new biomarker of therapeutic efficacy in patients with CAD.

Aged↗
PubMed2005

Comparison of serum tryptase and urine N-methylhistamine in patients with suspected mastocytosis.

BACKGROUND: The disease extent of mastocytosis can be assessed by measurement of mediators or their metabolites, secreted from mast cells. In the present study, we compared results of urinary N-methylhistamine measurements with analysis of total tryptase in serum from patients with suspected mastocytosis. METHODS: Tryptase in serum was determined with the UniCAP tryptase fluor-enzyme-immunoassay, according to the manufacturers' instructions (Pharmacia, Woerden, Netherlands). N-methylhistamine in urine was determined by competitive radioimmunoassay, according to the manufacturers' instructions (Pharmacia). RESULTS: A significant correlation between serum tryptase and urine N-methylhistamine was found both for 138 patients aged 14 or older (Spearman Rank r(s)=0.43, p<0.0001) and for 23 younger patients (Spearman Rank r(s)=0.46, p=0.0267). The between-run coefficient of variation of the tryptase assay was half (6.7%) of the one (13%) found with the urinary N-methylhistamine assay. Both for urine N-methylhistamine and serum tryptase, a significant difference was found between corresponding biopsies with an increased number of mast cell aggregates and biopsies without such an increase. The difference between tryptase levels however was stronger (Mann-Whitney: p=0.0012) than the difference between N-methylhistamine levels (Mann-Whitney: p=0.0140). CONCLUSION: Serum tryptase discriminates better than urinary N-methylhistamine between patients with an increased number of mast cell aggregates and persons without such an increase.

Humans↗
PubMed2006

Mast cell mediator tryptase levels after inhalation or intravenous administration of high doses pharmaceutically prepared heroin.

BACKGROUND: Opioids like morphine and heroin induce mast cell degranulation in vitro. The release of mast cell mediators like histamine and tryptase may lead to allergic symptoms. In this study it was investigated whether mast cell mediator release also occurs in vivo in addicted patients who participated in a heroin on medical prescription trial, and were under treatment with large doses of heroin in combination with methadone. METHOD: Plasma levels of tryptase, a specific marker for mast cell degranulation, were measured by immuno-assay at baseline and 60 min after heroin administration. Heroin was administered either by intravenous injection (11 subjects) or by inhalation (nine subjects). Single heroin doses varied from 200 to 450 mg. Besides tryptase, the plasma concentrations of heroin, its metabolite morphine and methadone were measured. RESULTS: After heroin injection, the mean tryptase plasma concentration increased dose dependently by on average 23.1% (95% CI 14.6-31.6%). After heroin inhalation, no tryptase release was observed. Heroin and morphine peak plasma concentrations were 3-5 times greater in heroin injectors than in inhalers. In heroin injectors, tryptase levels were related to morphine peak concentrations, but not to heroin concentrations. Tryptase plasma concentrations were not related to methadone levels. Mild allergic reactions were reported in five cases after intravenous heroin use, but not after inhalation. CONCLUSION: This study revealed that mast cell mediator tryptase concentrations increase after intravenous heroin injection in chronic opioid users, but not after heroin inhalation. This may be explained by the higher Cmax levels of metabolite morphine that were achieved after injection than after inhalation. Although statistical significance was reached, the degree of mast cell degranulation after intravenous injection of heroin was mild, and did not lead to clinically relevant side effects in this group of opioid-tolerant subjects.

Administration, Inhalation↗
PubMed2005

Potent pruritogenic action of tryptase mediated by PAR-2 receptor and its involvement in anti-pruritic effect of nafamostat mesilate in mice.

The pruritogenic potency of tryptase and its involvement in anti-pruritic effect of intravenous nafamostat mesilate (NFM) were studied in mice. An intradermal injection of tryptase (0.05-1 ng/site) elicited scratching in ICR mice, while chymase was without effects at doses of 0.05-50 ng/site. The dose-response curve of tryptase action was bell-shaped and the effect peaked at 0.1 ng/site (approximately 0.7 fmol/site). NFM (10 mg/kg) inhibited scratching induced by tryptase but not by histamine and serotonin. NFM (1-10 mg/kg) produced the dose-dependent inhibition of scratching induced by intradermal compound 48/80 (10 microg/site). The inhibition by NFM (10 mg/kg) was abolished in mast cell-deficient (WBB6F1 W/W(V)) mice, but not in wild-type (WBB6F1 +/+) mice. NFM (10 mg/kg) suppressed tryptase activity in the mouse skin. Proteinase-activated receptor-2 (PAR-2) neutralizing antibody (0.1 and 1 microg/site) and the PAR-2 antagonist FSLLRY (10 and 100 microg/site) inhibited scratching induced by tryptase (0.1 ng/site) and compound 48/80 (10 microg/site). These results suggest that mast cell tryptase elicits itch through PAR-2 receptor and that NFM inhibits itch-associated responses mainly through the inhibition of mast cell tryptase.

Animals↗
PubMed2001

Tryptase-induced airway microvascular leakage in guinea pigs: involvement of tachykinins and leukotrienes.

Tryptase, a serine protease synthesized by and stored in mast cells, is implicated as an important mediator in the pathogenesis of airway inflammation. In this study, tryptase was evaluated for its ability to induce microvascular leakage into the airways of guinea pigs. Dose- and time-dependent increases in airway microvascular leakage were produced by intratracheal tryptase (0.3-3 microg). Intratracheal tryptase (3-30 microg) had no effect on airway tone as measured by pulmonary insufflation pressure. Tryptase-induced airway microvascular leakage was partially blocked by the tachykinin NK1 receptor antagonist CP 99994 [(+)-(2S,3S)-3-(2-methoxybenzylamino)-2-phenylpiperidine] and an inhibitor of leukotriene formation SCH 37224 (1-(1,2-dihydro-4-hydroxy-2-oxo-1-phenyl-1,8-naphthyridin-2-yl)pyrrolidinium, hydroxide inner salt). Neither CP 99994 nor SCH 37224 inhibited tryptase proteolytic activity in-vitro. Pretreatment of guinea pigs with histamine H1 receptor antagonists or a tachykinin NK2 receptor antagonist had no affect on the airway microvascular leakage induced by tryptase. It is speculated that tryptase may be important in the pathogenesis of airway inflammation, particularly in disorders that involve increased airway microvascular leakage such as asthma.

Analysis of Variance↗
PubMed1998

Tryptase mediates hyperresponsiveness in isolated guinea pig bronchi.

Hyperresponsiveness of airway smooth muscle to allergens and environmental factors has long been associated with the pathophysiology of asthma. Tryptase, a serine protease of lung mast cells, has been implicated as one of the mediators involved in the induction of hyperresponsiveness. As a consequence, tryptase inhibitors have become the subject of study as potential novel therapeutic agents for asthma. Secretory leukocyte protease inhibitor (SLPI) is a naturally occurring protein of human airways which exhibits anti-tryptase activity. To assess the potential therapeutic utility of SLPI in asthma, its effects were evaluated using in vitro and ex vivo models of airway hyperresponsiveness and compared with the effects of the small molecule tryptase inhibitor APC-366. Our results demonstrate that SLPI inhibits tryptase-mediated hyperresponsiveness in vitro and attenuates the hyperresponsiveness observed in airway smooth muscle from antigen-sensitized animals subjected to antigen exposure. The small molecule tryptase inhibitor APC-366 has a similar inhibitory effect. Thus, tryptase appears to be a significant contributor to the development of hyperresponsiveness in these models. To the extent that tryptase contributes to the development and progression of asthma, SLPI may possess therapeutic potential in this disease setting.

Animals↗
PubMed2003

Mast cell tryptase and hemolysis after trauma.

BACKGROUND: We have previously found increased mast cell tryptase in accidental deaths due to trauma, indicating that mast cell degranulation had occurred. The present study was designed to confirm the previous observation and to determine if tryptase release after trauma is acute or delayed. Furthermore, the importance of hemolysis and direct trauma to the mast cells was investigated. MATERIALS AND METHODS: Mast cell tryptase was measured in post-mortem blood from the femoral vein in 27 cases of death from trauma and in 27 control cases by means of a commercially available immunoassay. The trauma cases were further classified into groups with single versus multiple trauma, and groups with short survival time (i.e. death at the scene of the accident) versus longer survival time (death in hospital). In five multi-trauma deaths, blood was sampled locally from the sites of crush injury. RESULTS: The mean value of tryptase in femoral vein blood was 35.6+/-34.6 microg/l in the entire trauma group and 14.7+/-6.5 microg/l in the controls (P<0.005). In bloody liquid sampled from crush injuries, tryptase was substantially elevated in all cases, with a mean of 227+/-146 microg/l. In cases with short survival time, tryptase was significantly higher than in those who died after several hours or days in hospital (P<0.001). No statistically significant difference was seen between multi- and single-trauma cases. A correlation between hemolysis in the samples and elevated tryptase was found only in the trauma cases (P<0.05), but experimentally induced hemolysis in vitro was not found to influence the measurements. CONCLUSION: Mast cell tryptase becomes elevated in trauma deaths and this seems to be ascribable either to direct mechanical injury to tissue mast cells and/or to cell lysis. In patients initially surviving severe injuries, the effects of massive release of histamine and other mast cell mediators might be of importance for treatment strategies and prognosis.

Angiogenesis Inducing Agents↗
PubMed1998

Enzyme histochemistry of rat mast cell tryptase.

Fixation and staining conditions for rat mast cell tryptase and its histochemical distribution in different rat tissues were investigated. Prostate, skin, lung, gut, stomach and salivary glands were fixed in either aldehyde or Carnoy fixatives and then frozen or embedded in paraffin wax. Preservation of tryptase enzymic activity against peptide substrates required aldehyde fixation and frozen sectioning. Of the peptide substrates examined, z-Ala-Ala-Lys-4-methoxy-2-naphthylamide and z-Gly-Pro-Arg-4-methoxy-2-naphthylamide proved the most effective for the demonstration of tryptase. Double staining by enzyme cytochemistry followed by immunological detection of tryptase showed that, in all tryptase-containing mast cells, the enzyme is at least in part active. Conventional dye-binding histochemistry was used to confirm the identity of mast cells. Aldehyde-fixed mucosal mast cells required a much shorter staining time with Toluidine Blue if tissue sections were washed directly in t-butyl alcohol. Double staining by enzyme cytochemistry and dye binding showed that tryptase is absent from mucosal and subepidermal mast cells, which are also smaller in size and appear to contain fewer granules than connective tissue mast cells. This study demonstrates that rat mast cell tryptase, unlike tryptases in other species, is a soluble enzyme. It is stored in an active form and is absent from some mast cell subpopulations in mucosa, skin and lung.

Animals↗
PubMed2002

Genetic deficiency of human mast cell alpha-tryptase.

BACKGROUND: Human alpha- and beta-tryptases are proteases secreted by mast cells. Beta (but not alpha) tryptases are implicated in asthma. Genes encoding both types of tryptases cluster on chromosome 16p13.3. OBJECTIVE: This study examines the hypothesis, generated from mapping data, that alpha-alleles compete with some beta-alleles at one locus and that an adjacent locus contains beta-alleles exclusively. This hypothesis predicts that beta-alleles outnumber alpha and that some genomes lack alpha genes altogether. METHODS: To test this hypothesis, we developed PCR-based techniques to distinguish alpha from beta genes. We then genotyped genomic DNA from individuals and tryptase-expressing cell lines. RESULTS: In support of our hypothesis, we find that alpha-tryptase deficiency affects 80/274 (29%) of individuals surveyed. The genotype of the alpha-deficient individuals is betabetabetabeta, due to inheritance of four beta genes. The percentage of the population with the mixed genotypes alphaalphabetabeta and alphabetabetabeta is 21% and 50%, respectively. Accounting for all alpha- and beta-alleles at the tandem loci on 16p13.3, overall alpha-allele frequency is only 0.23, with beta-alleles considerably outnumbering alpha as hypothesized. In samples of defined ethnicity, alpha deficiency affects 45% of Caucasians, but a much lower percentage of other backgrounds, including African-Americans and Asians. Examination of cell lines reveals that HMC-1 and U-937 lack alpha-genes; thus, lack of alpha transcripts in these cells is due to absence of alpha-genes rather than beta-selective transcription. By contrast, alpha-transcribing Mono Mac 6 and KU812 cells contain alpha- and beta-genes. CONCLUSIONS: Genetic alpha-tryptase deficiency is common and varies strikingly between ethnic groups. Because beta-tryptases are implicated in allergic disorders, inherited differences in alpha/beta-genotype may affect disease susceptibility, severity and response to tryptase inhibitor therapy.

Base Sequence↗
PubMed2001

Release of mast cell tryptase from human colorectal mucosa in inflammatory bowel disease.

BACKGROUND: Histologic detection of mast cells cannot adequately reflect their function and state of activation, since degranulated mast cells may escape from histologic assessment. To better define the role of mast cells in inflammatory bowel disease, the spontaneous secretion of mast cell tryptase, a highly mast cell specific protease, was measured from colorectal samples. METHODS: After detection of the initial basal tryptase release, gut mucosal samples were incubated in a modified Hanks/RPM1 medium using a mucosa oxygenation system. Spontaneous tryptase secretion from 153 viable samples of 22 controls, 30 patients with Crohn disease (CD) and 19 with ulcerative colitis (UC) was followed over 4 h. Tryptase was measured by radioimmunoassay. RESULTS: The rates of the initial basal tryptase release revealed that mast cell activation occurs during active inflammation in CD and UC. While the time course of tryptase release was similar in all three groups, spontaneous tryptase secretion (over 4 h) was found to be significantly enhanced and prolonged only in UC (P < 0.01 compared to controls), but not in CD. CONCLUSIONS: This study provides clear evidence from viable endoscopic colorectal samples that mast cell mediators were secreted during active inflammation in CD and UC. However, the extent of mast cell involvement and activation differs considerably between CD and UC. Significantly increased rates of tryptase secretion were found both in non-inflamed and inflamed tissue of UC, indicating that mast cell involvement is a typical feature of UC.

Adult↗
PubMed2005

Possible molecular mechanisms to account for the involvement of tryptase in the pathogenesis of psoriasis.

Tryptase has been suggested to take part in the pathophysiology of psoriasis mainly through the production of C3a by cleaving C3. However, studies using tryptase preparations of high purity do not support this notion. Therefore, although tryptase is unanimously believed to be involved in the immunopathogenesis of psoriasis, no convincing mechanism has been proposed for its role. This paper proposes several mechanisms by which this enyme may exert its role in the pathobiology of psoriasis. Tryptase is a mitogen for epithelial cells and stimulates IL-8 production and ICAM-1 expression by these cells. It also induces the expression of mRNA for IL-1beta and IL-8 and stimulates the selective release of IL-8 from endothelial cells and TNF-alpha, IL-1beta, and IL-6 from lymphocytes and monocytes. Besides itself being a chemoattractant for neutrophils, tryptase activates mast cells and generates kinins from kininogen, thereby playing a crucial role in leukocyte infiltration into psoriatic lesions. This enzyme also induces leukocyte infiltration partly through activating endothelial PAR-2, which contributes to leukocyte rolling, adherence and recruitment by inducing the release of endothelial platelet-activating factor. Through activating PAR-2, tryptase could also trigger the development of Langerhans cells which play a crucial role in the pathophysiology of psoriasis. This enzyme is a mitogen for fibroblasts, which are probably involved in the pathophysiology of psoriasis through production of insulin-like growth factor-I (IGF-I). Tryptase is a gelatinase and also activates stromelysin-1 (MMP-3), thereby contributing to the disruption of psoriatic basement membrane and to the joint damage seen in psoriatic arthritis. Increase of tryptase levels following trauma could also provide a mechanism for Koebner phenomenon seen in psoriasis.

Animals↗
PubMed2002

Tryptase a novel biochemical marker of acute myeloid leukemia.

Despite maturation arrest, blast cells in acute myeloid leukemia (AML) are often capable of expressing lineage-restricted (granulomonocytic or myelomastocytic) differentiation antigens. Tryptases are lineage-associated serine proteases primarily expressed in mast cells, and less abundantly in blood basophils. We have recently shown that myeloblasts in a group of patients with AML (approximately 40%) produce significant amounts of tryptase(s). In these patients, serum tryptase levels are elevated (> 15 ng/ml) and reflect the total burden of leukemic cells. In most cases, myeloblasts express alpha-tryptase mRNA in excess over beta-tryptase mRNA, and secrete the respective protein (= pro-alpha-tryptase) in a constitutive manner. It was also found that these AML blasts frequentlyco-express tryptase with additional mast cell lineage- and/or basophil-related differentiation antigens including KIT (CD117), histamine, and 2D7. We hypothesize that tryptase-positive AMLs arise from a leukemic progenitor that exhibits a limited potential to differentiate into mast cells and/or basophils.

Acute Disease↗