Tryptase Concentrations Research Articles

Involvement of alpha-4 integrins in allergic airway responses and mast cell degranulation in vivo.

Antibodies against integrins have been shown to inhibit allergic airway responses. The purpose of this study was to test the hypothesis that the beta1 integrin, very late antigen-4 (VLA-4), is involved in mast cell activation triggered by allergen exposure in sensitized animals. To do this we studied Brown Norway rats that were sensitized to ovalbumin (OA; 1 mg subcutaneously) using Bordetella pertussis as an adjuvant. Two weeks later rats were challenged with OA, pulmonary resistance (RL) was determined, and the concentrations of histamine and tryptase in bronchoalveolar lavage fluid and N-acetyl-leukotriene (LT)E4 in bile were measured. Pretreatment with a monoclonal antibody against VLA-4 (TA-2) attenuated the early response after OA challenge (342.9 +/- 24.4% baseline RL versus 153.3 +/- 19.4%; p < 0.01). There were significantly lower concentrations of histamine (67.11 +/- 11.90 microgram/ml versus 26.69 +/- 1.84; p < 0.01) and tryptase (0.143 +/- 0. 035 microgram/ml versus 0.053 +/- 0.022 microgram/ml; p < 0.01) in TA-2-treated animals. The increases in the concentrations of biliary N-acetyl-LTE4 after OA challenge were also significantly lower in TA-2-treated animals. These data suggest that a selective anti-VLA-4 monoclonal antibody prevents early responses through inhibition of mast cell activation.

Spontaneous inactivation of human tryptase involves conformational changes consistent with conversion of the active site to a zymogen-like structure.

The conformational changes accompanying spontaneous inactivation and dextran sulfate (DS) mediated reactivation of the serine protease human tryptase were investigated by analysis of (i) intrinsic fluorescence, (ii) inhibitor binding, and (iii) catalytic efficiency. Spontaneous inactivation produced a marked decrease in fluorescence emission intensity that was reversed by the addition of DS. Fluorescence decreases at high (4.0 microM) and low (0.1 microM) tryptase concentrations were similar at early times and coincided with loss of enzymatic activity but deviated significantly from activity loss at later times by showing a difference in the extent of change. The fluorescence losses were best described by a two-step kinetic model in which the major decrease correlated to activity loss (t1/2 of 4.3 min in 0.2 M NaCl, pH 6.8, 30 degrees C) and was followed by a further decrease (t1/2 approximately 60 min) whose extent differed with tryptase concentration. The ability to bind the competitive inhibitor p-aminobenzamidine was reversibly lost upon spontaneous inactivation, providing evidence for conformational changes affecting the major substrate binding site (S1-pocket). Estimation of catalytic efficiency using an active site titrant showed that the specific activity of tryptase remained unchanged upon inactivation and reactivation. Return of enzymatic activity, intrinsic fluorescence, and the S1 pocket appeared to occur in the same time frame (t1/2 approximately 3 min). These studies indicate that spontaneous inactivation involves reversible changes which convert the active site to a nonfunctional state. The association of activity loss with an intrinsic fluorescence decrease and loss of the S1-pocket is consistent with the disruption of a critical ionic bond at the active site. Formation of this ionic bond is the basis of zymogen activation for the chymotrypsin family of serine proteases.

β-Tryptase measurements post-mortem in anaphylactic deaths and in controls

The reliability of measuring mast cell tryptase in post-mortem blood to diagnose anaphylactic deaths has been questioned because moderate elevation of tryptase can be seen also in control cases. Very high tryptase concentrations have been recorded even in a few control cases with known cause of death such as myocardial infarction or trauma. Aiming to compare findings we measured tryptase in 193 cases: 176 with known cause of death, 10 unexplained deaths and seven anaphylactic or anaphylactoid deaths (AADs). Using binary logistic regression we calculated the sensitivity and specificity of the tryptase test at different cut-off values, and found 10 μg/l to be optimal, the sensitivity being 86% and the specificity 88%. Traumatic deaths ( n=23), sudden infant death syndrome ( n=40) or deaths after heroin-injection ( n=22) showed elevated tryptase values in 35%, 35% and 32%, respectively, and in 40% of the unexplained deaths ( n=10), which was higher than expected (12%). Heart blood tryptase level was elevated in 22% of the controls and femoral blood tryptase in 10%. No correlations were seen with age or post-mortem delay. It is concluded that tryptase measurements are useful in confirming death from AAD, and that blood should be sampled from the femoral vessels. In unexplained deaths tryptase measurement is a useful indicator, but the diagnosis is not to be based on the test alone.

Eosinophil Cationic Protein (ECP) and Tryptase in the Nasal lavage Fluid (NLF) of Children with Grass Pollen Rhinitis: levocabastine Effect

This study was carried out to determine the concentrations of eosinophil cationic protein (ECP) and tryptase in the nasal lavage fluid (NLF) of 24 children (C) with grass pollen rhinitis as well as rhinitis symptoms before and after nasal provocation tests with or without a levocabastine (anti-H1 topical antihistamine) pretreatment. All C were monosensitized to grasses only. Twelve patients (Active Group = AG) were tested with a nasal provocation test with grass pollen (NPT) carried out by the insufflation of increasingly higher doses of an allergenic extract powder, while the other 12 patients (Placebo Group = PG) underwent just a nasal provocation test with lactose (placebo) (NPTp). The prechallenge NLF, obtained both before (C) and after (AG) levocabastine pretreatment, was compared to that obtained after periods of 2 and 24 hours postchallenge. In the AG, before and after levocabastine pretreatment, the tryptase concentrations had not significantly increased, whereas the ECP concentrations were found to be significantly higher (p < 0.05) in just the 24-hour postchallenge samples. In the PG the rhinitis symptoms were not induced by the NPTp and there was no significant change in either ECP or tryptase concentrations. In the AG a levocabastine pretreatment induced a significant increase (p < 0.05) in the cumulative allergen doses administered by the NPT. There was a reduction of the nasal symptoms in 7 patients, while in 3 subjects there was only a slight improvement, but in 2 subjects no effect was encountered. In conclusion this study shows that a levocabastine pretreatment before an NPT in patients with grass pollen rhinitis, outside the grass pollen season, induces a significant increase in the cumulative allergen doses (administered by the NPT) which provoked rhinitis symptoms but is not able to demonstrate any significant reduction in the ECP concentrations of the NLF.

Mast cells in bronchiectasis

Bronchiectasis (BE) is a chronic severe inflammatory lung disease characterized by frequent bacterial infections and polymorphonuclear neutrophil-dominated inflammatory reaction. We have attempted to elucidate the role of mast cells (MCs) in BE lung inflammation by measuring in the bronchoalveolar lavage fluid (BALF) the MC-derived tryptase levels by radioimmunoassay and immunoblotting and also by measuring the tryptase-like activities in 36 BE patients and in 14 healthy controls. The amount of MC in the lung tissue was assessed by immunohistochemical staining of resected lung tissue samples. Based on the clinical and radiological parameters the patients were divided into subgroups according to the severity of the disease. The MC tryptase concentrations (μg/L; median (range)) in BALF of BE patients were higher compared to healthy controls (4.7(1.4–20.1) and 2.0 (0.1–3.5), respectively, P < 0.01). Tryptase concentrations in the groups of mild, moderate and severe BE were 3.8 (0.9–10.8), 4.3 (3.0–12.6) and 9.6 (1.2–20.1), respectively. All the values differed significantly from those observed in the healthy controls. The tryptase-like activities (nmol/sec/L) in BE patients were also markedly increased (174 (31–2874)) compared to healthy controls (28 (9–45) P < 0.0001). The tryptase-like activities in the patient subgroups were 45 (36–598) in mild, 91 (31–1437) in moderate and 1336 (37–2874) in severe BE. Again, all values differed significantly from those observed in the healthy controls. Moreover, immunoblot experiments disclosed the most intensive immunoreactivity of the 27.5 kD tryptase monomer in BALF of patients with severe BE followed by weaker immunoreactivity in groups of moderate and mild BE and in healthy controls. No significant difference could be observed in the amount of tryptase-positive cells between BE patients and controls. However, the presence of degranulated MCs was more evident in BE lung tissue. Significant correlation could also be observed between the degree of activation of latent procollagenase and tryptase concentration (r = 0.8, P = 0.0004) in BALF of individual BE patients. The observed strong correlation between tryptase levels and disease severity suggests that MCs may be involved in the inflammatory reaction in the BE lung. Importantly, the high levels of tryptase, observed also in patients with mild BE, suggests that activation of and proteinase release from MCs may be one of the reasons for the perpetuation of tissue injury even during the clinically quiescent periods in BE.

Mast cell tryptase in anaesthetic anaphylactoid reactions

Increased concentrations of mast cell tryptase are a highly sensitive indicator of anaphylactic reactions during anaesthesia. We obtained serum specimens from 350 patients after possible anaphylactic reactions during anaesthesia. Serum was collected from patients in our own institution (27), and transported by mail and courier from other hospitals in response to a request in the medical literature (323). Concentrations of mast cell tryptase were measured in 416 specimens. Intradermal testing was performed in 217 patients and radioimmunoassay for drug-specific antibodies with serum in 198 patients. Mast cell tryptase concentrations were increased in 158 patients, equivocal in 10 and not increased in 182. There was a significant difference in the incidence of positive intradermal tests, radioimmunoassay tests and evidence of an IgE-mediated reaction in patients whose mast cell tryptase concentrations were increased. Seven of 143 patients whose mast cell tryptase concentrations were not increased at appropriate sampling times had positive tests for IgE antibodies, and in 33 of 158 patients with increased mast cell tryptase concentrations no IgE antibodies were detected. We conclude that increased mast cell tryptase concentrations are a valuable indicator of an anaphylactic reaction during anaesthesia. Their presence favours an IgE-mediated cause but does not always distinguish between anaphylactoid and anaphylactoid reactions, and patients in whom mast cell tryptase concentrations are not increased still require skin testing.

Anaphylactoid shock--a common cause of death in heroin addicts?

We measured mast-cell tryptase in postmortem blood from 22 heroin addicts dying suddenly after injection. In 32%, the concentration of tryptase was elevated (> or = 10 micrograms/l), and the mean value of tryptase was significantly different from a control group dying from known, nonimmunologic causes (P < 0.05). The increased tryptase concentrations indicate that death was preceded by systemic mast-cell degranulation. All victims of drug deaths had morphine in blood, most below 0.2 microgram/ml. In 71% of the victims of drug-related deaths with tryptase values > or = 10 micrograms/l, the intermediate degradation product, 6-monoacetyl-morphine, was not found in blood, whereas this was the case in only two victims with values below that cutoff point. This indicates that those with high tryptase concentrations survived longer than those with lower values. No correlation was found between the IgE levels and tryptase in either group, supporting the hypothesis that tryptase release was not mediated by an allergic reaction. The well-known property of opiates to stimulate unspecifically the liberation of histamine and other constituents of mast-cell granules offers one explanation of our observations. The results suggest that many heroin fatalities are caused by an anaphylactoid reaction.

A rapid increase in foot tissue temperature predicts cardiovascular collapse during anaphylactic and anaphylactoid reactions.

Cardiovascular collapse during anaphylactic and anaphylactoid reactions results from release of histamine and other vasoactive substances. Intense arteriolar vasodilation associated with severe allergic reactions is likely to increase convective transfer of heat and peripheral tissue temperature, and finally to provoke cardiovascular collapse. Therefore the authors tested the hypothesis that during anaphylactic and anaphylactoid reactions, an acute increase in peripheral tissue temperature precedes cardiovascular collapse and that the magnitude of the increase correlates with the severity of the reaction. During a 13-yr period, approximately 120,000 patients were screened for clinical evidence of intraoperative anaphylactic and anaphylactoid reactions. Core temperature was measured in the distal esophagus, and "deep" foot tissue temperature was measured on the sole of one foot in all these patients. Otherwise unexplained cardiovascular collapse accompanied by bronchospasm and/or cutaneous signs such as urticaria, flushing, or angioedema occurred in 32 patients who were entered into a prospective diagnostic protocol. Among these, 15 met laboratory criteria for anaphylactic or anaphylactoid reactions. Anaphylaxis was confirmed in nine of them by a positive skin test to the suspected agent, the in vitro leukocyte histamine-release test, or the Praunitz-Küstner test. Reactions were considered anaphylactoid in six others when laboratory evidence did not support anaphylaxis, but plasma histamine or tryptase concentrations were much greater during episodes than 6 weeks later. Development of anaphylactic and anaphylactoid reactions followed a characteristic pattern: (1) Foot temperature, which was initially 3.3 +/- 1.7 degrees C less than core temperature, increased to within 0.3 degrees C of core temperature 3.2 +/- 1.4 min after drug administration; (2) onset of cardiovascular collapse ensued 1.8 +/- 0.8 min later; and (3) core temperature increased from 34.7 +/- 1.0 degrees C to peak values 37.1 +/- 0.6 degrees C 13 +/- 5 min after drug administration. The most severe reactions were associated with shorter times to comparable core and foot temperatures, faster onset of cardiovascular collapse, and higher maximum core temperatures. The normal core-to-peripheral tissue temperature gradient was obliterated several minutes before hemodynamic consequences associated with anaphylactic and anaphylactoid reactions. Further, a rapid increase in deep foot temperature and maximum core temperature correlated with clinical severity.

Histamine release during cardiopulmonary bypass in neonates and infants.

Histamine release has been previously documented in adults and children during cardiopulmonary bypass (CPB). It has not been studied in neonates nor during deep hypothermic circulatory arrest (DHCA). Histamine effects could explain many perioperative complications of congenital cardiac surgery such as dysrhythmias and massive oedema. Therefore, documentation of histamine release in the perioperative period is of clinical importance. The source of histamine can be determined by measurement of tryptase which is released with histamine from mast cells but not basophils. Blood samples for histamine and tryptase were taken before and after specific events eg. cross-clamp removal, during anaesthesia and CPB in 14 infants and seven neonates undergoing complex congenital heart repairs and were analysed by commercial radioimmunoassays. Haemodynamic variables and pre and post-op weights were recorded to look for correlation between pathophysiological events and histamine release. Histamine concentration decreased at the start of bypass (0.69 to 0.38 ng.ml-1 at five minutes, (P < .005). There were no changes associated with DHCA and a small rise with reventilation (P < 0.02). Histamine concentration was lower in neonates than in infants (P < 0.05) during CPB. Plasma histamine and tryptase concentrations did not correlate, suggesting histamine release was from basophils and not from mast cells. Haemodynamic variables did not correlate with histamine concentrations. There was no major histamine release during CPB in infants and neonates. There was no relationship between histamine concentrations and clinical variables. Histamine released during CPB appears to come from basophils and may be a function of age.

Mast cell tryptase stimulates the synthesis of type I collagen in human lung fibroblasts.

Mast cell activation is a characteristic feature of chronic inflammation, a condition that may lead to fibrosis as a result of increased collagen synthesis by fibroblasts. We have investigated the potential of tryptase, the major protease of human mast cells, to stimulate collagen synthesis in the human lung fibroblast cell line MRC-5. Tryptase was isolated from human lung tissue by ion-exchange and affinity chromatography. At concentrations of 18 and 36 mU/ml, tryptase stimulated both an increase in cell numbers, and a fivefold increase in DNA synthesis as determined by methyl-[3H]thymidine incorporation. Similar concentrations of tryptase resulted in a 2.5-fold increase in collagen synthesis as determined both by incorporation of [3H]proline into collagen, and by assay of hydroxyproline concentrations in the supernatants. There was also a twofold increase in collagenolytic activity in the culture medium after tryptase treatment, indicating that the increase in collagen synthesis was not a consequence of decreased collagenase production. All of these actions of tryptase were reduced in the presence of the protease inhibitors leupeptin and benzamidine hydrochloride, indicating a requirement for an active catalytic site. SDS-PAGE and autoradiographic analysis of the [3H]collagen produced by the cells revealed it to be predominantly type I collagen. Our findings suggest that the release of tryptase from activated mast cells may provide a signal for abnormal fibrosis in inflammatory disease.

Human mast cells activate fibroblasts: tryptase is a fibrogenic factor stimulating collagen messenger ribonucleic acid synthesis and fibroblast chemotaxis.

The effect of human mast cells on fibroblast activity was studied using an organotypic skin-equivalent culture system. Human mast cell-1 (HMC-1) cells were embedded in a collagen gel with neonatal dermal fibroblasts at a ratio of 1:4; keratinocytes then were allowed to stratify above this composite culture. Analysis of type a1(I) procollagen mRNA synthesis by in situ hybridization revealed a substantial increase in mRNA levels in the presence of mast cells and especially following degranulation, induced by calcium ionophore A23187. Tryptase, a major product of human mast cells, could substitute for mast cells in this culture system, up-regulating procollagen mRNA synthesis. Tryptase pretreated with the specific protease inhibitor bis(5-amidino-2-benzimidazo-lyl)methane (BABIM) markedly attenuated the collagen mRNA up-regulation. Further studies revealed HMC-1 cell sonicates stimulated fibroblast chemotaxis and procollagen mRNA synthesis. Inhibition of HMC-1 sonicates with either BABIM or a neutralizing mAb against tryptase resulted in significant reduction of fibroblast chemotaxis and procollagen mRNA, implying that tryptase accounted for the majority of HMC-1 sonicate activity. Tryptase directly stimulated fibroblast chemotaxis with optimal concentrations between 10 pM and 1 nM. The maximal response of optimal concentrations of tryptase was comparable with the known fibrogenic factor, TGF-beta. Inhibition of tryptase with BABIM resulted in approximately 50% reduction in chemotactic activity. Additional studies revealed that tryptase (0.3-3 nM) stimulated procollagen mRNA synthesis in confluent monolayers of dermal fibroblasts.

Nasal responsiveness to allergen and histamine in patients with perennial rhinitis with and without a late phase response.

BACKGROUND: In the lower airways an association has been found between early phase reaction (EPR), late phase reaction (LPR), and bronchial hyperreactivity. However, this association has not been shown for...

Interactions of Mast Cell Tryptase with Thrombin Receptors and PAR-2

Tryptase is a serine protease secreted by mast cells that is able to activate other cells. In the present studies we have tested whether these responses could be mediated by thrombin receptors or PAR-2, two G-protein-coupled receptors that are activated by proteolysis. When added to a peptide corresponding to the N terminus of PAR-2, tryptase cleaved the peptide at the activating site, but at higher concentrations it also cleaved downstream, as did trypsin, a known activator of PAR-2. Thrombin, factor Xa, plasmin, urokinase, plasma kallikrein, and tissue kallikrein had no effect. Tryptase also cleaved the analogous thrombin receptor peptide at the activating site but less efficiently. When added to COS-1 cells expressing either receptor, tryptase stimulated phosphoinositide hydrolysis. With PAR-2, this response was half-maximal at 1 nM tryptase and could be inhibited by the tryptase inhibitor, APC366, or by antibodies to tryptase and PAR-2. When added to human endothelial cells, which normally express PAR-2 and thrombin receptors, or keratinocytes, which express only PAR-2, tryptase caused an increase in cytosolic Ca2+. However, when added to platelets or CHRF-288 cells, which express thrombin receptors but not PAR-2, tryptase caused neither aggregation nor increased Ca2+. These results show that 1) tryptase has the potential to activate both PAR-2 and thrombin receptors; 2) for PAR-2, this potential is realized, although cleavage at secondary sites may limit activation, particularly at higher tryptase concentrations; and 3) in contrast, although tryptase clearly activates thrombin receptors in COS-1 cells, it does not appear to cleave endogenous thrombin receptors in platelets or CHRF-288 cells. These distinctions correlate with the observed differences in the rate of cleavage of the PAR-2 and thrombin receptor peptides by tryptase. Tryptase is the first protease other than trypsin that has been shown to activate human PAR-2. Its presence within mast cell granules places it in tissues where PAR-2 is expressed but trypsin is unlikely to reach.

Tryptase concentration in skin blister fluid from patients with bullous skin conditions

Tryptase concentration in skin blister fluid from patients with bullous skin conditions

The immunopharmacology of mild asthma

If cell numbers, activation state, or mediators, for example, can be correlated with some clinical measure of disease severity, a major effector role in the disease may be postulated. Mast cells, along with eosinophils and lymphocytes, are present in increased numbers in the airways of patients with asthma. Mast cell mediators are also increased in persons with allergies, with the concentrations of histamine, tryptase, and prostaglandin D 2 being proportional to the degree of airway obstruction and bronchial hyperresponsiveness. Increased numbers of activated mast cells and eosinophils (but not T cells or macrophages) were also found in bronchoalveolar lavage fluid in children. The mast cell is also known to release a range of cytokines (e.g., tumor necrosis factor–α and IL-4) that have various important functions, including upregulation of the endothelial adhesion molecules that are responsible for eosinophil recruitment from the microvascular circulation into the airways and subsequent activation. Mast cell staining for secreted IL-4 was found to be proportional to the infiltration of eosinophils and lower airway symptoms in patients with seasonal asthma, which is compatible with the concept that mast cells alone can sustain a continuing allergic inflammatory response. The mast cell proteases chymase and tryptase are also important for eosinophil recruitment and activation and for increasing mucus secretion and microvascular permeability. The evidence that the human mast cell is capable of releasing proteases and cytokines that have the capacity to initiate and maintain a chronic inflammatory response provides a mechanism whereby the clinical efficacy of nedocromil sodium in patients with chronic mild to moderate asthma can be explained. (J A LLERGY C LIN I MMUNOL 1996;98:S7-16.)

THE ANAPHYLAXIS HYPOTHESIS OF SUDDEN INFANT DEATH SYNDROME (SIDS): MAST CELL DEGRANULATION IN COT DEATH REVEALED BY ELEVATED CONCENTRATIONS OF TRYPTASE IN SERUM

This study found that elevated concentrations of serum tryptase are associated with sudden unexplained infant death, and this may be consistent with anaphylaxis as a mechanism in some cases of SIDS. Further studies are needed to determine if mast cell degeneration in these cases is secondary to terminal respiratory failure or some other event common to most cases of SIDS. The measurement of 9α, 11β-PGF2, as a specific marker of mast cell activation was not helpful under the conditions of this study.

A rationale for the use of nedocromil sodium in the treatment of asthma

A rationale for the use of nedocromil sodium in the treatment of asthma

Prostaglandin D2 measurement in nasal secretions is not a reliable marker for mast cell activation in atopic patients.

Prostaglandin D2 (PGD2) is a very important mast cell product during the early-phase nasal allergic reaction. However, the quantification of PGD2 in nasal secretions has not yet been well established. Quantitative determination of PGD2 in nasal secretions of atopic patients (n = 17) after nasal allergen challenge (NAC) and in non-allergic healthy volunteers (n = 10). The nasal microsuction sampling technique was used to obtain the nasal secretions with an exactly known and minimally diluted volume. A sensitive and specific enzyme immunoassay was chosen to measure the more stable 11-methoxime derivative of PGD2, which was obtained after extraction in acetone/ethanol and conversion using methoxamine-HCl. The concentrations of PGD2 in nasal secretions obtained from 10 non-allergic healthy volunteers were used as reference values. There was no significant difference in the concentrations of PGD2 between men (median: 569 pg/mL) and women (median: 407 pg/mL), nor between the baseline concentrations from atopic patients (median: 410 pg/mL) and non-allergic controls (median: 477 pg/mL). In the atopic patient group, PGD2 did not significantly increase during the entire sampling period after NAC. The absence of PGD2 response contrasted with the nasal symptoms manifested by sneezing, increased nasal airway resistance, and the significant increases of the concentrations of histamine, tryptase, and leukotriene C4 (LTC4) 5 min after NAC. This observation suggests that the measurement of PGD2 alone in the nasal secretions does not give reliable information on mast cell activation during a nasal allergic reaction.

Immunoglobulin E, mast cell-specific tryptase and the complement system in sudden death from coronary artery thrombosis

We tested the hypothesis of anaphylaxis as a pathogenic factor in acute myocardial infarction. Mast cells were counted in the myocardium, coronary arteries and airways. Total serum IgE, mast cell tryptase, complements C3, C4, and factor B, were measured in 29 cases of sudden death from coronary artery thrombosis and in 27 controls. We found increased numbers of mast cells in the coronary arteries following coronary death: 46 ± 21 (SD) compared with 22 ± 10 (SD) in the control group ( P < 0.002). In the myocardium and airways there were no differences between the groups. The concentrations of tryptase and IgE in serum did not differ between the groups although 20% of the coronary deaths had elevated values (> 200 kU/1) compared with 8% in the control group. Of the complement factors, C3 was higher in the coronary deaths ( P < 0.05) than in the controls. The results give no evidence of anaphylactic reaction in the pathogenesis of acute myocardial infarction.

Inhaled Salmeterol and Albuterol in Asthmatic Patients Receiving High-dose Inhaled Corticosteroids

Salmeterol may be useful in the treatment of asthmatic patients requiring high-dose inhaled steroids, and there have been debates about its anti-inflammatory action. We have compared the efficacy and effects on serum inflammatory markers, including soluble interleukin 2R (sIL-2R), eosinophil cationic protein (ECP), and tryptase of salmeterol and albuterol in 20 patients with moderate to severe asthma who were all receiving high-dose inhaled corticosteroids and inhaled beta 2-agonist on demand. After a 2-week run-in period, they received, in a randomized, crossover, double-blind and placebo-controlled manner, either salmeterol, 50 micrograms twice a day, or albuterol 400 micrograms, four times a day, from a powder inhaler during two 2-week treatment periods, separated by a 2-week washout. Compared with albuterol, salmeterol treatment was associated with better morning and mean peak expiratory flow (p = 0.013 and 0.016, respectively), less daytime and nocturnal symptoms (p = 0.008 and 0.01, respectively), reduced requirement of rescue albuterol (p = 0.04), and better efficacy rating by patients (p = 0.04). However, serum concentration of sIL-2R was significantly higher during regular albuterol treatment (p = 0.014) but no differences were seen in the concentrations of ECP and tryptase between the two treatment periods. We conclude that inhaled salmeterol, 50 micrograms twice daily, confers a better control of asthma than albuterol, 400 micrograms four times daily, in patients with moderate to severe disease, and the latter treatment may be associated with increased T-lymphocyte activation.