Biomedical subjects

J W Lammers

Publications and source records attributed to J W Lammers.

At least 55 records · Page 3Linked to original sources

PubMed1998

Cloning and characterization of the human interleukin-3 (IL-3)/IL-5/ granulocyte-macrophage colony-stimulating factor receptor betac gene: regulation by Ets family members.

High-affinity receptors for interleukin-3 (IL-3), IL-5, and granulocyte-macrophage colony-stimulating factor (GM-CSF) are composed of two distinct subunits, a ligand-specific chain and a common beta chain (betac). Whereas the mouse has two homologous beta subunits (betac and betaIL-3), in humans, only a single beta chain is identified. We describe here the isolation and characterization of the gene encoding the human IL-3/IL-5/GM-CSF receptor beta subunit. The gene spans about 25 kb and is divided into 14 exons, a structure very similar to that of the murine betac/betaIL-3 genes. Surprisingly, we also found the remnants of a second betac chain gene directly downstream of betac. We identified a functional promoter that is active in the myeloid cell lines U937 and HL-60, but not in HeLa cells. The proximal promoter region, located from -103 to +33 bp, contains two GGAA consensus binding sites for members of the Ets family. Single mutation of those sites reduces promoter activity by 70% to 90%. The 5' element specifically binds PU.1, whereas the 3' element binds a yet-unidentified protein. These findings, together with the observation that cotransfection of PU.1 and other Ets family members enhances betac promoter activity in fibroblasts, reinforce the notion that GGAA elements play an important role in myeloid-specific gene regulation.

Animals↗

PubMed1998

An AP-1 site in the promoter of the human IL-5R alpha gene is necessary for promoter activity in eosinophilic HL60 cells.

Interleukin-5 (IL-5) plays a crucial role in the proliferation, differentiation and activation of eosinophils. The IL-5 receptor is composed of an IL-5-specific alpha subunit, which is expressed by eosinophils and basophils, and a beta c-subunit shared with the receptors for IL-3 and GM-CSF. We identified an AP-1 element which is important for IL-5R alpha promoter activity in eosinophilic HL60 cells. The AP-1 site and the previously identified EOS1 site cooperate, since single mutation of either of the sites decreased promoter activity. We show that the AP-1 site of the IL-5R alpha promoter binds multiple proteins, including cJun, CREB, and CREM.

Base Sequence↗

PubMed1998

Analysis of signal transduction pathways in human eosinophils activated by chemoattractants and the T-helper 2-derived cytokines interleukin-4 and interleukin-5.

Activation and recruitment of eosinophils in allergic inflammation is in part mediated by chemoattractants and T-helper 2 (Th2)-derived cytokines. However, little is known concerning the signal transduction mechanisms by which this activation occurs. We have investigated tyrosine kinase-mediated activation of phosphatidylinositol 3-kinase (PI3K) and compared this with the activation of the p21ras-ERK signaling pathway in human eosinophils. The related cytokines interleukin-3 (IL-3), IL-5, and granulocyte-macrophage colony-stimulating factor (GM-CSF), all induced PI3K activity detected in antiphosphotyrosine immunoprecipitates. Furthermore, the chemoattractants platelet-activating factor (PAF), RANTES, and C5a were also able to induce phosphotyrosine-associated PI3K activity. Protein kinase B (PKB) is a downstream target of PI3K activation by growth factors. Induction of PKB phosphorylation in human eosinophils was transiently induced on activation with the cytokines IL-4 and IL-5, as well as the chemoattractants PAF, C5a, and RANTES showing a broad activation profile. Surprisingly, analysis of the activation of the mitogen-activated protein (MAP) kinases p44(ERK1) and p42(ERK2), showed that ERK2, but not ERK1, was transiently activated in human eosinophils after stimulation with IL-5 or PAF. Activation kinetics correlated with activation of p21ras by both cytokines and chemoattractants as measured by a novel assay for guanosine triphosphate (GTP)-loading. Finally, using specific inhibitors of both the p21ras-ERK and PI3K signaling pathways, a role was demonstrated for PI3K, but not p21ras-ERK, in activation of the serum-treated zymosan (STZ)-mediated respiratory burst in IL-5 and PAF-primed eosinophils. In summary, these data show that in human eosinophils, Th2-derived cytokines differentially activate both PI3K and MAP kinase signal transduction pathways with distinct functional consequences showing complex regulation of eosinophil effector functions.

Cells, Cultured↗

PubMed1998

The role of transcription factor PU.1 in the activity of the intronic enhancer of the eosinophil-derived neurotoxin (RNS2) gene.

Eosinophil-derived neurotoxin (EDN) found in the granules of human eosinophils is a cationic ribonuclease toxin. Expression of the EDN gene (RNS2) in eosinophils is dependent on proximal promoter sequences in combination with an enhancer located in the first intron. We further define here the active region of the intron using transfections in differentiated eosinophilic HL60 cells. We show that a region containing a tandem PU.I binding site is important for intronic enhancer activity. This region binds multiple forms of transcription factor PU.I as judged by gel-shift analysis and DNA affinity precipitation. Importantly, introducing point mutations in the PU.I site drastically reduces the intronic enhancer activity, showing the importance of PU.I for expression of EDN in cells of the eosinophilic lineage.

Binding Sites↗

PubMed1998

Comparison of the roles of mitogen-activated protein kinase kinase and phosphatidylinositol 3-kinase signal transduction in neutrophil effector function.

Although it is known that many stimuli can activate mitogen-activated protein kinases (MAPKs) and phosphatidylinositol 3-kinases (PI3K) in human neutrophils, little is known concerning either the mechanisms or function of this activation. We have utilized a selective inhibitor of MAPK kinase (MEK), PD098059, and two inhibitors of PI3K, wortmannin and LY294002, to investigate the roles of these kinases in the regulation of neutrophil effector functions. Granulocyte/macrophage colony-stimulating factor, platelet-activating factor (PAF) and N-formylmethionyl-leucyl-phenylalanine are capable of activating both p44ERK1 and p42ERK2 MAPKs and phosphotyrosine-associated PI3K in human neutrophils. The activation of extracellular signal-related protein kinases (ERKs) is correlated with the activation of p21ras by both tyrosine kinase and G-protein-coupled receptors as measured by a novel assay for GTP loading. Wortmannin and LY294002 inhibit, to various degrees, superoxide generation, neutrophil migration and PAF release. Incubation with PD098059, however, inhibits only the PAF release stimulated by serum-treated zymosan. This demonstrates that, while neither MEK nor ERK kinases are involved in the activation of respiratory burst or neutrophil migration, inhibition of PAF release suggests a potential role in the activation of cytosolic phospholipase A2. PI3K isoforms, however, seem to have a much wider role in regulating neutrophil functioning.

Androstadienes↗

PubMed1998

P-selectin and MAC-1 mediate monocyte rolling and adhesion to ECM-bound platelets under flow conditions.

Accumulation of monocyte-derived foam cells in focal areas of the atherosclerotic (A.S.-) lesion is one of the key events in early atherogenesis. Using a flow model for the damaged vessel wall, we examined the ability of ECM-bound platelets to induce monocyte tethering and adhesion. Whereas ECM-proteins alone induced monocyte adhesion only at low shear stresses (< 100 mPa), ECM-bound platelets induced monocyte rolling and adhesion at shear stresses up to 240 mPa. Studies with specific antibodies showed that monocyte adhesion to platelets was mainly mediated by P-selectin and monocyte PSGL-1 (maximum inhibition 90%). beta2-Integrin blocking CD18 and CD11b antibodies partly inhibited the arrest of rolling cells. Antibodies against other adhesion molecules such as LFA-1, PECAM-1, and beta1-integrins had no effect. Even sparsely adhered platelets (approximately 10% coverage of the surface) already strongly supported monocyte tethering. In conclusion, activated platelets present on ECM are a powerful adhesive substrate for monocyte recruitment under flow conditions.

Antibodies, Monoclonal↗

PubMed1998

Differential activation of functionally distinct STAT5 proteins by IL-5 and GM-CSF during eosinophil and neutrophil differentiation from human CD34+ hematopoietic stem cells.

Interleukin-5 (IL-5) and granulocyte macrophage-colony stimulating factor (GM-CSF) are important cytokines for the proliferation, differentiation, and activation of myeloid lineages. The JAK/STAT pathway is one of the signaling pathways implicated in mediating biological responses induced by these cytokines. Previous studies have demonstrated that these cytokines predominantly activate an 80 kDa STAT5 isoform in mature granulocytes. To better understand the role of STAT proteins during growth and differentiation of granulocytes, we evaluated differentiation of human CD34+ hematopoietic stem cells ex vivo toward eosinophils and neutrophils. Bandshift experiments showed that in an early stage of both differentiation pathways (14 days), the 94 kDa STAT5B protein was activated by both IL-5 (eosinophil lineage) and GM-CSF (neutrophil lineage). However, during maturation of both lineages (days 21 and 28), increased expression of a functionally distinct 80 kDa STAT5 isoform was observed, resulting in heterodimer DNA-binding complexes containing both the 94 and 80 kDa STAT5 proteins. The finding that functionally distinct isoforms of STAT5 are activated during the early and late differentiation stages of granulocytes suggests that they might be involved in regulating different biological functions in these cells.

Antigens, CD34↗

PubMed1998

The efficacy of a low-dose, monodisperse parasympathicolytic aerosol compared with a standard aerosol from a metered-dose inhaler.

OBJECTIVE: In previous experiments we showed that monodisperse bronchodilator aerosols with a median mass aerodynamic diameter of 2.8 microm induced stronger bronchodilatations than larger aerosols and that the dilatations were clinically relevant at low doses. To discover whether the bronchodilator effects of these low-dose monodisperse aerosols differed from those of standard dosages delivered by metered-dose inhalers, we carried out a comparative trial. METHODS: Ten stable outpatients with a mean forced expiratory volume in 1 s (FEV1) of 58.1% of the predicted value inhaled a placebo aerosol, 8 microg of a 2.8-microm monodisperse ipratropium bromide aerosol and 40 microg from a metered-dose inhaler plus spacer; lung-function measurements followed. Data were analysed with repeated measurements analysis of variance (ANOVA). RESULTS: Greater improvements than with placebo were evident for the forced vital capacity (FVC), the FEV1, the specific airway conductance (sGaw), the peak flow (PEF) and the maximum expiratory flow at 75% of the forced vital capacity (MEF75). In these cases, the low-dose 2.8-microm aerosol proved to be equivalent to the higher-dose metered-dose inhaler. CONCLUSION: By changing the polydisperse characteristic of inhaled aerosols to a monodisperse pattern, the dose of the drug administered can be reduced without loss of efficacy.

Adult↗

PubMed1998

Cytokine-induced protein tyrosine phosphorylation is essential for cytokine priming of human eosinophils.

BACKGROUND: Human eosinophils are strongly modulated by the eosinophilotrophic cytokines IL-5, IL-3, and granulocyte-macrophage colony-stimulating factor (GM-CSF). A clear intracellular effect of these cytokines is the induction of tyrosine phosphorylation of multiple cellular substrates. However, the relevance of tyrosine phosphorylation for eosinophil functioning has not been established. OBJECTIVE: In this study we have investigated dose-response and time curves of IL-5-, IL-3-, and GM-CSF-induced tyrosine phosphorylation in eosinophils. Moreover, we have evaluated the importance of IL-5-induced tyrosine phosphorylation for priming of human eosinophils. METHODS: Cytokine-induced tyrosine phosphorylation was monitored on western blot with an antiphosphotyrosine antibody (4G10). To probe the relevance of tyrosine phosphorylation for priming, eosinophils were primed with IL-5 in the presence of the tyrosine kinase inhibitor herbimycin A. Platelet activating factor (PAF) was used as a control priming agent. Subsequently, the eosinophils were incubated with serum-treated zymosan (STZ) to activate the respiratory burst. Binding of STZ was determined by FACS analysis. RESULTS: IL-5-, IL-3-, and GM-CSF-induced tyrosine phosphorylation was found at concentrations that primed eosinophil effector mechanism (median effective dose values: approximately 5.10(-11) mol/L, approximately 5.10(-10) mol/L, and approximately 5.10(-12) mol/L for IL-5, IL-3, and GM-CSF, respectively). Cytokine-induced tyrosine phosphorylation was transient with an optimum value at 15 minutes. IL-5 priming of STZ-induced activation of the respiratory burst was blocked by herbimycin A, whereas PAF still primed this response. In fact, herbimycin A inhibited IL-5 priming of STZ binding to human eosinophils. On the other hand, PAF priming of STZ binding was not affected by herbimycin A. Both IL-5-induced and PAF-induced tyrosine phosphorylation were inhibited by herbimycin A. CONCLUSION: These data demonstrate for the first time that IL-5 priming of opsonized particle-induced responses is mediated by tyrosine kinase activity in human eosinophils.

Benzoquinones↗

PubMed1998

Characteristics and complaints of patients prescribed long-term oxygen therapy in The Netherlands.

In patients prescribed long-term oxygen therapy (LTOT), compliance is often poor. Both patient- and treatment-related factors seem to be involved. As a base for improvements in LTOT, the characteristics and complaints of LTOT patients were investigated. A survey was set up in a random sample of clients of the largest oxygen company in the Netherlands. Patients were selected if they were > or = 18 years old, had a phone and if they had had oxygen equipment for > or = 6 months. All patients were visited at home by a medical student. Data are presented for a total of 528 patients (response rate 62%). The typical LTOT patient was a 70-year-old male with chronic obstructive pulmonary disease (COPD), who had had oxygen equipment for 3.5 years and who used oxygen cylinders and nasal cannulae for 13 h day-1. Twenty percent of the patients still smoked. Although LTOT was prescribed in 80% of the patients by a chest physician, prescription was often inadequate. Only 33% of the patients were informed adequately about the therapy. Twenty percent of the patients used oxygen for fewer hours per day than prescribed. Non-compliant patients were mainly men (P = 0.006) and more often ashamed of their therapy (P = 0.023) than compliant patients. The blood oxygen level was monitored regularly in 73% of the patients. Most complaints concerned the oxygen equipment, especially the concentrator. The single most important complaint had to do with restricted autonomy. Only 19% of the patients had no complaints at all. It is concluded that LTOT should be improved with regard to the education, motivation and monitoring of patients. The prescribing physician needs to be included in an education programme. Given the numerous problems these patients experience, LTOT should be improved in particular with regard to equipment convenience.

Adult↗

PubMed1998

Effects of granulocyte colony-stimulating factor (G-CSF) treatment on granulocyte function and receptor expression in patients with ventilator-dependent pneumonia.

Considerable experimental evidence in animals suggests that treatment with G-CSF may have a beneficial effect in the management of severe infections in non-neutropenic hosts. This beneficial effect is attributed to an enhancement of granulopoiesis and neutrophil function, the latter possibly involving up-regulation of receptors on neutrophils that are involved in antibody-mediated cytotoxicity and killing of microorganisms. We compared neutrophil function and phenotype in blood and bronchoalveolar lavage fluid (BALF) of 10 patients with severe ventilator-dependent pneumonia, at baseline and following initiation of G-CSF treatment as adjunct to standard therapy. G-CSF treatment was associated with three-fold increased blood neutrophil counts at day 3 of treatment compared with baseline counts. Mean serum G-CSF concentration increased from 313 to 2007 pg/ml. After correction for lavage dilution effects, BALF G-CSF levels did not differ significantly from baseline, nor did neutrophil receptor expression (FcgammaRI, FcgammaRII, FcgammaRIII, CR3, and L-selectin) or indicators of neutrophil function such as respiratory burst activity, phagocytosis and killing of Candida albicans in BALF or blood. The mortality in this group of patients was 30% and compared favourably to the APACHE II-derived predicted mortality of 60%. We conclude that the possible therapeutic benefit of G-CSF administration in the early phase of severe bacterial pneumonia is not readily explained by its effect on baseline indicators of neutrophil function or receptor expression.

Adult↗

PubMed1998

Effects of fluticasone propionate and beclomethasone dipropionate on parameters of inflammation in peripheral blood of patients with asthma.

Bronchial inflammation plays a central role in asthma. We investigated whether parameters of inflammation were increased in peripheral blood. Furthermore, we tested whether fluticasone propionate (FP), a new inhaled corticosteroid (ICS), and beclomethasone dipropionate (BDP) affected these parameters. FP 750 microg/day and BDP 1500 microg/day were compared in a randomized, crossover study consisting of two 6-week treatment periods, each preceded by a 3-week placebo period. Twenty-one patients with symptomatic asthma completed the study. The results were compared with those of six normal subjects (controls). Immunophenotyping of inflammatory cells was performed in whole blood, and serum eosinophil cationic protein (ECP) was measured. With regard to clinical efficacy, ICS increased PC20 histamine by more than 1.9 doubling doses and FEV1 by more than 0.34 l. The number of CD3/HLA-DR+ lymphocytes was significantly increased in asthmatics compared to the normal subjects, both after placebo (P<0.01) and after therapy (P<0.05). The CD3/HLA-DR+ lymphocytes decreased significantly after treatment with FP (P<0.05). Serum ECP was elevated in patients without ICS and decreased after treatment with BDP (P<0.001). In conclusion, the number of CD3/HLA-DR+ lymphocytes and serum ECP levels were raised in the peripheral blood of symptomatic asthmatics, and decreased by clinically effective doses of ICS. In this respect, FP 750 microg/day was at least as effective as BDP 1500 microg/day.

Administration, Inhalation↗

PubMed1998

Eosinophil chemotactic activity in bronchoalveolar lavage from idiopathic pulmonary fibrosis is dependent on cytokine priming of eosinophils.

Increased numbers of eosinophils have been found in bronchoalveolar lavage (BAL) fluid obtained from patients with idiopathic pulmonary fibrosis (IPF). This suggests the presence of one or more cytokines in the lung tissue of patients with IPF, which are involved in the induction of migration of eosinophils towards the pulmonary compartment. To evaluate this hypothesis, we studied migratory responses of blood eosinophils towards BAL fluid. Migratory responses were tested by means of a modified Boyden chamber assay in 21 patients with IPF and 14 healthy controls. Experiments were performed with unprimed eosinophils and in vitro primed eosinophils (preincubated with 10(-11) M granulocyte macrophage-colony-stimulating factor). Changes in intracellular free Ca2+ ([Ca2+]i) in eosinophils in response to BAL fluid were also investigated, to characterize putative chemotaxins further. Chemotactic responses of eosinophils were observed towards BAL fluid from both patients with IPF and controls, provided that the eosinophils were primed. No changes in [Ca2+]i in eosinophils were detected in response to BAL fluid. Furthermore, neither a blocking antibody against interleukin-8 nor one against regulated on activation, normal T-cell, expressed and secreted (RANTES) influenced the response. Since a chemotactic response of in vitro primed eosinophils was also observed towards bronchoalveolar lavage fluid from normals, it was concluded, that in idiopathic pulmonary fibrosis, apart from the presence of a chemotactic factor in the lung tissue, other mechanisms such as priming of eosinophils in the peripheral blood are responsible for the extravasation of eosinophils into the pulmonary compartment. As no changes in [Ca2+]i were observed in the eosinophils after incubation with bronchoalveolar lavage fluid, the chemotaxin responsible for the migratory responses is probably not one of the known eosinophil-activating chemokines.

Adult↗

PubMed1998

Relationship between external resistances, lung function changes and maximal exercise capacity.

In upper airway obstruction (UAO) the relationship between the degree of obstruction, exercise limitation and lung function indices is not well established. Therefore, we investigated in nine healthy subjects (age 36+/-9 yrs) the effects of two added resistances at the mouth (R1 = added resistance with 7.8 mm diameter; R2 = 5.7 mm) on forced expiratory volume in one second (FEV1), peak expiratory flow (PEF), airway resistance (Raw) and maximal breathing capacity (measured during 15 s = measured maximum breathing capacity (MBCm); calculated as FEV1x37.5 = calculated maximum breathing capacity (MBCc)) on the one hand, and maximum exercise capacity (W'max), minute ventilation (V'E) and CO2 elimination (V'CO2) on the other. We found that R1 had almost no influence on FEV1 but decreased PEF by approximately 35% and increased Raw by almost 300%; it decreased W'max by merely approximately 10% while maximal exercise ventilation (V'Emax) was only 65% of control and only reached approximately 40% MBCc and approximately 70% MBCm; yet V'E and V'CO2 were significantly reduced at high exercise levels indicating hypoventilation. With R2, FEV1 was reduced by 25% and PEF by 55%, and Raw was increased by 600%; W'max was approximately 60% of control, V'Emax was only 35% of control and reached approximately 30% MBCc and approximately 60% MBCm, V'E was already reduced at moderate exercise levels. We conclude that: 1) an upper airway obstruction of 6 mm diameter (but not of 8 mm) had a marked influence on maximum exercise capacity due to hypoventilation; 2) calculated maximum breathing capacity markedly overestimated measured maximum breathing capacity because the forced expiratory volume in one second is an insensitive index of upper airway obstruction and because it does not take inspiratory flow limitation into account; and 3) a 10% decrease in maximum exercise capacity was linearly related with a 7% decrease in the forced expiratory volume in one second and a 150% increase in airway resistance. A 10% decrease in maximal exercise ventilation was related to a 8.5% decrease in peak expiratory flow and 9% decrease in measured maximum breathing capacity.

Adult↗

PubMed1998

Accuracy of oxygen delivery by liquid oxygen canisters.

The oxygen flow rate delivered by liquid oxygen canisters may be less than intended, owing to inaccuracies of the set flow rates and/or as a result of the outflow resistance caused by the humidifier, oxygen tubing, delivery or conserving device. The aim of this study was to investigate the accuracy of oxygen delivery by liquid oxygen canisters at different flow rates and levels of outflow resistance. Four stationary and 18 portable liquid oxygen canisters from three manufacturers were tested. All flows were measured using a Timemeter RT 200 Calibration Analyser. An adjustable obstruction was used to calculate the effect of the outflow resistance on the delivered flow rate. The measured and set flow rates of both stationary and portable canisters were strongly correlated. Expressed as a percentage of the set flow rate, the measured flow rate of the canisters varied from 36-128%, with the lowest values at flow rates <1 L x min(-1). Sixty-two (26%) of the measured flow rates differed > or =10% from the set flow rate. A difference of 0.5-1.0 L x min(-1) occurred in 16 (7%) of the measurements, but only at set flow rates >2 L x min(-1). Irrespective of the set flow rate, the measured flow rate was hardly affected by the outflow resistance. We conclude that the accuracy of oxygen delivery by liquid oxygen canisters depends on the inaccuracy of the set flow rates rather than on the outflow resistance, even at high flow rates. Although the differences between the measured and set flow rates were mostly small, they may have clinical significance, particularly in patients with chronic obstructive pulmonary disease. To prevent inaccuracy, monthly checks of the canisters by the oxygen provider at the patient's home are more important than yearly maintenance.

Calibration↗

PubMed1998

Platelet associated fibrinogen and ICAM-2 induce firm adhesion of neutrophils under flow conditions.

Surface-bound platelets support selectin-mediated rolling and beta2-integrin-mediated firm adhesion of neutrophils (PMN) under flow conditions. We examined which ligands on platelets mediate this firm adhesion. Surface-bound platelets express ICAM-2 and GPIIbIIIa-bound fibrinogen, which are ligands for LFA-1 and MAC-1. In a well defined model for vessel wall injury, blood from an afibrinogenemic patient was perfused over ECM-coated coverslips to obtain fibrinogen-free platelet surfaces. At high shear rates, PMN-adhesion to fibrinogen-free platelet surfaces decreased compared to fibrinogen-containing controls. Under these conditions, firm adhesion and not rolling was blocked demonstrating the importance of fibrinogen in this process. In addition, MAC-1 and LFA- on PMN and ICAM-2 on platelets played a role in firm adhesion; the effect of blocking antibodies was most evident at high shear. The effects of fibrinogen depletion and ICAM-2 blocking were additive. In conclusion, multiple redundant ligands, like ICAM-2 and fibrinogen, induce firm and shear resistant PMN adhesion to platelets under flow conditions. Individually these ligands become critical at higher shear. Blocking of two or more interactions also interferes with low shear adhesion.

Antigens, CD↗

PubMed1997

[Anglo-Saxon guidelines for the treatment of community-acquired pneumonia applicable in The Netherlands as well].

There are three Anglo-Saxon guidelines for the management of patients with a community-acquired pneumonia: an American, a British and a Canadian one. The guidelines correspond fairly well. There is a subdivision into categories according to whether the patients are treated at home (formerly healthy patients younger than 60 years versus patients with pre-existent disease or aged 60 years and more) or in the hospital (patients not needing intensive care versus those who do need it). For each category the most common causative micro-organisms are listed together with recommended antibiotic treatment. The Canadian guidelines have nursing home patients as a separate category because of slightly different causative organisms due to frequent microaspiration. The guidelines are applicable to the situation in the Netherlands, with a few exceptions: antibiotic resistance is not a major problem in the Netherlands (as yet), and contrary to what the guidelines state an agent with activity against Pseudomonas aeruginosa is not necessary; the same agents as in category III can be prescribed in these patients. A macrolide or azalide antibiotic is advisable for intensive care patients in view of the possibility of infection with Legionella pneumophila or Mycoplasma pneumoniae.

Adult↗

PubMed1997

Differential effects of the T helper cell type 2-derived cytokines IL-4 and IL-5 on ligand binding to IgG and IgA receptors expressed by human eosinophils.

Increased numbers of eosinophilic granulocytes that exhibit an activated phenotype are found in bronchial tissue and bronchial alveolar lavage fluid of patients with allergic asthma. Little is known about the processes that lead to activation of eosinophils in vivo, but Igs might be important stimulants. In the present study we investigated the capacity of human eosinophils to interact with beads coated with human serum IgG or IgA. Binding of IgG/IgA-coated beads to eosinophils from normal donors appeared to be dependent on priming with Th2-derived cytokines. Priming with granulocyte-macrophage CSF, IL-4, or IL-5 is required for eosinophils to form rosettes with IgA-beads. IL-4 priming resulted in a fast and transient effect on binding of IgA-beads, whereas the effect of IL-5 priming was slower and longer lasting. The expression of Fc alphaR (CD89) was low compared with that on neutrophils, and experiments with the blocking mAb My43 (CD89) showed no inhibition of rosette formation between eosinophils and IgA-coated beads. However, polymeric myeloma IgA effectively inhibited the rosette formation of IgA-coated beads to eosinophils. Binding of IgG-beads could only be primed with granulocyte-macrophage CSF and IL-5, not with IL-4. These data are concurrent with the hypothesis that Th2-derived cytokines spatially produced at the side of an allergic inflammatory response can direct eosinophils to a rather restricted primed phenotype by IL-4 or to a more generalized primed phenotype by IL-5.

Antibodies, Monoclonal↗