Quantitative, rather than qualitative, differences in CD69 upregulation in human blood eosinophils upon activation with selected stimuli

Eosinophils as potential biomarkers in respiratory viral infections

Eosinophils are bone marrow-derived granulocytes that, under homeostatic conditions, account for as much as 1-3% of peripheral blood leukocytes. During inflammation, eosinophils can rapidly expand and infiltrate inflamed tissues, guided by cytokines and alarmins (such as IL-33), adhesion molecules and chemokines. Eosinophils play a prominent role in allergic asthma and parasitic infections. Nonetheless, they participate in the immune response against respiratory viruses such as respiratory syncytial virus and influenza. Notably, respiratory viruses are associated with asthma exacerbation. Eosinophils release several molecules endowed with antiviral activity, including cationic proteins, RNases and reactive oxygen and nitrogen species. On the other hand, eosinophils release several cytokines involved in homeostasis maintenance and Th2-related inflammation. In the context of SARS-CoV-2 infection, emerging evidence indicates that eosinophils can represent possible blood-based biomarkers for diagnosis, prognosis, and severity prediction of disease. In particular, eosinopenia seems to be an indicator of severity among patients with COVID-19, whereas an increased eosinophil count is associated with a better prognosis, including a lower incidence of complications and mortality. In the present review, we provide an overview of the role and plasticity of eosinophils focusing on various respiratory viral infections and in the context of viral and allergic disease comorbidities. We will discuss the potential utility of eosinophils as prognostic/predictive immune biomarkers in emerging respiratory viral diseases, particularly COVID-19. Finally, we will revisit some of the relevant methods and tools that have contributed to the advances in the dissection of various eosinophil subsets in different pathological settings for future biomarker definition.

The aryl hydrocarbon receptor contributes to tissue adaptation of intestinal eosinophils in mice

Eosinophils are potent sources of inflammatory and toxic mediators, yet they reside in large numbers in the healthy intestine without causing tissue damage. We show here that intestinal eosinophils were specifically adapted to their environment and underwent substantial transcriptomic changes. Intestinal eosinophils upregulated genes relating to the immune response, cell-cell communication, extracellular matrix remodeling, and the aryl hydrocarbon receptor (AHR), a ligand-activated transcription factor with broad functions in intestinal homeostasis. Eosinophils from AHR-deficient mice failed to fully express the intestinal gene expression program, including extracellular matrix organization and cell junction pathways. AHR-deficient eosinophils were functionally impaired in the adhesion to and degradation of extracellular matrix, were more prone to degranulation, and had an extended life span. Lack of AHR in eosinophils had wider effects on the intestinal immune system, affecting the T cell compartment in nave and helminth-infected mice. Our study demonstrates that the response to environmental triggers via AHR partially shapes tissue adaptation of eosinophils in the small intestine.

Impact of blood storage and sample handling on quality of high dimensional flow cytometric data in multicenter clinical research

Obtaining reliable and reproducible high quality data in multicenter clinical research settings requires design of optimal standard operating procedures. While the need for standardization in sample processing and data analysis is well-recognized, the impact of sample handling in the pre-analytical phase remains underestimated. We evaluated the impact of sample storage time (≈transport time) and temperature, type of anticoagulant, and limited blood volume on reproducibility of flow cytometric studies. EDTA and Na-Heparin samples processed with the EuroFlow bulk lysis protocol, stained and stored at 4 °C showed fairly stable expression of cell surface markers and distribution of the major leukocyte populations for up to 72 h. Additional sample fixation (1% PFA, Fix & Perm) did not have any beneficial effects. Blood samples stored for <24 h at room temperature before processing and staining seemed suitable for reliable immunophenotyping, although losses in absolute cell numbers were observed. The major losses were observed in myeloid cells and monocytes, while lymphocytes seemed less affected. Expression of cell surface markers and population distribution were more stable in Na-Heparin blood than in EDTA blood. However, storage of Na-Heparin samples was associated with faster decrease in leukocyte counts over time. Whole blood fixation strategies (Cyto-Chex, TransFix) improved long-term population distribution, but were detrimental for expression of cellular markers. The main conclusions from this study on healthy donor blood samples were successfully confirmed in EDTA clinical (patient) blood samples with different time delays until processing. Finally, we recognized the need for adjustments in bulk lysis in case of insufficient blood volumes. Despite clear overall conclusions, individual markers and cell populations had different preferred conditions. Therefore, specific guidelines for sample handling should always be adjusted to the clinical application and the main target leukocyte population.

FACS - based isolation of human eosinophils allows purification of high quality RNA

Here we extensively describe a FACS-based protocol for isolating intact non-stained human eosinophils from peripheral blood; a stop forward from our recently published initial study. This method of purification could be accomplished in <3 h with only small volumes of whole blood necessary, even in healthy subjects generally exhibiting low levels of circulating eosinophils. Eosinophil activation during the isolation steps appeared to be minimal and this purification procedure yielded high quality RNA. Moreover, these FACS-isolated eosinophils had prolonged viability in culture and were suitable for further activation assays.

Microparticles in nasal lavage fluids in chronic rhinosinusitis: Potential biomarkers for diagnosis of aspirin-exacerbated respiratory disease

BACKGROUND

Microparticles (MPs) are submicron-sized shed membrane vesicles released from activated or injured cells and are detectable by flow cytometry. MP levels have been used as biomarkers to evaluate cell injury or activation in patients with pathological conditions.

OBJECTIVE

We sought to compare MP types and levels in nasal lavage fluids (NLFs) from controls and patients with chronic rhinosinusitis without nasal polyps (CRSsNP), chronic rhinosinusitis with nasal polyps (CRSwNP), and aspirin-exacerbated respiratory disease (AERD).

METHODS

We collected NLFs from patients with CRSsNP (n = 33), CRSwNP (n = 45), and AERD (n = 31) and control (n = 24) subjects. Standardized flow cytometry methods were used to characterize the following MP types: endothelial MPs, epithelial MPs (epithelial cell adhesion molecule [EpCAM](+)MPs, E-cadherin(+)MPs), platelet MPs (CD31(+)CD41(+)MPs), eosinophil MPs (EGF-like module-containing mucin-like hormone receptor-like 1[EMR1](+)MPs), mast cell MPs (high-affinity IgE receptor [FcεRI](+)c-kit(+)MPs), and basophil MPs (CD203c(+)c-kit(-)MPs). Basophil activation was evaluated by the mean fluorescence intensity of CD203c on basophil MPs.

RESULTS

Activated mast cell MPs (CD137(+) FcεRI(+)c-kit(+)MPs) were significantly increased in NLFs of controls compared with NLFs of patients with CRSsNP (2.3-fold; P < .02), CRSwNP (2.3-fold; P < .03), and AERD (7.4-fold; P < .0001). Platelet MPs (3.5-fold; P < .01) and basophil MPs (2.5-fold; P < .05) were increased only in patients with AERD. Mean fluorescence intensity of CD203c on MPs was increased in patients with CRSwNP (P < .002) and AERD (P < .0001), but not in patients with CRSsNP. EpCAM(+)MPs in patients with CRSwNP were no different from control (P = .91) and lower than those in patients with CRSsNP (P < .02) and AERD (P < .002).

CONCLUSIONS

Based on released MPs, mast cells, platelets, and basophils were more highly activated in patients with AERD than in patients with CRS. Epithelial injury was lower in patients with CRSwNP than in patients with CRSsNP and AERD. MP analysis may help identify phenotypes of CRS, and in distinguishing AERD from CRSwNP.

Activation of Human Peripheral Blood Eosinophils by Cytokines in a Comparative Time-Course Proteomic/Phosphoproteomic Study

Activated eosinophils contribute to airway dysfunction and tissue remodeling in asthma and thus are considered to be important factors in asthma pathology. We report here comparative proteomic and phosphoproteomic changes upon activation of eosinophils using eight cytokines individually and in selected cytokine combinations in time-course reactions. Differential protein and phosphoprotein expressions were determined by mass spectrometry after 2-dimensional gel electrophoresis (2DGE) and by LC-MS/MS. We found that each cytokine-stimulation produced significantly different changes in the eosinophil proteome and phosphoproteome, with phosphoproteomic changes being more pronounced and having an earlier onset. Furthermore, we observed that IL-5, GM-CSF, and IL-3 showed the greatest change in protein expression and phosphorylation, and this expression differed markedly from those of the other five cytokines evaluated. Comprehensive univariate and multivariate statistical analyses were employed to evaluate the comparative results. We also monitored eosinophil activation using flow cytometry (FC) analysis of CD69. In agreement with our proteomic studies, FC indicated that IL-5, GM-CSF, and IL-3 were more effective than the other five cytokines studied in stimulating a cell surface CD69 increase indicative of eosinophil activation. Moreover, selected combinations of cytokines revealed proteomic patterns with many proteins in common with single cytokine expression patterns but also showed a greater effect of the two cytokines employed, indicating a more complex signaling pathway that was reflective of a more typical inflammatory pathology.

Allergic Inflammation Is Associated With Coronary Instability and a Worse Clinical Outcome After Acute Myocardial Infarction

BACKGROUND

The role of allergic inflammation in acute coronary syndromes (ACS) has not been clearly defined to date. Aim of this study was to assess eosinophil and basophil activation in ACS and the prognostic role of eosinophil cationic protein in ST-segment-elevation myocardial infarction.

METHODS AND RESULTS

In a cross-sectional study, we prospectively enrolled 51 patients undergoing percutaneous coronary intervention (60.8% patients with ACS and 39.2% with stable angina). Flow cytometry analysis assessed CD66b, CD69, and CD203c median fluorescence intensity expression. In a follow-up study, 181 patients presenting with ST-segment-elevation myocardial infarction, undergoing primary percutaneous coronary intervention, were prospectively enrolled with a follow-up of 24 months. Eosinophil activation (CD66b) was similar in patients with ACS and stable angina (6.61 [4.91-7.72] versus 6.62 [5.27-8.73], P=0.63), whereas eosinophil degranulation (CD69) and basophil activation (CD203c) were higher in ACS patients compared with stable angina patients (1.38 [1.16-1.52] versus 1.17 [1-1.31], P=0.01); 0.97 [0.89-1.11] versus 0.92 [0.87-0.95], P=0.03, respectively). Eosinophil cationic protein serum levels were significantly higher in ST-segment-elevation myocardial infarction patients with major adverse cardiac events as compared with those without (21.1 [10.37-25.65] versus 7.83 [3.37-12.8] μg/L, P=0.01) and in patients with thrombus score >3 compared with those with thrombus score ≤3 (15.0 [9.8-24.7] versus 5.2 [3.5-22.9] μg/L, P=0.006). Eosinophil cationic protein serum levels predicted major adverse cardiac events during follow-up (odds ratio =1.041, 95% confidence interval 1.012-1.071, P=0.005). C-reactive protein serum levels showed a borderline statistical significance (odds ratio =0.904, 95% confidence interval 0.806-1.014, P=0.085).

CONCLUSIONS

These findings are the first demonstration of in vivo eosinophil degranulation and basophil activation during ACS and of the prognostic role of eosinophil cationic protein in ST-segment-elevation myocardial infarction.

Changes in genital tract immune cell populations after initiation of intrauterine contraception

OBJECTIVE

The primary target cells for the human immunodeficiency virus (HIV) infection in the genital tract are CD4 T cells that express CCR5 on the surface. Alterations in genital tract T cells that express CCR5 could impact HIV acquisition risk. We hypothesized that, when compared with baseline, the use of a hormonal intrauterine device (IUD) would alter HIV target cells (primarily CCR5+ CD4 cells) in the female genital tract more than a nonhormonal IUD.

STUDY DESIGN

Thirty-four healthy HIV-negative women aged 18-40 years who were seeking an IUD for contraception were assigned randomly to receive a levonorgestrel IUD or a copper T380A IUD. A parallel group of 8 control women who did not need contraception was also enrolled. Genital tract mucosal immune cell populations that were collected by cervical cytobrush and endometrial biopsy before and 2 months after IUD placement were analyzed by flow cytometry. Mean differences in cell number and percent that expressed receptors from baseline to follow-up examination were evaluated with the use of paired Student t tests.

RESULTS

Neither IUD altered the number of T cells within the upper and lower genital tracts. Levonorgestrel IUD users had a decrease in T cells that expressed the HIV coreceptor CCR5 in the endometrium and cervix after 2 months of use compared with baseline. There was a decrease in activated endometrial T cells in levonorgestrel IUD users and a decrease in activated cervical T cells in copper IUD users after 2 months of IUD use, compared with baseline.

CONCLUSION

Women who use IUDs have reduced expression of the CCR5 HIV coreceptor on T cells in the endometrium and cervix compared with expression before IUD placement. These findings suggest that susceptibility to HIV infection would not be increased by IUD use.

B cells secrete eotaxin-1 in human inflammatory bowel disease

BACKGROUND

Our previous studies have demonstrated that B cells in human inflammatory bowel disease (IBD) are highly activated and produce copious amounts of chemokines. Here, we showed that B cells produce eotaxin-1, a selective chemokine for acute eosinophilia. Increased levels of activated eosinophils have been found in the intestinal mucosa in patients with IBD, but their role(s) and the regulation of their migration patterns remain poorly defined.

METHODS

To determine how B-cell secretion of eotaxin-1 influences eosinophil activation and migration, we performed immunoepidemiological approaches coupled with in vitro studies. B cells and eosinophils from patients with Crohn's disease and ulcerative colitis were isolated, and responses to Toll-like receptor ligands (TLR) were measured and assessed for the relationship with clinical disease.

RESULTS

Eotaxin-1 from recirculating B cells, and TLR ligands, regulated eosinophil homing mechanisms in IBD. B cells stimulated with hypo-acylated lipopolysaccharide (LPS) produced copious amounts of eotaxin-1, which influenced eosinophil activation profiles in the bloodstream. We also found that hexa-acylated LPS, such Escherichia coli LPS, directly activated TLR2-expressing and TLR4-expressing eosinophils from patients with IBD to express a different repertoire of mucosal homing receptors, namely CCR9 and CCR10. Whereas B-cell production of eotaxin-1 was correlated with reduced disease activity, eosinophil activation by hexa-acylated LPS was associated with increased disease activity.

CONCLUSIONS

These results suggest that systemic TLR ligands influence eosinophil migration patterns, both directly and indirectly, through B cells. Our report uncovers unexpected mechanisms of cross talk between certain immune cells that shed new light on IBD immunology.

Novel interferon-beta-induced gene expression in peripheral blood cells

Type I IFNs are used for treating viral, neoplastic, and inflammatory disorders. The protein products encoded by IFN-stimulated genes (ISGs) likely mediate clinical effects of IFN in patients. Macroarray assays, used for studying ISG induction in IFN-treated patients, comprise genes identified predominantly through analysis of long-term cell lines. To discover genes induced selectively by IFN-beta in PBMC, we exposed whole blood to physiological concentrations of IFN-beta. PBMC were prepared, and RNA was extracted, reverse-transcribed, and hybridized to cDNA microarrays, and microarray analysis identified 39 ISGs and 20 IFN-repressed genes (IRGs). Thirty-three ISGs were known previously, and six ISGs were novel. New ISGs included GTP cyclohydrolase 1; hypothetical protein LOC129607; hypothetical protein FLJ38348; leucine aminopeptidase 3; squalene epoxidase; and GTP-binding protein overexpressed in skeletal muscle. Twenty IRGs included IL-1beta and CXCL8, which had been identified earlier. CXCL1 was a novel IRG identified in the current study. PCR analysis demonstrated the regulation of six novel ISGs and CXCL1 as an IRG in PBMC and astrocytoma cells. Results were validated using RNA obtained ex vivo from blood of patients after injection with IFN-beta. Identification of new ISGs and IRGs in primary PBMC will enhance macroarray assays for monitoring IFN responsiveness.

Eosinophil activation in preterm infants with lung disease

AIM

We investigated the role of eosinophils in the pathogenesis of bronchopulmonary dysplasia (BPD) in preterm infants.

METHODS

Fifteen preterm infants with BPD were compared to 13 preterms with respiratory distress syndrome (RDS) and to 16 healthy preterms. We assessed total eosinophil and neutrophil counts in venous blood samples and the levels of the eosinophilic activity markers eosinophilic cationic protein (ECP) and the cellular surface antigen (CD9).

RESULTS

The eosinophil count was greater in BPD compared with RDS and healthy infants (1414 vs. 797 and 471 cells per microlitre, respectively, p = 0.03). ECP levels were elevated (34 vs. 12.8 and 9.8 microg/L, respectively, p = 0.002) and CD9 levels reduced (75 vs. 94 and 86 mean fluorescence intensity units, respectively, p = 0.01) in BPD compared with RDS and healthy infants, suggesting eosinophilic activation in BPD. These findings were not solely explained by differences between gestational age or birth weight of the different groups. ECP levels were positively correlated with the duration of oxygen supplementation in the BPD group. The eosinophil count fell promptly after steroid treatment was commenced in the BPD group.

CONCLUSION

The findings suggest that BPD is linked to eosinophil activation, which might contribute to the pathogenesis.

Cis-9,Trans-11-CLA exerts anti-inflammatory effects in human bronchial epithelial cells and eosinophils: Comparison to Trans-10,Cis-12-CLA and to linoleic acid

Interaction of eosinophils and bronchial epithelial cells plays a pivotal role in maintaining inflammatory airway disease. Since conjugated linoleic acids (CLA) are suggested to exert anti-inflammatory effects, one purpose of this study was to compare cis-9,trans-11-CLA and trans-10,cis-12-CLA with regard to their influence on the stimulus-induced activation of eosinophils. ECP (eosinophil cationic protein) released in co-culture of stimulated and CLA-treated eosinophils with stimulated bronchial epithelial cells (BEAS-2B) was measured and cis-9,trans-11-CLA was found to be most potent in inhibiting ECP formation. Further, expression of the activation markers CD69 and CD13 induced by various stimuli (TNF-alpha, IL-5, IL-3) was significantly reduced in the presence of cis-9,trans-11-CLA. Subsequently, various concentrations of cis-9,trans-11-CLA vs. linoleic acid (LA, cis-9,cis-12-octadecadienoic acid) were tested for the effect on proliferative response and release of the pro-inflammatory cytokine IL-8 in stimulated BEAS-2B. Addition of cis-9,trans-11-CLA attenuated cell growth and significantly reduced IL-8 production at mRNA and protein levels. In contrast, LA had a slight stimulating effect on proliferation and was less effective in reducing the cytokine release. It was demonstrated that the inhibitory effect of cis-9,trans-11-CLA on IL-8 production is mediated through activation of the nuclear receptor PPARgamma, since blocking the receptor with a selective antagonist (GW9662) restored the stimulus-induced enhancement in IL-8 mRNA expression and protein secretion. PPARgamma has previously been shown to be closely involved in the downregulation of inflammation during hyperresponsiveness related to pulmonary immune responses. Thus, targeting PPARgamma, cis-9,trans-11-CLA might be of therapeutic value in the focus of airway disease while ameliorating inflammatory processes by affecting epithelial and eosinophil functions.

Familial eosinophilia: a benign disorder?

Familial eosinophilia (FE) is an autosomal dominant disorder characterized by marked eosinophilia and progression to end organ damage in some, but not all, affected family members. To better define the pathogenesis of FE, 13 affected and 11 unaffected family members (NLs) underwent a detailed clinical evaluation at the National Institutes of Health (NIH). No clinical abnormalities were more frequent in the family members with FE compared with the NLs. There was, however, a decreased prevalence of asthma in family members with FE compared with unaffected family members. Eosinophil morphology as assessed by either light or transmission electron microscopy was normal in family members with and without FE. Although levels of eosinophil-derived neurotoxin (EDN) and major basic protein (MBP) were elevated in patients with FE compared with NL, levels of both granule proteins were lower than in nonfamilial hypereosinophilic syndrome (HES). Similarly, increased surface expression of the activation markers CD69, CD25, and HLA-DR was detected by flow cytometry on eosinophils from patients with FE compared with NL, albeit less than that seen in HES. These data suggest that, despite prolonged marked eosinophilia, FE can be distinguished from HES by a more benign clinical course that may be related to a relative lack of eosinophil activation.

Induction of CD69 activation molecule on human neutrophils by GM-CSF, IFN-gamma, and IFN-alpha

The CD69 glycoprotein is an early activation antigen of T and B lymphocytes but it expression is induced in vitro on cells of most hematopoietic lineages, including neutrophils after stimulation with PMA or fMLP. In this study, we investigated whether CD69 expression on human neutrophils could be modulated by inflammatory or anti-inflammatory cytokines (IL-1beta, IL-2, IL-4, IL-6, IL-8, IL-10, IL-12, IL-18, G-CSF, GM-CSF, TNF-alpha, TGF-beta, IFN-alpha, IFN-gamma). Resting neutrophils from healthy subjects did not express CD69 on the cell surface; moreover, a preformed intracellular pool of CD69 was not evident in these cells. CD69 was barely detectable on these cells after overnight incubation in medium while overnight incubation with GM-CSF, IFN-gamma or IFN-alpha significantly induced CD69 expression on neutrophils with GM-CSF appearing to be the most potent inducer. This induction was dependent on a new protein synthesis as it was significantly inhibited by cycloheximide (about 50% inhibition). CD69 cross-linking on GM-CSF-primed neutrophils sinergized with LPS and increased TNF-alpha production and secretion suggesting a role for CD69-positive neutrophils in the pathogenesis and maintenance of different inflammatory diseases.

Activation and Proliferation of T Lymphocyte Subpopulations in Patients with Brucellosis

BACKGROUND

T-cell proliferation is a standard method to evaluate cellular immune responses against intracellular infectious agents. The present study was undertaken to look for expression of an early activation marker (CD69) and proliferation using a nonradioactive method to evaluate cellular immune response against a salt-extractable antigen from Brucella melitensis 16M (RCM-BM) in patients suffering from brucellosis.

METHODS

Expression of CD69 on membrane of CD4+ and CD8+ T-cells was determined by flow cytometry. Lymphoproliferation was determined by tritiated thymidine and 5-bromo-2'-deoxyuridine (BrdU) incorporation using liquid scintillation counter or flow cytometry, respectively, to evaluate DNA synthesis.

RESULTS

Thirty healthy donors and 24 patients suffering from brucellosis were included in this study. In all cases, incubation with mitogen induced expression of CD69 and proliferation of both CD4+ and CD8+ T-cells. In contrast, only brucellosis patients responded with expression of CD69 and proliferation against RCM-BM antigen from Brucella melitensis (p < 0.001).

CONCLUSIONS

Methods used in this study were useful to evaluate immune response against specific antigen or polyclonal stimulation. CD4+ and CD8+ T cells from patients became equally activated and proliferated in response to RCM-BM antigen. Our data suggest that both T-cell subpopulations play an important role in immune response against Brucella.

Increased CD69 expression on peripheral blood eosinophils after specific inhalation challenge

BACKGROUND

CD69 is a molecule expressed on human eosinophils after cytokine-activation. Different studies have described the eosinophil activation, evaluated by CD69 expression, at the site of an allergic inflammation. In this study we evaluated the expression of CD69 on peripheral blood eosinophils after a specific inhalation challenge (SIC), in order to better define the state of activation of peripheral blood eosinophils after exposure to sensitizers.

METHODS

CD69 expression was evaluated by flow cytometry in nine asthmatic patients before and after a positive SIC with high or low molecular weight agents (pollens, house dust mites, Penicillia, isocyanates) and in 11 asthmatic patients who underwent an inhalation challenge with placebo. CD69 expression was evaluated at baseline, 120 min, and 240 min after the SIC or the placebo.

RESULTS

Baseline (before challenge) CD69 expression was comparable between the group of SIC positive patients and the placebo group. CD69 expression on peripheral eosinophils significantly increased 240 min after the challenge in positive SIC patients compared to placebo. In patients with a positive SIC the percentage of peripheral blood eosinophils significantly decreased at 120 and 240 min after the inhalation challenge with respect to the baseline.

CONCLUSION

CD69 expression on peripheral blood eosinophils is significantly increased in asthmatic patients after exposure to the sensitizing agent. These data show that the effects of a bronchial stimulation are also detectable on peripheral blood eosinophils.

Down-regulated IL-5 receptor expression on peripheral blood eosinophils from budesonide-treated children with asthma

BACKGROUND

The expression and function of cytokine receptors on peripheral blood eosinophils (PBE) from healthy and asthmatic children are poorly characterized.

METHODS

The PBE count and expression of IL-5 receptor (R) and GM-CSFR positive PBE was analyzed in nonsteroid-treated asthmatic children (n = 13), budesonide-treated asthmatic children (n = 24) and healthy children (n = 16) by flow cytometry. Alterations in intracellular EG2-epitope expression were used to measure the in vitro responsiveness of PBE to recombinant IL-5 and GM-CSF.

RESULTS

The PBE count was increased (P < 0.05) in both asthmatic groups, independent of treatment, as compared to healthy children. The IL-5R expression on PBE, as well as the in vitro responsiveness of PBE to recombinant IL-5, was reduced (P < 0.05), in budesonide-treated asthmatic children compared to nonsteroid-treated asthmatic children and healthy children. The proportion of GM-CSFR positive PBE and in vitro responsiveness of PBE to recombinant GM-CSF were not different between the groups. In vitro treatment with budesonide did not down-regulate the proportion of IL-5R positive PBE.

CONCLUSIONS

Budesonide-treatment of asthmatic children induces a selectively reduced IL-5R expression on PBE, concomitant with a reduced in vitro responsiveness of PBE to IL-5. We suggest that this budesonide-related down-regulation of the IL-5R might be a mechanism by which steroid treatment inhibits the action of IL-5 on eosinophil accumulation and activation in vivo.

Comparison of inflammatory responses to genetically engineered hypoallergenic derivatives of the major birch pollen allergen bet v 1 and to recombinant bet v 1 wild type in skin chamber fluids collected from birch pollen-allergic patients

BACKGROUND

Nearly 60% of birch pollen-allergic patients react exclusively to Bet v 1. With use of the skin blister model, previously only established for installation of crude allergens, we have for the first time characterized the inflammatory response in vivo to recombinant birch pollen allergen, rBet v 1, molecules (rBet v 1 wild type, fragments and trimer).

OBJECTIVE

Our purpose was to examine whether challenge with rBet v 1 derivatives (fragments and trimer) compared with rBet v 1 wild type differs with respect to influx of activated eosinophils and detectable levels of cytokines/chemokines related to allergic inflammation in skin chambers applied to birch pollen-allergic patients.

METHODS

The skin blister chambers were filled for 2 hours with rBet v 1, the derivatives or PBS and heparin (negative control). The fluids were analyzed after 2 and 8 hours. The number of eosinophils was determined and EG2 and CD69 expression measured by flow cytometry. Cytokines and mediators were analyzed by ELISA and RIA techniques.

RESULTS

Comparable numbers of eosinophils were recruited to the chambers challenged with rBet v 1 molecules, but the eosinophils from the rBet v 1 wild-type challenged chambers showed a significantly higher expression of CD69. The levels of eotaxin were similar in all 4 chambers, whereas rBet v 1 wild type induced significantly higher levels of histamine, eosinophil cationic protein, and GM-CSF than the derivatives did. Recombinant Bet v 1 trimer elicited significantly lower levels of IL-4 compared with rBet v1 wild type.

CONCLUSION

Genetically engineered hypoallergenic rBet v 1 derivatives recruited eosinophils analogously with rBet v 1 wild type. However, the derivatives exhibited a lower capacity to activate eosinophils and to release proinflammatory mediators and T helper type 2-derived cytokines. The derivatives may therefore be candidate molecules for specific immunotherapy of birch pollen allergy with reduced risk of inducing allergenic or inflammatory side effects.