Effective antigen presentation to helper T cells by human eosinophils.

Although eosinophils are inflammatory cells, there is increasing attention on their immunomodulatory roles. For example, murine eosinophils can present antigen to CD4+ T helper (Th) cells, but it remains unclear whether human eosinophils also have this ability. This study determined whether human eosinophils present a range of antigens, including allergens, to activate Th cells, and characterized their expression of MHC class II and co-stimulatory molecules required for effective presentation. Human peripheral blood eosinophils purified from non-allergic donors were pulsed with the antigens house dust mite extract (HDM), Timothy Grass extract (TG) or Mycobacterium tuberculosis purified protein derivative (PPD), before co-culture with autologous CD4+ Th cells. Proliferative and cytokine responses were measured, with eosinophil expression of HLA-DR/DP/DQ and the co-stimulatory molecules CD40, CD80 and CD86 determined by flow cytometry. Eosinophils pulsed with HDM, TG or PPD drove Th cell proliferation, with the response strength dependent on antigen concentration. The cytokine responses varied with donor and antigen, and were not biased towards any particular Th subset, often including combinations of pro- and anti-inflammatory cytokines. Eosinophils up-regulated surface expression of HLA-DR/DP/DQ, CD80, CD86 and CD40 in culture, increases that were sustained over 5 days when incubated with antigens, including HDM, or the major allergens it contains, Der p I or Der p II. Human eosinophils can, therefore, act as effective antigen-presenting cells to stimulate varied Th cell responses against a panel of antigens including HDM, TG or PPD, an ability that may help to determine the development of allergic disease.

Anti-IL-4/-13 based therapy in asthma.

It is recognised that airway inflammation is key to asthma pathogenesis. Biopharmaceutical approaches have identified new therapies that target key cells and mediators that drive the inflammatory responses in the asthmatic lung. Such an approach resulted in the development of biologics targeted at inhibition of IL-4, IL-5 and IL-13. However, early clinical trials with these biologics in patients with asthma were for the most part disappointing even though they were highly effective in animal models of asthma. It is becoming apparent that significant clinical effects with anti-cytokine-based biologic therapies are more likely in carefully selected patient populations that take asthma phenotypes into account. The development of discriminatory biomarkers and genetic profiling may aid identification of such patients with asthma. This review is an update of the evidence demonstrating the effectiveness or otherwise of the targeting of the TH2 cytokines IL-4 and IL-13 with biologics in patients with asthma.

Recent developments in the use of monoclonal antibodies targeting the type 2 cytokines for severe asthma treatment.

Severe or refractory asthma is seen in approximately 5% of asthmatic subjects who have unsatisfactory symptom control despite adherence to high-dose inhaled glucocorticoid therapies resulting in significant morbidity, reduced quality of life with attendant implications for healthcare costs. Marked heterogeneity in symptoms and at the molecular phenotypic level are hallmarks of asthma resulting in the requirement of specifically targeted treatments to block the key pathways of the disease. Monoclonal antibody (mAb)-based biologics targeted at inhibition of the type 2 cytokines IL-4, IL-5 and IL-13 have become established as effective treatments for severe asthma, with significant clinical benefit seen in carefully selected patient populations that take asthma phenotypes and endotypes into account. The further development of reproducible and straightforward discriminatory biomarkers may aid identification of those patients most likely to benefit from treatment with these interventions.

An update on emerging drugs for asthma.

INTRODUCTION: It is recognized that airway inflammation is key to asthma pathogenesis. Biopharmaceutical approaches have identified new therapies that target key cells and mediators that drive the inflammatory responses in the asthmatic lung. Such an approach resulted in the development of biologics including IL-4, IL-5 and IL-13. However, clinical trials with these biologics in patients with asthma were for the most part disappointing even though they proved to be highly effective in animal models of asthma. AREAS COVERED: This review based on English-language original articles in PubMed or MedLine published in the last 5 years will update the current status, therapeutic potential and potential problems of recent drug developments in asthma therapy. EXPERT OPINION: It is becoming apparent that significant clinical effects with anti-cytokine-based therapies are more likely in carefully selected patient populations that take asthma phenotypes into account. It might also be more clinically effective if more than one cytokine and/or chemokine were to be targeted rather than a single mediator.

Molecular Biology of Eosinophils: Introduction.

The eosinophil is an enigmatic cell with a continuing ability to fascinate. A considerable history of research endeavor on eosinophil biology stretches from the present time back to the nineteenth century. Perhaps one of the most fascinating aspects of the eosinophil is how accumulating knowledge has changed the perception of its function from passive bystander, modulator of inflammation, to potent effector cell loaded with histotoxic substances through to more recent recognition that it can act as both a positive and negative regulator of complex events in both innate and adaptive immunity. This book consists of chapters written by experts in the field of eosinophil biology that provide comprehensive clearly written protocols for techniques designed to underpin research into the function of the eosinophil in health and disease.

Anti-IL-5 monoclonal antibodies for the treatment of asthma: an update.

INTRODUCTION: Asthma exhibits marked heterogeneity in symptoms with severe or refractory asthma representing a clear area of unmet medical need. These patients require more specifically targeted treatments with monoclonal antibody-based biologics targeted at inhibition of the type 2 cytokines IL-4, IL-5 and IL-13 having considerable potential as effective treatments for severe asthma. For the most part, anti-cytokine-based biologic therapies are more likely to give significant clinical benefit in carefully selected patient populations that take asthma phenotypes and endotypes into account. AREAS COVERED: This review is based on recent English-language original articles in Pub Med or MedLine that reported significant clinical findings on the current status, therapeutic potential and safety of the anti-IL-5 biologics mepolizumab, reslizumab and benralizumab in the treatment of severe refractory asthma. EXPERT OPINION: Anti-IL-5 treatment appears effective in patients with eosinophilic asthma through exacerbation prevention with accumulating evidence of glucocorticoid-sparing effects with an acceptable safety profile for these biologics.

Defective apoptotic cell clearance in asthma and COPD--a new drug target for statins?

Asthma and chronic obstructive pulmonary disease represent increasingly common respiratory conditions with a clear unmet need for more effective and safer therapy. Airway inflammation is key to both asthma pathogenesis and exacerbations of symptoms in chronic obstructive pulmonary disease. Several lines of evidence are now emerging implicating the increased persistence of apoptotic cells in patients with chronic inflammatory lung diseases and that this is largely due to a combination of inhibition of, or defects in, the apoptotic process and/or impaired apoptotic cell removal mechanisms.

Montelukast inhibition of resting and GM-CSF-stimulated eosinophil adhesion to VCAM-1 under flow conditions appears independent of cysLT(1)R antagonism.

Montelukast (MLK) is a cysteinyl leukotriene receptor-1 (cysLT(1)R) antagonist with inhibitory effects on eosinophils, key proinflammatory cells in asthma. We assessed the effect of MLK on resting and GM-CSF-stimulated eosinophil adhesion to recombinant human (rh)VCAM-1 at different flow rates using our novel microflow system. At 1 or 2 dyn cm(-2), shear-stress unstimulated eosinophils tethered immediately to rhVCAM-1, "rolled" along part of the channel until they tethered, or rolled without tethering. At flow rates greater than 2 dyn cm(-2), adherent eosinophils began to be displaced from rhVCAM-1. MLK (10 nM and 100 nM) gave partial ( approximately 40%) but significant (P<0.05) inhibition of unstimulated eosinophil adhesion to rhVCAM-1 at 1 or 2 dyn cm(-2) shear stress. Once adhered, unstimulated eosinophils did not exhibit morphological changes, and GM-CSF-stimulated eosinophil adhesion under flow was characterized by greater cell flattening with significant (P<0.05) inhibition of adherent cell numbers by 100 nM MLK observed. This effect appeared specific for MLK, as the analog (E)-3-[[[3-[2-(7-chloro-2-quinolinyl)ethenyl]phenyl]-[[3-dimethylamino)-3-oxopropyl]thio]methyl]thio]-propanoic acid, sodium salt, had no significant effect on eosinophil adhesion to VCAM-1. The possibility that LTC(4), released from unstimulated or GM-CSF-treated eosinophils, contributed to their adhesion to VCAM-1 was excluded as the LT biosynthesis inhibitor 3-[1-(p-Chlorobenzyl)-5-(isopropyl)-3-t-butylthioindol-2-yl]-2,2-dimethylpropanoic acid had no inhibitory effect, and exogenously added LTC(4) did not enhance eosinophil adhesion. In contrast, LTD(4) enhanced eosinophil adhesion to VCAM-1, an effect blocked by MLK (10 and 100 nM). These findings demonstrate that MLK-mediated inhibition of unstimulated and GM-CSF-stimulated eosinophil adhesion to VCAM-1 under shear-stress conditions appears independent of cysLT(1)R antagonism.

The anti-inflammatory effects of levocetirizine--are they clinically relevant or just an interesting additional effect?

Levocetirizine, the R-enantiomer of cetirizine dihydrochloride has pharmacodynamically and pharmacokinetically favourable characteristics, including rapid onset of action, high bioavailability, high affinity for and occupancy of the H1-receptor, limited distribution, minimal hepatic metabolism together with minimal untoward effects. Several well conducted randomised clinical trials have demonstrated the effectiveness of levocetirizine for the treatment of allergic rhinitis and chronic idiopathic urticaria in adults and children. In addition to the treatment for the immediate short-term manifestations of allergic disease, there appears to be a growing trend for the use of levocetirizine as long-term therapy. In addition to its being a potent antihistamine, levocetirizine has several documented anti-inflammatory effects that are observed at clinically relevant concentrations that may enhance its therapeutic benefit. This review will consider the potential or otherwise of the reported anti-inflammatory effects of levocetirizine to enhance its effectiveness in the treatment of allergic disease.

Nasal epithelial cells as surrogates for bronchial epithelial cells in airway inflammation studies.

The nose is an attractive source of airway epithelial cells, particularly in populations in which bronchoscopy may not be possible. However, substituting nasal cells for bronchial epithelial cells in the study of airway inflammation depends upon comparability of responses, and evidence for this is lacking. Our objective was to determine whether nasal epithelial cell inflammatory mediator release and receptor expression reflect those of bronchial epithelial cells. Paired cultures of undifferentiated nasal and bronchial epithelial cells were obtained from brushings from 35 subjects, including 5 children. Cells were subject to morphologic and immunocytochemical assessment. Mediator release from resting and cytokine-stimulated cell monolayers was determined, as was cell surface receptor expression. Nasal and bronchial cells had identical epithelial morphology and uniform expression of cytokeratin 19. There were no differences in constitutive expression of CD44, intercellular adhesion molecule-1, alphavbeta3, and alphavbeta5. Despite significantly higher constitutive release of IL-8, IL-6, RANTES (regulated on activation, normal T cell expressed and secreted), and matrix metalloproteinase (MMP)-9 from nasal compared with bronchial cells, the increments in release of all studied mediators in response to stimulation with IL-1beta and TNF-alpha were similar, and there were significant positive correlations between nasal and bronchial cell secretion of IL-6, RANTES, vascular endothelial growth factor, monocyte chemoattractant protein-1, MMP-9, and tissue inhibitor of metalloproteinase-1. Despite differences in absolute mediator levels, the responses of nasal and bronchial epithelial cells to cytokine stimulation were similar, expression of relevant surface receptors was comparable, and there were significant correlations between nasal and bronchial cell mediator release. Therefore, nasal epithelial cultures constitute an accessible surrogate for studying lower airway inflammation.

Emerging drugs for asthma.

BACKGROUND: Current therapies for asthma are aimed at controlling disease symptoms and for the majority of asthmatics inhaled corticosteroid anti-inflammatory therapy is effective. However, this approach requires life-time therapy while a subset of patients remains symptomatic despite optimal treatment creating a clear unmet medical need. OBJECTIVES: It is recognised that airway inflammation is key to asthma pathogenesis. Biopharmaceutical approaches may identify new therapies that target key cells and mediators that drive the inflammatory responses in the asthmatic lung. Such an approach may provide disease-modifying treatments. RESULTS: Significant areas of drug development include humanised monoclonal antibodies (mAb) for asthma therapy including those against IgE, IL-4 and IL-5. Asthma-relevant cytokines or chemokines have been targeted in a number of other ways. These include the use of humanised receptor blocking mAb or the removal of cytokines or chemokines via their binding to soluble receptor constructs. Small-molecule receptor antagonists also target receptors or the cellular signal transduction pathways that are activated following cytokine or chemokine receptor ligation. Another approach is to target asthma relevant mediators or the pathways controlling pro-inflammatory leukocyte accumulation within the asthmatic lung. CONCLUSIONS: This review will discuss the current status, therapeutic potential and potential problems of these novel drug developments in asthma therapy. Current therapies for asthma are aimed at controlling disease symptoms, and for the majority of asthmatics inhaled corticosteroid anti-inflammatory therapy is effective. However, this approach requires lifetime therapy; and a subset of patients remains symptomatic despite optimal treatment, creating a clear unmet medical need. It is recognised that airway inflammation is key to asthma pathogenesis. Biopharmaceutical approaches may identify new therapies that target key cells and mediators that drive the inflammatory responses in the asthmatic lung. Such an approach may provide disease-modifying treatments. Significant areas of drug development include humanised mAb for asthma therapy, including those against IgE, IL-4 and IL-5. Asthma-relevant cytokines or chemokines have been targeted in a number of other ways. These include the use of humanised receptor blocking mAb or the removal of cytokines or chemokines via their binding to soluble receptor constructs. Small-molecule receptor antagonists also target receptors or the cellular signal transduction pathways that are activated following cytokine or chemokine receptor ligation. Another approach is to target asthma-relevant mediators, or the pathways controlling pro-inflammatory leukocyte accumulation within the asthmatic lung. This review will discuss the current status, therapeutic potential and potential problems of these novel drug developments in asthma therapy.

Reslizumab in the treatment of severe eosinophilic asthma: an update.

A marked heterogeneity is exhibited by asthma both clinically and at the molecular level with different phenotypes driven by diverse mechanistic pathways that require specifically targeted treatments. Biologics aimed at IL-4/13, IL-5 or IgE are proven or potentially effective treatments for patients with difficult to treat eosinophilic asthma. Importantly, it is now widely accepted that biologic-based therapies give significant clinical improvements in those patient populations where asthma phenotypes are taken into account. Such asthma phenotypes have been identified by reproducible and straightforward discriminatory biomarkers. This short review discusses recent studies of the effectiveness of the anti-IL-5 reslizumab in relation to the use of simple reproducible biomarkers in eosinophilic asthma.

Recent developments in the use of biologics targeting IL-5, IL-4, or IL-13 in severe refractory asthma.

INTRODUCTION: Severe or refractory asthma is seen in approximately 5% of asthmatic subjects who have unsatisfactory symptom control despite adherence to high-dose inhaled glucocorticoid therapies resulting in significant morbidity, reduced quality of life and health-care cost implications. Asthma exhibits marked heterogeneity both clinically and at the molecular phenotypic level requiring specifically targeted treatments to block the key pathways of the disease. Monoclonal antibody-based biologics targeted at inhibition of the type 2 cytokines IL-4, IL-5, and IL-13 have considerable potential as effective treatments for severe asthma. Areas covered: This review is based on recent English-language original articles in PubMed or Medline that reported significant clinical findings on the current status, therapeutic potential, and safety of biologics targeted at IL-4, IL-5, and IL-13 in the treatment of asthma together with the potential utility of simple reproducible non-invasive biomarkers to guide the effective use of biologic-based therapy that do not require direct sampling of the airways Expert commentary: The further development of reproducible and straightforward discriminatory non-invasive biomarkers may aid identification of those patients most likely to benefit from treatment with these interventions.

Pro-inflammatory mediator responses from neonatal airway epithelial cells and early childhood wheeze.

BACKGROUND: Airway epithelial cell (AEC) function differs between children with and without asthma. Here, we associated neonatal AEC function with asthma symptoms at 4 years of age. METHODS: Nasal AEC were collected from neonates within 48 h of birth. Cells were cultured and stimulated with tumor necrosis factor alpha/interleukin-1 beta (TNFα/IL-1ß), lipopolysaccharide (LPS), or house dust mite (HDM). Absolute concentrations of pro-inflammatory mediators in the culture supernatant were quantified and expressed as median [interquartile range] in pg/mg protein. A parent-completed respiratory questionnaire was returned when the child was 4 years old. RESULTS: AEC were successfully cultured in 139 neonates, of whom 120 were contacted at 4 years and 91 (76%) questionnaires were returned. Sixteen children had wheezed ever and 11 had recent wheeze. At birth, when compared to those with no recent wheeze, supernatants from cultured neonatal AEC from the children with recent wheeze had reduced median IL-8 (CXCL8) release after treatment with culture medium alone (P = 0.049), with TNFα/IL-1ß (P < 0.001) and LPS (P = 0.004). Additionally, and when compared to those with no recent wheeze, 4 year olds with recent wheeze had reduced neonatal AEC release of IL-6 (P = 0.013), GMCSF (P = 0.012), and ICAM-1 (P = 0.017) after treatment with TNFα/IL-1ß and reduced release of ICAM-1 (P = 0.038) and RANTES (P = 0.042) after treatment with HDM. CONCLUSIONS: Abnormalities in AEC function are present at birth before the onset of childhood wheeze. The relationship between reduced AEC function at birth and wheeze at 4 years was not exclusive, suggesting that post-natal factors are required for the AEC abnormality to translate into symptoms.

Biologics targeting IL-5, IL-4 or IL-13 for the treatment of asthma - an update.

INTRODUCTION: The development of monoclonal antibody-based biologics targeted at inhibition of the Th2 cytokines IL-4, IL-5 and IL-13 represent potentially effective treatments for patients with the glucocorticoid refractory eosinophilic asthma phenotype. Areas covered: Asthma exhibits marked heterogeneity both clinically and at the molecular phenotypic level, requiring specifically targeted treatments to block the key pathways of the disease. It is becoming apparent that significant clinical effects with anti-cytokine-based biologic therapies are more likely in carefully selected patient populations that take asthma phenotypes into account. The development of reproducible and straightforward discriminatory biomarkers may aid identification of those patients most likely to benefit from treatment with these expensive interventions. This narrative review is based on English-language original articles in PubMed or Med-Line that reported significant clinical findings published in the last two years on the evidence demonstrating the effectiveness or otherwise of the targeting of IL-4, IL-5, or IL-13 in carefully selected patients with severe refractory asthma. Expert commentary: The use of a baseline peripheral blood eosinophilia as a simple reproducible biomarker to identify patients with particular sub-phenotypes of asthma to guide the effective use of biologic therapy represents a significant step forward.

Biologics for asthma and allergy.

PURPOSE OF REVIEW: The development of monoclonal antibody-based biologics targeted at inhibition of the Th2 cytokines interleukin-4, interleukin-5 and interleukin-13 represent potentially effective treatments for asthma and allergic diseases. This short review is based on English-language original articles in PubMed or MedLine that reported significant clinical findings on the evidence demonstrating the effectiveness or otherwise of the targeting of interleukin-4, interleukin-5 or interleukin-13 in asthma or allergic disease. RECENT FINDINGS: Asthma exhibits marked heterogeneity both clinically and at the molecular phenotypic level requiring specifically targeted treatments to block the key pathways of the disease. It is becoming apparent that significant clinical effects with anticytokine-based biologic therapies are more likely in carefully selected patient populations that take asthma phenotypes into account. Biologics aimed at interleukin-4/13, interleukin-5 or immunoglobulin E are potentially effective treatments for patients with difficult to treat allergic disease. The development of reproducible and straightforward discriminatory biomarkers may aid identification of those patients most likely to benefit from treatment with these expensive interventions. SUMMARY: Overall these biologics-based therapies are effective treatments for difficult to treat asthma and allergic disease with a safety profile comparable with placebo in the majority of published studies.

Targeting airway inflammation: novel therapies for the treatment of asthma.

It is now widely accepted that airway inflammation is the key factor underlying the pathogenesis of asthma. Inhaled corticosteroids remain the most important anti-inflammatory treatment for asthma. However, they are rather non-specific in their actions and their use raises concerns over side effects and compliance issues, particularly in children and adolescents. Moreover, a significant sub-group of asthmatic patients responds poorly or not at all to high-dose inhaled or systemic steroid treatment. Therefore, much effort is being made to develop novel more specific and safer therapy for asthma. Significant areas of drug development include humanised monoclonal antibodies (mAb) for asthma therapy including those against IL-4, IL-5, TNF and IL-13. Asthma-relevant cytokines or chemokines have been targeted in a number of other ways. These include: (1) the use of humanised blocking mAb to their receptors; (2) removal of cytokines or chemokines via binding to soluble receptors or small molecule receptor antagonists; and (3) drugs that block the signal transduction pathways activated following the interaction of cytokines or chemokines with their receptors. Another approach is to use anti-inflammatory cytokines directly or encourage their production thereby suppressing the allergic inflammatory process; these chemokines include IL-10, IL-12 and IFN-gamma. Finally, a further promising area involves targeting the allergic portion of the asthma phenotype using humanised anti-IgE mAb. This review will discuss the current status, therapeutic potential and potential problems of these novel drug developments in asthma therapy.

Levocetirizine: an update.

Histamine plays a prominent and diverse role in the pathophysiology of allergic disease and therapeutic intervention is therefore typically focused on blocking the effects of this biogenic amine. A new antihistamine, levocetirizine, is the R-enantiomer of cetirizine dihydrochloride and like its parent compound undergoes minimal hepatic metabolism. Levocetirizine has pharmacodynamically and pharmacokinetically favourable characteristics, including high bioavailability, rapid onset of action, limited distribution and a low degree of metabolism. Clinical trials indicate that it is safe and effective for the treatment of allergic rhinitis and chronic urticaria with a minimal number of untoward effects. Furthermore, several recent studies have demonstrated that, in addition to its being a potent antihistamine, levocetirizine has several anti-inflammatory effects that are observed at clinically relevant concentrations that may enhance its therapeutic benefit.

Novel therapies for asthma--advances and problems.

It is now widely accepted that airway inflammation is the key factor underlying the pathogenesis of asthma. While corticosteroids remain the most important anti-inflammatory treatment for asthma they are rather non-specific in their actions. Their use also raises concerns over side effects and compliance issues, particularly in children and adolescents. There is therefore much effort being made to develop novel more specific and safer therapy for asthma. Efforts are being made to improve existing drugs together with the use of combination therapy with anti-histamines and leukotriene antagonists. An important area for potential advances in glucocorticoid (GC) development include the elucidation of the crystal structure of the GC receptor ligand-binding domain that may provide vital information in dissociating the anti-inflammatory effects of GCs from unwanted side-effects. Other areas include the development of humanised monoclonal antibodies for asthma therapy including those against IgE, IL-4 and IL-5 together with the inhibition of adhesion pathways and/or chemokines responsible for inflammatory cell accumulation in the asthmatic lung. The potential for immunotherapy using T cell peptide epitopes or DNA-based vaccines and the use of anti-inflammatory cytokines such as IL-10 or IFN-gamma are discussed. Several avenues of research are currently underway in an attempt to define mechanisms by which pro-inflammatory cells such as eosinophils can be safely removed from the asthmatic lung through apoptosis induction and their subsequent ingestion by phagocytes. Novel strategies include elucidation of the intracellular pathways controlling granulocyte apoptosis and the receptor mediated events employed by macrophages and bronchial epithelial cells in the recognition and removal of apoptotic cellular corpses. This paper will provide an overview of both the potential and shortcomings of these diverse approaches to drug development for asthma.

Membrane receptor-mediated apoptosis and caspase activation in the differentiated EoL-1 eosinophilic cell line.

Caspases are key molecules in the control of apoptosis, but relatively little is known about their contribution to eosinophil apoptosis. We examined caspase-3, -8, and -9 activities in receptor ligation-dependent apoptosis induction in the differentiated human eosinophilic cell line EoL-1. Differentiated EoL-1 exhibited bi-lobed nuclei, eosinophil-associated membrane receptors, and basic granule proteins. Annexin-V fluorescein isothiocyanate binding to EoL-1 revealed significant (P<0.01) apoptosis induction in cells cultured for 20 h with monoclonal antibodies (mAb) specific for CD45 (71%+/-4.3), CD45RA (58%+/-2.3), CD45RB (68%+/-2.4), CD95 (47%+/-2.6), and CD69 (52%+/-2.1) compared with control (23%+/-1.6) or CD45RO mAb (27%+/-3.9). The pan-caspase inhibitor Z-Val-Ala-Asp-fluoromethylketone (fmk) and inhibitors of caspase-8 (Z-Ile-Glu-Thr-Asp-fmk) and caspase-9 (Z-Leu-Glu-His-Asp-fmk) significantly inhibited mAb-induced apoptosis of EoL-1 but had no effect on constitutive (baseline) apoptosis at 16 and 20 h. Caspase activity was analyzed using the novel CaspaTag trade mark technique and flow cytometry. EoL-1 treated with pan-CD45, CD45RA, CD45RB, and CD95 mAb exhibited caspase-3 and -9 activation at 12 h post-treatment, which increased at 16 and 20 h. Activated caspase-8 was detected 12 and 16 h after ligation with CD45, CD45RA, CD45RB, and CD95 mAb followed by a trend toward basal levels at 20 h. CD69 ligation resulted in caspase-3 activation, a modest but significant activation of caspase-8, and a loss in mitochondrial transmembrane potential but had no significant effect on activation of caspase-9. Thus, the intrinsic and extrinsic caspase pathways are involved in controlling receptor ligation-mediated apoptosis induction in human eosinophils, findings that may aid the development of a more targeted, anti-inflammatory therapy for asthma.