Eosinophils and asthma. What do measurements tell us?

Aeroallergen and food IgE sensitization and local and systemic inflammation in asthma

BACKGROUND

We recently reported an independent association between IgE sensitization to food allergens and increased airway inflammation, assessed by fraction of exhaled nitric oxide (FeNO), in a population-based study (J Allergy Clin Immunol, 130, 2012, 397). Similar studies have not been performed in populations with asthma. The aim of the present study was to investigate the allergic sensitization profile in asthmatics and examine FeNO, airway responsiveness and blood eosinophilia in relation to type and degree of IgE sensitization.

METHOD

FeNO, airway responsiveness, blood eosinophil count (B-Eos) and IgE sensitization to food allergens and aeroallergens were determined in 408 subjects with asthma, aged 10-34 years.

RESULTS

Asthmatics had higher prevalence of IgE sensitization against all allergens than controls (P < 0.001). Mite, pollen, furry animal, mould and food sensitizations were each associated with increased FeNO, airway responsiveness and B-Eos in asthmatics. IgE sensitization to mould, furry animals and food allergens was independently related to FeNO (all P < 0.05) after adjustment for age, sex, height, smoking history and medication. IgE sensitization to mould (P < 0.001) and furry animals (P = 0.02) was related to airway responsiveness in a similar model. Finally, IgE sensitization to mould (P = 0.001), furry animals (P < 0.001) and food allergens (P < 0.001) was independently related to B-Eos.

CONCLUSION

Independent effects of IgE sensitization to aeroallergens (furry animals and mould) and food allergens were found on both local and systemic markers of inflammation in asthma. The finding regarding food IgE sensitization is novel, and a clinical implication might be that even food sensitization must be assessed to fully understand inflammation patterns in asthma.

Serum eosinophil cationic protein for predicting the prognosis of a step-down in inhaled corticosteroid therapy in adult chronic asthmatics

We investigated whether the serum concentration of eosinophil cationic protein (s-ECP) can be used to determine when a step-down in inhaled corticosteroid therapy is indicated for patients with chronic asthma. A total of 24 adult patients, whose symptoms were well controlled with inhaled beclomethasone dipropionate (iBDP), were studied. The dosage of iBDP was reduced by half once a month until the dose reached one-quarter of the original level. s-ECP and blood eosinophil counts were determined once a month before and during the 6-month period after the step-down. In 12 patients, moderate and frequent exacerbation occurred, thus requiring a return to the initial or twice the initial dose of iBDP. Thus, the step-down here was defined as unsuccessful. In the remaining 12 patients, the symptoms were stable over the course of the 6 months, and the step-down was defined as successful. s-ECP correlated with eosinophil counts in peripheral blood (EOS) in both the successful and the unsuccessful groups. Although EOS before the step-down did not differ significantly between the two groups, s-ECP was significantly higher in the unsuccessful group (mean 35.7 microg/L) than in the successful group (mean 17.0 microg/L, p < 0.03). Thus, s-ECP appears to be a useful marker for determining when a step-down in iBDP therapy is indicated, and thus may contribute to successful long-term management of chronic asthma.

Conditions in blood sampling procedures that extend the ex vivo stability of eosinophil activity markers in peripheral blood from allergic patients and healthy controls

BACKGROUND

Serum-ECP, EG2-epitope on intracellular ECP and surface expression of CD9 and CD11b in peripheral blood eosinophils (PBE) are considered to be markers that mirror clinical parameters in allergic inflammation.

OBJECTIVE

The aim was to investigate the impact of the blood sampling procedure on PBE markers and to identify optimal conditions for extended pre-analysis storage.

METHODS

Blood, from healthy individuals and patients with allergic rhinitis/asthma, was collected in tubes with EDTA, citrate, or without anti-coagulant. The expression of EG2-epitope, CD9, and CD11b were analyzed in eosinophils and neutrophils after 1, 5, and 24 hours of storage at +4 degrees C, according to the FOG-method and flow cytometry. In vitro stimulation with fMLP/PMA was used for metabolic activity analysis and CD11b mobilization. Following a 1-hour clotting period at +20 to 22 degrees C, samples were stored at +4 degrees C and serum-ECP levels were measured.

RESULTS

The EG2-epitope, serum-ECP, and CD9 were stable in samples from both healthy controls and allergic patients at all storage conditions. The EG2-epitope, serum-ECP and PBE count were significantly increased in the patient group, whereas no differences were observed in the expression of CD9 or CD11b. Both granulocytes and monocytes retained their metabolic activity for 24 hours. Neutrophils in citrate-blood increased their ability to respond to fMLP, as compared with EDTA-blood.

CONCLUSION

In vitro analysis of selected activity markers and functional tests could be performed on granulocytes from both healthy individuals and allergic patients after 24 hours storage at +4 degrees C. The anticoagulant citrate seems to be preferable to EDTA when monocytes or CD11b expression are analyzed.

Prevention of Th2-Like Cell Responses by Coadministration of IL-12 and IL-18 Is Associated with Inhibition of Antigen-Induced Airway Hyperresponsiveness, Eosinophilia, and Serum IgE Levels

Allergic asthma is thought to be regulated by Th2 cells, and inhibiting this reponse is a promising mode of intervention. Many studies have focused on differentiation of Th cells to the Th1 or Th2 subset in vitro. IL-4 is essential for Th2 development, while IL-12 induces Th1 development, which can be enhanced by IL-18. In the present study, we investigated whether IL-12 and IL-18 were able to interfere in Th2 development and the associated airway symptoms in a mouse model of allergic asthma. Mice were sensitized with OVA using a protocol that induces IgE production. Repeated challenges by OVA inhalation induced elevated serum levels of IgE, airway hyperresponsiveness, and a predominantly eosinophilic infiltrate in the bronchoalveolar lavage concomitant with the appearance of Ag-specific Th2-like cells in lung tissue and lung-draining lymph nodes. Whereas treatments with neither IL-12 nor IL-18 during the challenge period were effective, combined treatment of IL-12 and IL-18 inhibited Ag-specific Th2-like cell development. This inhibition was associated with an absence of IgE up-regulation, airway hyperresponsiveness, and cellular infiltration in the lavage. These data show that, in vivo, the synergistic action of IL-12 and IL-18 is necessary to prevent Th2-like cell differentiation, and consequently inhibits the development of airway symptoms in a mouse model of allergic asthma.

Serum eosinophil cationic protein as a marker of eosinophilic inflammation in asthma

BACKGROUND

The serum level of eosinophil cationic protein (ECP) has been used as a clinical marker in asthma, on the assumption that it reflects ongoing eosinophilic inflammation of the airways. However, only a few studies have investigated this issue, using bronchial secretions but not tissue specimens.

OBJECTIVE

To evaluate cross-sectionally the correlation between serum ECP level or blood eosinophil count, and the degree of eosinophilia in bronchoalveolar lavage fluid (BALF) and bronchial biopsy tissue, and disease activity, in asthmatic patients.

METHODS

Thirty-three adults with symptomatic asthma and six healthy controls were studied. The blood eosinophil count, ECP levels in serum and BALF, percentage of eosinophils in BALF, number of eosinophils in bronchial tissue, pulmonary function, and methacholine bronchial responsiveness of these subjects were clarified. An asthma severity score and inhaled beta2-agonist requirement (puffs/day) were also assessed for the asthmatic patients.

RESULTS

The asthmatic patients, compared with the controls, had more obstructive (as tested by %FEV1, FEV1/FVC, and FEF25-75%) and more responsive airways, and showed a significant increase in the number of eosinophils in the blood, BALF, and tissue, and in the serum ECP levels. The ECP levels in BALF were below the detection limit for most of the subjects in both groups examined. In the asthmatic patients, serum ECP level demonstrated correlations with the number or percentage of eosinophils in BALF and tissue, whereas the blood eosinophil count correlated only with the percentage of eosinophils in BALF. Serum ECP level correlated with all indices of disease activity examined; %FEV1, FEV1/FVC, FEF25-75% bronchial responsiveness, severity score and beta2-agonist usage, whereas the blood eosinophil count correlated only with %FEV1 and bronchial responsiveness.

CONCLUSION

The data suggest that serum ECP level reflects the intensity of eosinophilic airway inflammation, as well as the disease activity, and may be useful as an inflammatory marker in asthma.

The mouse trap

Mouse models of asthma are now being used extensively in drug research. However, the successful unravelling of combinatorial interplays of cells and molecules in the murine airways may not be matched by equally successful demonstrations of an asthma-like pathophysiology. Here, Carl Persson, Jonas Erjefält, Magnus Korsgren and Frank Sundler discuss the fact that major features of asthma may still need to be demonstrated in the airways of allergic mice.

Eosinophilic leukocyte accumulation during vagally induced bronchoconstriction

Eosinophilic leukocytes (eosinophils) are important effector cells in allergic inflammatory diseases such as asthma, in which significant accumulation of these cells is observed in the bronchial mucosa. However, there is little information about the relationships between bronchoconstriction and accumulation of eosinophils. We hypothesized that eosinophils are retained in the bronchial vasculature in the inner airway wall during bronchoconstriction because of deformation of the mucosal membrane. To test this hypothesis we induced unilateral bronchoconstriction in open chest guinea pigs by stimulating the right vagus nerve and compared the accumulation of eosinophils in the airway wall of the constricted and contralateral unconstricted lungs using histologic specimens. Results show that the density of eosinophils (number of cells/wall area) significantly increased in the inner wall and decreased in the adventitia of the constricted airways compared with the contralateral unconstricted airways. There was a positive relationship between the amount of smooth muscle shortening and the eosinophil density in the inner wall. On the other hand, this relationship was significantly negative in the adventitia. Atropine completely inhibited the eosinophil accumulation in the inner wall. These data suggest that eosinophils can accumulate in the airway inner wall during bronchoconstriction because of geometrical factors.