M. J. Woolley

Granulocyte-macrophage colony-stimulating factor, eosinophils and eosinophil cationic protein in subjects with and without mild, stable, atopic asthma

Increasing evidence implicates the eosinophil as an important effector cell in asthma, but little is known regarding its regulation in vivo. Granulocyte-macrophage colony-stimulating factor (GM-CSF) has been shown to regulate eosinophil function in vitro. We investigated the in vivo role of eosinophils and GM-CSF in mild asthma. We compared the number and function of eosinophils and the presence of GM-CSF in blood, bronchoalveolar lavage (BAL) and biopsy tissue obtained from eight mild, stable, atopic asthmatics and 10 nonasthmatics, five of whom were atopic and five nonatopic. Eosinophils were significantly increased in the blood, BAL and biopsy tissue from asthmatics. Activated eosinophils, assessed by immunostaining for the secreted form of eosinophil cationic protein (EG2), were also increased in asthmatic BAL cells and biopsy tissue. Significant increases in GM-CSF in BAL cells and biopsy tissue from asthmatics were also evident. Significant positive correlations existed between GM-CSF in BAL and EG2, and GM-CSF in biopsy tissue and BAL and biopsy eosinophils. Airway responsiveness was also significantly positively correlated with eosinophil number and activation, and with GM-CSF. These results demonstrate that there are increased numbers of activated eosinophils and GM-CSF is increased in patients with mild asthma. Furthermore, GM-CSF is correlated with eosinophil number and function in vivo and these indices are significantly correlated with airway function. These findings emphasize the importance of eosinophils, potentially regulated in vivo by GM-CSF, in contributing to the disordered airway function evident even in mild asthma.

Basophil and eosinophil differentiation in allergic reactions

Basophil and eosinophil participation in allergic reactions constitutes a hallmark of this type of inflammatory state. Mechanisms underlying the accumulation of these cells in tissues where allergen is present include the effect of cytokines and other inflammatory mediators on the egress from blood and migration of these cells into the tissue. Much progress has been made recently in the understanding of in vitro chemotactic and adherence mechanisms putatively involved in the accumulation of the mature basophil and eosinophil in IgE-dependent reactions in vivo? A concept we have developed in our studies over the past decade is that the bone marrow, through the release of progenitors into the peripheral blood, contributes a pool of differentiating cells, which accumulate in response to signals from allergic inflamed tissues. 2s In this review we summarize the basis for this concept, citing both basic and applied studies and expanding on the evidence supporting the progenitor hypothesis for accumulation of basophils and eosinophils by using recently acquired information in an animal model and in human beings.

Allergen-Induced Changes in Bone Marrow Progenitors and Airway Responsiveness in Dogs

An increased production of inflammatory cell progenitors (colony-forming cells, CFUs) may contribute to airway inflammation, since CFUs increase after allergen inhalation in asthmatics. We examined the effect of allergen inhalation, with or without budesonide pretreatment, on bone marrow CFU production in dogs with allergen-induced airway hyperresponsiveness. Allergen inhalation increased airway responsiveness (p < 0.001) as well as the number of CFUs induced in vitro by recombinant canine stem cell factor (p < 0.001) and granulocyte-colony-stimulating factor (p = 0.035). Budesonide reduced the allergen-induced increases in airway responsiveness (p = 0.005) and abolished the allergen-induced increases in the numbers of CFUs (p < 0.005). These findings provide the first direct evidence that allergen inhalation increases bone marrow granulocyte progenitor production and suggest that such increases may contribute to the development of airway hyperresponsiveness in asthma. The effectiveness of inhaled corticosteroids in asthma may result, in part, from effect on bone marrow production of inflammatory cells.

The effects of an inhaled corticosteroid on oxygen radical production by bronchoalveolar cells after allergen or ozone in dogs.

Both ozone and allergen inhalation increase the capacity to produce oxygen radicals by bronchoalveolar lavage cells in dogs. The purpose of these studies was to determine whether inhaled corticosteroids inhibits these increases in oxygen radical production from bronchoalveolar lavage cells. Six random source dogs were studied after dry air or ozone inhalation (3 ppm, 30 min). Seven random source dogs were studied after diluent or allergen inhalation. The dogs inhaled budesonide (2.74 mg/day) or lactose powder, twice daily for 7 days before ozone and allergen. 90 min after ozone or dry air, and 24 h after Ascaris suum or diluent a bronchoalveolar lavage was carried out. Spontaneous luminol-enhanced chemiluminescence was measured from bronchoalveolar lavage cells (4 x 10(6) cells) for 10 min, followed by a measurement of phorbol myristate acetate (PMA 2.4 micromol/l) stimulated chemiluminescence for 10 min. Both ozone and allergen inhalation caused an increase in PMA stimulated chemiluminescence (P<0.05). Budesonide pretreatment inhibited ozone-induced (P<0.008), but not allergen-induced PMA stimulated chemiluminescence (P>0.90). Both ozone and allergen inhalation caused an increase in the bronchoalveolar lavage neutrophils. Budesonide pretreatment significantly inhibited the ozone-induced (P=0.007), but not the ascaris-induced neutrophil influx (P=0.93). These results demonstrate that ozone, but not allergen, stimulated oxygen radical release and neutrophil influx are attenuated by inhaled corticosteroids. This suggests that luminol-enhanced chemiluminescence from bronchoalveolar lavage cells measures oxygen radicals derived from neutrophils, and that ozone-and allergen-induced bronchoalveolar lavage neutrophilia are caused by different mechanisms.