Interleukin-8 secretion and neutrophil recruitment accompanies induced sputum eosinophil activation in children with acute asthma

Although airway inflammation is recognized as a key feature of asthma, the characteristics of airway inflammation in children with acute severe asthma are not well defined. The aim of this study was to describe the characteri stics of airway inflammation in children with an acute exacerbation of asth ma using sputum cell counts and fluid-phase measurements and to examine the changes in these parameters upon resolution of the exacerbation. Children (n = 38) presenting to the Emergency Department with acute asthma underwent successful sputum induction using ultrasonically nebulized normal saline ( n = 22), or expectorated sputum spontaneously (n = 16). Sputum induction wa s repeated at least 2 wk later when the children had recovered (n = 28). Sp utum portions were selected, dispersed and total and differential cell coun ts performed. Neutrophil elastase and EG2-positive eosinophils were assesse d and fluid-phase eosinophil cationic protein (ECP), myeloperoxidase (MPO), interleukin-8 (IL-8), and IL-5 were measured. During the acute exacerbatio n the median (range) total cell count was 8.4 x 10(6)/ml (0.5 to 190.3), an d fell significantly at resolution to 1.3 x 10(6)/ml (p < 0.01). The inflam matory cell infiltrate was mixed and included eosinophils (0.8 x 10(6)/ml), neutrophils (3.3 x 106/ml), and mast cells. EC2(+) cells were high and cor related with the degree of airflow obstruction (r = -0.5, p = 0.02). They d ecreased significantly at resolution as did supernatant ECP (1,078 versus 2 72 ng/ml), suggesting that eosinophils were activated during the exacerbati on. MPO was 220 ng/ mi at exacerbation and fell significantly to 1 ng/ml at resolution. Levels of IL-8 and IL-5 were elevated during the acute exacerb ation and IL-8 concentrations decreased at resolution. In conclusion, airwa y inflammation can be studied in children with acute asthma by sputum induc tion. Airway inflammation is present during an acute exacerbation of asthma , and is characterized by infiltration and activation of both eosinophils a nd neutrophils. The heterogeneity of airway inflammation in acute asthma ma y influence response to corticosteroid therapy.