EOSINOPHILIC INFLAMMATION IS ASSOCIATED WITH ELEVATION OF INTERLEUKIN-5 IN THE AIRWAYS OF PATIENTS WITH SPONTANEOUS SYMPTOMATIC ASTHMA

In vitro and in vivo studies have shown an important role for interleu kin-5 (IL-5) in regulating eosinophil proliferation, survival, and eff ector function. Because eosinophilic inflammation is an important comp onent of symptomatic episodes of asthma, we have investigated whether increased levels of IL-5 protein are present in bronchoalveolar lavage (BAL) fluid of patients with spontaneously symptomatic asthma (FEV(1) , 61% predicted; FEF(25%-75%), 30% predicted) compared with patients w ith asymptomatic asthma (FEV(1), 88% predicted; FEF(25%-75%), 76% pred icted). The percent of BAL eosinophils (10.5% vs 0.6%) (p = 0.0001) an d eosinophil-derived neurotoxin (386.0 ng/ml vs 6.3 ng/ml) (p = 0.0001 ) was greater in BAL fluids derived from patients with symptomatic ast hma compared with patients with asymptomatic asthma. Levels of IL-5 me asured with an immunoradiometric assay were significantly higher in pa tients with symptomatic asthma (n = 26) compared with those with asymp tomatic asthma (n = 18) (274 pg/ml vs < 13 pg/ml) (p = 0.02). The incr eased IL-5 levels were noted in a subset of patients with symptomatic asthma with BAL absolute eosinophil counts greater than 10(6) (IL-5, 6 64 pg/ml; n = 10) as opposed to patients with symptomatic asthma with BAL eosinophil counts less than 10(6) (IL-5, < 13 pg/ml; n = 16) (p = 0.005). This study Suggests that IL-5 is not only induced in experimen tal models of allergen-induced asthma but can also be detected as asth ma progresses from the asymptomatic to the clinically symptomatic stat e in subjects with significant BAL eosinophilia.