Serum levels of eosinophil cationic protein and IL-5 in patients with asthma without systemic corticosteroids.

We measured the serum levels of eosinophil cationic protein (ECP) and interleukin-5 (IL-5) in 39 patients with asthma (symptomatic 12, asymtomatic 27) without systemic corticosteroids and 49 healthy subjects. There were significant differences in serum levels in both ECP and IL-5 between symptomatic and asymptomatic asthma, and healthy subjects. A significant positive correlation was found between serum levels of ECP and IL-5. No significant correlation was found between %FEV1 and serum level of ECP or IL-5, however, when the analysis was restricted to patients of less than 60 years of age, the correlations were significant. These results suggest that IL-5 is one of the factors that activate eosinophils even in peripheral blood, and that measurement of serum levels of ECP and IL-5 is useful for in vitro monitoring of asthma.