Interleukin 5 release into asthmatic airways 4 and 24 hours after endobronchial allergen challenge: Its relationship with eosinophil recruitment

Interleukin 5 (IL-5), a cytokine with a range of activities on eosinophils, has been implicated in the allergic asthmatic reaction. We have investigat ed the kinetics of release of this cytokine into asthmatic airways as web a s its relationship to eosinophil recruitment following allergen challenge, Twelve asthmatic patients underwent endobronchial allergen challenge and br onchoalveolar lavage (BAL) fluid was obtained either 4 h (n=6) or 24 h (n=6 ) after challenge. Four hours after challenge, levels of IL-5 were signific antly increased in BAL fluid (10-fold concentration obtained from the aller gen-challenge site compared,vith the saline control (median 2.67 pg/ml, ran ge 1.0-7.4 pg/ml vs 1.0 pg/ml <1.0-2.4 pg/ml, P<0.05). At 24 h levels of IL -5 increased further at the allergen site but not at the saline control lav age (31.1 pg/ml, range 3.6-59.0 pg/ml vs 1.5 pg/ml, range 1.5-4.9 pg/ml, re spectively P<0.02), At 4 h there was almost a three fold increase in IL-5 l evel, whereas at 24 h IL-5 levels were 20-fold greater. Differential cell c ounts show ed that eosinophil numbers obtained 4 and 24 h after allergen ch allenge were 7 and 32 times higher than numbers after saline challenge. The parallel increase of eosinophil numbers and IL-5 concentrations in BAL flu id suggests that this cytokine may contribute to the eosinophil recruitment observed into asthmatic airways after allergen challenge. (C) 1999 Academi c Press.