Role of IL-5 and eotaxin in airway eosinophilic inflammation

Kim, Chang Keun; Kita, Hirohito; Yu, Jin Ho; Koh, Young Yull

Abstract

BACKGROUND
IL-5 and eotaxin are the most important cytokines/chemokines responsible for regulating eosinophil locomotion.
OBJECTIVE
We investigated the role of IL-5 and eotaxin in airway eosinophilic inflammation in patients with chronic cough by analyzing sputum from patients. METHODS: Thirty-one patients who had chronic cough and seven normal control subjects were enrolled. Patients were divided into two groups, asthma group (n=15) and non-asthma group (n=16). Sputum was induced by inhalation of hypertonic saline. Total cell counts and differentials were determined. The levels of IL-5 and eotaxin were measured by ELISA, and the levels of EDN and MBP were measured by RIA. RESULTS: Patients in the asthma group showed higher percentage of eosinophils and higher levels of EDN and IL-5 (P<.001, P<.05 and P<.05, respectively) compared to subjects in the control group and higher % eosinophils, higher levels of EDN and MBP (P<.001, P<.05 and P<.05, respectively) compared to subjects in the control group. Non-asthma group patients also showed higher percentage of eosinophils and increased IL-5 levels (P<.05 and P<.05, respectively) compared to the control group. The eotaxin level correlated positively with percentage of eosinophils (Rs = 0.60, P<.001), the EDN (Rs = 0.59, P<.001) and MBP (Rs = 0.73, P<.01) levels, and correlated inversely with FEV1 % pred. (Rs = -0.71, P<.01). Unexpectedly, the IL-5 levels did not correlate significantly with any of sputum eosinophil indices or FEV1 % pred. CONCLUSION: Good correlation of eotaxin with sputum eosinophil indices or pulmonary function and no correlation of IL-5 with them suggest that eotaxin may play a more important role in the specific recruitment and degranulation of airway eosinophils, although both IL-5 and eotaxin are involved in local eosinophilic inflammation.