Interleukin-8 secretion in patients with allergic rhinitis after an allergen challenge: interleukin-8 is not the main chemotactic factor present in nasal lavages.

BACKGROUND: Interleukin-8 (IL-8) is a chemotactic cytokine for neutrophils and primed eosinophils. In allergic rhinitis, allergen exposure triggers leucocyte recruitment.

OBJECTIVE: We evaluated in this study IL-8 secretion and the neutrophil chemotactic activity in nasal lavages collected after a nasal allergen challenge. Moreover, the participation of IL-8 in the neutrophil chemotactic activity was quantified.

METHODS: Four healthy subjects and 19 patients with allergic rhinitis were exposed to a nasal allergen challenge. As a control, saline challenge was performed in four patients with allergic rhinitis. Concentration of IL-8 was measured by ELISA in nasal lavages collected before and after challenge. Neutrophil chemotactic assay was developed using a 48-well chemotaxis microassembly.

RESULTS: After allergen challenge, the healthy subjects, the four patients receiving saline and one patient exposed to allergen did not respond; seven patients presented a single early reaction and 11 patients a dual response. For healthy subjects and the four patients exposed to saline, the level of IL-8 did not increase after challenge in comparison with that at baseline. After allergen challenge, two peaks of IL-8 release were observed for patients with allergic rhinitis during the early (30 min to 1 h 30 min) and the late periods (3 h 30 min to 9 h 30 min), however the difference was not significant for the early period. During the late period, a significant increase in IL-8 concentrations was detected for the patients developing a dual response, whereas the difference was not significant for those presenting only an early reaction. The neutrophil chemotactic activity of nasal lavages from patients with allergic rhinitis collected during the early and the late reactions (17 +/- 2.1 and 23.3 +/- 2.8 neutrophils per high power field (hpf), respectively) was significantly higher than the activity of lavage fluid collected at baseline (9.2 +/- 1.8 neutrophils per hpf). Nevertheless, the addition of a neutralizing anti-IL-8 antibody inhibited weakly the chemotactic activity of lavage fluid from rhinitic patients collected during the early or the late periods (18 and 11% of inhibition) (P = NS).

CONCLUSION: These data show that allergen challenge increased significantly the secretion of IL-8 for the patients with allergic rhinitis. However, neutralization of IL-8 in nasal lavages by a specific antibody revealed that the role of this chemokine in granulocyte infiltrate was limited, suggesting that IL-8 acts in connection with other chemotactic factors in this recruitment.