Exhaled NO level and number of eosinophils in nasal lavage as markers of pollen-induced upper and lower airway inflammation in children sensitive to grass pollen.

Abstract

This study investigates the upper and lower inflammatory response induced by natural exposure to grass pollen in atopic and non-atopic children. After children's atopic profile had been assessed, their nasal lavage fluid (NAL) and exhaled air was sampled once before and once during the pollen season. Level of nitric oxide (NO) was determined in exhaled air, and the following mediators were measured in NAL: ECP, IL-6, IL-8, albumin, uric acid, and urea. The number of eosinophils in NAL was determined after Giemsa staining. During the experiment ozone and pollen levels were measured continuously. During the pollen season the level of grass pollen was 95 pollen grains per cubic metre. At baseline, 8.0% and 5.4% of total cells in NAL of children sensitive to, respectively, house dust mite (HDM) and pollen + HDM were eosinophils, whereas virtually no eosinophils were observed in NAL of non-atopic children. In contrast to the non-atopic and HDM groups, in children sensitive only to grass pollen, grass pollen induced a threefold increase in the percentage of NAL eosinophils and a 2.5-fold increase in the NAL level of ECP ( P<0.05). In all groups, the NAL levels of albumin, uric acid, urea, IL-6 and IL-8 were not significantly increased by pollen exposure. At baseline, children sensitive to HDM showed significantly higher exhaled nitric oxide (eNO) values than non-atopic subjects and children sensitive only to pollen (79 to 141% increase). During pollen exposure eNO of children sensitive only to pollen increased from 35.8 to 64.5 ppb ( P<0.05), whereas no increase in eNO was observed in the other children. Pollen-sensitive children show a season-dependent upper and lower airway inflammatory response, resembling the continuous inflammation in HDM-sensitive children.