The Effect of Allergen Inhalation on Sputum Myeloid and Plasmacytoid Dendritic Cells in Mild Atopic Asthmatics

Overview

Summary: A picture is emerging of dendritic cells migrating through the blood to the airways following allergen inhalation in atopic asthmatics. Although the Koh and McCarthy articles present novel findings, both do not provide a comprehensive view of sputum DCs following allergen challenge. Therefore, the proposed study will examine the kinetics of mDCs and pDCs in the induced sputum of atopic asthmatics following inhalation of allergen. Hypothesis: Following allergen challenge, sputum myeloid and plasmacytoid DCs will migrate into the airway lumen in atopic asthmatics during the timeframe of the late asthmatic response. Objective: The objective of this study is to examine the kinetics of dendritic cells in induced sputum following allergen challenge in atopic asthmatic subjects.

Subjects will be put through two study periods. Each study period will consist of four visits and will be separated by 2-4 weeks. On the first visit, subjects will undergo screening procedures, including complete history and physical examination. In addition, methacholine inhalation challenge and skin-prick testing will be preformed to assess airway hyper-responsiveness and determine atopic status respectively. Lastly, sputum will be induced before challenge (0 hrs) and peripheral blood will be collected. On the second visit, subjects will inhale diluent or allergen and sputum will be collected 7 hours following inhalation challenge. Next, on the third visit, subjects will return 24 hours following inhalation challenge and sputum will be induced. On the final visit, subjects will return 72 hours following inhalation challenge and sputum will be collected, along with peripheral blood. Before the next study period begins, there will be a washout period of 2-4 weeks. On the first visit of the second study period, a methacholine challenge will be performed to ensure the return of PC20 to within one doubling dose of baseline values. Also, sputum will be induced before challenge (0hrs) and peripheral blood will be collected. On the second visit, subjects will inhale diluent or allergen and sputum will be collected 7hrs following inhalation challenge. Next, on the third visit, subjects will return 24 hours following inhalation challenge and sputum will be induced. On the final visit, subjects will return 72 hours following inhalation challenge and sputum will be collected, along with peripheral blood.