Effect of antigen dose on the recruitment of inflammatory cells to the lung by segmental antigen challenge

Abstract

Bronchoscopic antigen challenge of atopic volunteers results in an immediate release of inflammatory mediators and, after a number of hours, the recruitment of inflammatory cells to the lung. The purpose of this work was to investigate the effect of antigen dose on the subsequent recruitment of inflammatory cells to the lung. Twenty-two volunteers without asthma, eight nonatopic control subjects, and 14 ragweed-allergic subjects underwent 25 local antigen-challenge procedures that consisted of a baseline lavage of a control segment, antigen challenge of another segment in the contralateral lung, and lavage of the challenged segment 24 hours later. A 25,000-fold range of antigen doses was used from 0.004 to 100 PNU/ml (0.02 to 500 ng/ml of ragweed antigen E [ Amb aI]). Challenge of nonatopic control subjects resulted in the recruitment of only a small number of inflammatory cells, less than a twofold increase in comparison with the cells of control lavage; this increase was primarily due to an increase in neutrophils. Challenge of atopic subjects, in contrast, resulted in approximately a threefold to ninefold increase in inflammatory cells with more cells recruited at larger doses of antigen. Only subjects challenged with a “high” dose of antigen (≥1 PNU/ml) recruited significant quantities of eosinophils to the lung. In these subjects, a twofold increase in macrophages, a fourfold increase in lymphocytes, a 90-fold increase in neutrophils, and an 800-fold increase in eosinophils were observed; the number of neutrophils and eosinophils recruited averaged between 30 and 60 million. There was a direct relationship between the log of the dose of antigen used for challenge and the log of the number of eosinophils recruited ( r = 0.75; p < 0.001). We conclude that the dose of antigen used for local antigen challenge is an important factor that affects both the number and type of inflammatory cells recruited to the lung.