Association between airway hyperreactivity and bronchial macrophage dysfunction in individuals with mild asthma

Little is known about the functional capabilities of bronchial macrophages (BMs) and their relationship to airway disease such as asthma. We hypothesi ze that BMs from asthmatics may be modulated in their function compared wit h similar cells from healthy individuals. BMs obtained by induced sputum fr om mild asthmatics (n = 20) and healthy individuals (n = 20) were analyzed using flow cytometry for CD16, CD64, CD11b, CD14, and human leukocyte antig en-DR expression, phagocytosis of IgG opsonized yeast, and oxidant producti on. Asthma status was assessed by lung function [percent predicted forced v ital capacity and forced expiratory volume in 1 s (FEV1)], percent sputum e osinophils, and nonspecific airway responsiveness [provocative concentratio n that produces a 20% fall in FEV1 (PC20,FEV1)]. Asthmatics with >5% airway eosinophils (AEo+) had decreased BM CD64 expression and phagocytosis compa red with asthmatics with <5% eosinophils (AEo-). Among asthmatics, a signif icant correlation was found between CD64 expression and BM phagocytosis (R = 0.7, P < 0.009). Phagocytosis was also correlated with PC20,FEV1 (R = 0.6 , P < 0.007), lung function (%predicted FEV1, R = 0.7, P < 0.002) and perce nt eosinophils (R = -0.6, P < 0.01). In conclusion, BM from asthmatics are functionally modulated, possibly by Th2 cytokines involved in asthma pathol ogy.