chapter  18
Macrophages and Macrophage Diversity in Asthma
Pages 26

Alveolar macrophages (AMs) are the most prevalent cells in the airways of normal subjects and symptomatic or asymptomatic asthmatics. Although eosinophils are clearly most characteristic of asthma and correlate with its severity (1,2), the critical processes that control eosinophil influx are not known. It has been proposed that AMs subserve this regulatory role in asthma (3). This chapter reviews the evidence suggesting that macrophages, particularly alveolar macrophages, can and do participate in the production and maintenance of airway inflammation in asthma and allergic diseases. An extensive literature has developed over the last decade that collectively supports the concept that macrophages are important regulators of airway inflammation (3,4). Thus, macrophages may play a pivotal role in asthma and allergic disease by directing the recruitment and activation of inflammatory cells, by generating factors that directly promote bronchospasm and tissue injury, and by producing and releasing cytokines that modulate and control the airway inflammatory response. Our hypothetical concept of these relationships is diagrammed in Fig. I. Existing data suggest that AMs are heterogeneous, and that subpopulations of AMs have distinct

IL-2. IFN-y , TNF-a, GMCSF

IL-3, IL-5, IL-4 IL-10, GMCSF

Daftary et al.