Macrophage-Mediated Inflammation and Disease: A Focus on the Lung

Figure 1

Alveolar macrophage-mediated disease in the lung. AMs are the dominant cell type in the uninfected airway. Following virus infection (1), AMs are restrained from overreacting and inducing bystander damage to tissues by the CD200R on their surface (2) which induces a negative signalling cascade. (3) Pandemic influenza strains induce the upregulation of TRAIL on the AM surface and of its receptor DR5 on the alveolar epithelial cells, which leads to increased apoptosis in the epithelium and consequent morbidity. Both the presence of TRAIL and the absence of CD200R can induce epithelial damage and spread of virus out of the alveolus (4). Bacterial infection (5) induces AM to produce inflammatory cytokines (6), leading to activation of bystander cells and tissue damage. AMs are also triggered to produce growth factors (7) which leads to epithelial hyperplasia, deposition of ECM and fibrosis.