A 68-year-old coal miner with a history of smoking and emphysema develops severe air-flow obstruction and expires. Autopsy reveals a "black lung," with coal-dust nodules scattered throughout the parenchyma and a central area of dense fibrosis. The coal dust entrapped within this miner's lung was sequestered primarily by which of the following cells?
Endothelial cells Fibroblasts Lymphocytes Macrophages