Alveolar macrophage phagocytosis of E. coli, coloured scanning electron micrograph (SEM). A red blood cell is near the macrophage filopodia (mammal lung pleural cavity). Note the macrophage has short filopodia that extend from the cell and aid in finding bacteria for phagocytosis. A tissue macrophage is a large, mature phagocyte that can ingest and destroy invading microbes, foreign particles, cancerous or diseased cells and cellular debris. Alveolar (lung pleural cavity) macrophages are part of the reticuloendothelial system. Magnification: x875 when shortest axis printed at 25 millimetres.