Greek phagein – to eat. Mechanism of uptake from particles to small cells in a single eukaryotic cell. Usually, particles are taken up by the cells as membrane-bound aggregates, i.e. large aggregates in vesicles, vacuoles or lamellar bodies (cell compartments surrounded by membranes) through phagocytosis. In mammals, phagocytosis is performed mainly by special cells of the immune system, including the macrophages, monocytes (precursor cells of macrophages), and neutrophils (or neutrophilic granulocytes, belonging to the white blood cells). This uptake is an active, regulated process.