Phagocytosis, defined as the cellular uptake of particulates (>0.5 m) within a plasma-membrane envelope, is closely related to and partly overlaps the endocytosis of soluble ligands by fluid-phase macropinocytic and receptor pathways. The uptake of exogenous particles (heterophagy) has features in common with autophagy, an endogenous process of sequestration and lysosomal disposal of damaged intracellular organelles. There is a spectrum of uptake mechanisms depending on the particle size, multiplicity of receptor-ligand interact...