The vesicular transport process that occurs primarily in some white blood cells and macrophages is phagocytosis. This is a type of endocytosis where cells engulf and internalize large particles, such as bacteria or dead cells, into a specialized membrane-bound compartment called a phagosome. The phagosome then fuses with lysosomes, which contain digestive enzymes, to form a phagolysosome. Within the phagolysosome, the engulfed particle is broken down and digested by the lysosomal enzymes. Phagocytosis is an important mechanism for immune cells to eliminate pathogens and debris from the body.