Phagocytosis refers to the process in which cells consume large particles (>0.5 micrometers) and vesicle-bound membrane vesicles known as phagosomes. These vesicles are then directed to the lysosomes where they will be subjected to enzymatic degrading. Optonization of bacteria can greatly enhance phagocytosis. Although phagocytosis may occur without the attachment of an IgG or complement fragment (C3), it can be greatly enhanced by attaching a specific IgG.