Phagocytosis: A Fundamental Process in Immunity

Figure 7

Phagosome maturation. (A) The nascent phagosome gets transformed into a microbicidal vacuole, the phagolysosome, by sequential interactions with vesicles from the endocytic pathway. Four stages of maturation have been described: early (a), intermediate (b), late (c), and phagolysosome (d). In this process, the phagosome becomes increasingly acidic by the action of a proton-pumping V-ATPase and gets various degradative enzymes. The composition of the membrane also changes to include molecules that control membrane fusion, such as the GTPases Rab. See text for details. EEA1, early endosome antigen 1; ESCRT, endosomal-sorting complex required for transport; HOPS, homotypic protein sorting; ILV, intraluminal vesicle; LAMP, lysosomal-associated membrane protein; NADPH, nicotinamide adenine dinucleotide phosphate oxidase; RILP, Rab-interacting lysosomal protein; vPS34, vacuolar protein-sorting 34.