•− ), a precursor of H 2 O 2 and other powerful oxidants such as hydroxyl radical and peroxynitrite (in the presence of nitric oxide), collectively called ROS [3, 51, 52] . Each of the seven oxidase family members is characterized by a distinct catalytic subunit (i.e., Nox1-5 and Duox1-2), and has differing requirements for additional protein subunits [51, 52] . The prototypic member of the Nox family, Nox2 oxidase (or gp91 phox oxidase), is best known for its role in neutrophil and macrophage phagocytosis. Genetic defects in the enzyme are related to chronic granulomatous disease, a condition in which affected children suffer from recurrent severe fungal and bacterial infections due to defective phagocyte function [51] . Each Nox isoform forms heterodimers with a lower molecular weight p22 phox subunit and is predicted to be membrane-bound. Nox2 is normally quiescent and acutely activated by agonists such as PMA, LPG, and cytokines in a tightly regulated process in which cytosolic subunits (p47 phox , p67 phox , p40 phox , and Rac1 in the case of macrophages and dendritic cells, or Rac2 in neutrophil) associate with the Nox2-p22 phox heterodimer to initiate enzyme activity [51, 52] . Nox2 also has electrogenic features [53] and in APC cells is linked to the regulation of phagosome/lysosome pH and antigen processing [54, 55] . Usually, phagosome acidity is maintained by a vacuolar ATPase (V-ATPase) that transports protons from the cytosol into the phagosome lumen, therefore regulating the function of lysosome proteases in the fused phagolysosomes. Savina et al. [56] [57] [58] have shown that Nox2-derived superoxide in the phagosomal vesicle promptly consumes protons maintaining a higher pH ambient in dendritic cells during particle internalization, which favours antigen processing and presentation [56] [57] [58] . Opposite results were found in macrophages [56] [57] [58] . The selective role of Nox2 in different phagocytic cells remains to be defined. The jury is out on whether the results shown in macrophages (association of Nox2 to Rab27a; a member of Rab family of GTPases) are related to vesicle traffic molecule assembly and quality, or rather associated to degradation processes [59] .