NADPH oxidase controls phagosomal pH and antigen cross-presentation in human dendritic cells Running title: Phagosomal pH regulation in human DC

The phagocyte NADPH oxidase (NOX2) is critical for the bactericidal activity of phagocytic cells and plays a major role in innate immunity. We showed recently that NOX2 activity in mouse dendritic cells (DC) prevents acidification of phagosomes, promoting antigen crosspresentation. In order to investigate the role of NOX2 in the regulation of the phagosomal pH in human DC, we analyzed the production of reactive oxygen species (ROS) and the phagosomal/endosomal pH in monocyte-derived DC and macrophages (MØ) from healthy donors or chronic granulomatous disease (CGD) patients. As expected, we found that human MØ acidify their phagosomes more efficiently than human DC. Accordingly, the expression of the vacuolar proton ATPase (V-H+-ATPase) was higher in MØ than in DC. Phagosomal ROS production, however, was also higher in MØ than in DC, due to higher levels of gp91phox expression and recruitment to phagosomes. In contrast, in the absence of active NOX2, the phagosomal and endosomal pH decreased. Both in the presence of a NOX2 inhibitor and in CGD patients-derived DC, the cross-presentation of two model tumor antigens was impaired. We conclude that NOX2 activity participates in the regulation of the phagosomal and endosomal pH in human DC, and is required for efficient antigen cross-presentation. For personal use only. on August 31, 2017. by guest www.bloodjournal.org From