Studies of DC phagosomes and cross-presentation using K/O and mutant mouse strains

Our laboratory obtained data from studies of DC phagosomes and cross-presentation using K/O and mutant mouse strains. Cross presentation is the process by which Dendritic cells (DC) phagocytose pathogens or dying cell fragments, and present proteolytic peptides derived from these antigens in association with MHC class I molecules. The reasons why DCs are the only antigen presenting cells that efficiently cross present antigens are not well understood.

We have demonstrated that the NADPH oxidase NOX2 is recruited to DC early phagosomes mediating a sustained production of low levels of reactive oxygen species and causing a maintained alkalynization of the phagosomal lumen. DCs lacking NOX2 show increased antigen degradation due to an enhanced phagosome acidification. As a result, the efficiency of in vitro and in vivo antigen cross presentation is significantly reduced in NOX2-deficient DCs. We also show that DCs derived from ashen mice, which are defective for the small GTPase Rab27a, fail to cross present antigens efficiently, due to increased phagosome acidification and antigen degradation. This defect in Rab27a-deficient DCs results from the impaired recruitment to phagosomes of the NOX2 membrane components. Therefore phagosomal alkalinization by NOX2 is controlled by Rab27a, and is required for efficient cross presentation in DCs.

In vivo, different subsets of DCs are considered with different competences to cross present antigens. The reasons why CD8+ DCs subset is the only one that efficiently carry out this phenomenon are not well understood. We have found that only CD8+ DCs display a NOX2 activity selectively localized to in phagosomes, causing alkalynization and preventing Ag degradation. In contrast, CD8- DCs, which exhibit higher total NOX2 activity than their counterparts but lack phagosomal ROS production, acidify their phagosomes causing more important antigen degradation which is unfavourable for cross presentation. Rac proteins are key components of NOX2 activation. Interestingly, we found that differential expression of Rac1 and Rac2 in the two DCs subsets, are responsible for the differential localization of ROS production in both cell types.

• molecule type
• peptide,
• NADPH oxidase 2,
• Major histocompatibility complex class I,
• Rab27a

• cell type
• dendritic cell

• organism type
• ashen mouse

• cell component type
• phagosome

• experimental design type
• in vivo design experiment

created over 16 years ago (2 March 2009)    last modified over 13 years ago (28 September 2011)   [ RDF ]   [ RelFinder ]