Unraveling mechanisms behind cross presentation during phagocytic signaling
Date
2014-01-29
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Abstract
MHC class I antigens come from endogenous syntheses, while class II antigens are obtained extracellularly via endocytosis. Cross presentation is the link between the two by which external antigens are targeted to the MHC class I pathway. It is generally accepted that particulate antigens are more efficient in this pathway switch. However the reason behind this phenomenon is unknown. We report that dendritic cell engagement of a phagocytic target limits endocytic maturation and inhibits the associated proteolytic activities. In this scenario, early endosomes show reduced progression towards late endosomes/lysosomes and remain spatially close to the cell membrane. In phagocytosis, the microtubular (MT) system, including tubulin filaments and microtubule organization centers (MTOCs), are heavily skewed toward the engulfed particulate matter; the remaining cytoplasmic volumes are relatively devoid of MT presence. This is accompanied by a reduced centripetal movement inward and the maturation of endosomes. The antigen processing in these arrested endosomes is under the control of Nicotinamide adenine dinucleotide phosphate-oxidase (NAPDH)-associated ROS. We also show that cathepsin S is responsible for the generation of the class I epitope for cross presentation. The rerouted antigen presentation is at least 40 fold more efficient than the same amount of antigen delivered through the phagocytic pathway, and is operational in vivo. Our results suggest that in DCs in addition to solid structure uptake, phagocytosis directs a coordinated set of enzymatic and cytoskeletal events that regulate endosomal trafficking and maturation. As a consequence, external soluble antigens are driven away from their conventional MHC class II processing, into the class I cross presentation pathway.
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Immunology
Citation
Hari, A. (2014). Unraveling mechanisms behind cross presentation during phagocytic signaling (Doctoral thesis, University of Calgary, Calgary, Canada). Retrieved from https://prism.ucalgary.ca. doi:10.11575/PRISM/28591