Using a combination of pulse-chase, staining, visualization, and T cell stimulation techniques, Ho et al. showed that internalization of extracellular antigen in cDC1s and cDC2s via two different receptor pathways (FcγR and a lectin receptor (MLG1/CLEC10A)) transited the antigen to a novel, perinuclear compartment for extended storage prior to presentation. This compartment lacked the canonical endopeptidase Cathepsin S activity found in lysosomal vacuoles, but contained the carboxypeptidase Cathepsin X. Presentation of antigen from this compartment persisted for days, which may be important during DC migration and antigen transfer to LN-resident DCs.
Contributed by Ed Fritsch
ABSTRACT: An exclusive feature of dendritic cells (DCs) is their capacity to present exogenous antigens by MHC class I molecules, called cross-presentation. Here we show that protein antigen can be conserved in mature murine DCs for several days in a lysosome-like storage compartment, distinct from MHC class II and early endosomal compartments, as an internal source for the supply of MHC class I ligands. Using two different uptake routes via Fc_ receptors and C-type lectin receptors, we could show that antigens were routed towards the same endolysosomal compartments after 48 hours. The antigen-containing compartments lacked co-expression of molecules involved in MHC class I processing and presentation including TAP and proteasome subunits as shown by single cell imaging flow cytometry. Moreover, we observed the absence of cathepsin S but selective co-localization of active cathepsin X with protein antigen in the storage compartments. This indicates cathepsin S-independent antigen degradation and a novel but yet undefined role for cathepsin X in antigen processing and cross-presentation by DCs. In summary, our data suggest that these antigen-containing compartments in DCs can conserve protein antigens from different uptake routes and contribute to long-lasting antigen cross-presentation.
Author Info: (1) Department of Immunology, Leiden University Medical Center, Postbus, 9600, 2300 RC, Leiden, The Netherlands. (2) Department of Immunology, Leiden University Medical Center, Pos
Author Info: (1) Department of Immunology, Leiden University Medical Center, Postbus, 9600, 2300 RC, Leiden, The Netherlands. (2) Department of Immunology, Leiden University Medical Center, Postbus, 9600, 2300 RC, Leiden, The Netherlands. (3) Department of Molecular Cell Biology and Immunology, VU university Medical Center, Postbus, 7057, 1007 MB, Amsterdam, The Netherlands. (4) Department of Molecular Cell Biology, Section Electron Microscopy, Leiden University Medical Center, Postbus, 9600, 2300 RC, Leiden, The Netherlands. (5) Department of Molecular Cell Biology, Section Electron Microscopy, Leiden University Medical Center, Postbus, 9600, 2300 RC, Leiden, The Netherlands. (6) Department of Tumor Immunology, Radboud Institute for Molecular Life Sciences, Radboud University Medical Center, Nijmegen, The Netherlands. (7) Department of Molecular Cell Biology and Immunology, VU university Medical Center, Postbus, 7057, 1007 MB, Amsterdam, The Netherlands. (8) Department of Immunology, Leiden University Medical Center, Postbus, 9600, 2300 RC, Leiden, The Netherlands.
