Cutting Edge: Limited Specialization of Dendritic Cell Subsets for MHC Class II-Associated Presentation of Viral Particles

Dendritic cells (DCs) are the most important APC. It was recently reported that there is a dichotomy for Ag presentation by DC subsets; exogenous Ags reach the MHC class I pathway, but not the MHC class II pathway, in CD8+ DCs, whereas CD8− DCs only process Ags for the MHC class II pathway. In this study, we used virus-like particles (VLPs) to show that CD8+ and CD8− DCs efficiently capture and process VLPs for presentation in association with MHC class II in vivo. In contrast, CD8+ DCs, but not CD8− DCs, cross presented VLP-derived peptides. This pattern was changed in an FcγR-dependent fashion in the presence of VLP-specific Abs, because under those conditions both DC subsets failed to efficiently cross present. Thus, the presentation of viral particles to CD4+ T cells is not restricted to distinct DC subsets, whereas the presentation of viral particles to CD8+ T cells is limited to CD8+ DCs.