Ligand-conjugated quantum dots monitor antigen uptake and processing by dendritic cells.

The dendritic cell (DC) specific pathogen-uptake receptor (DC-SIGN) internalizes antigens for degradation and presentation onto MHC molecules. At the cell membrane, DC-SIGN forms nanoclusters that facilitate virus capture. However, internalized viruses, such as HIV-1, escape degradation. Here, we exploit ligand-conjugated, virus-sized, highly photostable quantum dots (QDs) to monitor in living cells antigen binding, entry, and trafficking. The antigen-coated QDs specific uptake and persistence in live DCs open the possibility for tracking antigen-presenting cells in vivo.