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Perfluorocarbon (PFC) particles are currently on the rise as cell labeling agents for 19F-MRI tracking of dendritic cell (DC)-based vaccines. In this work, we design theranostic PFC particles for single-step loading of DCs with both antigenic protein and with a liquid PFC for 19F-MRI detection of the antigen-loaded cells. Upon addition to DCs in vitro, the antigen-loaded PFC particles are efficiently internalized, resulting in intracellular presence of up to 40 pmol 19F atoms per cell. At the same time, the DCs become loaded with antigenic proteins, that can be efficiently processed, without important effects on cell viability or altering the DC's phenotype and the cell's capacity to respond to danger signals. In addition, antigen-loaded PFC particle containing DCs are capable of inducing extensive proliferation of antigen-specific CD8+ T cells in vitro. Importantly, the antigen-coated PFC particles allow in vitro19F-MRI-based detection of the antigen-containing DCs with detection limits as low as 103 cells μl−1. The dual-modality characteristics of the designed particles could assure that only those DCs that have taken up the antigen, and hence are responsible for an immune response, are traceable via 19F-MRI. Taken together, these novel dual-modality particles represent an interesting strategy in the development of a traceable DC vaccine.