Dendritic cells (DCs) are crucial in the initiation of immune responses and are primary targets in vaccination. Here, we describe fluorescent, carbon magnetic nanoparticles (CMNPs) within the 20-80 nm size range that are non-toxic and preferentially endocytosed by DCs. These attributes allow for DC tracing in vitro, ex vivo and in vivo, by both fluorescence and MRI. We show that CMNPs conjugated with an array of proteins are able to induce strong immune responses in mice. The addition of TLR ligand, CpG, to the CMNPs along with protein results in both T cell activation, but also a selective IFNgamma response. The magnetism afforded by the CMNPs facilitates a simple DC enrichment ex vivo by magnetic means from both secondary lymphoid organs, and sites of chronic inflammation. The magnetic and fluorescent properties of the CMNPs allow for visualization, recovery, and potentially the facilitation of directed DC migration. These particles may support more efficient immunization protocols or new diagnostic assays to characterize functionalities of DCs from patients.
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