Labelling dendritic cells with SPIO has implications for their subsequent in vivo migration as assessed with cellular MRI.

An optimized non-invasive imaging modality capable of tracking and quantifying in vivo DC migration in patients would provide clinicians with valuable information regarding therapeutic DC-based vaccine outcomes. Superparamagnetic iron oxide (SPIO) nanoparticles were used to label bone marrow-derived DC. In vivo DC migration was tracked and quantified non-invasively using cellular magnetic resonance imaging (MRI) in a mouse model. Labelling DC with SPIO reflects the kinetics of DC migration in vivo but appears to reduce overall DC migration, in part due to nanoparticle size. Magnetic separation of SPIO-labelled (SPIO(+)) DC from unlabelled (SPIO(-)) DC prior to injection improves SPIO(+) DC migration to the lymph node. Corresponding MR image data better correlate with the presence of DC in vivo; an improved immunological response is also seen. Cellular MRI is a viable, non-invasive imaging tool that can routinely track DC migration in vivo. Consideration should be given to optimizing MRI contrast agent-labelling of clinical-grade DC in order to accurately correlate DC fate to immunological outcomes in patients.