In vivo cytometry of antigen-specific t cells using 19F MRI.

Noninvasive methods to image the trafficking of phenotypically defined immune cells are paramount as we attempt to understand adaptive immunity. A (19)F MRI-based methodology for tracking and quantifying cells of a defined phenotype is presented. These methods were applied to a murine inflammation model using antigen-specific T cells. The T cells that were intracellularly labeled ex vivo with a perfluoropolyether (PFPE) nanoemulsion and cells were transferred to a host receiving a localized inoculation of antigen. Longitudinal (19)F MRI over 21 days revealed a dynamic accumulation and clearance of T cells in the lymph node (LN) draining the antigen. The apparent T-cell numbers were calculated in the LN from the time-lapse (19)F MRI data. The effect of in vivo T-cell division on the (19)F MRI cell quantification accuracy was investigated using fluorescence assays. Overall, in vivo cytometry using PFPE labeling and (19)F MRI is broadly applicable to studies of whole-body cell biodistribution.