Mapping Therapeutic Regulatory T Cell Fate with MRI: Current Strategies and Translational Outlook.

Adoptive cell therapies, and more specifically, regulatory T cell (Treg) therapies, have shown significant therapeutic promise across multiple immune-mediated diseases including graft-versus-host disease (GvHD), solid organ transplant (SOT) rejection, and autoimmune diseases. One key challenge is the lack of insight into the biodistribution and fate of adoptively transferred T cells and Tregs in living organisms. These uncertainties delay progress on establishing optimal dosage(s), infusion timing and route, as well as investigations into off-target effects. Magnetic resonance imaging (MRI) cell tracking is particularly beneficial in this setting because it enables real-time, deep-tissue coverage without ionizing radiation. In this review, we compare existing MRI T cell tracking strategies using iron oxide particles and fluorinated agents. We describe preclinical and clinical applications of MRI for cell therapy tracking and provide a perspective on the potential impact on the field.