Figure 3.

In vivo detection of NIS-GFP⁺ Tregs in human skin grafts

(A) Experimental scheme, including imaging conditions (radiotracer and time between its administration and SPECT imaging). (B) Representative example of a human skin transplant atop the spine of a BRG mouse on the day of adoptive immune cell transfer. All animals in this experiment (n = 3 in each group) received the same human skin and Tregs from the same donor; all mice were depleted of Gr-1⁺ innate immune cells. (C and D) Sagittal sections of SPECT/CT images from representative animals that received 5 × 10⁶ CD25-depleted PBMCs but (C) no NIS-GFP⁺ Tregs or (D) 5 × 10⁶ NIS-GFP⁺ Tregs 30 days prior to imaging. Overlays of SPECT images in hue (and on the same scale) with co-registered CT images (grayscale) are shown. Purple frames indicate magnified areas in different planes, with the human skin graft circumscribed by dark yellow dotted lines; thin red crosshair lines indicate how the indicated sections connect to one another. Endogenous (murine) mNIS expressing organs are visible in both groups and include thyroid/salivary glands (T/S), stomach (S), and small intestine (Int),³⁷ whereas bladder (Bl) signals are caused by radiotracer excretion. Images demonstrate (C) that the transplant area atop the spine remained free of any SPECT signals when no NIS-GFP⁺ Tregs were administered and (D) that administered NIS-GFP⁺ Tregs were detected by SPECT imaging at the skin graft as they trafficked to this site over time.