Figure 3.

PD-1 immunoPET/CT in tumor-bearing mice. (A) Treatment scheme for analyzed mice. Subcutaneous flank tumors were locally irradiated with 2×12 Gy when their volume reached 500 mm³, and the mice were treated with α-PD-L1/CTLA-4 as indicated. Five days later, mice received 1.5 µg ⁶⁴Cu-NOTA-PD-1 mAb (ca. 1.44 ± 0.32 MBq) and PET images were acquired 24 h p.i. Antigen-blocked mice were pretreated with unlabeled α-PD-1 (1 mg) 24 h before tracer injection. Scanning duration was ca. 45-55 min. (B) Representative FACS histogram overlays acquired 5 days post treatment start comparing PD-1 expression from lymph node and tumor-infiltrating T cells. (C) Representative coronal (C), transverse (T), and sagittal (S) PD-1 immunoPET/CT sections. White ticks in the C-sections indicate the positions of the T- and S-sections. (D) Uptake of ⁶⁴Cu-NOTA-PD-1 mAb as measured by microPET in various organs. n = 7 (WT) and 5 (antigen-blocked). Abbreviations: RT - radiotherapy, Sp - spleen, Tu - tumor, td iLN - tumor-draining inguinal lymph node.