Fig. 5

IL-2c immunoPET/CT in tumor-bearing mice and analyses of IL-2c target binding in blood, spleen, and tumor. a Flow cytometry analysis of CD122+ tumor-resident leukocytes 5 days after hRT in mice with or without depletion of CD122+ cells. b, c Mice bearing an s.c. B16 tumor were locally irradiated with 2 × 12 Gy when their volume reached 400 mm³. Five days later, they received 5 μg ⁶⁴Cu-NOTA-IL-2c (~ 7.5 MBq) and PET images were acquired 24 h later. b Representative coronal and transverse IL-2c immunoPET/CT sections are shown. White ticks in the C-sections indicate the positions of the T-sections. c Ex vivo biodistribution of radiotracer uptake 24 h p.i. in irradiated tumors of CD122-depleted and non-depleted mice. d Binding of IL-2c-CF680 with CD122+ NK and CD8+ T cells in vivo. IL-2c-CF680 was injected i.v. 24 h before. In the upper right quadrant of the NK1.1/CD122 plots, the proportions of CD122+ cells within NK1.1+ CD3– cells (i.e., NK cells) and CD8+ CD3+ cells (i.e., CD8+ T cells), respectively, are given. The proportion of CD122+ cells bound by the i.v. injected CF680-labeled IL-2c is given in the CF680/CD122 plots. e Proportion of IL-2-secreting CD45+ cells in spleen, lymph nodes, and tumor. f Demonstration that pretreatment with IL-2 strongly reduces the binding of IL-2c to CD122+ cells. Splenocytes were collected from naïve mice. In the blocking setting, CD8+ splenocytes were incubated with IL-2 or (for control) with interferon-β at 37 °C for 30 min. Thereafter, the binding of IL-2c to CD122-positive T cells was determined by flow cytometry