IGF-1R blockade up-regulates IFN-γR2 surface expression. (A) Flow cytometric analysis of IFN-γR2 surface expression in ST4-E (i), ST4-WT (ii), and ST4-DN (iii) cells maintained in complete medium. Expression of IFN-γR2 (gray histograms) and the background of mouse IgG1 negative control (open histograms) are shown for 1 representative experiment of 3 independently performed. (B) IGF-1-induced IFN-γR2 internalization was evaluated by flow cytometry. ST4-E (i-ii), ST4-WT (iii-iv), and ST4-DN (v-vi) cells, cultured for 24 hours in serum-free medium to eliminate the IGF-1 present in serum, were incubated with or without IGF-1 (100 ng/mL) and with unconjugated anti–IFN-γR2 mAb or with an isotype-matched mAb at 37°C. After 1 hour, cell surface–associated mAb was removed, and cells were permeabilized and stained with PE-conjugated rabbit anti–mouse Ig. Mean specific internalized fluorescence was calculated by subtracting the mean internalized fluorescence obtained with isotype-matched control Ig from that detected with the anti–IFN-γR2 mAb.