and its isotype rat IgG2b (clone LTF-2) and antimouse PD-1 (CD279,
clone J43) and its isotype polyclonal Armenian hamster IgG were obtained
from Bio X Cell (West Lebanon, NH). Bifunctional chelators 2-(4-isothiocyanatobenzyl)-1,4,7,10-tetraazacyclododecane
tetraacetic acid (p-SCN-Bn-DOTA) and 2-(4-isothiocyanatobenzyl)-1,4,7-triazacyclononane-1,4,7-triacetic
acid (p-SCN-Bn-NOTA) were obtained from Macrocyclics
(Plano, TX). PD-10 columns were purchased from GE Healthcare (Pittsburgh,
PA). [64Cu]CuCl2 (specific activity, 21.42 Ci/μmol)
was obtained from the Cyclotron Radiochemistry Facility at The University
of Texas MD Anderson Cancer Center (Houston, TX).