R-Phycoerythrin-labeled anti-PD-1 neutralizing recombinant murine/human chimeric antibody recognizing the PD-L1/PD-L2 binding region of human PD-1. This antibody does not cross-react with mouse PD-1, but does cross-react with monkey (M. fascicularis) PD-1. It has not been tested with other species.