(                                                                                                                                          Equation   5                Percentage   of   receptor   binding   (flow   cytometry)                Based   on   geometric   mean   fluorescence%   of   specific   binding=((sample   value-non-specific   binding)/(total   binding-non-specific   binding))×100Total   binding=biotinylated   PD-1   or   CD 80   only   (no   antibody)Non-specific   binding=no   ligand   streptavidin   AlexaFluor   647   only)