1x10^6 HEK-293T cells transfected with human PD-L1  were surface stained with Anti-PD-L1(block binding), AlpSdAbs® VHH(500-307-001) and Anti-VHH, AlpHcAbs® Rabbit antibody(iFluor594) (red), or Rabbit IgG Isotype Control(iFluor594)(blue).