Fig. 2 Detection of SARS-CoV-2 RBD binding to human ACE2 receptor. a Flow cytometry analysis of receptor expression in stable cell lines. (left panel) 293T cells alone expressed neither human ACE2 (hACE2) receptor (orange line) nor hDPP4 receptor (cyan line); (middle panel) hACE2-expressing 293T (hACE2/293T) cells expressed only hACE2 (orange line), but not hDPP4 (cyan line); (right panel) hDPP4-expressing 293T (hDPP4/293T) cells expressed only hDPP4 (cyan line), but not hACE2 (orange line).