Pe labeled goat anti human igg fc antibody

For Figure 4, flow cytometry analyses were performed to detect the binding abilities of antibodies to Spike protein in HEK293T cells freshly expressing of SARS-CoV-2, SARS-CoV and MERS-CoV. Briefly, 10 thousand cells in 100 μl were incubated with indicated antibodies for 30 min at room temperature, after twice washes then PE-labeled goat anti-human IgG-Fc antibody was added (1:5,000; Abcam) for 30 min, followed by flow cytometry analyses.
Flow cytometry analysis was also performed to detect the ACE2 competition (Figures 3A and S3). Then 10 thousand S expressing cells in 100 μl were first incubated with free ACE2 at 50nM for 30 min at room temperature, then different concentrations of antibodies were added for 30 min, followed by incubation with PE-labeled goat anti-human IgG-Fc antibody (1:5000; Abcam) for 30 min and analyzed by flow cytometry.
For Figure S4, to test S protein expression on cell membrane, recombinant ACE2-Cter-6xHis labeled by rabbit anti-His-PE antibody in 1.2:1 (n:n) ratio was added to 10 thousand cells expressing S protein. Detection was done similarly as above.