Fig 1: Characterization of constructed cells. (a) The expression level of PD-L1, PD-1, and B2M as measured by flow cytometry in wild-type MDA-MB-231 and double-KO MDA-MB-231 (Red: blank; Blue: Isotype antibody; Yellow: anti-PD-L1, anti-PD-1, or anti-B2M antibody). (b) Fluorescent image of PD-L1, PD-1, and B2M in wild-type and double-KO MDA-MB-231 cells (scale bar is 10 µm). (c) The expression level of PD-L1 and havPD-1 as measured by flow cytometry and fluorescence microcopy in double-KO/havPD-1 knock-in MDA-MB-231 cells (Red: blank; Blue: Isotype antibody; Yellow: anti-PD-L1 or anti-PD-1 antibody; scale bare is 10 µm). (d) B2M, PD-L1, and havPD-1 proteins were extracted and identified from wild-type and constructed MDA-MB-231 cells. (e) Fluorescent image of constructed double-KO/havPD-1 knock-in/CD81-GFP fusion MDA-MB-231 cells (scale bar is 10 µm) and the expression level of CD81-GFP as measured by flow cytometry (Red: blank; Blue: MDA-MB-231 cells w/o CD81-GFP fusion protein; Yellow: MDA-MB-231 cells expressing CD81-GFP fusion protein). (f) Fluorescent image of constructed MDA-MB-231-tdTomato cells (scale bar is 10 µm).