Fig. 1. Construction and identification of the recombinant plasmids.
a Local secondary structure of programmed death 1 (PD-1) mRNA at the regions targeted by the three PD-1 small interfering RNAs (siRNAs) synthesized in the study. b Effect of three plasmids containing different sequences of PD-1-specific short hairpin RNA (shRNA) on EL4 cells for 24 h. c Quantification of PD-1 protein levels in (b) from three independent experiments. d Effect of three plasmids containing different sequences of PD-1-specific shRNA on EL4 cells for 48 h. e Quantification of PD-1 protein levels in (d) from three independent experiments. Media indicate untreated cells. The data are presented as the mean ± standard deviation (SD). **P < 0.01 vs the media group