KLF4 and infection: To facilitate reprogramming by increasing the infection efficiency of PBMCs, cells were infected with lentiviruses containing octamer-binding transcription factor 4 (OCT4), Kruppel-like factor 4 (KLF4), SRY-box transcription factor 2 (SOX2), and MYC proto-oncogene (c-MYC) using a reprogramming Kit (CytoTuneTM-iPS 2.0 Sendai Kit, A16517, Thermo Fisher Scientific, Waltham, MA, USA).