Methods: HepG2 or HepG2.2.15 were co-cultured with Jurkat cells, with blocking test by adding anti-PD-1 antibody. The PD-1 expression was detected by flow cytometry (FCM); Cytokines in culture supernatant in blocking groups and controls were measured by enzyme-labeled immunosorbent assay (ELISA); Cytotoxic test of T cells were measured by methyl thiazolyl tetrazolium (MTT).