CD28 and hepatocellular carcinoma: Kaplan–Meier survival curves showed that patients with high CD28+PD1+ Tc-cell levels exhibited notably poorer prognosis than those with low levels (Figure 3A); the predictive performance of CD28+PD-1+ T-cell levels was evaluated using receiver operating characteristic curves (Figure 3B).Cox regression analysis indicated that the presence of CD28+PD-1+ Tc cells was an independent prognostic risk factor for patients with HCC (Figures 4A, B).