PDCD1 and neoplasm: Meanwhile, the PD-1 and TIM-3 expression and percentage of PD-1+TIM-3+ subsets were lower in CD8+ IL-21R-TCR-T than conventional TCR-T during repetitive coculture with HepG2 (Fig. 6e and Supplementary Fig. 6a, b), indicating that engineered IL-21R expression alleviated the exhaustion of TCR-T during repetitive tumor antigen stimulation.