These progenitor exhausted T cells with high PD-1 expression and low Tim-3 expression are characterized by a rapid proliferative response to exert anti-tumor effects after the application of anti-PD-1 mAbs; however, these cells gradually lose TCF-1 expression and stemness under the continuous stimulation of tumor antigens, thus entering the terminal exhaustion phase [134, 135]. Here, PDCD1 is linked to neoplasm.