By examining 14 paired (pre- and post-treatment) fresh tumor samples obtained from 2 HPD and 12 non-HPD gastric cancer patients, the authors found that after anti-PD-1 antibody treatment, the ratio between proliferating (Ki67+) effector Tregs (eTregs) and Ki67+ CD8+ T cells among the tumor-infiltrating lymphocyte (TIL) compartment remained stable in HPD patients, while it was reduced in the non-HPD group. The gene discussed is PDCD1; the disease is neoplasm.