Fig. 1: Intratumoral PD-1⁺CD8⁺ T cells were accumulated in gastric cancer and correlated with tumour progression.

a Left: representative immunohistochemistry images for tumour-infiltrating PD-1⁺CD8⁺ T cells in gastric tissues. PD-1⁺ cells were stained in brown, while CD8⁺ cells were stained in red. Cells double-stained in brown and red were recognised as PD-1⁺CD8⁺ T cells (black arrows). Magnification: ×200; Scale bar, 100 μm. Right: scatterplots indicated the cumulative frequency of PD-1⁺CD8⁺ T cells in the gastric tumour and peritumor tissues (n = 441, Paired t test, P < 0.05). b PD-1⁺CD8⁺ T signature score in the EBV, MSI, GS and CIN subgroups (TCGA classification) and in the MSI, MSS/EMT, MSS/TP53⁻ and MSS/TP53⁺ subgroups (ACRG classification). c Association between PD-1⁺CD8⁺ T cells and tumour TNM stage was examined based on IHC staining (P = 0.049, One-way ANOVA followed by Tukey multiple comparisons). CIN Chromosomal instability, EBV EBV-positive, GS genomically stable, MSI microsatellite instable, MSS/EMT microsatellite stable and epithelial-to-mesenchymal transition, MSS/TP53⁺ microsatellite stable and tumour protein 53 active, MSS/TP53⁻ microsatellite stable and tumour protein 53 inactive. Small horizontal lines indicate the mean (±SD). *P < 0.05, **P < 0.01, ***P < 0.001, ns refers to not significant. ANOVA analysis of variance, PD-1 programmed cell death protein 1, SD standard deviation.