Malignant B cells are in frequent contact with PD-1⁺ T cells. (A) Representative high-power mIF image demonstrating PD-1 expression on the surface of CD3⁺ T cells in contact with a PAX5⁺ B cells). (B) Cell-cell contact map of the mIF image shown in panel A (same scale). PD-1⁺ T cells, PD-1⁻ T cells, and other cells (solid gray) in contact with malignant cells and PD-1⁺ T cells and PD-1⁻ T cells (outlined) not in contact with malignant cells. (C) Proportion of malignant cell contacts for individual cases (●) displayed according to the proportion of PD-1⁺ T-cell contacts vs PD-1⁻ T-cell contacts (n = 26). (D) Low-power, maximum field-of-view mIF image of TCRLBCL in panel A: PD-1 on CD3⁺ T cells intermixed with PAX5⁺ B cells. (E) Cell phenotype map corresponding to the mIF image in panel D: PD-1⁺ T cells, PD-1⁻ T cells, and malignant B cells. (F) T-cell density for individual cases (●) displayed according to the density of PD-1⁺ T cells and PD-1⁻ T cells. (G) Intermediate-power mIF image of the boxed region in panel D: PD-1 expression on CD3⁺ T cells intermixed with PAX5⁺ B cells. (H) Cell proximity map of the region highlighted in panel E: spatial distribution of PD-1⁺ T cells and PD-1⁻ T cells relative to malignant cells, showing T cells that are located <75 μm from malignant cells and those that are located ≥75 μm from malignant cells. (I) The ratio of PD-1⁺ T cells to total T cells for individual cases (●) displayed according whether the T cells are located <75 or ≥75 μm from malignant B cells. For the box-and-whisker plots (C,F,I), the median (line), 25th and 75th percentiles (boxes), and extreme values (whiskers) are indicated. Statistical comparisons by the 2-sided Mann-Whitney U test, Wilcoxon matched-pairs signed-rank test, and the Kruskal-Wallis test with Dunn’s test for multiple comparisons.