PD-1 expression among case and control patients displayed as heatmap. PD-1 expressing cells were quantified at the time of HSCT (0 months) and at multiple post-HSCT time points (1, 2, 3, 6, and 12 months after HSCT) in a control cohort (left columns, yellow top bar) and in patients previously treated with PD-1 (right columns, blue top bar). Each column represents an individual patient. The PD-1 cohort is arranged by time from last PD-1 treatment to HSCT (see legend). The percentage of PD-1⁺ cells among various T-cell subsets is displayed as a heatmap where blue, white, and red represent low-, intermediate-, and high-subset frequency, respectively. Gray indicates missing value. Values in each row were subtracted from row median and divided by row median absolute deviation. Treg, T-regulatory cells; Tcon, conventional CD4 cells. PD-1 expression was significant lower on Treg cells, Tcon cells, and CD8⁺ cells at 0, 1, 2, 3, and 6 months. N, no; Y, yes.