Comparison of levels of multifunctional CD8⁺ T cells in D⁺/R⁺ and D⁻/R⁺ HCT recipients. The percentages of 8 combinations of single-, double-, triple-, and quadruple-functional subsets within the total population of IFN-γ–CD8⁺ were compared between D⁺/R⁺ and D⁻/R⁺ recipients at 3 time points after HCT. Each dot represents an individual measurement. Average percentages are shown as horizontal black bars. Four combinations of TNF-α⁺ subsets are shown in (A) and 4 combinations of TNF-α⁻ subsets are shown in panel B. (C) All 8 possible combinations of response categories are summarized and shown in the pie chart, in which each slice of the pie represents the average response across all individual samples. The fraction of the total IFN-γ–CD8⁺ response for 8 different functional marker combinations are shown sequentially in different colors from single-functional cells (blue) through double-functional (yellow), triple-functional (pink), and quadruple-functional (red).