Treg homeostasis in recipients without aGVHD after HCT. Shown are results for donor/recipients couples without aGVHD from cohort 1. (A) Frequency of FOXP3⁺ cells within the CD4⁺ population in donors (D) and recipients (R) at day 90 post-HCT. (B) Frequencies of Ki-67⁺, within the CD4⁺ FOXP3⁺ Treg population, in donors (D) and recipients (R) at day 90 post-HCT. (C) Frequency of proliferating (Ki-67⁺) cells within the CD4⁺FOXP3⁺ Treg and CD4⁺FOXP3⁻ Tconv populations in donors (D) and recipients (R) (left panel) and ratios of proliferating (Ki-67⁺) Treg/Tconv in donors (D) and recipients (R) at day 90 post-HCT (right panel). (D) Frequencies of CTLA4⁺, ICOS⁺, and PD1⁺ cells within the CD4⁺FOXP3⁺ Treg population in donors (D) and recipients (R) at day 90 post-HCT. Horizontal lines indicate the median. P values were calculated using a Wilcoxon matched-pairs Student t test or a Mann-Whitney U test. Differences are considered significant for P < .05.