(A) Study design of the human single ascending dose study, generated in BioRender. (B) Frequency among CD3⁺CD4⁺ T cells and absolute number of CD25⁺CD127^loFOXP3⁺ Tregs before and after treatment (gating in Supplemental Figure 3A). Absolute number based on lymphocyte complete blood counts obtained from clinical laboratory tests. *Significant after adjusting for multiple testing (P values in Supplemental Table 1), using mixed model for repeated measures (n as depicted in A); dose cohort annotated by asterisk color. (C) Log₂-transformed average fold change in absolute cell number from baseline to day 8, using hypothesis-based gating of IL-2–responsive populations (gating in Supplemental Figure 3B). Paired 2-tailed t test, significance of 0.01 to account for multiple testing (n as in A). Participant-level data in Supplemental Figure 4. Cell type represented by shape; dose represented by color. “CD4 Tconv” group includes total CD4⁺ Tconv, CD25⁺CD4⁺ Tconv, Ki67⁺CD4⁺ Tconv, and Th1 subsets. “CD8 Tconv” group includes total CD8⁺ Tconv, CD25⁺CD8⁺ Tconv, Ki67⁺CD8⁺ Tconv, and Tc1 subsets. “Innate” group includes γδ T cells and innate lymphoid cell 2–like cells. “NK” group includes CD56^hi NK cells (NKhi) and CD56^lo NK (NKdim) cells. (D) Log₂-transformed average fold change from baseline to day 8 in relative frequency of DISCOV-R automated CyTOF metaclusters. The 18 metaclusters were grouped into categories of Tregs, CD4⁺ Tconv, CD8⁺ Tconv, Innate, NK, and B cells as in B, represented by shape. Dose represented by color, as in B. Paired 2-tailed t test, significance of 0.01 to account for multiple testing (n as in A). Metacluster definitions and participant-level data shown in Supplemental Figure 5.