Widely varying frequencies of CD4⁺FoxP3⁺ T cells in patient PBMCs after adoptive immunotherapy. (A) Samples of patient PBMCs from 5 NMA clinical trials (detailed in “Methods”) were analyzed for the presence of CD4⁺FoxP3⁺ T cells. Numbers in parentheses indicate the total number of patients enrolled in these trials. (B) The percentages (% of CD3⁺ T cells) and (C) absolute cell count per microliter of CD4⁺FoxP3⁺ T cells in patient peripheral blood were analyzed before (PRE), approximately 1 week (week 1), and 4 weeks (week 4) after adoptive transfer. The maximum, 75th percentile, median, 25th percentile, and minimum values are shown. The number of CD4⁺FoxP3⁺ T cells represents the product of the absolute lymphocyte count, the fraction of the absolute lymphocyte count corresponding to CD3⁺ T cells, and the fraction of CD3⁺ T cells expressing FoxP3⁺ T cells.