Expansion of FoxP3⁺ CD4⁺ T cells across dose levels of anti-CTLA4 antibody. (A) PBMCs from baseline, week 4, and week 16 were stained for CD4 and intracellular FoxP3. Stained cells were then assessed by flow cytometry and gated on CD4⁺ T cells. Each row represents results from individual patients corresponding to subjects presented in Figure 2A at different dose levels assessed longitudinally at each of the time points. Numbers on plots represent the percentage of cells for each quadrant. (B) The counts of FoxP3⁺ CD4⁺ T cells per volume of blood was calculated by multiplying the percentage of FoxP3⁺ CD4⁺ T cells by the absolute lymphocyte counts measured simultaneously in a complete blood count. Each row represents the corresponding dose level. Each line represents the counts for each evaluable subject within the specified dose level. (C) The change in the number of FoxP3⁺ CD4⁺ T cells per volume of blood is compared by plotting the baseline count (x-axis) versus the week-16 measurement (y-axis). The solid line indicates no change in cell count between the 2 time points. There was a significant increase in cell count among patients treated on dose levels 2 to 5, with different symbols indicating the different dose cohorts (Wilcoxon matched pairs test: P = .001). All data points residing above the line indicate an increase in the number of cells.