IL-2 decreases long-term proliferation in CD4⁺ and CD8⁺ T cells. Paired percentages of CD4⁺ (A) and CD8⁺ (B) T cells expressing Ki67 at months 0 and 12 from each individual participant from cohort 2 are shown. Solid symbols represent values from IL-2 group patients and open symbols represent measurements from the control group. No significant differences in Ki67 expression of CD4⁺ or CD8⁺ T cells were noted between the IL-2 and the control groups at month 0. At month 12, a significant difference was found between the 2 groups in the percent Ki67 expression in both CD4⁺ and CD8⁺ T cells (P < .01 for both comparisons). A significant decrease at month 12 compared to month 0 was found in the expression of Ki67 in the CD4⁺ T cells from the IL-2 group only (P < .001).