IL-15 administration alters the peripheral blood count of multiple lymphocyte subsets. IL-15 was administered daily for a total of 12 days, at 3 different doses: 10 μg/kg (●), 20 μg/kg (▲), and 50 μg/kg (■). Animals treated with placebo alone (♦) were included as control. Each point corresponds to the mean ± SEM and indicates the fold change in the absolute count relative to day −7 before treatment and is depicted with log scaling. Values for the absolute lymphocyte, CD4⁺ and CD8⁺ (CD3⁺) T-cell, monocyte, NK-cell (defined as CD3⁻CD14⁻CD20⁻ and either CD56⁺ or CD16⁺), and CD20⁺ B-cell counts are shown. Total lymphocyte and monocyte counts were obtained from the complete blood counts, while all other subpopulations were calculated by multiplying the percentages obtained from flow cytometric data to the complete blood counts. The gray bar on the x-axis of each graph indicates the time frame of IL-15 therapy. *P < .05 for Wilcoxon rank test in all IL-15–treated animals versus sham. By analyzing single-dose groups independently, we saw a statistical significant increase in NK, CD8⁺, and CD4⁺ T cells at day 8 and in NK and CD8⁺ T cells at day 13 after 1-way analysis of variance test (data not shown).