Pharmacokinetics of IL-15 when administered by continuous intravenous infusion versus subcutaneous dosing. (A) Serum levels of IL-15 were obtained at 0.25, 0.5, 1, 2, 4, 8, and 24 hours after dose on treatment days 1 and 10 in animals receiving 20 μg/kg/ (♦) or 40 μg/kg/d (■) of IL-15 by SC injection. Each point corresponds to the mean ± SD for 3 animals. (B) Serum IL-15 levels were measured on days 2 and 10 in RMs receiving 20 μg/kg/d of IL-15 given by CIV. Levels were measured during 2 treatment cycles given 8 weeks apart. Each point corresponds to the mean ± SD. For day 2 versus day 10 in cycle 1, P = .06 by Wilcoxon rank test.