Pharmacokinetics of rhIL-2 and rhSCF-PEG treatment in mice. (A) 1 × 10⁴ IU per day rIL-2 was delivered by constant subcutaneous infusion via Alzet osmotic pump, and measurement of serum IL-2 was performed by ELISA on days 0, 4, 10, and 12 after implantation. (B) PK of rhSCF-PEG administered as a single i.p. injection of 100 μg/kg body weight. Serum levels were measured by ELISA 0, 4, 8, 12, and 24 hours after injection. Results for each cytokine represent the mean ± SEM obtained from two mice with each measurement performed in duplicate.