Administration of slowly released recombinant interleukin 2. Augmentation of the efficacy of adoptive immunotherapy with lymphokine-activated killer (LAK) cells.

When recombinant human interleukin 2 (r-IL-2) was given to mice by single subcutaneous (s.c.) injection it rapidly disappeared from the blood. However, administration of slowly released r-IL-2 using mini-osmotic pumps caused a significant prolongation of serum levels of IL-2. Using a method for assaying IL-2 in vivo, it was also demonstrated that both the viability and the cytotoxicity of lymphokine-activated killer (LAK) cells could be maintained at a high level in vivo by administration of slowly released r-IL-2 rather than by a single injection of r-IL-2. In addition, we successfully treated EL4-bearing mice by combination therapy consisting of LAK cells and slowly released r-IL-2.