Use of Millipore diffusion chambers to assay in vivo IL-2 activity

Lymphokine-activated killer (LAK) cells were grown from C57BL/6 mouse spleen cells by culturing the cells with recombinant human IL-2 (r-IL-2). The unlabeled or [3H]uridine-labeled LAK cells were enclosed in a diffusion chamber, which was implanted into the peritoneal cavity of a syngeneic mouse, and the mouse was treated with an i.p. injection of r-IL-2 or saline (control). In order to detect the activity of administered r-IL-2, the diffusion chambers were taken out from the mice 20-40 h after the implantation, and the viability and cytotoxic activity of LAK cells in the chambers were determined by measuring the radioactivity of the cells and their cytotoxicity to EL 4 mouse leukemia cells respectively. When the mice were treated with saline, the radioactivity of LAK cells was greatly decreased. However, when the mice were treated with r-IL-2, the radioactivity of LAK cells was sustained. An i.p. administration of IL-2 also prevented any decrease in the cytotoxic activity of LAK cells.