Functional analysis of interleukin-2 in immune surveillance against brain tumors.

We studied the capacity of peripheral blood lymphocytes (PBLs) from patients with malignant brain tumors to produce interleukin-2 (IL-2) and to respond to IL-2. The role of IL-2 in the generation of T cells cytotoxic against tumor cells was also studied. PBLs from the patients with malignant brain tumors tended to produce a level of IL-2 lower than that in normal controls because of the decreased number of IL-2-producing T cells. Phytohemagglutinin activated PBLs from normal controls and the patients, however, responded equally well to IL-2. This indicates that the expression of IL-2 receptors is abundant in PBLs of these patients, although IL-2 production may be depressed. Furthermore, after incubation with IL-2, PBLs from the patients with malignant glioma exhibited higher natural killer activity and strong cytotoxicity against glioma cells. This increased cytotoxicity was evident by Day 3 of culture in IL-2 and remained effective for at least 2 days. These observations of antitumor cytotoxicity make IL-2 a likely candidate for use in adoptive immunotherapy.