The in vitro function of lymphocytes from 25 cancer patients receiving four to seven consecutive days of recombinant IL-2.

Twenty-five cancer patients received human recombinant interleukin-2 (IL-2) for 4 to 7 consecutive days in a Phase I trial. IL-2 was administered either as a daily intravenous bolus infusion (lasting 15 min), or as a continuous infusion lasting 24 h each day. Prior studies have demonstrated that in vivo administration of IL-2 at high doses is associated with changes in the phenotype of circulating peripheral blood lymphocytes (PBL) (determined with monoclonal antibodies), and the induction of augmented in vitro natural killer activity (NK) by PBL obtained following in vivo IL-2. We have noted that fresh lymphocytes obtained after 4-7 consecutive days of IL-2 (greater than or equal to 10(6) U/m2/day) show an augmented ability to kill NK-sensitive and -insensitive target cells (K562 and Daudi targets, respectively), especially when tested with IL-2 present during the 4-h 51Cr release assay. We have further analyzed lymphocytes in a battery of in vitro proliferative and cytotoxic assays. We present here the summary of this quantitative analysis of their responses in both antigen-specific and -nonspecific immune responses. Striking in vitro changes were observed in the proliferative response to IL-2 and in cytotoxicity stimulated by (or requiring) in vitro IL-2. Proliferative responses to antigens and to mitogens were not as dramatically altered following in vivo IL-2, nor were allospecific or allo-activated cytotoxic interactions. These studies indicate that the most striking changes in lymphocyte function measured in vitro following in vivo IL-2 are seen in those functions requiring IL-2.