Activation of eosinophils in cancer patients treated with IL-2 and IL-2-generated lymphokine-activated killer cells.

Of 16 patients, a total of 13 who received IL-2 and autologous IL-2-generated lymphokine-activated killer LAK cells developed eosinophilia late during the course of treatment. To understand the direct or indirect effects of IL-2 on eosinophils, the physical and functional characteristics of the late-treatment eosinophils were compared to those of early-treatment and control eosinophils. Late-treatment eosinophils differed from early-treatment and control eosinophils in the following respects: they had somewhat reduced density, hypersegmented nuclei, eosinophil cationic protein converted from the storage form to the secretory form, and a greater than 200% increased ability to kill larvae of Schistosoma mansoni by an antibody-dependent mechanism (cytotoxic function). In vitro, IL-2 (1000 U/ml in medium as used to culture LAK cells) did not affect the cytotoxic function of eosinophils from cancer patients or from control subjects. However, LAK cell-conditioned medium enhanced the cytotoxic function of eosinophils from early-treatment cancer patients and from normal subjects by greater than 150%. Thus, eosinophils late in the course of IL-2/LAK cell treatment undergo physical changes and become functionally activated. The involvement of IL-2 in these changes is probably indirect, as an inducer of factors that enhance eosinophil function.