Interleukin-2 therapy enhances salicylate oxidation by blood granulocytes

These studies determined the effect of interleukin-2 (IL-2) immunotherapy on the oxidative metabolism of the blood granulocytes of eight patients with metastatic renal cancer. We quantitated the rate of the hexose monophosphate shunt activity (HMPS), hydrogen peroxide (H2O2) production, and salicylate oxidation of the unstimulated and phorbol myristate acetate (PMA)-stimulated granulocyte cultures before, during, and after a 5-day continuous infusion of IL-2. There was no change in the rate of HMPS activity. However, the rate of salicylate oxidation of the unstimulated and PMA-stimulated cultures of these patients was significantly increased after the therapy was complete. Overall, there was no increase in the rate of H2O2 production, although the PMA-stimulated cultures of three of eight patients had a twofold higher production of H2O2 after treatment compared with the pretreatment values. The enhanced rate of salicylate oxidation by the granulocytes after treatment indicates that these cells were "stimulated" in vivo to produce a potent oxidant, which is most likely hydroxyl radical or an oxidant of comparable activity. Further, the granulocytes were primed ("activated"), since they had an augmented response to PMA. IL-2 did not stimulate the oxidative metabolism of granulocyte cultures in vitro, suggesting that the IL-2 effect in vivo is not a direct one. Our results indicate that IL-2 immunotherapy is associated with the activation of blood granulocyte oxidative metabolism and that these activated granulocytes may be related to some of the toxic side effects of IL-2 therapy such as the capillary leak syndrome. Further oxidant injury to the granulocytes may explain the reported defect in chemotaxis.