In vivo induction of gamma interferon and tumor necrosis factor by interleukin-2 infusion following intensive chemotherapy or autologous marrow transplantation

Interleukin-2 (IL-2) therapy may improve immune reconstitution and reduce the risk of leukemic relapse in the setting of minimal residual disease by augmenting cytotoxic effector mechanisms directed at residual malignant cells. In addition, IL-2 in vitro promotes the release of cytokines including γ-interferon (γ-IFN) and tumor necrosis factor (TNF), which also possess antileukemic activity and can enhance granulocyte function. To determine if IL-2 infusion induces release of γ-IFN and TFN in vivo in sufficient quantity to mediate these effects, we have measured serum levels of these cytokines and secretion by lymphocytes obtained from patients receiving this cytokine in a phase 1 trial. Serum γ-IFN was undetectable pre-IL-2 and increased to 1.5 to 17 U/mL during IL-2 infusion (P < .05). Culture of patient lymphocytes for 48 hours produced 1.2 U γ-IFN/2 x 10⁶ cells/mL pre-IL-2 rising to 50 U/2 x 10⁶ cells/mL when the lymphocytes were obtained during therapy (P < .05). Lymphocyte subset analysis showed that both CD3+ and CD16+ cells secreted γ-IFN in response to IL-2. TNF secretion by lymphocytes also rose during IL-2 infusion from a mean of 5 U/mL to 14.4 U/mL (P < .01) although no rise was seen in serum levels. The material secreted by IL-2-stimulated lymphocytes is bioactive as addition of supernatants from lymphocytes obtained during IL-2 therapy to cultures of myeloid blasts significantly inhibited clonogenic growth. IL-2-induced secretion of these cytokines mediated this inhibition as it could be partially blocked by either anti-γ-IFN or anti-TNF antibodies. Preincubation of granulocytes with the same supernatants produced enhanced oxidative metabolism, measured by chemiluminescence in response to N-formyl-methionyl-leucyl-phenylalanine (FMLP). This effect also coud be partially abrogated by anti-γ-IFN and anti-TNF antibodies. Therefore, secondary cytokine secretion may boost granulocyte function and contribute to the antileukemic effects of IL-2 infusion in patients following bone marrow transplantation or chemotherapy.