Interleukin 2 (IL-2) treatment of malignancies is often associated with severs toxicity, and the alterations observed after high dose administration of IL-2 are similar to those induced by recombinant tumor necrosis factor (TNF). We therefore examined the hypothesis that IL-2 induces TNF gene expression in vivo. Purified, recombinant human IL-2 was injected intraperitonealy into mice which had been previously primed with complete Freund's adjuvant (CFA). Biologically-active TNF was detected in the ascites fluid of CD-1 mice; it was detectable 30 minutes after IL-2 and peaked at 1 hour (500 ± 158 units/ml). Plasma levels of TNF also peaked at 1 hour at 32 ± 4 units/ml. Similar kinetics were observed in CBA/J mice. TNF specific mRNA was also present in the ascites cells, and peaked 30 minutes after IL-2 injection into CBA/J mice. Injection of vehicle containing 10 times the maximum contaminating dose of endotoxin did not induce TNF above background levels. As a further control for potential endotoxin contamination, IL-2 was injected into endotoxin hyporesponsive C3H/HeJ mice. These mice also demonstrated the rapid upregulation of biologically-active TNF in the ascites, with peak production occuring at 1 hour (125 ± 47 units/ml). The induction of biologically-active TNF in the C3H/HeJ mice was associated with a peripheral blood neutrophilia and lymphopenia, pathophysiologic alterations that have been attributed to TNF. These data show that a single injection of purified, recombinant IL-2 induces TNF gene expression in vivo.
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