Interleukin-4 prevents mortality from acute but not chronic murine peritonitis and induces an accelerated tumor necrosis factor-α response

Interleukin-4 (IL-4) demonstrates properties in vitro that suggest an anti-inflammatory role in the immune response, one of which is the inhibition of tumor necrosis factor-α (TNF) release. We examined the effects of IL-4 administration on mortality and serum TNF levels in two murine models of peritonitis. Animals infected with intraperitoneal injections of Escherichia coli and Bacteroides fragilis (acute peritonitis) had a decreased mortality and earlier TNF-α peak when pretreated with 5,000 units IL-4. Animals infected with bacteria and a sterile fecal adjuvant (chronic peritonitis) had no alteration in mortality or serum TNF levels (which were consistently low) with IL-4 pretreatment. These data demonstrate that, under some in vivo conditions, IL-4 can significantly ameliorate a septic insult, but this effect appears to be highly model-dependent and not clearly related to its effects on TNF-α.