INTERLEUKIN-4 PREVENTS MORTALITY FROM ACUTE BUT NOT CHRONIC MURINE PERITONITIS AND INDUCES AN ACCELERATED TUMOR NECROSIS FACTOR-ALPHA RESPONSE

Interleukin-4 (IL-4) demonstrates properties in vitro that suggest an anti-inflammatory role in the immune response, one of which is the inh ibition of tumor necrosis factor-alpha (TNF) release. We examined the effects of IL-4 administration on mortality and serum TNF levels in tw o murine models of peritonitis. Animals infected with intraperitoneal injections of Escherichia coli and Bacteroides fragilis (acute periton itis) had a decreased mortality and earlier TNF-alpha peak when pretre ated with 5,000 units IL-4. Animals infected with bacteria and a steri le fecal adjuvant (chronic peritonitis) had no alteration in mortality or serum TNF levels (which were consistently low) with IL-4 pretreatm ent. 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-alpha.