Severe sepsis induces deficient interferon-gamma and interleukin-12 production, but interleukin-12 therapy improves survival in peritonitis.

BACKGROUND: After severe sepsis, there is an increase of Th2 cytokine and a decrease in Th1 cytokine that may account for impaired cellular immunity. The aim of this study is to evaluate the Th1, Th2 cytokine balance in the serum, peritoneal lavage fluid (PLF) and liver mononuclear cells (MNC) of experimental peritonitis mice, and determine the effect of interleukin-12 (IL-12), a cytokine stimulating Th1 cytokine production, when administered to septic mice.
METHODS: Experimental bacterial peritonitis mice was induced by cecal ligation and puncture (21-gauge needle, mild peritonitis) or cut (5 mm, severe peritonitis). Serum and PLF levels and liver MNC production of interferon (IFN)-gamma, IL-10, and IL-12 were measured after the procedure. Mild and severe peritonitis mice were treated intraperitoneally with recombinant IL-12 (r-IL-12) either 6 hours before or 6 and 24 hours after the procedure. The survival rates were then compared with nontreated mice.
RESULTS: Serum and PLF IFN-gamma, IL-12 levels in severe peritonitis mice were significantly lower than those in mild peritonitis mice at 6 and 12 hours after the procedure. On the other hand, serum and PLF IL-10 levels in severe peritonitis mice were significantly higher than those in mild peritonitis mice at 6 hours after the procedure. Furthermore, liver MNC IFN-gamma production in severe peritonitis mice was significantly higher than that in mild peritonitis mice at 6 hours after the procedure, but liver MNC IL-12 production in severe peritonitis mice was significantly lower than that in mild peritonitis mice at 12 hours after the procedure. Severe peritonitis mice treated with r-IL-12 at 6 hours before the procedure improved survival rate, and mild peritonitis mice treated with r-IL-12 at 24 hours after the procedure showed significantly improved survival rates.
CONCLUSIONS: Change in the Th1, Th2 cytokine balance in peritonitis mice might induce a shift toward a Th2 dominant phenotype according to the severity of peritonitis, and the capacity to produce IFN-gamma and IL-12 by liver MNC is reduced. Therapies designed to augment the production of Th1 cytokines, such as IL-12, may thus prove to be beneficial in the treatment of severe sepsis after peritonitis.