Effect of glucan on neutrophil dynamics and immune function in Escherichia coli peritonitis

Abstract

Previous studies from our laboratory have demonstrated that glucan, a nonspecific immunomodulator, modifies the course of murine Escherichia coli peritonitis. The protective effect of glucan was mediated, in part, by macrophages. In the present study, leukocyte dynamics in the peritoneal cavity and peripheral blood of glucan-treated mice following E. coli challenge was examined. Additional studies examined in vitro bone marrow proliferation, as well as phagocytosis and intracellular killing of E. coli by neutrophils following glucan administration. ICR/HSD mice were injected ip with glucan (150 mg/kg) or dextrose (5% w/v) on Days 5 and 3 prior to ip challenge with 1 × 10 8 E. coli. Glucan increased ( P < 0.05) total peritoneal neutrophil numbers prior to and following septic challenge. Examination of peripheral blood revealed that ip glucan treatment in E. coli peritonitis significantly ( P < 0.001) increased the number of circulating neutrophils. Additionally, neutrophils from glucan-treated mice showed increased phagocytosis of E. coli in vitro. Glucan therapy also increased bone marrow proliferation. We conclude that (1) glucan enhances peritoneal neutrophil levels, (2) peripheral blood neutrophils are increased following glucan and E. coli, (3) ip glucan increases bone marrow proliferation, and (4) neutrophils from glucan-treated mice showed enhanced phagocytosis of E. coli in vitro. Thus, the beneficial effect of glucan is mediated not only by activated macrophages, but also by the neutrophilic leukocyte.