Injection of recombinant interleukin 3 hastens worm expulsion in mice infected with Trichinella spiralis

Abstract

 The effects of interleukin 3 (IL-3) on worm expulsion were studied in mice infected with Trichinella spiralis. C3H/He mice were treated with a total of 10⁴ U IL-3 or saline by daily peritoneal injection from day-5 to day-1. Muscle larvae were given orally to both groups of mice on day 0. The muscle worm burden in infected mice was assessed on day 28. The worm burden in mice treated with recombinant IL-3 (rIL-3) was significantly suppressed as compared with that in control mice. A reduction in the worm burden was observed in mice treated with rIL-3 from day-5 to day-1 but not in those treated day 16 to day 20. This suggests that IL-3 could up-regulate the host defense response to intestinal worms but not to parenteral stage worms. When various doses of rIL-3 were given to mice and the intestinal worm burden was assessed on day 5, protection was observed only in mice treated with a total of 10⁴ U rIL-3 but not in those given either 3.5×10³ or 10³ U. A kinetics study on the recovery of intestinal adult worms showed that rIL-3 treatment hastened worm expulsion. The mucosal mast-cell response observed in the small intestine of rIL-3-treated mice was induced earlier and was greater than that seen in the control. The host defense response induced by rIL-3 could not be inhibited by treatment with anti-IL-4 or anti-IL-5 monoclonal antibody. Under such an experimental condition in this study, at least, the numbers of mast cells per villus crypt unit observed in mice treated with rIL-3 and anti-IL-4 antibody were slightly lower than those seen in mice treated with rIL-3, but the difference was not significantly different. These results suggest that IL-3 can induce the expulsion of T. spiralis worms without the cooperation of IL-4 or IL-5 in mice.