Trichinella spiralis: intestinal expression of systemic stage-specific immunity to newborn larvae.

Rats immunized with newborn Trichinella spiralis larvae i.v. were found to confer a specific anti-newborn larvae immunity in the small intestine. In rats immunized with newborn larvae i.v. and then challenged with adult worms intraintestinally, total newborn larvae recovery was reduced by 75-90% in thoracic duct lymph and in hepatic portal vein blood. No newborn larvae were found in the peritoneal fluid of immunized rats. In addition to an absolute reduction in number, larval migration from the small intestine to the thoracic duct was delayed by 6-12 h and migration to the portal vein was inhibited for at least 8 h. The establishment of adult worms in the small intestine and female worm fecundity were not affected by anti-newborn larvae immunity. Identical quantitative effects on newborn larvae migration from the small intestine were achieved by homologous transfer of anti-newborn larvae immune serum i.v. into naive recipient rats.