Schistosome eggs in the portal vein can induce tolerance

Schistosoma japonicum lives in the portal vein and/or mesenteric vein of patients, producing numerous eggs which eventually induce multiple granulomas in the liver and the intestine. The experimental administration of Schistosoma japonicum eggs via the portal vein in the mouse induces tolerance both in the footpad reaction and granuloma formation in the lung. Thus, the presence of Schistosoma japonicum in the portal vein is beneficial to the parasites, not only for receiving enriched nutrition from the blood of the portal vein, but also for inducing immunological tolerance in the hosts. However, prior intravenous injection of gadolinium chloride abolishes such tolerance, indicating the role of Kupffer cells in the induction of tolerance via the portal vein.