Studies on the Host Parasite Relationships to Schistosoma japonicum. IV. Resistance Acquired by Infection, by Vaccination and by the Injection of Immune Serum, in Monkeys, Rabbits and Mice

Abstract

Monkeys, rabbits, and mice developed an acquired resistance to Schistosoma japonicum following a previous infection with the same trematode. This resistance was manifested by the reduction in number and size of the developing worms. No difference in the sex ratio of the developing worms was observed in the immunized animals. Attempts to develop resistance in mice both with worm extracts and with worm metabolites were also successful. Likewise a certain degree of resistance to the development and growth of the parasites was conferred by injections of immune sera. The resistance conferred by the injection of antigens and by passive transfer of the serum was less marked than that encountered in animals which were immunized by a previous experimental infection. The results add support to the evidence already available that animals develop an acquired immunity to S. japonicum and that this immunity is, partly at least, serological in nature.