Acquired Immunity Against a Metazoan Parasite by Use of Non-Specific Worm Materials. ∗

Abstract

Both active and passive immunization of the rat against infection by onchospheres of Taenia taeniaeformis have been adequately demonstrated. 1 A series of 6 injections of a 1% suspension of the powdered worm usually results in complete protection against infection. Only one attempt, previous to the present experiments, was made to produce immunity by the use of related worm materials; injection of powdered T. pisiformis, a tapeworm of the dog, did not protect rats against infection by larvae of T. taeniaeformis.

In experiment I powdered Diphyllobothrium latum, Taenia saginata, Hymenolepis sp., and Dipylidium sp. were used. One lot of control rats received a similar series of injections of T. taeniaeformis material and another (uninjected) served as controls on the viability of the taeniaeformis onchospheres with which all rats were fed. Autopsy data (Table I) show that little or no protection was afforded by these non-specific cestode materials, following their injection as suspensions of powdered worm.

On the other hand, introduction into the peritoneal cavity of rats of whole, or long pieces of, living Taenia pisiformis resulted in a high degree of protection against infection by the larvae of T. taeniaeformis, as was shown by infecting the rats some weeks after the operations (Exp. 2). The control animals into whose body cavities the cysticercus stage of taeniaeformis had been placed contained no living cysts at autopsy, while the untreated controls were heavily infected.

On one earlier occasion the mistake had been made, in one experiment, of feeding onchospheres of T. pisiformis instead of T. taeniaeformis. When these rats were subsequently fed onchospheres of the proper species it was found that the control (untreated) animals were refractory to infection, although control rats of other experiments to which portions of the same lot of onchospheres had been fed became heavily infected.