Factors affecting the acquisition of resistance against Schistosoma mansoni in the mouse: III. The failure of primary infections with cercariae of one sex to induce resistance to reinfection.

Mice which were given a primary infection consisting of male or female Schistosoma mansoni cercariae alone failed to acquire the same degree of resistance against homologous challenge as did mice with a bisexual primary infection. The degree of resistance acquired by "single-sex"-infected mice was not augmented either by increasing the number of cercariae administered in the primary infection, or by increasing the interval between primary infection and challenge, or by injection of S. mansoni eggs. The results are discussed in relation to previous observations on the capacity of "single-sex" schistosome infections to induce resistance.