Investigation into the protective processes involved when C3Hf/St inbred mice are infected with Hymenolepis Citelli

A model system was established in investigate host-parasite relationships using C3Hf/St inbred mice as the host, and Hymenolepis citelli McLeod as the non-invasive intestinal dwelling cestode. The C3H mice proved to be highly susceptible to infections of H. citelli, in that about 50% of the cysticercoids administered developed into adult worms. Primary infections of ten cysticercoids per mouse appeared to result in a low grade protective response beginning 21 days post infection. In addition, a form of protective response appeared with secondary infections of ten cysticercoids, when preceded by an initial infection of ten cysticercoids followed by a booster of five cysticercoids. This protection may be influenced by physiological factors; such as crowding and competition, and/or the use of an antihelmintic that could increase the potential infect ability by depressing the host responses. This model provides a system that allows more controlled experiments and is the initial step in investigations leading to a definitive understanding of the protective mechanisms responsible for the host's response to the parasite. Specific antibody has been demonstrated in the serum and directly on the worm taken from C3H mice infected with H. citelli by using immunofluorescence. Anti-H citelli antibodies of both IgG and IgA classes were found within the serum, and directly on sections of worms taken from infected mice. Stronger IgG specific fluorescence was observed in the serum, while IgA was the predominant class of antibody found on sections of worm taken directly for the gut of infected mice. A kinetic analysis of the humoral and secretory components following a primary infection of ten cysticercoids revealed the ability to detect antibody in the serum as well as directly on sections approximately three weeks post infection. Interestingly, antibody was only detectable on worms taken between three and five weeks post infection. No antibody was detectable on worms taken from mice with greater than five week only infections. It was, however, possible to detect the presence of antibody in concentrated intestinal chyme and fecal pellets taken from mice previously infected for 35 to 39 days. The relationship between these observations and the natural history of H. citelli infections in C3H mice are discussed.