Loss of Pre-irradiation Immunity to Hymenolepis Nana in the Rat-mouse Chimera

Summary

Mice were immunized by infection with Hymenolepis nana eggs. Intestinal tapeworms developed and were eventually expelled. The mice were then x-irradiated (950 r) and injected with 40 million syngeneic bone-marrow cells from non-immune mice or with 140 million rat bone-marrow cells. At different times after irradiation and treatment with bone-marrow, groups of mice were given a challenge dose of parasite eggs to test for persistence of immunity. Comparisons between groups were based on the number of worms that developed after the egg-challenge. The mice treated with syngeneic bone-marrow and the rat-mouse chimeras both resisted reinfection when challenged one day after irradiation. Two and three weeks after irradiation, the degree of infection after egg-challenge was greater in the rat-mouse chimeras than in the mice treated with syngeneic marrow. These results indicate that persistence of immunity acquired before irradiation is influenced by the type of bone-marrow implanted after irradiation.