Stimulation of immunity to Nematospiroides dubius in mice using larvae attenuated by cobalt 60 irradiation.

Infective larvae of Nematospiroides dubius attenuated by cobalt 60 irradiation are extremely effective at stimulating immunity. Previously, such levels of protection could only be obtained with multiple immunizations of normal larvae. The critical factor underlying this protective response appears to be the dose of irradiation given to the immunizing infection. Various doses of irradiation have been tested and the most effective of these range between 10 and 30 krad. The experiments show that provided this level of irradiation is used, the number of immunizing infections is relatively unimportant. Such use of irradiated larvae will be of value in attempting to analyse the immune mechanisms which operate against N. dubius. The possible mechanisms of immunity to N. dubius are discussed.