Immunity to Nematospiroides dubius: Parasite Stages Responsible for and Subject to Resistance in High Responder (LAF 1 /J) Mice

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Abstract
In the LAF1/J mouse strain, a single prior exposure to infective larvae of N. dubius given per os resulted in > 90% reduction of an homologous larval challenge; a single larval sensitizing infection had no effect on adult worms introduced directly into the duodenum via laparotomy. The LAF1/J mice given a single sensitizing infection of adult worms via laparotomy did not exhibit resistance to homologous challenge of either infective larvae or adult worms. Because all sensitizing infections were removed chemotherapeutically before administration of challenge inocula, potential effects of overcrowding on establishment or development of challenge infections were precluded. Worm-specific antibody determinations indicated that adult worms introduced into the gut lumen did not prime the host for a secondary response to a challenge by larval or adult worms. A challenge with larvae of mice previously sensitized with an homologous larval infection did stimulate an anamnestic antibody response. Apparently, in a highly responsive mouse strain (LAF1/J), larval stages were requisite in stimulation of host resistance to reinfection and a larval challenge was fully susceptible to the effects of that response. Mature adult worms apparently did not stimulate nor were they susceptible to the host''s immune response.