Nippostrongylus brasiliensis in the rat: immune response in serum and intestinal secretions.

The kinetics of local and serum hemagglutinins production was observed following infections of rats with N. brasiliensis. Antibodies which appeared in the gut immediately after parasite localization had occured there 6 days following infection with 3,000 larvae. Serum antibodies were detected on day 18. Parasites were still being expelled at this time from the intestine. When rats were infected with 83 larvae, which is the smallest immunizing dose, local antibodies appeared in the same manner as in the first experiment, serum antibodies appearing only after challenge with 3,000 larvae. Local antibody activity is mainly due to IgA molecules. The presence of parasites and, at the same time, of local antibodies suggests an hypothesis for the mechanism of worm expulsion.