Agar gel diffusion tests were performed with antisera produced by infecting rabbits with Trichinella spiralis, against 1:25, 1:50 and 1:100 dilutions of test antigens prepared from the adults and larval forms of the parasite.
The sera of animals receiving repeated feedings with infective larvae revealed three bands of precipitate when tested against the larval test antigen. When an adult test antigen was used against the same sera, two bands were formed. The differences in location and the noncoalescence of bands formed against larval and adult test antigens indicate differences in the two antigen-antibody systems.
Absorptions of the sera with appropriate dilutions of adult or larval antigens removed the homologous but not the heterologous antibodies.
The presence of qualitatively different antigenantibody systems which develop during infection is discussed in connection with acquired immunity in trichinosis.
Post doctoral fellow, Training Grant No. 2E-15 from the National Institutes of Health, Bethesda, Maryland.