FASCIOLA-HEPATICA - SOME PROPERTIES OF A PRECIPITATE WHICH FORMS WHEN METACERCARIAE ARE CULTURED IN IMMUNE RAT SERUM

When Fasciola hepatica metacercariae are cultured in immune rat serum a precipitate forms on their teguments which is a complex of parasite metabolic antigen and rat immunoglobulin, possibly IgG. Continuous secretion of the antigen by the parasite and its precipitation with antibody leads to the eventual appearance of precipitate in the culture medium. Ouchterlony double diffusion tests indicate that only one antigen/antibody interaction appears to be involved in precipitate formation. When rats were vaccinated with precipitate emulsified with Freund's complete adjuvant then given an oral challenge with metacercariae, there was a reduction of as much as 50% in their worm burdens compared with controls. This evidence suggests that the precipitate contains a functional antigen of the parasite. The rat immunoglobulin component is therefore presumed to be protective antibody. © 1979.