The antibody response in serum, intestinal wall and intestinal lumen of NMRI mice infected with Echinostoma caproni.

Groups of mice (NMRI) were infected with 0, 6 and 25 metacercariae of the intestinal trematode Echinostoma caproni. An enzyme linked immunosorbent assay (ELISA) was developed for measuring the specific IgM, IgG and IgA antibody responses in serum, small intestinal tissue and small intestinal lumen of the mice, by using a crude adult E. caproni antigen. In infected mice, significant levels of IgM were measured in the sera from day 14 after infection and of IgG and IgA from day 28 after infection. Early in the infection, the mean level of serum IgM was higher in 6-worm infections than in 25-worm infections. Late in the infection, higher mean levels of IgA were reached in the serum of mice with high than in those with low dose infections. The onset of appearance of antibodies in the tissue of the small intestine reflected the picture seen in the serum. For IgM, and to a lesser degree for IgG, the highest mean antibody levels appeared in the posterior sections of the small intestinal wall, where also the parasites were located. The mean level of IgA, however, was uniform throughout the length of the small intestinal tissue. High levels of specific IgA were detected in the lumen of the small intestine on day 28 after infection, especially in the anterior sections, where only few parasites were located. No specific IgM or IgG could be detected in the intestinal lumen on this day. The results are related to the intestinal location and the pattern of expulsion of E. caproni in the mouse host.