Previous work has shown that Trichinella spiralis-infected rats transport IgE from plasma to intestinal tissue and fluids. In this study we quantitate IgE transport to the gut and circulation during T. spiralis infection in rats. Total IgE levels in intestinal fluid from infected rats were elevated by 4 days post-infection (dpi), but were not elevated in serum and lymph until 7 dpi. IgE levels in intestinal fluid ranged from 1 to 6 microg between 10 and 21 dpi, and serum and lymph IgE levels ranged from 100 to 200 ng/ml. Immunoprecipitation of intestinal fluid and enterocyte lysate at 11 dpi showed a protein of 190 kDa that was recognized by mouse anti-rat IgE-MARE-1 in Western blots. This protein was removed from intestinal wash samples with anti-IgE (A2)-Sepharose. The half-life of intact IgE in the intestinal lumen of rats 10 days after infection was 3.25 min. In serum, the half-life of IgE was 5 h. Analysis of IgE production and consumption in 10-day T. spiralis infected rats showed that about 4.67 microg IgE/day entered the serum, while 2570.00 microg IgE/day entered the intestinal lumen. The IgE present in serum 10 days after T. spiralis infection originated in the gut and/or associated lymphoid tissue and was transported to the circulation via thoracic duct lymph. However, most IgE produced in the intestine was transported to the gut lumen at a rate that exceeded transport to plasma by a factor of several-hundredfold.