“…In MLNx rats, the dramatic increase in circulating IgE that follows infestation (2,8] did not occur, and the le vels of parasite-specific IgE antibodies in serum were significantly lower. This result is consistent with earli er observations that the MLN in Nb-infested rats con tains large numbers of cells producing IgE [5,6] and is active in synthesis of parasite-specific homocytotrop ic antibody [8], We have also found that introduction of adult Nb directly into the duodenum of intact rats produces serum IgE levels comparable with those in larval in festation [Allan and Mayrhofer, unpubl. results], sug gesting that the intestinal stage is probably the major stimulus for IgE production.…”