Rat IgE production. II. Primary and booster reaginic antibody responses following intradermal or oral immunization.

Primary and booster IgE antibody responses have been elicited in Hooded Lister rats by the intradermal injection or oral administration of very small quantities of egg albumin. Oral immunization was effected by giving antigen by stomach tube or in the drinking water. The minimum primary dose of antigen found to be effective was 1 mug intradermally and 10 mug orally, administered together with an intraperitoneal injection of B. pertussis adjuvant. In rats immunized with these doses secondary responses could be evoked by giving even smaller quantities of antigen, thus 1 ng intradermally or 1 mug orally without adjuvant. Smaller challenge doses were not tried. Large primary doses of antigen (greater than 100 mug) presented by these routes were, on the other hand, found to be inhibitory to the production of secondary IgE responses, this effect being similar to that observed in previously reported intraperitoneal immunization experiments. By contrast with previous experiments, however, tertiary responses could be obtained following immunization by these routes, and we believe this to be reflection of the absorption of smaller and therefore less inhibitory quantities of antigen. Our results are discussed in relation to the control of IgE antibody production, current concepts of the control of antigen absorption through mucosal barriers, and possible implications of the genesis of naturally occurring IgE responses in man.