Functional characterization of specific IgE antibodies for tetanus toxoid.

The specific IgE response that appears in subjects immunized with tetanus toxoid does not induce hypersensitivity reactions at subsequent immunizations. The type I immune response, therefore, was studied both in vivo and in vitro, in 11 subjects who had specific IgE antibodies for tetanus toxoid. The results showed that: 1. the specific IgE antibodies are heterogeneous regarding their affinity for the mast cell and basophil receptors; 2. the specific IgG antibodies for tetanus toxoid, at serum concentrations, are not able to interfere with the in vitro specific basophil degranulation; 3. in the PEG precipitate there are aggregates of specific IgE antibodies for tetanus toxoid. In vitro, these molecular aggregates are not able to sensitize the basophil cells.