Inhibition of the Prausnitz-Küstner reaction by an immunoglobulin epsilon-chain fragment synthesized in E. coli.

The Prausnitz-Küstner (P-K) reaction is a sensitive test for the presence and activity in the skin of immunoglobulin E, an important class of immunoglobulin mediating allergic reactions. A fragment of the human myeloma ND epsilon-chain gene, encoding the second, third and fourth domains of the IgE constant region (C epsilon 2-4) was assessed here for its ability to inhibit the P-K reaction in vivo. Injection of the fragment in skin sites of healthy human adults prevented subsequent sensitization with serum containing IgE antibody to ragweed antigen. Inhibition of the P-K reaction required a 200-fold molar excess of the C epsilon fragment over the IgE present in the sensitizing serum. The efficacy of the C epsilon fragment in inhibiting the P-K reaction compared favourably with that of natural myeloma IgE (PS) in terms of both blocking concentrations and duration of the blocking effect. The inhibition of the P-K reaction by C epsilon 2-4 fragments was specific and probably caused by the saturation of IgE receptors on mast cells by the recombinant gene product.