Mechanism of allergic cross-reactions--II. Cross-stimulation, by chemically unrelated ligands, of rat basophilic leukemia cells sensitized with an anti-DNP IgE antibody.

Serotonin release from rat basophilic leukemia (RBL) cells, sensitized with a DNP-binding monoclonal IgE, was stimulated with solid surface (polystyrene)-bound DNP-amino acids. The stimulatory potency of DNP-amino acids was dependent on the structure of amino acid attached to DNP. Generally, DNP-amino acids with high affinities to the sensitizing IgE (I(50) less than 10 microM) were stimulatory in polystyrene-bound form; DNP-amino acids with lower affinities (Pro, Cys, Trp), and aliphatic aromatic DNP-amino acid derivatives were inactive. In addition to structural analogues of DNP, lymecycline, that is chemically unrelated to DNP but was found to have high affinity to IgE(aDNP), was also stimulatory in this system. This drug, and various quinones (e.g. acenaphthene-quinone) in BSA-conjugated forms also stimulated serotonin release from RBL cells sensitized with IgE(aDNP). These studies suggest that (1) There is a threshold of intrinsic ligand binding affinities at approximately I(50) = 10-100 microM; ligands with lower affinities do not stimulate mediator release even if they are presented in multivalent forms; (2) The above affinity threshold for mediator cell stimulation is valid for various ligands, irrespective of their chemical similarity to the immunogen; (3) Multispecific stimulation of mediator release may contribute to the frequently observed allergic cross-reactions, false positive tests for allergies, and anaphylactic reactions to drugs upon first exposure.