Mechanism of allergic cross-reactions--I. Multispecific binding of ligands to a mouse monoclonal anti-DNP IgE antibody.

A recently developed solid-phase binding assay was used to investigate the specificity of ligand binding to a mouse monoclonal anti-dinitrophenyl IgE [IgE(aDNP)]. All DNP-amino acids, that were tested, inhibited the binding of radio-labeled IgE(aDNP) to DNP covalently attached to polystyrene microtiter plates; however, the concentration for 50% inhibition varied within four orders of magnitude, DNP-L-serine being the most, DNP-proline the least potent inhibitor. In addition to DNP analogues a large number (2074) of drugs and other compounds were tested for their ability to compete with DNP for the binding site of IgE(aDNP). At the concentrations used for screening 59% of the compounds had no significant inhibition; 19% inhibited the binding of IgE(aDNP) more than 50%. Several families of compounds (tetracyclines, polymyxines, phenotiazines, salicylates and quinones) of effective competitors were found. Within these families change in the functional groups attached to the "family stem" had major effects on the affinity of ligand binding. The occurrence frequencies of interactions of ligands with IgE(aDNP) is in good agreement with a semi-empirical model for multispecific antibody-ligand interactions.

HNK-1-reactive novel oligosaccharide, sulfate-O-3GlcA beta 1-4Xyl beta 1-(4-methylumbelliferone), synthesized by cultured human skin fibroblasts.

4-Methylumbelliferyl-beta-D-xyloside (Xyl-MU) was added to the medium of cultured human skin fibroblasts. After incubation, the culture medium was pooled, and the Xyl-MU-induced oligosaccharides in the medium were purified by gel filtration chromatography. A novel Xyl-MU derivative was obtained, in addition to the previously reported Xyl-MU derivatives such as Gal-Gal-Xyl-MU, Gal-Xyl-MU, Sia-Gal-Xyl-MU, GlcA-Xyl-MU, and Xyl-Xyl-MU. The novel Xyl-MU derivative was purified using gel-filtration chromatography and high performance liquid chromatography and then subjected to carbohydrate composition analysis, enzymic digestion, Smith degradation, and ion spray mass spectrometric analysis. The results indicated that it was sulfate-O-3GlcA beta 1-4Xyl beta 1-MU. The structure of the nonreducing terminal of this Xyl-MU-induced oligosaccharide was the same as that of the oligosaccharide chain of a human peripheral nerve-derived glycolipid, reactive with the mouse monoclonal antibody HNK-1, and this Xyl-MU-induced oligosaccharide also reacted with HNK-1. These results suggest that the oligosaccharide, which is structurally identical to that of human peripheral nerve-derived glycolipid synthesized by nervous tissue and related to cell adhesion, is synthesized also by mesenchymal cells.

Rapid fluorogenic assay for differentiation of the Candida parapsilosis group from other Candida spp.

A 30-min fluorogenic test was developed for differentiation of members of the Candida parapsilosis group from other Candida species commonly encountered in clinical material. The fluorogenic substrate, 4-methylumbelliferyl-beta-D-glucoside, was utilized to assay beta-glucosidase activity. A total of 50 C. parapsilosis isolates and 135 isolates of four other Candida species were tested. Assay sensitivity and specificity were 100 and 99.3%, respectively. The procedure was adapted for use with a spectrofluorometer.