Reaction with, and fine structural recognition of polyamines by human IgE antibodies

Human IgE antibodies from nine allergic subjects were found to react with p oly-L-lysine (PLL) and other polyamines. Radioimmunoassay inhibition studie s indicated that the two amino groups, but not the carboxyl, in lysine cont ributed to the antibody binding and 4-aminomethyl-1,8-octanediamine, a comp ound containing three primary amino groups, was a better inhibitor than com pounds containing only two primary amino groups. Ethylamine showed weak but clear inhibition indicating that even a single amino group could bind to t he antibody combining site. Substituted ethanolamine and quaternary ammoniu m compounds were well recognized by some sera but with others, substitution hampered recognition. Inhibition studies with compounds containing an amin o and a carboxyl group at different distances revealed that an adjacent car boxyl group interfered with recognition of the amino group by some IgE anti bodies. IgE binding to PLL was examined at different pHs and ionic strength s. Binding was greatest at pH 5-6 to 8 and decreased markedly outside this range. Ionic strengths higher than 0.3 M significantly diminished the bindi ng. These results indicated that binding of specific antibody to polyamine was due to electrostatic interactions of positively charged amino groups in the polyamine with the antibody combining site. These results may be relev ant to mechanisms underlying recognition of some allergens in some atopic c onditions. (C) 2000 Elsevier Science Ltd. All rights reserved.