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

Human IgE antibodies from nine allergic subjects were found to react with poly-L-lysine (PLL) and other polyamines. Radioimmunoassay inhibition studies indicated that the two amino groups, but not the carboxyl, in lysine contributed to the antibody binding and 4-aminomethyl-1,8-octanediamine, a compound containing three primary amino groups, was a better inhibitor than compounds containing only two primary amino groups. Ethylamine showed weak but clear inhibition indicating that even a single amino group could bind to the antibody combining site. Substituted ethanolamine and quaternary ammonium compounds were well recognized by some sera but with others, substitution hampered recognition. Inhibition studies with compounds containing an amino and a carboxyl group at different distances revealed that an adjacent carboxyl group interfered with recognition of the amino group by some IgE antibodies. IgE binding to PLL was examined at different pHs and ionic strengths. 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 binding. 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 relevant to mechanisms underlying recognition of some allergens in some atopic conditions.