Detection of complexed IgE in sera of patients allergic to the pollen of Parietaria officinalis.

34 sera of patients allergic to the pollen of Parietaria officinalis were analyzed by ultracentrifugation on sucrose gradient (40-10%) in 0.9% NaCl at 24,000 rpm with a SW 27.1 rotor for complexed circulating IgE. Total and specific anti-PO IgE content of the gradient's fractions were determined by radioimmunoassay. IgE presence was demonstrated in at least two peaks; one corresponding to monomeric IgE, another corresponding to IgE with a sedimentation constant higher than that of the monomers. The ratio between monomeric and complexed IgE was different for each serum. Discordant results of PRIST and RIST analyses suggest that complexed IgE has fewer sites available for reaction with anti-IgE than the monomers.