Reactivity to IgE‐dependent histamine‐releasing factor is due to monomeric IgE

Background: IgE‐dependent histamine‐releasing factor (HRF) can distinguish between IgE+ and IgE−. In contrast to IgE−, IgE+ sensitizes basophils to release histamine in response to HRF. But we do not know what particular feature distinguishes IgE+ from IgE−. The objective was to investigate the hypothesis that IgE+ is polymeric IgE. Methods: IgE+plasma was separated by size‐exclusion chromatography. The basophil‐sensitizing capacity of the fractions was analyzed in response to HRF produced by mononuclear cells. Results: We showed that monomeric IgE sensitized basophils to release histamine in response to HRF and to house‐dust mite, whereas no enhanced reactivity was found in the fractions containing polymeric IgE. Conclusions: HRF reacts with monomeric IgE, and not (exclusively) with polymeric IgE.