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.