Reactivity to IgE-dependent histamine-releasing factor is due to monomericIgE

Background: IgE-dependent histamine-releasing factor (HRF) can distinguish between IgE(+) and IgE(-). In contrast to IgE(-), IgE(+) sensitizes basophi ls to release histamine in response to HRF. But we do not know what particu lar feature distinguishes IgE(+) from IgE(-). The objective was to investig ate 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 basophilis to release: his tamine in response to HRF and to house-dust mite, whereas no enhanced react ivity was found in the fractions containing polymeric IgE. Conclusions: HRF reacts with monomeric IgE, and not (exclusively) with poly meric IgE.