IGHE and acute basophilic leukemia: Despite the recombinant protein showed reactivity with Ara h 2-specific IgE from about 70% of the tested sera, it resulted ineffective in inducing the release of β-hexosaminidase, a marker of IgE-mediated cell degranulation, from sensitized rat basophil leukemia (RBL) cells at concentrations up to 100 ng/mL.