Recombinant human IgE (clone SUS-11-NBS01) produced from a human B cell hybridoma cell line established from a healthy donor (CD40 cell culture system). IgE (SUS-11) binds to the alpha-chain of the human high affinity IgE receptor and the human low affinity IgE receptor (CD23) and does not interact with the corresponding IgE receptors of other species. It can be used for IgE monitoring in biological research samples (ELISA; FACS; W-blot, isotype control) or as functional reagent in mast cell / basophil cellular assays, e.g. for controlled sensitization of such cells and subsequent cross-linking with either anti-human IgE mAbs like NBS-C BioScience mAb LE27 or a specific recombinant cross-linking agent.