Background: We have identified a monoclonal anti-human immunoglobulin E (IgE) antibody, which recognizes FcepsilonRI-bound IgE and prevents binding of IgE to FcepsilonRI. In this study, we assessed the binding kinetics and affinity of monoclonal antibody 12 (mAb12) for IgE and investigated whether mAb12 can be used for depletion of IgE and isolation of IgE-bearing cells from peripheral blood.
Methods: Binding kinetics and affinity for IgE were studied using Biacore surface plasmon resonance technique experiments. IgE antibodies were depleted from serum using sepharose-coupled mAb12 and IgE-bearing cells were enriched from heparinized blood samples with mAb12. The extent and biological relevance of IgE depletion were studied by quantitative IgE measurements and basophil histamine release experiments. Specific binding of mAb12 to IgE-bearing cells (basophils, mast cells, IgE-secreting plasma cells) was demonstrated by FACS.
Results: Monoclonal antibody 12 shows rapid association (k(a) = 5.46e5/Ms) with IgE, almost no dissociation (k(d) = 8.8e-5/s) and an affinity for IgE (K(D) = 1.61e-10 M), which is as high as that of FcepsilonRI. Immobilized mAb12 could be used to deplete IgE antibodies and isolate IgE-bearing cells from peripheral blood in a single-step procedure.
Conclusions: Monoclonal antibody 12 is a high affinity anti-human IgE antibody, which efficiently removes IgE and IgE-bearing cells from peripheral blood and may thus be used for extracorporeal depletion of IgE and IgE-bearing cells.