title: Effects of target antigen density on the efficacy of immunomagnetic cell separation.
abstract: Immunomagnetic cell separation uses binding of an antibody to its epitope to identify the target cell, which is then removed by attachment to an anti-immunoglobulin-coated paramagnetic bead, and passage through a magnetic field. This method has previously been shown to be less sensitive to the effects of low target antigen density than are other cell elimination methods, such as complement-mediated lysis. In this paper we demonstrate that, with certain antibody/target cell combinations, the efficiency of immunomagnetic depletion can be adversely affected by high expression of the target antigen. This can occur by two non-mutually exclusive mechanisms. These are (i) steric hindrance of bead binding due to crowding of monoclonal antibodies on the cell surface; and (ii) binding of the monoclonal antibody molecule in a configuration that is poorly-accessible to the anti-immunoglobulin immobilized on the microspheres. The predominant effect operating in any system can be determined by analysis of the cells remaining after the separation procedure. In both cases pre-attachment of the monoclonal to the beads results in improved separation efficiency. These results emphasize the necessity of optimizing experimental conditions in each system that is investigated.
authors.affiliation: Baxter Healthcare Corporation, Fenwal Division-Irvine, Santa Ana, CA 92705.
authors.forename: A P
authors.initials: AP
authors.lastname: Gee
authors.forename: V H
authors.initials: VH
authors.lastname: Mansour
authors.forename: M B
authors.initials: MB
authors.lastname: Weiler
mesh_terms: D000911:Antibodies, Monoclonal; D000912:Antibodies, Neoplasm / Q000032:analysis*; D000951:Antigens, Neoplasm / Q000276:immunology*; D001665:Binding Sites; D001943:Breast Neoplasms / Q000276:immunology*; D002469:Cell Separation; D000939:Epitopes; D005434:Flow Cytometry; D006801:Humans; D008280:Magnetics; D008863:Microspheres; D009447:Neuroblastoma / Q000276:immunology; D018241:Neuroectodermal Tumors, Primitive, Peripheral / Q000276:immunology; D014407:Tumor Cells, Cultured
chemical_list: D000911:Antibodies, Monoclonal; D000912:Antibodies, Neoplasm; D000951:Antigens, Neoplasm; D000939:Epitopes