Effects of target antigen density on the efficacy of immunomagnetic cell separation.
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.
Gee
A P
AP
Baxter Healthcare Corporation, Fenwal Division-Irvine, Santa Ana, CA 92705.
Mansour
V H
VH
Weiler
M B
MB
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
D000911:Antibodies, Monoclonal; D000912:Antibodies, Neoplasm; D000951:Antigens, Neoplasm; D000939:Epitopes