Effects of target antigen density on the efficacy of immunomagnetic cell separation

J Immunol Methods. 1991 Aug 28;142(1):127-36. doi: 10.1016/0022-1759(91)90300-5.


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.

MeSH terms

  • Antibodies, Monoclonal
  • Antibodies, Neoplasm / analysis*
  • Antigens, Neoplasm / immunology*
  • Binding Sites
  • Breast Neoplasms / immunology*
  • Cell Separation
  • Epitopes
  • Flow Cytometry
  • Humans
  • Magnetics
  • Microspheres
  • Neuroblastoma / immunology
  • Neuroectodermal Tumors, Primitive, Peripheral / immunology
  • Tumor Cells, Cultured


  • Antibodies, Monoclonal
  • Antibodies, Neoplasm
  • Antigens, Neoplasm
  • Epitopes