Physical characterization and in vitro biological impact of highly aggregated antibodies separated into size-enriched populations by fluorescence-activated cell sorting

J Pharm Sci. 2015 May;104(5):1575-91. doi: 10.1002/jps.24379. Epub 2015 Mar 5.


An IgG2 monoclonal antibody (mAb) solution was subjected to stirring, generating high concentrations of nanometer and subvisible particles, which were then successfully size-enriched into different size bins by low-speed centrifugation or a combination of gravitational sedimentation and fluorescence-activated cell sorting (FACS). The size-fractionated mAb particles were assessed for their ability to elicit the release of cytokines from a population of donor-derived human peripheral blood mononuclear cells (PBMC) at two phases of the immune response. Fractions enriched in nanometer-sized particles showed a lower response than those enriched in micron-sized particles in this assay. Particles of 5-10 μm in size displayed elevated cytokine release profiles compared with other size ranges. Stir-stressed mAb particles had amorphous morphology, contained protein with partially altered secondary structure, elevated surface hydrophobicity (compared with controls), and trace levels of elemental fluorine. FACS size-enriched the mAb particle samples, yet did not notably alter the overall morphology or composition of particles as measured by microflow imaging, transmission electron microscopy, and scanning electron microscopy-energy dispersive X-ray spectroscopy. The utility and limitations of FACS for size separation of mAb particles and potential of in vitro PBMC studies to rank-order the immunogenic potential of various types of mAb particles are discussed.

Keywords: IgG; immune response; immunogenicity; PBMC; in vitro; monoclonal antibody; particles; protein aggregation; proteins.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Antibodies, Monoclonal / analysis*
  • Antibodies, Monoclonal / chemistry*
  • Flow Cytometry / methods*
  • Humans
  • Immunoglobulin G / analysis
  • Immunoglobulin G / chemistry
  • Leukocytes, Mononuclear / cytology
  • Microspheres
  • Nanoparticles / analysis
  • Nanoparticles / chemistry
  • Particle Size*


  • Antibodies, Monoclonal
  • Immunoglobulin G