Numerous diseases, recently reported to associate with elevated
microvesicle/microparticle (MP) counts, have also long been
known to be characterized by accelerated immune complex (IC)
formation. The goal of this study was to investigate the
potential overlap between parameters of protein complexes (e.g.
ICs or avidin-biotin complexes) and MPs, which might perturb
detection and/or isolation of MPs. In this work, after
comprehensive characterization of MPs by electron microscopy,
atomic force microscopy, dynamic light scattering analysis and
flow cytometry, for the first time we drive attention to the
fact that protein complexes, especially insoluble ICs, overlap
in biophysical properties (size, light scattering,
sedimentation) with MPs. This, in turn, affects MP
quantification by flow cytometry and purification by
differential centrifugation, especially in diseases in which IC
formation is common, including not only autoimmune diseases, but
also hematological disorders, infections and cancer. These data
may necessitate reevaluation of certain published data on
patient-derived MPs, and contribute to correct the clinical
laboratory assessment of the presence and biological functions
of MPs in health and disease.
