Flow cytometric analysis of cell membrane microparticles.

Cell membrane microparticles (MPs) are phospholipid microvesicles shed from the plasma membrane of most eukaryotic cells undergoing activation or apoptosis. The presence of MPs is common in healthy individuals. However, an increase in their release is a controlled event and is considered a hallmark of cellular alteration. Microparticles display cell surface proteins that indicate their cellular origin. In addition, they may also express other markers, e.g., markers of cellular activation. Elevated levels of circulating MPs are associated with various vascular pathologies and their pathogenic potential has been widely documented. MPs have been analyzed in plasma and cell cultures by means of flow cytometry or solid phase assays. Here we present a three-color flow cytometric assay for immunophenotyping of MPs in plasma. This assay has been used to study elevated counts of different phenotypes of circulating endothelial MPs in several hematological and vascular diseases. A modified version of this assay can also be used for MP analysis in blood products and cell cultures.