P. Krailadsiri et al., MICROVESICLES IN BLOOD COMPONENTS - LABORATORY AND CLINICAL ASPECTS, Clinical and applied thrombosis/hemostasis, 3(2), 1997, pp. 86-95
There is ample evidence for the presence of microvesicles (MV) of diff
erent sizes and functions in various blood components. A variety of me
chanisms have been proposed for the formation of MV. These include mec
hanical injury, shear stress, cell activation, activation of complemen
ts, hypoxia, and the cell aging process. While MV share many biologica
l properties and surface receptors of their parental cells, they demon
strate significant differences in membrane asymmetry of the inner memb
rane phospholipid, in particular phosphatidylserine (PS). This provide
s high-affinity binding sites for the components of the prothrombinase
complex. To what extent these MV contribute to hemostatic effectivene
ss, immudomodulation, and some untoward effects of the transfused bloo
d components remains to be fully elucidated. Several methods for quali
tative and semiquantitative characterization of MV are now available.
Although in most cases it is necessary to separate MV from the intact
cells for improved characterization, recent advances in flow cytometry
make it possible to accurately differentiate MV in the presence of th
eir parental cells on the basis of light scattering and fluorescent in
tensity. This review focuses on four main areas of MV in blood compone
nts: (1) the proposed mechanisms of platelet vesiculation, (2) factors
influencing the formation of MV, (3) laboratory analysis of MV, and (
4) the clinical impact of the presence of MV in blood components.