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2014 ; 411
(ä): 55-65
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Isolation of biologically-active exosomes from human plasma
#MMPMID24952243
Muller L
; Hong CS
; Stolz DB
; Watkins SC
; Whiteside TL
J Immunol Methods
2014[Sep]; 411
(ä): 55-65
PMID24952243
show ga
Effects of exosomes present in human plasma on immune cells have not been
examined in detail. Immunological studies with plasma-derived exosomes require
their isolation by procedures involving ultracentrifugation. These procedures
were largely developed using supernatants of cultured cells. To test biologic
activities of plasma-derived exosomes, methods are necessary that ensure adequate
recovery of exosome fractions free of contaminating larger vesicles, cell
fragments and protein/nucleic acid aggregates. Here, an optimized method for
exosome isolation from human plasma/serum specimens of normal controls (NC) or
cancer patients and its advantages and pitfalls are described. To remove
undesirable plasma-contaminating components, ultrafiltration of
differentially-centrifuged plasma/serum followed by size-exclusion chromatography
prior to ultracentrifugation facilitated the removal of contaminants. Plasma or
serum was equally acceptable as a source of exosomes based on the recovered
protein levels (in ?g protein/mL plasma) and TEM image quality. Centrifugation on
sucrose density gradients led to large exosome losses. Fresh plasma was the best
source of morphologically-intact exosomes, while the use of frozen/thawed plasma
decreased exosome purity but not their biologic activity. Treatments of frozen
plasma with DNAse, RNAse or hyaluronidase did not improve exosome purity and are
not recommended. Cancer patients' plasma consistently yielded more isolated
exosomes than did NCs' plasma. Cancer patients' exosomes also mediated higher
immune suppression as evidenced by decreased CD69 expression on responder CD4+ T
effector cells. Thus, the described procedure yields biologically-active,
morphologically-intact exosomes that have reasonably good purity without large
protein losses and can be used for immunological, biomarker and other studies.