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Biochem Biophys Res Commun. 2008 Feb 8;366(2):579-84. Epub 2007 Dec 17.

Circulating TNFR1 exosome-like vesicles partition with the LDL fraction of human plasma.

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Pulmonary-Critical Care Medicine Branch, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD 20892, USA.


Extracellular type I tumor necrosis factor receptors (TNFR1) are generated by two mechanisms, proteolytic cleavage of TNFR1 ectodomains and release of full-length TNFR1 in the membranes of exosome-like vesicles. Here, we assessed whether TNFR1 exosome-like vesicles circulate in human blood. Immunoelectron microscopy of human serum demonstrated TNFR1 exosome-like vesicles, with a diameter of 27-36nm, while Western blots of human plasma showed a 48-kDa TNFR1, consistent with a membrane-associated receptor. Gel filtration chromatography revealed that the 48-kDa TNFR1 in human plasma co-segregated with LDL particles by size, but segregated independently by density, demonstrating that they are distinct from LDL particles. Furthermore, the 48-kDa exosome-associated TNFR1 in human plasma contained a reduced content of N-linked carbohydrates as compared to the 55-kDa membrane-associated TNFR1 from human vascular endothelial cells. Thus, a distinct population of TNFR1 exosome-like vesicles circulate in human plasma and may modulate TNF-mediated inflammation.

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