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Biochem Biophys Res Commun. 2010 Jun 25;397(2):251-6. doi: 10.1016/j.bbrc.2010.05.094. Epub 2010 Jun 1.

A membranous form of ICAM-1 on exosomes efficiently blocks leukocyte adhesion to activated endothelial cells.

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Department of Life Science, Division of Molecular and Life Sciences, Pohang University of Science and Technology, Pohang 790-784, Republic of Korea.


While intercellular adhesion molecule-1 (ICAM-1) is a transmembrane protein, two types of extracellular ICAM-1 have been detected in cell culture supernatants as well as in the serum: a soluble form of ICAM-1 (sICAM-1) and a membranous form of ICAM-1 (mICAM-1) associated with exosomes. Previous observations have demonstrated that sICAM-1 cannot exert potent immune modulatory activity due to its low affinity for leukocyte function-associated antigen-1 (LFA-1) or membrane attack complex-1. In this report, we initially observed that human cancer cells shed mICAM-1(+)-exosomes but were devoid of vascular cell adhesion molecule-1 and E-selectin. We demonstrate that mICAM-1 on exosomes retained its topology similar to that of cell surface ICAM-1, and could bind to leukocytes. In addition, we show that exosomal mICAM-1 exhibits potent anti-leukocyte adhesion activity to tumor necrosis factor-alpha-activated endothelial cells compared to that of sICAM-1. Taken together with previous findings, our results indicate that mICAM-1 on exosomes exhibits potent immune modulatory activity.

[Indexed for MEDLINE]

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