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Microvesicles (MVs) are extracellular vesicles released by several cell types upon activation or apoptosis. MVs have the potential to activate complement, which has been suggested to mediate their clearance. However, it is not clear how complement-opsonized MVs are prevented from activating circulating polymorphonuclear leukocytes (PMNs) with release of reactive oxygen species (ROS) and potential damage of endothelium and other bystander cells as consequence. We hypothesized that binding of opsonized MVs to erythrocytes (Es) attenuates MV-induced PMN activation. To test this, normal PMNs were exposed to MVs in the presence and absence of Es from allogenic healthy donors. As analyzed by flow cytometry, the presence of Es restricted the PMN binding of MVs by about 85% (p = 0.002) and mediated a 60-70% inhibition of the PMN production of the ROS H2 O2 , induced by MVs, when lipopolysaccharide was used as a primer (p = 0.002). The competitive binding of MVs to Es was partly dependent on complement, since EDTA inhibited MV binding to Es by 75%. These data suggest that Es, through competitive binding, may restrict MV-induced activation of circulating PMNs and thereby serve a role as a regulator of PMN activation.

Original publication

DOI

10.1111/apm.12954

Type

Journal article

Journal

APMIS : acta pathologica, microbiologica, et immunologica Scandinavica

Publication Date

07/2019

Volume

127

Pages

538 - 542

Addresses

Copenhagen Lupus and Vasculitis Clinic, Copenhagen University Hospital, Center for Rheumatology and Spine Diseases, Rigshospitalet, Copenhagen, Denmark.

Keywords

Endothelium, Erythrocytes, Humans, Reactive Oxygen Species, Leukocyte Count, Flow Cytometry, Adult, Female, Male, Cell-Derived Microparticles, Young Adult