Erythrocytes restrict microvesicle-induced production of reactive oxygen species by polymorphonuclear leukocytes.

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.

Microparticles from patients with systemic lupus erythematosus induce production of reactive oxygen species and degranulation of polymorphonuclear leukocytes.

Background: The interaction of circulating microparticles (MPs) with immune cells in systemic lupus erythematosus (SLE) is sparsely investigated. We examined the ability of MPs from SLE patients to induce production of reactive oxygen species (ROS) and degranulation of polymorphonuclear leukocytes (PMNs).

Methods: Plasma MPs, leukocytes and sera isolated from 20 SLE patients and 10 healthy controls were mixed in different combinations, with or without lipopolysaccharide (LPS), and incubated for 30 min.

Surface complement C3 fragments and cellular binding of microparticles in patients with SLE.

Objectives: To examine microparticles (MPs) from patients with SLE and healthy controls (HCs) by determining the cellular origin of the MPs, quantifying attached fragments of complement component 3 (C3) and assessing the ability of MPs to bind to circulating phagocytes and erythrocytes. These features may be relevant for clearance of MPs in SLE pathogenesis.

Methods: Attached C3 fragments (C3b, iC3b, C3d), membrane integrity and cell surface markers of MPs from 18 patients with SLE and 11 HCs were measured by adding specific antibodies, 7-aminoactinomycin D (7AAD) and annexin V.