title: Differential stimulation of monocytic cells results in distinct populations of microparticles.
abstract: BACKGROUND
  Microparticles (MPs), small vesicles shed from stimulated cells, permit cross-talk between cells within a particular environment. Their composition is thought to reflect their cell of origin, and differs according to whether they are produced by stimulation or by apoptosis. Whether MP properties vary according to stimulus is not yet known.
  
  
  METHODS
  We studied the characteristics of MPs produced from monocytic THP-1 cells upon stimulation with lipopolysaccharide or a soluble P-selectin chimera, using proteomics, flow cytometry, western blotting, and electron microscopy.
  
  
  RESULTS
  Utilizing a novel criterion of calcein-AM staining to define MPs, we found that MP populations were similar with respect to size, presence and organization of cytoskeleton, and expression of certain antigens. The MPs shared the same level of procoagulant activity. We found that MPs also have distinct characteristics, depending on stimuli. These include differences in phosphatidylserine expression and expression of proteins from specific subcellular locations such as the mitochondria, and of unique antigens such as leukocyte-associated immunoglobin-like-receptor (LAIR)-1, which was found only upon stimulation with the soluble P-selectin chimera.
  
  
  CONCLUSIONS
  We found that the properties of MPs depend on the stimulus that produced them. This supports the concept that monocytic MPs differentially modulate thrombosis, inflammation and immune regulation according to stimulus.
authors: Immune Disease Institute, Boston, MA 02115, USA.
authors: M
authors: M
authors: Bernimoulin
authors: E K
authors: EK
authors: Waters
authors: M
authors: M
authors: Foy
authors: B M
authors: BM
authors: Steele
authors: M
authors: M
authors: Sullivan
authors: H
authors: H
authors: Falet
authors: M T
authors: MT
authors: Walsh
authors: N
authors: N
authors: Barteneva
authors: J-G
authors: JG
authors: Geng
authors: J H
authors: JH
authors: Hartwig
authors: P B
authors: PB
authors: Maguire
authors: D D
authors: DD
authors: Wagner
mesh_terms: D015153:Blotting, Western; D002460:Cell Line; D005434:Flow Cytometry; D006801:Humans; D008854:Microscopy, Electron; D009000:Monocytes / Q000276:immunology*; D010316:Particle Size; D040901:Proteomics