title: Effects of polyclonal IgG derived from patients with different clinical types of the antiphospholipid syndrome on monocyte signaling pathways.
abstract: A major mechanism of hypercoagulability in the antiphospholipid syndrome (APS) is antiphospholipid Ab-mediated upregulation of tissue factor (TF) on monocytes via activation of TLRs, p38 MAPK, and NF-kappaB pathways. We examined whether monocyte signaling pathways are differentially activated by IgG from patients with vascular thrombosis (VT) alone compared with IgG from patients with pregnancy morbidity (PM) alone. We purified IgG from 49 subjects. A human monocyte cell line and ex vivo healthy monocytes were treated with 100 microg/ml IgG for 6 h, and cell extracts were examined by immunoblot using Abs to p38 MAPK and NF-kappaB. To further investigate intracellular signaling pathways induced by these IgGs, specific inhibitors of p38 MAPK, NF-kappaB, TLR4, and TLR2 were used to determine their effect on TF activity. Only IgG from patients with VT but no PM (VT+/PM-) caused phosphorylation of NF-kappaBand p38 MAPK and upregulation of TF activity in monocytes. These effects were not seen with IgG from patients with PM alone (VT-/PM+), anti-phospholipid Ab-positive patients without APS, or healthy controls. TF upregulation caused by the VT+/PM- samples was reduced by inhibitors of p38 MAPK, NF-kappaB, and TLR4. The effects of VT+/PM- IgG on signaling and TF upregulation were concentrated in the fraction that bound beta-2-glycoprotein I. Our findings demonstrate that IgGs from patients with diverse clinical manifestations of APS have differential effects upon phosphorylation of NF-kappaB and p38 MAPK and TF activity that may be mediated by differential activation of TLR4.
authors.affiliation: Medical Molecular Biology Unit, Institute of Child Health, Department of Medicine, Centre for Rheumatology Research, University College London, London, UK. n.lambrianides@ich.ucl.ac.uk
authors.forename: Anastasia
authors.initials: A
authors.lastname: Lambrianides
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: Carroll
authors.forename: Silvia S
authors.initials: SS
authors.lastname: Pierangeli
authors.forename: Charis
authors.initials: C
authors.lastname: Pericleous
authors.forename: Ware
authors.initials: W
authors.lastname: Branch
authors.forename: Jurhee
authors.initials: J
authors.lastname: Rice
authors.forename: David S
authors.initials: DS
authors.lastname: Latchman
authors.forename: Paul
authors.initials: P
authors.lastname: Townsend
authors.forename: David A
authors.initials: DA
authors.lastname: Isenberg
authors.forename: Anisur
authors.initials: A
authors.lastname: Rahman
authors.forename: Ian P
authors.initials: IP
authors.lastname: Giles
mesh_terms: D000328:Adult; D016736:Antiphospholipid Syndrome / Q000276:immunology* / Q000378:metabolism; D015153:Blotting, Western; D005260:Female; D006801:Humans; D007074:Immunoglobulin G / Q000276:immunology*; D008297:Male; D008875:Middle Aged; D009000:Monocytes / Q000276:immunology* / Q000378:metabolism; D016328:NF-kappa B / Q000276:immunology / Q000378:metabolism; D010766:Phosphorylation; D011247:Pregnancy; D011248:Pregnancy Complications / Q000276:immunology; D015398:Signal Transduction / Q000276:immunology*; D013925:Thromboplastin / Q000276:immunology* / Q000378:metabolism; D051197:Toll-Like Receptor 4 / Q000276:immunology / Q000378:metabolism; D048051:p38 Mitogen-Activated Protein Kinases / Q000276:immunology / Q000378:metabolism
chemical_list: D007074:Immunoglobulin G; D016328:NF-kappa B; C495345:TLR4 protein, human; D051197:Toll-Like Receptor 4; D013925:Thromboplastin; D048051:p38 Mitogen-Activated Protein Kinases