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Blood, 1 June 2007, Vol. 109, No. 11, pp. 4803-4805. Prepublished online as a Blood First Edition Paper on February 13, 2007; DOI 10.1182/blood-2006-12-062695. This Article Full Text Full Text (PDF) All Versions of this Article: blood-2006-12-062695v1 109/11/4803    most recent Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Rights and Permissions Citing Articles Citing Articles via HighWire Citing Articles via CrossRef Citing Articles via Google Scholar Google Scholar Articles by Semple, J. W. Articles by Freedman, J. Search for Related Content PubMed PubMed Citation Articles by Semple, J. W. Articles by Freedman, J. Related Collections Brief Reports Hemostasis, Thrombosis, and Vascular Biology Immunobiology Phagocytes Social Bookmarking                   What's this?  Previous Article  |  Table of Contents  |  Next Article  HEMOSTASIS, THROMBOSIS, AND VASCULAR BIOLOGY Brief Report Platelet-bound lipopolysaccharide enhances Fc receptor–mediated phagocytosis of IgG-opsonized platelets John W. Semple1,6, Rukhsana Aslam5,6, Michael Kim6, Edwin R. Speck5,6, and John Freedman1,3,6 1 Department of Laboratory Medicine, St Michael's Hospital, Toronto, ON, Canada; Departments of 2 Pharmacology 3 Medicine, and 4 Laboratory Medicine and Pathobiology, University of Toronto, ON, Canada; 5 Canadian Blood Services; 6 The Toronto Platelet Immunobiology Group, ON, Canada Platelets express Toll-like receptor 4 (TLR4), and this has been shown to be responsible for the thrombocytopenia induced by lipopolysaccharide (LPS) administration in vivo. We studied the role of LPS in mediating platelet phagocytosis by THP-1 cells in vitro by flow cytometry. Opsonization of platelets with an IgG monoclonal (W6/32) antibody or with IgG autoantibody-positive sera from patients with autoimmune thrombocytopenia (AITP) significantly enhanced platelet phagocytosis (P < .001). In contrast, platelet phagocytosis did not occur if platelets were bound with only LPS. If, however, the LPS-bound platelets were also opsonized with either W6/32 or autoantibody-positive sera with titers greater than 4, there was a significant and synergistic increase in Fc-dependent platelet phagocytosis (P < .001, P = .003, P = .048, and P = .047). These results suggest that, in the presence of antiplatelet antibodies, bacterial products can significantly alter platelet phagocytosis, and this may have relevance to how Gram-negative infections enhance platelet destruction in some patients with AITP. CiteULike    Connotea    Del.icio.us    Digg    Reddit    Technorati    What's this? This article has been cited by other articles: M. Kjaersgaard, R. Aslam, M. Kim, E. R. Speck, J. Freedman, D. I. H. Stewart, E. J. Wiersma, and J. W. Semple Epitope specificity and isotype of monoclonal anti-D antibodies dictate their ability to inhibit phagocytosis of opsonized platelets Blood, August 15, 2007; 110(4): 1359 - 1361. [Abstract] [Full Text] [PDF]

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