title: Evidence of Toll-like receptor molecules on human platelets.
abstract: Platelets are primarily involved in thrombosis and haemostasis, and they have recently been shown to have a role in innate immunity and in inflammation. We have determined the markers of innate immunity that are expressed by platelets, specifically the Toll-like receptors (TLR), originating from mixes of platelet concentrates (MPC, n = 5) between day zero and day five after blood collection. The surface membrane and intracellular expression of TLR were measured, both after and without permeabilization, using flow cytometry. We observed weak expression of TLR2, TLR4 and TLR9 on the surface of CD41(+) platelets. The expression levels of TLR4 were high (59 +/- 2.2%). Moreover, there was a significant expression of TLR2 (47.5 +/- 4.8%), TLR4 (78.8 +/- 1.3%) and TLR9 (34.2 +/- 7.5%) in the cytoplasm of CD41(+) platelets. The expression of the three receptors did not change significantly during the course of the 5 day observation period. The percentage of TLR expression is significantly modulated between activated versus non-activated platelets, both after and without permeabilization (P < 0.01). Study of the expression of TLR could increase our knowledge of the level of platelet participation during an immune reaction and inflammation. In the same way as the platelet ligand/receptor pair CD40L/CD40 is, the TLR are expressed by platelets, and could serve as a link between innate and adaptive immunity.
authors.affiliation: The Auvergne-Loire Regional Blood Bank (EFS), Auvergne-Loire, France.
authors.forename: Fabrice
authors.initials: F
authors.lastname: Cognasse
authors.forename: Hind
authors.initials: H
authors.lastname: Hamzeh
authors.forename: Patricia
authors.initials: P
authors.lastname: Chavarin
authors.forename: Sophie
authors.initials: S
authors.lastname: Acquart
authors.forename: Christian
authors.initials: C
authors.lastname: Genin
authors.forename: Olivier
authors.initials: O
authors.lastname: Garraud
mesh_terms: D001792:Blood Platelets / Q000378:metabolism*; D006801:Humans; D008562:Membrane Glycoproteins / Q000378:metabolism*; D010539:Permeability; D040201:Platelet Membrane Glycoprotein IIb / Q000378:metabolism; D011956:Receptors, Cell Surface / Q000378:metabolism*; D019087:Selectins / Q000378:metabolism; D051195:Toll-Like Receptor 2; D051197:Toll-Like Receptor 4; D051217:Toll-Like Receptor 9; D051193:Toll-Like Receptors
chemical_list: D008562:Membrane Glycoproteins; D040201:Platelet Membrane Glycoprotein IIb; D011956:Receptors, Cell Surface; D019087:Selectins; C495342:TLR2 protein, human; C495345:TLR4 protein, human; C495371:TLR9 protein, human; D051195:Toll-Like Receptor 2; D051197:Toll-Like Receptor 4; D051217:Toll-Like Receptor 9; D051193:Toll-Like Receptors