Neutrophil accumulation on activated, surface-adherent platelets in flow is mediated by interaction of Mac-1 with fibrinogen bound to alphaIIbbeta3 and stimulated by platelet-activating factor.
We have studied the pathways that lead to arrest and firm adhesion of rolling PMN on activated, surface-adherent platelets. Stable arrest and adhesion strengthening of PMN on thrombin-stimulated, surface-adherent platelets in flow required distinct Ca2+- and Mg2+-dependent regions of Mac-1 (alphaMbeta2), and involved interactions of Mac-1 with fibrinogen, which was bound to platelets via alphaIIbbeta3. Mac-1 also bound to other unidentified ligands on platelets, which were not intracellular adhesion molecule-2 (ICAM-2), heparin, or heparan-sulfate proteoglycans. This was shown by inhibition with mAbs or peptides, by treatment of platelets with heparitinase, and by using platelets with defective alphaIIbbeta3 from a patient with Glanzmann thrombasthenia. Tethering of PMN on platelet ICAM-2 via LFA-1 (alphaLbeta2) was observed, which may facilitate the transition between rolling on selectins and Mac-1-dependent arrest. Arrest and adhesion strengthening was pertussis toxin sensitive and in flow was mainly induced by platelet-activating factor but not through activation of the chemokine receptor CXCR2. In stasis, spreading occurred and the CXCR2 contributed to firm adhesion.
Weber
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The Center for Blood Research and Department of Pathology, Harvard Medical School, Boston, Massachusetts 02115, USA.
Springer
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D015703:Antigens, CD / Q000378:metabolism; D001792:Blood Platelets / Q000502:physiology*; D002118:Calcium / Q000494:pharmacology; D002448:Cell Adhesion / Q000187:drug effects; D015815:Cell Adhesion Molecules / Q000378:metabolism; D005340:Fibrinogen / Q000378:metabolism*; D006801:Humans; D016023:Integrins / Q000378:metabolism*; D016169:Lymphocyte Function-Associated Antigen-1 / Q000378:metabolism; D016177:Macrophage-1 Antigen / Q000378:metabolism; D008274:Magnesium / Q000494:pharmacology; D009068:Movement; D009504:Neutrophils / Q000502:physiology*; D010972:Platelet Activating Factor / Q000378:metabolism*; D015539:Platelet Activation; D019039:Platelet Glycoprotein GPIIb-IIIa Complex / Q000235:genetics / Q000378:metabolism; D013915:Thrombasthenia / Q000378:metabolism
D015703:Antigens, CD; D015815:Cell Adhesion Molecules; C065289:ICAM2 protein, human; D016023:Integrins; D016169:Lymphocyte Function-Associated Antigen-1; D016177:Macrophage-1 Antigen; D010972:Platelet Activating Factor; D019039:Platelet Glycoprotein GPIIb-IIIa Complex; D005340:Fibrinogen; D008274:Magnesium; D002118:Calcium