Summary Background Increasing evidence implicates both platelets and neutrophils in the formation, stabilization, and growth of peripheral and coronary thrombi. Neutrophil extracellular traps (NETs) play a key role. The early events in the deregulated cross‐talk between platelets and neutrophils are poorly characterized. Objectives To identify at the molecular level the mechanism through which platelets induce the generation of NETs in sterile conditions. Patients/Methods The presence of NETs was determined in 26 thrombi from patients with acute myocardial infarction by immunohistochemistry and immunofluorescence and markers of NETs assessed in the plasma. In vitro NET generation was studied in static and in physiological flow conditions. Results Coronary thrombi mainly consist of activated platelets, neutrophils, and NETs in close proximity of platelets. Activated platelets commit neutrophils to NET generation. The event abates in the presence of competitive antagonists of the high mobility group box 1 (HMGB1) protein. Hmgb1−/− platelets fail to elicit NETs, whereas the HMGB1 alone commits neutrophils to NET generation. Integrity of the HMGB1 receptor, Receptor for Advanced Glycation End products (RAGE), is required for NET formation, as assessed using pharmacologic and genetic tools. Exposure to HMGB1 prevents depletion of mitochondrial potential, induces autophagosome formation, and prolongs neutrophil survival. These metabolic effects are caused by the activation of autophagy. Blockade of the autophagic flux reverts platelet HMGB1‐elicited NET generation. Conclusions Activated platelets present HMGB1 to neutrophils and commit them to autophagy and NET generation. This chain of events may be responsible for some types of thromboinflammatory lesions and indicates novel paths for molecular intervention.

Objective-Regulatory T (Treg) cells play a protective role in experimental atherosclerosis. In the present study, we investigated whether the levels of circulating Treg cells relate to the degree of atherosclerosis in carotid and coronary arteries. Methods and Results-We studied 2 distinct populations: (1) 113 subjects, selected from a free-living population (carotid study), in which we measured the intima-media thickness of the common carotid artery, as a surrogate marker of initial atherosclerosis; and (2) 75 controls and 125 patients with coronary artery disease (coronary study): 36 with chronic stable angina, 50 with non-ST-elevation acute coronary syndrome, 39 with ST-elevation acute myocardial infarction. Treg-cell levels were evaluated by flow cytometry (Treg cells identified as CD3 ϩ CD4 ϩ CD25 high CD127 low ) and by mRNA expression of forkhead box P3 or of Treg-associated cytokine interleukin 10. In the carotid study, no correlation was observed between Treg-cell levels and intima-media thickness. No differences in Treg-cell levels were observed comparing rapid versus slow intima-media thickness progressors from a subgroup of patients (nϭ65), in which prospective data on 6-year intima-media thickness progression were available. In the coronary group, Treg-cell levels were not altered in chronic stable angina patients. In contrast, nonunivocal variations were observed in patients suffering an acute coronary syndrome (with a Treg-cell increase in ST-elevation acute myocardial infarction and a Treg-cell decrease in non-ST-elevation acute coronary syndrome patients). Key Words: regulatory T cells Ⅲ coronary artery disease Ⅲ flow cytometry Ⅲ carotid artery intima-media thickness Ⅲ acute coronary syndrome T cells play a role in atherosclerosis and in acute manifestation of plaque destabilization. 1 The activation of inflammatory pathways in atherosclerosis and in coronary artery disease (CAD) is not confined to coronary lesions but involves the activation of neutrophils, monocytes, and lymphocytes (ie, CD69 Conclusion-Theϩ , HLA-DR ϩ , and CD 137 ϩ T cells) in peripheral blood in particular during acute coronary syndromes (ACSs). [2][3][4] On the other hand, regulatory T (Treg) cells reduce the development of experimental atherosclerosis acting both systemically and within the lesion. 5,6 Immunostaining of human atherosclerotic plaques showed that Treg cells are present during all stages of plaque development in the intima and adventitia. 7 In general, Treg cells play a key role in the maintenance of immunologic self-tolerance and negative control of a variety of pathological immune responses. 8 Several subsets of Treg cells with distinct phenotypes and distinct mechanisms of action have been described (see Sakaguchi et al,8 Roncarolo et al, 9 and O'Garra and Vieira 10 for review). Treg cells mediate the immunoregulatory function by producing cytokines, such as interleukin (IL)-10 and See accompanying article on page 1679 ϩ Treg cells, which have increased ability of homing and trafficking to inflamed nonly...

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