The role of T-lymphocyte subpopulations in acute myocardial infarction

Predictive value of lymphocyte-to-C-reactive protein ratio for left ventricular thrombus in patients with ST-segment elevation myocardial infarction

Background and purpose

Current evidence suggested a correlation between inflammation and Left Ventricular Thrombus (LVT). The lymphocyte to C-reactive protein ratio (LCR) has been established as be a reliable inflammation marker and is associated with the prognosis of patients with ST-segment elevation myocardial infarction (STEMI). However, its relationship with the occurrence of LVT remains unclear. This study aims to evaluate the effectiveness of LCR in predicting LVT in patients with STEMI after undergoing primary percutaneous coronary intervention (pPCI).

Methods

A total of 564 STEMI patients who underwent pPCI at the Affiliated Hospital of Xuzhou Medical University from September 2019 to June 2024 were included. Cardiac magnetic resonance imaging (CMR) was used to assess myocardial infarction characteristics and the presence of LVT. The definition of LCR is the lymphocyte to C-reactive protein ratio.

Results

Out of 564 patients, 57 were diagnosed with LVT. The median time for CMR testing was 5 (4, 6) days. Univariate regression analysis showed significant differences in left ventricular ejection fraction (LVEF), peak N-terminal pro B-type natriuretic peptide (peak NT-proBNP), peak high-sensitivity troponin T (peak hsTnT), LCR, Late Gadolinium Enhancement% (LGE%), and Microvascular Obstruction% (MVO%) (p < 0.05). Multivariate regression analysis indicated that LCR was an independent predictor for LVT (P = 0.007, OR: 0.001 95% CI: 0.00-0.123). Receiver operating characteristic (ROC) curve analysis showed that LCR has good predictive ability for LVT (Area under the curve: 0.704, p < 0.001). Integration of integral LCR could significantly improve the discrimination and reclassification accuracy for LVT after STEMI (NRI = 0.517, IDI = 0.030; p < 0.001).

Conclusion

Lower LCR is independently associated with the risk of LVT in patients with STEMI after pPCI. Integration of LCR can significantly improve the risk model for LVT.

Evaluation of Hematological and Biochemical Parameters that Predict the No-reflow Phenomenon in Patients Undergoing Primary Percutaneous Coronary Intervention

Acute coronary syndromes (ACS) are one of the most common causes of morbidity and mortality worldwide. Primary percutaneous coronary intervention (pPCI) is the main treatment strategy to restore myocardial perfusion. However, the no-reflow phenomenon (NRP) may block coronary flow. The present study focused on assessing and contrasting predictive parameters for NRP in ACS patients. Our research is a retrospective analysis. We assessed the parameters significantly associated with NRP using Cox regression and Receiver operating characteristic (ROC) Curve analysis. The study included 5122 patients who met the criteria. The average age of the patients was 63.9 + 13.2, and 74.4% were male. It was observed that NRP developed in 1.8% of all patients. Age, hemoglobin (Hb), white blood cell (WBC), glucose and low density lipoprotein cholesterol (LDL-C) were determined to be independent predictors of NRP. The power of these parameters to predict NRP was similar, and WBC was the most predictive (Area Under Curve (AUC): 0.605 95% CI: 0.539-0.671, P = .001). We believe that the use of these simple, practical, and routinely used hematological and biochemical parameters will help us predict the risk of developing NRP before pPCI. This information should improve management.

Inflammation as the nexus: exploring the link between acute myocardial infarction and chronic obstructive pulmonary disease

Chronic obstructive pulmonary disease (COPD), particularly following acute exacerbations (AE-COPD), significantly heightens the risks and mortality associated with acute myocardial infarction (AMI). The intersection of COPD and AMI is characterised by a considerable overlap in inflammatory mechanisms, which play a crucial role in the development of both conditions. Although extensive research has been conducted on individual inflammatory pathways in AMI and COPD, the understanding of thrombo-inflammatory crosstalk in comorbid settings remains limited. The effectiveness of various inflammatory components in reducing AMI infarct size or slowing COPD progression has shown promise, yet their efficacy in the context of comorbidity with COPD and AMI is not established. This review focuses on the critical importance of both local and systemic inflammation, highlighting it as a key pathophysiological connection between AMI and COPD/AE-COPD.

HMGB1-Mediated Activation of the Inflammatory-Reparative Response Following Myocardial Infarction

Different cell types belonging to the innate and adaptive immune system play mutually non-exclusive roles during the different phases of the inflammatory-reparative response that occurs following myocardial infarction. A timely and finely regulation of their action is fundamental for the process to properly proceed. The high-mobility group box 1 (HMGB1), a highly conserved nuclear protein that in the extracellular space can act as a damage-associated molecular pattern (DAMP) involved in a large variety of different processes, such as inflammation, migration, invasion, proliferation, differentiation, and tissue regeneration, has recently emerged as a possible regulator of the activity of different immune cell types in the distinct phases of the inflammatory reparative process. Moreover, by activating endogenous stem cells, inducing endothelial cells, and by modulating cardiac fibroblast activity, HMGB1 could represent a master regulator of the inflammatory and reparative responses following MI. In this review, we will provide an overview of cellular effectors involved in these processes and how HMGB1 intervenes in regulating each of them. Moreover, we will summarize HMGB1 roles in regulating other cell types that are involved in the different phases of the inflammatory-reparative response, discussing how its redox status could affect its activity.

Correlation in gene expression between the aggravation of chronic obstructive pulmonary disease and the occurrence of complications

Aggravation of the chronic obstructive pulmonary disease (COPD) often leads to a slew of complications, but the correlation between COPD aggravation and the complications on the basis of molecular level remains unclear. In this study, gene expression profiles of COPD in patients at early and aggravation stages were collected and differentially-expressed genes were selected. Meanwhile, gene expression data implicated in COPD complications were analyzed to establish a regulatory network of COPD aggravation and COPD related complications. In addition, the gene enrichment function of DAVID6.7 was utilized to evaluate the similarities between COPD aggravation and COPD complications in term of biological process. By analyzing the genes of COPD aggravation and the COPD complications, we found 18 genes highly related to COPD aggravation, among which haptoglobin (HP) was correlated with 14 complications, followed by ADRB2, LCK and CA1, which were related to 13, 11 and 11 complications, respectively. As far as the complications concerned, obesity was regulated by 17 of the 18 genes, which indicated that there was a close correlation between COPD aggravation and obesity. Meanwhile, lung cancer, diabetes and heart failure were regulated by 15, 15 and 14 genes, respectively, among the 18 selected genes. This study suggested the driver genes of COPD aggravation were capable of extensively regulating COPD complications, which would provide a theoretical basis for development of cures for COPD and its complications.

The combination of neutrophil-to-lymphocyte ratio and platelet correlation parameters in predicting the no-reflow phenomenon after primary percutaneous coronary intervention in patients with ST-segment elevation myocardial infarction

OBJECTIVE

To evaluate the predictive value of the neutrophil-to-lymphocyte ratio (NLR), mean platelet volume (MPV), and platelet distribution width (PDW) for the no-reflow phenomenon in patients with ST-segment elevation myocardial infarction. Methods: Patients who underwent primary percutaneous coronary intervention from January 2017 to April 2019 were consecutively enrolled in this study and were split into the control and no-reflow groups. Logistic regression analysis was used to determine the independent predictors. Receiver operating characteristic curves were carried out to evaluate the predictive value. Results: A total of 455 patients were included and the incidence of the no-reflow was 19.6%. After the adjustment of confounding factors, logistic regression analyses showed that the NLR (odds ratio [OR] per unit increase: 1.107, 95% confidence interval [CI]: 1.044-1.172, p = .001), MPV (OR: 1.398, 95% CI: 1.010-1.937, p = .044), and PDW (OR: 1.392, 95% CI: 1.012-1.914, p = .042) were all independent predictors. In the prediction of the no-reflow, the NLR had the largest area under the curve of 0.650 (95% CI: 0.593-0.708) with 90% sensitivity and 36% specificity. The area under the curve of the combination of NLR + MPV was 0.676 and that of NLR + PDW was 0.654. Conclusions: The NLR, MPV and PDW are all associated with the no-reflow. However, there is no significant difference in the predictive value of these indicators. The combinations of NLR and platelet-associated parameters also do not show a better predictive value than NLR alone.

Inflammatory cells and their non-coding RNAs as targets for treating myocardial infarction

Myocardial infarction triggers infiltration of several types of immune cells that coordinate both innate and adaptive immune responses. These play a dual role in post-infarction cardiac remodeling by initiating and resolving inflammatory processes, which needs to occur in a timely and well-orchestrated way to ensure a reestablishment of normalized cardiac functions. Thus, therapeutic modulation of immune responses might have benefits for infarct patients. While such strategies have shown great potential in treating cancer, applications in the post-infarction context have been disappointing. One challenge has been the complexity and plasticity of immune cells and their functions in cardiac regulation and healing. The types appear in patterns that are temporally and spatially distinct, while influencing each other and the surrounding tissue. A comprehensive understanding of the immune cell repertoire and their regulatory functions following infarction is sorely needed. Processes of cardiac remodeling trigger additional genetic changes that may also play critical roles in the aftermath of cardiovascular disease. Some of these changes involve non-coding RNAs that play crucial roles in the regulation of immune cells and may, therefore, be of therapeutic interest. This review summarizes what is currently known about the functions of immune cells and non-coding RNAs during post-infarction wound healing. We address some of the challenges that remain and describe novel therapeutic approaches under development that are based on regulating immune responses through non-coding RNAs in the aftermath of the disease.

(Re) Solving Repair After Myocardial Infarction

Cardiovascular diseases, including myocardial infarction and its complications such as heart failure, are the leading cause of death worldwide. To date, basic and translational research becomes necessary to unravel the mechanisms of cardiac repair post-myocardial infarction. The local inflammatory tissue response after acute myocardial infarction determines the subsequent healing process. The diversity of leukocytes such as neutrophils, macrophages and lymphocytes contribute to the clearance of dead cells while activating reparative pathways necessary for myocardial healing. Cardiomyocyte death triggers wall thinning, ventricular dilatation, and fibrosis that can cause left ventricular dysfunction and heart failure. The ultimate goal of cardiac repair is to regenerate functionally viable myocardium after myocardial infarction to prevent cardiac death. Current therapies for heart failure after myocardial infarction are limited and non-curative. At the moment in clinic, conventional surgical interventions such as coronary artery bypass graft or percutaneous coronary interventions are only able to partially restore heart function, with a minor improvement in the left ventricular ejection fraction. The goal of this review is to provide an overview of endogenous myocardial repair mechanisms possibly transferable to future treatment strategies. Among the innovative factors identified as essential in cardiac healing, we highlight specialized pro-resolving mediators as the emerging factors that provide the key molecular signals for the activation of the reparative cells in the myocardium.

Leukocyte diversity in resolving and nonresolving mechanisms of cardiac remodeling

In response to myocardial infarction (MI), time-dependent leukocyte infiltration is critical to program the acute inflammatory response. Post-MI leukocyte density, residence time in the infarcted area, and exit from the infarcted injury predict resolving or nonresolving inflammation. Overactive or unresolved inflammation is the primary determinant in heart failure pathology post-MI. Here, our review describes supporting evidence that the acute inflammatory response also guides the generation of healing and regenerative mediators after cardiac damage. Time-dependent leukocyte density and diversity and the magnitude of myocardial injury is responsible for the resolving and nonresolving pathway in myocardial healing. Post MI, the diversity of leukocytes, such as neutrophils, macrophages, and lymphocytes, has been explored that regulate the clearance of deceased cardiomyocytes by using the classic and reparative pathways. Among the innovative factors and intermediates that have been recognized as essential in acute the self-healing and clearance mechanism, we highlight specialized proresolving mediators as the emerging factor for post-MI reparative mechanisms-translational leukocyte modifiers, such as aging, the source of leukocytes, and the milieu around the leukocytes. In the clinical setting, it is possible that leukocyte diversity is more prominent as a result of risk factors, such as obesity, diabetes, and hypertension. Pharmacologic agents are critical modifiers of leukocyte diversity in healing mechanisms that may impair or stimulate the clearance mechanism. Future research is needed, with a focused approach to understand the molecular targets, cellular effectors, and receptors. A clear understanding of resolving and nonresolving inflammation in myocardial healing will help to develop novel targets with major emphasis on the resolution of inflammation in heart failure pathology.-Tourki, B., Halade, G. Leukocyte diversity in resolving and nonresolving mechanisms of cardiac remodeling.

Systemic inflammatory response following acute myocardial infarction

Acute cardiomyocyte necrosis in the infarcted heart generates damage-associated molecular patterns, activating complement and toll-like receptor/interleukin-1 signaling, and triggering an intense inflammatory response. Inflammasomes also recognize danger signals and mediate sterile inflammatory response following acute myocardial infarction (AMI). Inflammatory response serves to repair the heart, but excessive inflammation leads to adverse left ventricular remodeling and heart failure. In addition to local inflammation, profound systemic inflammation response has been documented in patients with AMI, which includes elevation of circulating inflammatory cytokines, chemokines and cell adhesion molecules, and activation of peripheral leukocytes and platelets. The excessive inflammatory response could be caused by a deregulated immune system. AMI is also associated with bone marrow activation and spleen monocytopoiesis, which sustains a continuous supply of monocytes at the site of inflammation. Accumulating evidence has shown that systemic inflammation aggravates atherosclerosis and markers for systemic inflammation are predictors of adverse clinical outcomes (such as death, recurrent myocardial infarction, and heart failure) in patients with AMI.

Differentiating ischemic from non-ischemic chest pain using white blood cell-surface inflammatory and coagulation markers

Chest pain is one of the most common complaints seen in emergency departments (ED), up to 5-8 % of all ED visits. About 50-60 % of chest pain patients presenting to the ED are hospitalized. Seventy percentage of those patients not discharged from the ED are subsequently shown to not have acute cardiac disease. It has been estimated that emergency physician miss 2-6 % of acute coronary syndrome (ACS) that present to ED. While admitting a non-ACS patient is a financial burden on the medical system, releasing to home an undiagnosed ACS patient has life-threatening consequences. This study used flow cytometry to evaluate a panel of mononuclear cells, neutrophils, cytokines and fibrinolytic activation markers in patients presenting in ED with acute chest pain. The goal was to add diagnostic tools to the differentiation between true ischemic cardiac and non-ischemic chest pain in the process of triage. The study population consisted of 74 consecutive patients presenting with acute chest pain to the emergency department of Ziv Medical Center and were admitted to Intensive Cardiac Care Unit or Internal Wards of our hospital during the period September 2009 to February 2010. ACS has been clearly associated with a decrease in CD89+/CD62L+ population, an increase in percentage of cytotoxic T-cell subset, and an increase in platelet marker. Differences in thrombin receptor surface expression were also noted. The combination of multiple biomarkers may help to enhance diagnostic accuracy.

Lower prevalence of circulating invariant natural killer T (iNKT) cells in patients with acute myocardial infarction undergoing primary coronary stenting

Invariant natural killer T cells are a unique lymphocyte subtype that can recognize lipid antigens presented by CD1d and release pro-atherogenic cytokines such as interferon-gamma. We studied the importance of iNKT cells, other lymphocyte cell types and CD11b in the peripheral blood of patients diagnosed with acute myocardial infarction (AMI) before and after primary coronary stenting. Lymphocyte population profiles and CD11b were compared between patients with AMI and healthy control subjects using flow cytometry. Both the absolute number and cell fractions of iNKT, CD3+CD4+ lymphocytes were significant lower in AMI patients than health controls. The cell fraction of NK cells was also reduced, while there was a significant increase in the cell fractions and absolute numbers of CD3+CD8+ lymphocytes, B lymphocytes and mean fluorescence intensity values of labeled CD11b. The number of iNKT cells was significantly and positively correlated with cholesterol and low-density lipoprotein levels in blood samples from AMI patients before primary coronary stenting. Logistic regression analysis demonstrated that the absolute number of iNKT cells was a significant independent predictor for restenosis during the 243 day post-operative follow-up. This study demonstrates that iNKT cell number may be a useful predictor of clinical outcome in AMI patients with primary coronary stenting.

Immune responses after acute ischemic stroke or myocardial infarction

BACKGROUND

We recently demonstrated an immediate immunodepressive state after acute ischemic stroke in humans.

METHODS

In the present study, we prospectively analyzed immune responses in patients with middle cerebral artery stroke (n=20), acute myocardial infarction (n=20) and healthy controls (n=20, also matched for age and gender).

RESULTS

Compared to controls, a rapid depression of monocytic HLA-DR expression and a defective lymphocytic IFN-γ production was obvious after ischemic stroke or myocardial infarction, while total counts of leukocytes and monocytes were significantly higher after myocardial infarction. A T cell-mediated lymphopenia was accentuated in patients with severe stroke, obviously predisposing these patients for nosocomial infections.

CONCLUSIONS

Our data reveal an immediate and to some extent differential suppression of cell-mediated immune responses after ischemic stroke or myocardial infarction respectively.

Post-reperfusion lymphopenia and microvascular obstruction in ST-segment elevation acute myocardial infarction

INTRODUCTION AND OBJECTIVES

The presence of microvascular obstruction after ST-segment elevation acute myocardial infarction is associated with a poor outcome. The pathophysiology of this process has not been fully defined. The aim of this study was to investigate the relationship between post-reperfusion lymphopenia and microvascular obstruction.

METHODS

This prospective study involved 212 patients with a first ST-segment elevation acute myocardial infarction who underwent reperfusion with thrombolytic agents or primary angioplasty and who had an open infarct-related artery. Serial measurements of lymphocyte, neutrophil and monocyte counts were taken. Cardiac magnetic resonance was used to detect microvascular obstruction during the first week after the infarction. Imaging was repeated 6 months after infarction.

RESULTS

Microvascular obstruction was observed in 67 patients (32%). A post-reperfusion lymphocyte count <1800 cells/ml was associated with a higher risk of microvascular obstruction (44% versus 20%; P< .001) as well as with a low left ventricular ejection fraction and large left ventricular volumes (P< .05). After adjustment for baseline characteristics, ECG findings, necrosis marker levels and angiographic variables, multivariate analysis showed that a post-reperfusion lymphocyte count <1800 cells/ml was independently associated with an increased risk of microvascular obstruction (odds ratio=3.2; 95% confidence interval 1.6-6.3; P< .001).

CONCLUSIONS

In ST-segment elevation myocardial infarction, post-reperfusion lymphopenia is an early and powerful predictor of the presence of microvascular obstruction. The pathophysiological and therapeutic implications of this association require further study.

Downregulation of T helper cell type 3 in patients with acute coronary syndrome

BACKGROUND AND AIMS

There is an imbalance between Th1 and Th2 in the development and progression of atherosclerosis and in patients with acute coronary syndrome (ACS) including acute myocardial infarction (AMI) and unstable angina. T helper cell type 3 (Th3), which primarily secretes transforming growth factor beta-1 (TGF-beta1), has been shown to inhibit both Th1 and Th2 cells. The present study was designed to investigate whether Th3 cells are involved in plaque destabilization and the onset of ACS.

METHODS

Ninety one patients who underwent diagnostic catheterization were classified into four groups (AMI group, unstable angina group, stable angina group and chest pain syndrome group). The cell frequencies of Th1, Th2 and Th3 were detected using flow cytometry, and the concentrations of their related cytokines IFN-gamma, IL-4 and TGF-beta1 were studied by ELISA.

RESULTS

Apart from the imbalance between Th1 and Th2, results revealed a significant decrease in peripheral Th3 number and levels of TGF-beta1 in patients with ACS as compared with those in patients with stable angina and chest pain syndrome (p<0.01).

CONCLUSIONS

Downregulation of Th3 cells in patients with ACS may play a potential role in plaque destabilization and the onset of ACS.

Human cord blood mononuclear cells decrease cytokines and inflammatory cells in acute myocardial infarction

We investigated whether human umbilical cord blood mononuclear cells (HUCBC), which contain hematopoietic and mesenchymal progenitor cells, can limit myocardial cytokine expression and inflammatory cell infiltration in acute myocardial infarction. We permanently ligated the left coronary artery of rats and injected into the myocardium either Isolyte or 4 x 10(6) HUCBC in Isolyte and measured myocardial cytokines with antibody arrays at 2, 6, 12, 24, and 72 hours after infarction. We then measured with flow cytometry myocardial macrophages, neutrophils and lymphocytes at 12, 24, and 72 hours after infarctions in rats treated with either intramyocardial Isolyte or 4 x 10(6) HUCBC. In the Isolyte-treated hearts, between 2 and 12 hours after myocardial infarction, tumor necrosis factor-alpha increased from 6.7 +/- 0.9% to 52.3 +/- 4.7%, monocyte chemoattract protein increased from 9.5 +/- 1.2% to 39.8 +/- 2.1%, fractalkine increased from 11 +/- 1.5% to 28.1 +/- 1.3%, ciliary neurotrophic factor increased from 12.1 +/- 0.02% to 25.9 +/- 1.1%, macrophage inflammatory protein increased from 10.3 +/- 1.5% to 23.9.0 +/- 1.4%, interferon-gamma increased from 8.7 +/- 0.4% to 26.0 +/- 1.6%, interleukin-1beta increased from 6.1 +/- 0.04% to 19.0 +/- 1.2%, and IL-4 increased from 5.9 +/- 0.03% to 15 +/- 1.5% (all p < 0.001 compared with controls). The concentrations of fractalkine remained significantly increased at 72 hours after acute infarction. In contrast, the myocardial concentrations of these cytokines did not significantly change in HUCBC treated hearts at 2, 6, 12, 24, or 72 hours after infarction. The percentage of neutrophils increased from 0.04 +/- 0.2%/50,000 heart cells in the controls to 5.3 +/- 1.2%/50,000 heart cells 12 hours after infarction in Isolyte-treated hearts but averaged only 1.3 +/- 0.7%/50,000 heart cells in HUCBC treated hearts (p < 0.02). Thereafter, the percentages of neutrophils rapidly decreased at 24 and at 72 hours after infarction and averaged 0.6 +/- 0.2%/50,000 heart cells at 72 hours after infarction in Isolyte-treated hearts in contrast to 0.2 +/- 0.1%/50,000 cells in HUCBC hearts (p < 0.05). Moreover, the percentages of neutrophils at 24 and 72 hours in HUCBC hearts were not significantly different from controls. At 24 hours post infarction, the percentage of CD3 and CD4 lymphocytes were 10.7 +/- 1.4% and 6.3 +/- 1.1%/50,000 cells in Isolyte hearts in comparison with only 4.9 +/- 0.8% and 2.9 +/- 0.5% in HUCBC hearts (p < 0.005 for Isolyte versus HUCBC). The percentage of CD11b macrophages was 2.8 +/- 0.3% in Isolyte hearts and 1.9 +/- 0.2% in HUCBC treated hearts (p < 0.05). At 72 hours after infarction, the percentage of CD3 and CD4 lymphocytes averaged 8.0 +/- 1.1% and 5.1 +/- 0.8%/50,000 heart cells in Isolyte hearts in comparison with only 4.1 +/- 0.5% and 2.3 +/- 0.4%/50,000 heart cells in the HUCBC treated infarctions (p < 0.005). Left ventricular infarct sizes in Isolyte-treated hearts at 72 hours post infarction averaged 15.7 +/- 1.4% of the left ventricular muscle area in contrast to HUCBC treated infarctions that averaged 6.9 +/- 1.4% of the left ventricular muscle area (p < 0.02). Moreover in rats followed for 2 months post infarction, the LV ejection fractions decreased to 65.4 +/- 1.9% and 69.1 +/- 1.9% at 1 and 2 months after infarction in Isolyte-treated hearts and were significantly different from HUCBC treated hearts that averaged 72.1 +/- 1.3% and 75.7 +/- 1.4% (both p < 0.02). The present experiments suggest that an important mechanism whereby HUCBC limit infarct size and improve left ventricular ejection fraction is by significantly limiting inflammatory cytokines and inflammatory cells in infarcted myocardium.

Uncontrolled immune response in acute myocardial infarction: unraveling the thread

Recently, the theory that hyperinflammation is the body's primary response to potent stimulus has been challenged. Indeed, a deregulation of the immune system could be the cause of multiple organ failure. So far, clinicians have focused on the last steps of the inflammatory cascade. However, little attention has been paid to lymphocytes, which play an important role as strategists of the inflammatory response. Experimental evidence suggests a crucial role of T lymphocytes in the pathophysiology of atherosclerosis and acute myocardial infarction (AMI). In summary, from the bottom of an imaginary inverted pyramid, a few regulatory T-cells control the upper parts represented by the wide spectrum of the inflammatory cascade. In AMI, a loss of regulation of the inflammatory system occurs in patients with a decreased activity of regulatory T-cells. As a consequence, aggressive T-cells boost and anti-inflammatory T-cells drop. A pleiotropic proinflammatory imbalance with damaging effects in terms of left ventricular performance and patient outcome is the result of this uncontrolled immune response. It is needed to unravel the thread of the inflammatory cells to better understand the pathophysiology as well as to open innovative therapeutic options in AMI.

T Cell Recognition and Killing of Vascular Smooth Muscle Cells in Acute Coronary Syndrome

Loss of vascular smooth muscle cells (VSMCs) has been proposed to destabilize the atherosclerotic plaque and contribute to plaque rupture, superimposed thrombosis, and acute coronary syndromes (ACSs). We examined whether VSMCs are susceptible to T cell-induced apoptosis and found that CD4 T cells are highly effective in establishing cell-cell contact with VSMCs and triggering apoptotic death. Visualization of the T cell-VSMC contact zone on the single-cell level revealed that both patient-derived and control CD4 T cells reorganized their cell membrane to assemble an immunologic synapse with the VSMCs. Within 4 to 10 minutes, the membrane proximal signaling molecule ZAP-70 was recruited and phosphorylated. However, only patient-derived CD4 T cells sustained an intact immunologic synapse beyond 10 minutes and generated intracellular calcium signals. CD4 T cells that maintained a synaptic contact and appeared to be responsible for VSMC apoptosis accounted for approximately 20% of the circulating memory T cell population in ACS patients and were rare in the blood of age-matched controls. CD4 T cells from ACS patients were also hyperresponsive to T cell receptor-mediated stimulation when triggered by a superantigen and non-VSMC target cells. Lowered setting of the T cell activation threshold, attributable to excessive amplification of proximal CD3-mediated signals, may contribute to CD4 T cell-mediated killing of VSMCs and promote plaque instability.