Rationale:Patients with acute coronary syndrome (ACS) predisposed to recurrent coronary events have an expansion of a distinctive T-cell subset, the CD4 ؉ CD28 null T cells. These cells are highly inflammatory and cytotoxic in spite of lacking the costimulatory receptor CD28, which is crucial for optimal T cell function. The mechanisms that govern CD4 ؉ CD28null T cell function are unknown.Objective: Our aim was to investigate the expression and role of alternative costimulatory receptors in CD4 ؉ CD28 null T cells in ACS. Methods and Results: Expression of alternative costimulatory receptors (inducible costimulator, OX40, 4 -1BB,cytotoxic T lymphocyte associated antigen-4, programmed death-1) was quantified in CD4 ؉ CD28 null T cells from circulation of ACS and stable angina patients. Strikingly, in ACS, levels of OX40 and 4-1BB were significantly higher in circulating CD4 ؉ CD28null T cells compared to classical CD4 ؉ CD28 ؉ T lymphocytes. This was not observed in stable angina patients. Furthermore, CD4؉ CD28 null T cells constituted an important proportion of CD4 ؉ T lymphocytes in human atherosclerotic plaques and exhibited high levels of OX40 and 4-1BB. In addition, the ligands for OX40 and 4-1BB were present in plaques and also expressed on monocytes in circulation. Importantly, blockade of OX40 and 4-1BB reduced the ability of CD4 ؉ CD28null T cells to produce interferon-␥ and tumor necrosis factor-␣ and release perforin. Key Words: atherosclerosis Ⅲ coronary disease Ⅲ immune system Ⅲ lymphocytes Ⅲ receptors C oronary artery disease continues to be the leading cause of death in the developed world. Recent research has demonstrated that coronary artery disease results from an uncontrolled immune response and T lymphocytes have a central role in the development and progression of the disease. 1,2 Detailed analysis of CD4 ϩ T cells in coronary artery disease unveiled an increased frequency of a distinctive subset of lymphocytes called CD4 ϩ CD28 Conclusions: Costimulatory pathways are altered in CD4؉null T cells. 3 These cells are characterized by the lack of CD28, the main costimulatory receptor that regulates the response of T lymphocytes to antigen. 4 The CD4 ϩ CD28null T cell subset is present in low frequencies in healthy individuals and has also been shown to increase in patients with chronic inflammatory diseases such as autoimmunity. 5 In coronary artery disease, the frequency of CD4 The proinflammatory features of CD4 ϩ CD28 null T lymphocytes are surprising, as the activation and survival of T cells depends on costimulatory signals delivered via the CD28 receptor. 4 The activation of T cells requires not only the recognition of antigen, but also a second signal delivered by the interaction of the CD28 costimulatory receptor on T cells with its ligands on antigen presenting cells. 4 CD28 signaling controls the expression of interleukin-2 receptors and the production of interleukin-2 by activated T cells, which enable their proliferation, differentiation into effectors and survival. 12 Indeed, in th...

709M yocardial infarction and stroke caused by atherosclerosis are the most frequent cardiovascular causes of death and disability in the world despite the progress in prevention and therapy.1 Recent evidence clearly implicates the innate and adaptive immune system in the pathogenesis of atherosclerosis.2 T lymphocytes, the main orchestrators of adaptive immune responses, have pivotal roles in atherosclerosis. In particular, proinflammatory CD4+ T lymphocytes such as T helper 1 cells have been shown to promote atherosclerosis in animal models and constitute the predominant T cells in human atherosclerotic plaques. [3][4][5] We and others have demonstrated that CD4 + CD28null T cells, a unique subset of T helper 1 lymphocytes characterized by the lack of costimulatory receptor CD28, are present in high numbers in the circulation and atherosclerotic plaques of patients with acute coronary syndrome (ACS), 6-8 but these cells are not present in healthy individuals. Moreover, CD4 + CD28null T cells (from now on abbreviated as CD28 null T cells) produce higher levels of inflammatory cytokines interferon-γ and tumor necrosis factor-α than conventional CD4 + CD28+ (CD28 + ) T cells. 6,9 In stark contrast to CD28 + T lymphocytes, CD28 null T cells release cytotoxic molecules (ie, perforin and granzymes) 6 that are instrumental in killing endothelial and vascular smooth muscle cells in vitro. 10 These properties suggest that CD28 null T cells have harmful effects in atherosclerosis, although a direct causal link is yet to be established, because this subset of T cells is present only in humans with an equivalent population absent in mice. Recently, we were the first to show that the distinguishing feature between CD28 null and conventional CD28 + T cells in ACS patients is a significantly higher expression on CD28 null T cells of alternative costimulatory receptors . We further demonstrated that 4-1BB and OX40 have critical roles in regulating the production of inflammatory cytokines interferon-γ and tumor necrosis factor-α and perforin release from CD28 null T cells in ACS. 6 In addition to their roles in T-cell costimulation, 4-1BB and OX40 are important for the survival of T cells. 11,12 As mentioned, ACS patients are known to harbor significantly higher numbers of CD28 null T cells in comparison with patients who have stable angina (SA) and healthy subjects. 8,13 Importantly, Background-The number of CD4 + CD28 null (CD28 null ) T cells, a unique subset of T lymphocytes with proinflammatory and cell-lytic phenotype, increases markedly in patients with acute coronary syndrome (ACS). ACS patients harboring high numbers of CD28 null T cells have increased risk of recurrent severe acute coronary events and unfavorable prognosis. The mechanisms that govern the increase in CD28 null T cells in ACS remain elusive. We investigated whether apoptosis pathways regulating T-cell homeostasis are perturbed in CD28 null T cells in ACS. Methods and Results-We found that CD28null T cells in ACS were resistant to apoptosis induction...

Human red blood cells are emerging as a cell type capable to regulate biological processes of neighboring cells. Hereby, we show that human red blood cell conditioned media contains bioactive factors that favor proliferation of normal activated T cells and leukemic Jurkat T cells, and therefore called erythrocyte-derived growth and survival factors. Flow cytometry and electron microscopy in parallel with bioactivity assays revealed that the erythrocyte factors are present in the vesicle-free supernatant, which contains up to 20 different proteins. The erythrocyte factors are thermosensitive and do not contain lipids. Native polyacrylamide gel electrophoresis followed by passive elution and mass spectrometry identification reduced the potential erythrocyte factors to hemoglobin and peroxiredoxin II. Two-dimensional differential gel electrophoresis of the erythrocyte factors revealed the presence of multiple hemoglobin oxy-deoxy states and peroxiredoxin II isoforms differing in their isoelectric point akin to the presence of b-globin chains. Our results show that red blood cells release protein factors with the capacity to sustain T-cell growth and survival. These factors may have an unforeseen role in sustaining malignant cell growth and survival in vivo.

Red blood cells (RBC) have emerged as a novel regulatory cell type endowed with bioactivities toward activated human T cells. Herein we show that the RBC bioactivities act on intracellular pathways initiated by T cell receptor (TCR)-dependent and -independent stimuli,including IL-2, IL-15, and the mixture of phorbol dibutyrate and ionomycin. The RBC bioactivities preserve the antioxidant status and are capable of rescuing activated T cells from cell death induced by serum deprivation. They are not mediated by glycosylphosphatidylinositol-linked receptors or sialic acids, and kinetic studies revealed that they hasten the entrance into the cell cycle. By using cyclosporine A (CsA) and rapamycin (Rapa) we show that the RBC bioactivities are calcineurin-dependent. Thus, treatment of T cells with CsA, but not Rapa, impaired RBC bioactivities, and preincubation of RBC with CsA completely abolished their bioactivities. We have demonstrated that RBC carry out bioactivities that are sensitive to CsA.

Atherosclerosis is a chronic inflammatory disease that is mediated by both the innate and adaptive immune responses. T lymphocytes, that together with B cells are the cellular effectors of the adaptive immune system, are currently endowed with crucial roles in the development and progression of atherosclerosis. Costimulatory receptors are a class of molecules expressed by T lymphocytes that regulate the activation of T cells and the generation of effector T-cell responses. In this review we present the roles of costimulatory receptors of the tumour necrosis factor receptor (TNFR) superfamily in atherosclerosis and discuss the implications for future therapies that could be used to specifically modulate the immune response of pathogenic T cells in this disease.