血细胞的粘附分子

在机体内，血细胞间或血细胞与血管内皮间的相互作用主要由粘附分子介导来实现。粘附分子的作用广泛，涉及细胞的粘附、迁移、分化和信号传导等，它们维持血细胞的正常结构并协助血细胞发挥其各种生理功能。但是，粘附分子功能的异常或缺陷则会影响正常生理功能导致疾病发生。本文介绍了多种粘附分子，包括整合蛋白、选择蛋白、免疫球蛋白超家族等，并探讨了一些与粘附分子相关的病理生理过程，如炎症、止血、动脉粥样硬化、血栓形成和干细胞归巢等。因此了解血细胞粘附分子的结构与功能有助于人们深入认识疾病的发病机理，寻找疾病诊断和治疗的新的靶点。     

Bench-to-bedside review: Circulating microparticles - a new player in sepsis?

In sepsis, inflammation and thrombosis are both the cause and the result of interactions between circulating (for example, leukocytes and platelets), endothelial and smooth muscle cells. Microparticles are proinflammatory and procoagulant fragments originating from plasma membrane generated after cellular activation and released in body fluids. In the vessel, they constitute a pool of bioactive effectors pulled from diverse cellular origins and may act as intercellular messengers. Microparticles expose phosphatidylserine, a procoagulant phospholipid made accessible after membrane remodelling, and tissue factor, the initiator of blood coagulation at the endothelial and leukocyte surface. They constitute a secretion pathway for IL-1β and up-regulate the proinflammatory response of target cells. Microparticles circulate at low levels in healthy individuals, but undergo phenotypic and quantitative changes that could play a pathophysiological role in inflammatory diseases. Microparticles may participate in the pathogenesis of sepsis through multiple ways. They are able to regulate vascular tone and are potent vascular proinflammatory and procoagulant mediators. Microparticles' abilities are of increasing interest in deciphering the mechanisms underlying the multiple organ dysfunction of septic shock.     

Mycobacterium tuberculosis controls host innate immune activation through cyclopropane modification of a glycolipid effector molecule

Mycobacterium tuberculosis (Mtb) infection remains a global health crisis. Recent genetic evidence implicates specific cell envelope lipids in Mtb pathogenesis, but it is unclear whether these cell envelope compounds affect pathogenesis through a structural role in the cell wall or as pathogenesis effectors that interact directly with host cells. Here we show that cyclopropane modification of the Mtb cell envelope glycolipid trehalose dimycolate (TDM) is critical for Mtb growth during the first week of infection in mice. In addition, TDM modification by the cyclopropane synthase pcaA was both necessary and sufficient for proinflammatory activation of macrophages during early infection. Purified TDM isolated from a cyclopropane-deficient pcaA mutant was hypoinflammatory for macrophages and induced less severe granulomatous inflammation in mice, demonstrating that the fine structure of this glycolipid was critical to its proinflammatory activity. These results established the fine structure of lipids contained in the Mtb cell envelope as direct effectors of pathogenesis and identified temporal control of host immune activation through cyclopropane modification of TDM as a critical pathogenic strategy of Mtb.     

The effect of cytomegalovirus infection on the adherence of polymorphonuclear leucocytes to endothelial cells

Adherence of polymorphonuclear leucocytes (PMN) to the endothelial lining of blood vessels is an essential component of the inflammatory response. In this study the effect of cytomegalovirus (CMV) infection on the adherence of PMNs has been examined using an in vitro model system. Human umbilical venous endothelial cells (HUVEC) were grown on fibronectin-coated plastics. CMV infection of HUVEC resulted in the appearance of viral antigens in a small percentage of the cells. At 24 h post-infection when no virus-induced cytopathic effect could be observed in the cell monolayers, the adherence of PMNs was significantly increased. The virus-induced adherence effect was cell bound and could not be induced by soluble components in the medium of the virus-infected cells. The augmentation of the PMN adherence to CMV-infected endothelium was sensitive to tunicamycin suggesting that the virus infection induces the expression of glycoproteins on the HUVEC membranes which are responsible for the PMN adherence. Thus CMV infection of the endothelium results in an increased adherence of PMNs. In the in vivo situation systemic viral infection can potentially lead to infection of blood vessel endothelium and thus can induce a damage of endothelium. This phenomenon could play a role in the atherogenesis process.     

Correlation of the topographical arrangement and the functional pattern of tissue-infiltrating macrophages in giant cell arteritis.

End organ ischemia, fragmentation of elastic membranes, and aneurysm formation in patients with giant cell vasculitis results from an inflammation destroying the mural layers of large and medium sized arteries. Although the inflammatory infiltrate extends through all layers of the affected blood vessel, the most pronounced changes involve the intima and the internal elastic lamina. Analysis of the functional profile of tissue infiltrating CD68+ cells demonstrates that different subsets of macrophages can be distinguished. TGFbeta1-expressing CD68+ cells coproduce IL-1beta and IL-6, are negative for inducible nitric oxide synthase (iNOS), and exhibit a strong preference for localization in the adventitia. The adventitial homing of TGFbeta1+ CD68+ cells places them in the vicinity of IFN-gamma secreting CD4+ T cells which also accumulate in the exterior layer of the artery. Conversely, iNOS expressing CD68+ cells are negative for TGFbeta and are almost exclusively found in the intimal layer of the inflamed artery. The intimal-medial junction is the preferred site for 72-kD collagenase expressing CD68+ cells. Thus, TGFbeta1-producing macrophages colocalize with activated CD4+ T cells and home to an area of inflammation which is distant from the site of tissue damage but critical in regulating cellular influx, suggesting that TGFbeta1 functions as a proinflammatory mediator in this disease. iNOS- and 72-kD collagenase-producing macrophages accumulate at the center of pathology implying a role of these products in tissue destruction. These data indicate that the microenvironment controls the topographical arrangement as well as the functional commitment of macrophages.     

Antiviral CD8+ T cell effector activities in situ are regulated by target cell type

Cytotoxic T lymphocytes (CTLs) play a prominent role in the resolution of viral infections through their capacity both to mediate contact-dependent lysis of infected cells and to release soluble proinflammatory cytokines and chemokines. The factors controlling these antiviral effector activities in vivo at infection sites are ill defined. Using a mouse model of influenza infection, we observed that the expression of CTL effector activity in the infected lungs is dictated by the target cell type encountered. CD45(+) lung infiltrating inflammatory mononuclear cells, particularly CD11c(hi) dendritic cells, trigger both CTL cytotoxicity and release of inflammatory mediators, whereas CD45(-) influenza-infected respiratory epithelial cells stimulate only CTL cytotoxicity. CTL proinflammatory mediator release is modulated by co-stimulatory ligands (CD80 and CD86) expressed by the CD45(+) inflammatory cells. These findings suggest novel mechanisms of control of CTL effector activity and have potentially important implications for the control of excess pulmonary inflammation and immunopathology while preserving optimal viral clearance during respiratory virus infections.     

TNF-α drives remodeling of blood vessels and lymphatics in sustained airway inflammation in mice

Inflammation is associated with blood vessel and lymphatic vessel proliferation and remodeling. The microvasculature of the mouse trachea provides an ideal opportunity to study this process, as Mycoplasma pulmonis infection of mouse airways induces widespread and sustained vessel remodeling, including enlargement of capillaries into venules and lymphangiogenesis. Although the mediators responsible for these vascular changes in mice have not been identified, VEGF-A is known not to be involved. Here, we sought to determine whether TNF-α drives the changes in blood vessels and lymphatics in M. pulmonis–infected mice. The endothelial cells, but not pericytes, of blood vessels, but not lymphatics, were immunoreactive for TNF receptor 1 (TNF-R1) and lymphotoxin B receptors. Most TNF-R2 immunoreactivity was on leukocytes. Infection resulted in a large and sustained increase in TNF-α expression, as measured by real-time quantitative RT-PCR, and smaller increases in lymphotoxins and TNF receptors that preceded vessel remodeling. Substantially less vessel remodeling and lymphangiogenesis occurred when TNF-α signaling was inhibited by a blocking antibody or was silenced in Tnfr1^–/– mice. When administered after infection was established, the TNF-α–specific antibody slowed but did not reverse blood vessel remodeling and lymphangiogenesis. The action of TNF-α on blood vessels is probably mediated through direct effects on endothelial cells, but its effects on lymphangiogenesis may require inflammatory mediators from recruited leukocytes. We conclude that TNF-α is a strong candidate for a mediator that drives blood vessel remodeling and lymphangiogenesis in inflammation.     

Age of blood: does it make a difference?

During the past 20 years, the perceived value of blood transfusions has changed as it has become appreciated that transfusions are not without risk. Red blood cell transfusion has been associated with disease transmission and immunosuppression for some time. More recently, proinflammatory consequences of red blood cell transfusion have also been documented. Moreover, it has become increasingly evident that stored red blood cells undergo time-dependent metabolic, biochemical, and molecular changes. This 'storage lesion' may be responsible for many of the adverse effects of red blood cell transfusion. Clinically, the age of blood has been associated with multiple organ failure, postoperative pneumonia, and wound infection. The relationship between age of blood and clinical adverse effects needs further study.     

Apoptosis of human intestinal epithelial cells after bacterial invasion.

Epithelial cells that line the human intestinal mucosa are the initial site of host invasion by bacterial pathogens. The studies herein define apoptosis as a new category of intestinal epithelial cell response to bacterial infection. Human colon epithelial cells are shown to undergo apoptosis following infection with invasive enteric pathogens, such as Salmonella or enteroinvasive Escherichia coli. In contrast to the rapid onset of apoptosis seen after bacterial infection of mouse monocyte-macrophage cell lines, the commitment of human intestinal epithelial cell lines to undergo apoptosis is delayed for at least 6 h after bacterial infection, requires bacterial entry and replication, and the ensuing phenotypic expression of apoptosis is delayed for 12-18 h after bacterial entry. TNF-alpha and nitric oxide, which are produced as components of the intestinal epithelial cell proinflammatory program in the early period after bacterial invasion, play an important role in the later induction and regulation of the epithelial cell apoptotic program. Apoptosis in response to bacterial infection may function to delete infected and damaged epithelial cells and restore epithelial cell growth regulation and epithelial integrity that are altered during the course of enteric infection. The delay in onset of epithelial cell apoptosis after bacterial infection may be important both to the host and the invading pathogen since it provides sufficient time for epithelial cells to generate signals important for the activation of mucosal inflammation and concurrently allows invading bacteria time to adapt to the intracellular environment before invading deeper mucosal layers.     

The missing link between atherosclerosis,inflammation and thrombosis: is it tissue factor?

Acute thrombus formation on disrupted atherosclerotic plaques plays a key role during the onset of acute coronary syndromes. Lesion disruption facilitates the interaction between circulating blood and prothrombotic substances, such as tissue factor (TF) present within the atherosclerotic lesion. For a long period of time, vessel-wall TF has been considered the major determinant of thrombosis. However, this old dogma has been recently changed owing to the discovery of a different pool of TF that circulates in flowing blood (blood-borne TF). Several studies have shown that blood-borne TF circulates in different pools that are associated with selected blood cells, such as monocytes, granulocytes and platelets in cell-derived microparticles, and as a soluble protein generated by alternative splicing of its full-length mRNA. Recent studies have identified a hypercoagulable state associated with an increased circulating TF activity, leading to the concept of ‘vulnerable blood’. Part of the blood-borne TF circulates in an ‘inactive’ form and it is required to be ‘activated’ to exert its thrombogenic potential. Certain pathological conditions, such as smoking, hyperlipidemia and diabetes, show a higher incidence of thrombotic complications. These conditions are also characterized by the presence of high levels of circulating TF activity. Recent evidence may also suggest that an increased circulating TF activity may potentiate the initial thrombogenic stimulus represented by vessel wall-associated TF, leading to the formation of larger and/or more stable thrombus, and thus more severe acute coronary syndromes. It has been reported that inflammation increases TF expression and activity by different cell types. On the other hand, TF upregulation may facilitate inflammation by enhancing intravascular fibrin deposition, formation of proinflammatory fragments of fibrin, and by generating coagulation proteases, including FVIIa, FXa and thrombin, that activate protease-activated receptors. Furthermore, the biology of TF is know known to be more complex than previously thought by the demonstration that this protein, apart from its known effects on blood coagulation, can also function as a signaling receptor.     

Pathophysiology and diagnostic value of urinary trypsin inhibitors.

Inflammation is an important indicator of tissue injury. In the acute form, there is usually accumulation of fluids and plasma components in the affected tissues. Platelet activation and the appearance in blood of abnormally increased numbers of polymorphonucleocytes, lymphocytes, plasma cells and macrophages usually occur. Infectious disorders such as sepsis, meningitis, respiratory infection, urinary tract infection, viral infection, and bacterial infection usually induce an inflammatory response. Chronic inflammation is often associated with diabetes mellitus, acute myocardial infarction, coronary artery disease, kidney diseases, and certain auto-immune disorders, such as rheumatoid arthritis, organ failures and other disorders with an inflammatory component or etiology. The disorder may occur before inflammation is apparent. Markers of inflammation such as C-reactive protein (CRP) and urinary trypsin inhibitors have changed our appraisal of acute events such as myocardial infarction; the infarct may be a response to acute infection and (or) inflammation. We describe here the pathophysiology of an anti-inflammatory agent termed urinary trypsin inhibitor (uTi). It is an important anti-inflammatory substance that is present in urine, blood and all organs. We also describe the anti-inflammatory agent bikunin, a selective inhibitor of serine proteases. The latter are important in modulating inflammatory events and even shutting them down.     

Statins protect against fulminant pneumococcal infection and cytolysin toxicity in a mouse model of sickle cell disease

Sickle cell disease (SCD) is characterized by intravascular hemolysis and inflammation coupled to a 400-fold greater incidence of invasive pneumococcal infection resulting in fulminant, lethal pneumococcal sepsis. Mechanistically, invasive infection is facilitated by a proinflammatory state that enhances receptor-mediated endocytosis of pneumococci into epithelial and endothelial cells. As statins reduce chronic inflammation, in addition to their serum cholesterol-lowering effects, we hypothesized that statin therapy might improve the outcome of pneumococcal infection in SCD. In this study, we tested this hypothesis in an experimental SCD mouse model and found that statin therapy prolonged survival following pneumococcal challenge. The protective effect resulted in part from decreased platelet-activating factor receptor expression on endothelia and epithelia, which led to reduced bacterial invasion. An additional protective effect resulted from inhibition of host cell lysis by pneumococcal cholesterol-dependent cytotoxins (CDCs), including pneumolysin. We conclude therefore that statins may be of prophylactic benefit against invasive pneumococcal disease in patients with SCD and, more broadly, in settings of bacterial pathogenesis driven by receptor-mediated endocytosis and the CDC class of toxins produced by Gram-positive invasive bacteria.     

In vivo equilibrium of proinflammatory IL-17+ and regulatory IL-10+ Foxp3+ RORgamma t+ T cells

The nuclear hormone receptor retinoic acid receptor-related orphan receptor gamma t (RORgamma t) is required for the generation of T helper 17 cells expressing the proinflammatory cytokine interleukin (IL)-17. In vivo, however, less than half of RORgamma t(+) T cells express IL-17. We report here that RORgamma t(+) T alphabeta cells include Foxp3(+) cells that coexist with IL-17-producing RORgamma t(+) T alphabeta cells in all tissues examined. The Foxp3(+) RORgamma t(+) T alphabeta express IL-10 and CCL20, and function as regulatory T cells. Furthermore, the ratio of Foxp3(+) to IL-17-producing RORgamma t(+) T alphabeta cells remains remarkably constant in mice enduring infection and inflammation. This equilibrium is tuned in favor of IL-10 production by Foxp3 and CCL20, and in favor of IL-17 production by IL-6 and IL-23. In the lung and skin, the largest population of RORgamma t(+) T cells express the gammadelta T cell receptor and produce the highest levels of IL-17 independently of IL-6. Thus, potentially antagonistic proinflammatory IL-17-producing and regulatory Foxp3(+) RORgamma t(+) T cells coexist and are tightly controlled, suggesting that a perturbed equilibrium in RORgamma t(+) T cells might lead to decreased immunoreactivity or, in contrast, to pathological inflammation.     

The missing link between atherosclerosis, inflammation and thrombosis: is it tissue factor?

Acute thrombus formation on disrupted atherosclerotic plaques plays a key role during the onset of acute coronary syndromes. Lesion disruption facilitates the interaction between circulating blood and prothrombotic substances, such as tissue factor (TF) present within the atherosclerotic lesion. For a long period of time, vessel-wall TF has been considered the major determinant of thrombosis. However, this old dogma has been recently changed owing to the discovery of a different pool of TF that circulates in flowing blood (blood-borne TF). Several studies have shown that blood-borne TF circulates in different pools that are associated with selected blood cells, such as monocytes, granulocytes and platelets in cell-derived microparticles, and as a soluble protein generated by alternative splicing of its full-length mRNA. Recent studies have identified a hypercoagulable state associated with an increased circulating TF activity, leading to the concept of 'vulnerable blood'. Part of the blood-borne TF circulates in an 'inactive' form and it is required to be 'activated' to exert its thrombogenic potential. Certain pathological conditions, such as smoking, hyperlipidemia and diabetes, show a higher incidence of thrombotic complications. These conditions are also characterized by the presence of high levels of circulating TF activity. Recent evidence may also suggest that an increased circulating TF activity may potentiate the initial thrombogenic stimulus represented by vessel wall-associated TF, leading to the formation of larger and/or more stable thrombus, and thus more severe acute coronary syndromes. It has been reported that inflammation increases TF expression and activity by different cell types. On the other hand, TF upregulation may facilitate inflammation by enhancing intravascular fibrin deposition, formation of proinflammatory fragments of fibrin, and by generating coagulation proteases, including FVIIa, FXa and thrombin, that activate protease-activated receptors. Furthermore, the biology of TF is know known to be more complex than previously thought by the demonstration that this protein, apart from its known effects on blood coagulation, can also function as a signaling receptor.     

Early alterations in the number of circulating lymphocyte subpopulations and enhanced proinflammatory immune response during opioid-based general anesthesia

The balance between proinflammatory and anti-inflammatory processes is of key importance in the reaction of the body to infection, injury, and surgical trauma. Drugs commonly used in anesthesia and intensive care may modulate immunological reactions by influencing intercellular communication through modification of cytokine response and fluctuation of peripheral immune cells such as natural killer (NK) cells, B cells, and T lymphocyte subpopulations (CD4+ and CD8+ cells). To examine the effects of general anesthesia with the hypnotic agent propofol and the opioid fentanyl, 30 patients undergoing minor elective orthopedic surgery were studied before and 20 min after application of the anesthetic drugs, but before the start of surgery. We found a significant enhancement of TNF-alpha and IL-1beta release in lipopolysaccharide (LPS)-stimulated whole blood cultures after induction of anesthesia. Similar results were observed with interferon-gamma (IFN-gamma) in cultures stimulated with phytohemagglutinin (PHA). Conversely, synthesis of the anti-inflammatory cytokine interleukin 10 (IL-10) decreased significantly in LPS-stimulated cultures. During general anesthesia, we found a decrease of circulating lymphocytes, characterized by a significant increase in the percentage of T lymphocytes in favor of CD4+ cells, increased B lymphocytes, and a significant decrease of NK cells. These data suggest that anesthesia with propofol and fentanyl promotes proinflammatory immune responses and influences peripheral lymphocyte composition in patients, which may subsequently affect pathophysiological processes during opioid-based anesthesia.     

白细胞去除及其临床应用进展

输血可因输入同种异体血液及其制剂而导致白细胞介导的输血反应及输血相关病毒的传播。去除血液及其制剂中白细胞则可有效地减低免疫抑制效应及传播病毒的危险。成分血液因制备时采用白膜法,通常可去除全血中2／3的白细胞。采用白细胞专用滤器,则可去除血液中99．9％的白细胞,可以明显减少白细胞介导的输血反应,如非溶血性发热性输血反应和移植物抗宿主病。白细胞去除可减少输血传播病毒的危险。另外,白细胞去除对治疗心外科病人因白细胞介导的炎症和器官再灌注损伤、溃疡性结肠炎以及一些自身免疫性和神经性疾病等均有重要作用。     

Ketamine inhibits LPS-mediated BV2 microglial inflammation via NMDA receptor blockage

Microglial inflammation leads to the upregulation of proinflammatory cytokine and proinflammatory enzyme expression, resulting in inflammation-induced neuronal cell apoptosis. Ketamine, an anesthetic mostly used in critical patients, has been reported to possess neuroprotective effects. However, the potential mechanism is still not well understood. In the present study, we investigated how ketamine attenuates lipopolysaccharide (LPS)-mediated BV2 cell inflammation. LPS upregulated proinflammatory cytokine and proinflammatory enzyme expression, increased NF-κB phosphorylation and nuclear translocation, and augmented calcium (Ca²⁺)/calmodulin-dependent protein kinase II (CaMK II) phosphorylation and Ca²⁺ levels in BV2 cells. Ketamine could reverse these LPS-induced effects. Furthermore, AP5, an inhibitor of NMDA receptors, inhibited LPS-induced inflammatory effects in BV2 cells, which was similar to the effects of ketamine. Moreover, these effects of ketamine against LPS-mediated inflammation in BV2 cells could be reversed by D-serine, an activator of NMDA receptors. The present study suggests that ketamine, by inhibiting NMDA receptors, attenuating Ca²⁺ levels, and inhibiting CaMK II phosphorylation, NF-κB phosphorylation and nuclear translocation, may ameliorate LPS-mediated inflammation in BV2 cells.     

New horizon in platelet function: with special reference to a recently-found molecule,CLEC-2

Platelets play a key role in the pathophysiological processes of hemostasis and thrombus formation. However, platelet functions beyond thrombosis and hemostasis have been increasingly identified in recent years. A large body of evidence now exists which suggests that platelets also play a key role in inflammation, immunity, malignancy, and furthermore in organ development and regeneration, such as the liver.We have recently identified CLEC-2 on the platelet membrane, which induces intracellular activation signals upon interaction of a snake venom, rhodocytin. Later we discovered that podoplanin, present in renal podocytes and lymphatic endothelial cells, both of which are not accessible to platelets in blood stream, is an endogenous ligand for CLEC-2. In accord with our expectation, platelet-specific CLEC-2 knockout mice have a phenotype of edema, lymphatic vessel dilatation, and the presence of blood cells in lymphatic vessels. It is suggested that lymphatic/blood vessel separation during the developmental stage is governed by cytokines released from platelets activated by the interaction between platelet CLEC-2 and podoplanin present on lymphatic endothelial cells.Recombinant CLEC-2 bound to early atherosclerotic lesions and normal arterial walls, co-localizing with vascular smooth muscle cells (VSMCs). Flow cytometry and immunocytochemistry showed that recombinant CLEC-2, but not an anti-podoplanin antibody, bound to VSMCs, suggesting that CLEC-2 ligands other than podoplanin are present in VSMCs. Protein arrays and Biacore analysis were used to identify S100A13 as a CLEC-2 ligand in VSMCs. S100A13 was released upon oxidative stress, and expressed in the luminal area of atherosclerotic lesions.Megakaryopoiesis is promoted through the CLEC-2/podoplanin interaction in the vicinity of arterioles, not sinusoids or lymphatic vessels. There exist podoplanin-expressing bone-marrow (BM) arteriolar stromal cells, tentatively termed as BM fibroblastic reticular cell (FRC)-like cells, and megakaryocyte colonies were co-localized with periarteriolar BM FRC-like cells in the BM. CLEC-2/podoplanin interaction induces BM FRC-like cells to secrete CCL5 to facilitate proplatelet formation. These observations indicate that a reciprocal interaction with between CLEC-2 on megakaryocytes and podoplanin on BM FRC-like cells contributes to the periarteriolar megakaryopoietic microenvironment in mouse BM.     

Fibroblast activation in vascular inflammation

Summary. Vascular inflammation is implicated in both local and systemic inflammatory conditions. Endothelial activation and leukocyte extravasation are key events in vascular inflammation. Lately, the role of the stromal microenvironment as a source of proinflammatory stimuli has become increasingly appreciated. Stromal fibroblasts produce cytokines, growth factors and proteases that trigger and maintain acute and chronic inflammatory conditions. Fibroblasts have been associated with connective tissue pathologies such as scar formation and fibrosis, but recent research has also connected them with vascular dysfunctions. Fibroblasts are able to modulate endothelial cell functions in a paracrine manner, including proinflammatory activation and promotion of angiogenesis. They are also able to activate and attract leukocytes. Stromal fibroblasts can thus cause a proinflammatory switch in endothelial cells, and promote leukocyte infiltration into tissues. New insights in the role of adventitial fibroblasts have further strengthened the link between stromal fibroblasts and proinflammatory vascular functions. This review focuses on the role of fibroblasts in inducing and maintaining vascular inflammation, and describes recent findings and concepts in the field, along with examples of pathologic implications.