Process Of Leukocyte Recruitment Research Articles

Role of albumin on endothelial basement membrane and hemostasis in a rat model of hemorrhagic shock.

We sought to determine the extent of loss of endothelial basement membrane (BM), leukocyte recruitment, and changes in coagulation after hemorrhagic shock, followed by limited-volume resuscitation (LVR) with 5% albumin (ALB). Anesthetized rats were bled 40% of blood volume and assigned to treatment groups: untreated (n = 6), LVR with normal saline (NS; n = 8), or LVR with ALB (n = 8). Sham rats (n = 6) underwent all procedures except hemorrhage or resuscitation. Blood samples were assayed for active proteases, such as metalloproteinase 9 (MMP-9) and a disintegrin and metalloproteinase 10 (ADAM-10), BM-type heparan sulfate proteoglycan (perlecan), cell count, and coagulation function. Leukocyte transmigration was used to estimate the net efficiency of leukocyte recruitment in cremaster venules. Hemorrhage significantly lowered red cell count, but white cell and platelet counts did not change (vs. sham). Ionized calcium in plasma was significantly reduced in untreated and remained so after NS. In contrast, ionized calcium was normalized after ALB. Plasma expansion after NS and ALB further reduced leukocyte and platelet counts. Metalloproteinase 9, ADAM-10, and perlecan were significantly higher in untreated rats (vs. sham). Albumin normalized MMP-9, ADAM-10, and perlecan levels, while NS further increased MMP-9, ADAM-10, and perlecan (vs. sham). Transmigrated leukocytes doubled in the untreated group and remained elevated after NS (vs. sham) but normalized after ALB. Albumin reduced every stage of the leukocyte recruitment process to sham levels. Despite similar plasma expansion, NS weakened platelet function contrary to ALB. Plasma expansion with ALB resulted in restoration of BM integrity and attenuation of leukocyte recruitment to tissues, in contrast to NS. Albumin plays a critical role in restoring BM integrity, attenuating leukocyte recruitment to tissues, and optimizing hemostasis by increasing ionized calcium in plasma.

Galectin-3: A Positive Regulator of Leukocyte Recruitment in the Inflamed Microcirculation.

In vivo and ex vivo imaging were used to investigate the function of galectin-3 (Gal-3) during the process of leukocyte recruitment to the inflamed microcirculation. The cremasteric microcirculation of wild-type (C57BL/6), Gal-3-/-, and CX3CR1gfp/+ mice were assessed by intravital microscopy after PBS, IL-1β, TNF-α, or recombinant Gal-3 treatment. These cellular responses were investigated further using flow-chamber assays, confocal microscopy, flow cytometry, PCR analysis, and proteome array. We show that mechanisms mediating leukocyte slow rolling and emigration are impaired in Gal-3-/- mice, which could be because of impaired expression of cell adhesion molecules and an altered cell surface glycoproteome. Local (intrascrotal) administration of recombinant Gal-3 to wild-type mice resulted in a dose-dependent reduction in rolling velocity associated with increased numbers of adherent and emigrated leukocytes, ∼50% of which were Ly6G+ neutrophils. Intrascrotal administration of Gal-3 to CX3CR1gfp/+ mice confirmed that approximately equal numbers of monocytes are also recruited in response to this lectin. Exogenous Gal-3 treatment was accompanied by increased proinflammatory cytokines and chemokines within the local tissue. In conclusion, this study unveils novel biology for both exogenous and endogenous Gal-3 in promoting leukocyte recruitment during acute inflammation.

Cell‐type specific mechanisms regulate rhythmic leukocyte migration to tissues

Leukocyte recruitment from blood to tissues is a critical element of the immune system. However, the dynamics of leukocyte migration over the course of the day are unclear. Specifically, which leukocyte subtypes are being recruited to which specific tissue at what time during the daily cycle is unknown. Here, we screened the main leukocyte subpopulations in murine blood (neutrophils, B cells, CD4 T cells, CD8 T cells, natural killer (NK) cells, NKT cells, eosinophils, inflammatory as well non‐inflammatory monocytes) for oscillations in their migration behaviour. We examined surface protein expression levels of 28 adhesion molecules and chemokine receptors on these leukocyte subtypes in addition to 8 adhesion molecules expressed by endothelial cells in vascular beds of multiple organs using quantitative flow cytometry and imaging‐based approaches. Our data indicate the existence of a rhythmic leukocyte‐and tissue‐specific molecular signature in the expression of pro‐migratory factors. To test the relevance of these oscillations, we performed homing assays to investigate the recruitment capability of individual leukocyte subsets to tissues at specific times. These data revealed strong, >2‐fold time‐of‐day differences in the capacity of cells to emigrate out from blood. In addition, it exposed leukocyte‐distinct rhythms in their homing patterns to tissues, with the microenvironment and leukocyte‐autonomous oscillations co‐contributing in the recruitment process. Specifically, using B‐cell and T‐cell‐specific knockouts of the circadian gene Bmal1 demonstrated altered expression levels of specific oscillatory molecules and leukocyte numbers in tissues, which suggests that rhythmicity in these factors may be directly regulated by the circadian clock. Taken together, our data show discrete tissue and leukocyte mechanisms that control a broad and robustly rhythmic leukocyte recruitment process to organs.Support or Funding InformationFunded by the European Research Council (CIRCODE) and the German Research Foundation(EmmyNoether SCHE1645/2‐1 and SFB914 project B09).

Nitric oxide synthase promotes distension-induced tracheal venular leukocyte adherence.

The process of leukocyte recruitment to the airways in real time has not been extensively studied, yet airway inflammation persists as a major contributor to lung pathology. We showed previously in vivo, that neutrophils are recruited acutely to the large airways after periods of airway distension imposed by the application of positive end-expiratory pressure (PEEP). Given extensive literature implicating products of nitric oxide synthase (NOS) in lung injury after ventilatory over-distension, we questioned whether similar mechanisms exist in airway post-capillary venules. Yet, endothelial nitric oxide has been shown to be largely anti-inflammatory in other systemic venules. Using intravital microscopy to visualize post-capillary tracheal venules in anesthetized, ventilated mice, the number of adherent leukocytes was significantly decreased in eNOS-/- mice under baseline conditions (2±1 cell/60 min observation) vs wild type (WT) C57BL/6 mice (7±2 cells). After exposure to PEEP (8 cmH2O for 1 min; 5 times), adherent cells increased significantly (29±5 cells) in WT mice while eNOS-/- mice demonstrated a significantly decreased number of adherent cells (11±4 cells) after PEEP. A similar response was seen when thrombin was used as the pro-inflammatory stimulus. In addition, mouse tracheal venular endothelial cells studied in vitro after exposure to cyclic stretch (18% elongation) or thrombin both demonstrated increased p-selectin expression that was significantly attenuated by NG-nitro-L-arginine methyl ester, N-acetylcysteine amide (NACA) and excess BH4. In vivo treatment with the ROS inhibitor NACA or co-factor BH4 abolished completely the PEEP-induced leukocyte adherence. These results suggest that pro-inflammatory stimuli cause leukocyte recruitment to tracheal endothelium in part due to eNOS uncoupling.

Comparative suitability of CFDA‐SE and rhodamine 6G for in vivo assessment of leukocyte‐endothelium interactions

Intravital fluorescence microscopy (IVM) is a predestined tool for investigating the fate of leukocytes during the process of leukocyte recruitment. In the present study, the commonly used dye for this purpose, rhodamine 6G, and carboxyfluorescein diacetate succinimidyl ester (CFDA-SE) were compared for leukocytes labelling with respect to suitability for IVM studies. Their potential in labelling different leukocytes subpopulations as well as their fluorescence intensities were assessed by flow cytometry revealing distinct differences between both dyes. These differences had a profound impact on their application for in vivo imaging of leukocyte-endothelium interactions. In summary, CFDA-SE revealed superior in labelling leukocytes for in vivo microscopy with respect to image quality. In addition, we could show the efficiency of CFDA-SE also under disease condition in an animal model of sepsis.

The CXCR1/2 ligand NAP-2 promotes directed intravascular leukocyte migration through platelet thrombi

AbstractThrombosis promotes leukocyte infiltration into inflamed tissues, leading to organ injury in a broad range of diseases; however, the mechanisms by which thrombi guide leukocytes to sites of vascular injury remain ill-defined. Using mouse models of endothelial injury (traumatic or ischemia reperfusion), we demonstrate a distinct process of leukocyte recruitment, termed “directed intravascular migration,” specifically mediated by platelet thrombi. Single adherent platelets and platelet aggregates stimulated leukocyte shape change at sites of endothelial injury; however, only thrombi were capable of inducing directed intravascular leukocyte migration. Leukocyte recruitment and migration induced by platelet thrombi occurred most prominently in veins but could also occur in arteries following ischemia-reperfusion injury. In vitro studies demonstrated a major role for platelet-derived NAP-2 (CXCL-7) and its CXCR1/2 receptor in regulating leukocyte polarization and motility. In vivo studies demonstrated the presence of an NAP-2 chemotactic gradient within the thrombus body. Pharmacologic blockade of CXCR1/2 as well as genetic deletion of NAP-2 markedly reduced leukocyte shape change and intrathrombus migration. These studies define a distinct process of leukocyte migration that is initiated by homotypic adhesive interactions between platelets, leading to the development of an NAP-2 chemotactic gradient within the thrombus body that guides leukocytes to sites of vascular injury.

Imaging inflammatory leukocyte recruitment in kidney, lung and liver—challenges to the multi‐step paradigm

Intravital microscopy has been essential in establishing the multi-step paradigm that describes how leukocytes in the bloodstream interact with the blood vessel wall during the process of leukocyte recruitment. Much of this work has been performed in readily-visualized tissues such as the mesentery and the cremaster muscle, where leukocyte-endothelial cell interactions are restricted to postcapillary venules. However, the microvasculatures of the liver, lung and renal glomerulus differ markedly from these conventionally structured microvascular beds. Moreover, the liver, lung and kidney can be the target of life-threatening leukocyte-mediated inflammation. Therefore, a clear understanding of the mechanisms of leukocyte recruitment to these sites is critical. In this review, we examine the advances made in the understanding of leukocyte recruitment in the liver, lung and glomerulus, as determined using intravital microscopy. We describe how leukocyte recruitment to these sites occurs via mechanisms distinct from the conventional rolling/adhesion/transmigration paradigm, and in some cases involves adhesion molecules with minimal roles in conventional postcapillary venules. In addition, we describe how advanced forms of in vivo imaging in combination with novel approaches for labeling immune cell subsets is revealing new complexities in leukocyte function and immune cell interactions in these specialized microvascular beds.

Leukocyte-endothelial interactions within the ocular microcirculation in inflammation and infection

Leukocyte-endothelial interactions within the microvasculature represent a hallmark of inflammation regardless of whether the inflammation results from non-infectious or infectious triggers. In this review, we highlight features of leukocyte recruitment in ocular disease and postulate mechanisms by which the infiltrating cells may lead to the progression of the ocular inflammatory response, including cytokine and chemokine production, T cell or non-T cell responses. Additionally, ex-vivo and in vivo methods used to study the general features of the immune response are discussed, with a specific focus on intravital imaging, which allows real-time non-invasive examination of leukocyte-endothelial interactions in the ocular microvasculature. At the present time there are still significant gaps in our understanding of the process of leukocyte recruitment in vivo in different microvascular beds. Further studies using non-invasive imaging approaches, such as intravital microscopy, provide an opportunity to study dynamic tissue-specific leukocyte-endothelial interactions in vivo and identify novel targets for early intervention in the inflammatory process. This knowledge is essential to the rational use of therapeutics to resolve inflammation in ocular disease.

FAK and PAX‐illin get involved in leukocyte diapedesis

A major focus of researchers studying leukocyte recruitment has been to identify and understand how cell surface endothelial adhesion molecules, cell-to-cell junctional protein complexes, secreted chemokines and chemoattractants, and the vessel basement membrane structure organization coordinate the process of leukocyte recruitment. As research expands beyond the components initially identified as being necessary for leukocyte recruitment, attention has turned to the structures that regulate endothelial cell-to-matrix adhesion. In this issue of the European Journal of Immunology, Parsons et al. [Eur. J. Immunol. 2012. 42: 436-446] identify new players in the regulation of neutrophil diapedesis (transendothelial migration), namely the focal adhesion proteins, paxillin and focal adhesion kinase (FAK). While understudied, and indeed previously underappreciated, in leukocyte diapedesis, this Commentary discusses how the work by Parsons et al. implicates FAK and paxillin in the proximal (leukocyte rolling) and distal (diapedesis) steps of the multistep adhesion cascade of leukocyte recruitment.

Athérosclérose : sur la piste des chimiokines

Atherosclerosis, which is more than a problem of lipid metabolism, is associated with chronic inflammation of large arteries. This is notably caused by the recruitment of circulating blood monocytes to the arterial wall. Extensive studies in humans and mice have shown that the chemokines and their receptors, responsible for leukocyte recirculation, are strongly implicated in the initial onset of atherosclerosis. Murine models have provided further proof of the role of the CCR2/CCL2, CX3CR1/CXCL16 and CCR5/CCL5 axes in the different stages of disease, as well as the preventative roles of CCR1/CCL5 and CXCR6/CXCL16. The integration at the cellular level of various signals in the chemokine network underlines the complex process of leukocyte recruitment to the lesional area. Furthermore the capacity of chemokines to modulate atherosclerosis lies not just with their chemoattractant properties but also with their influence on leukocyte homeostasis. These molecules have therefore quickly become therapeutic targets for atherosclerosis and have opened up new avenues for treating inflammatory diseases. This review principally addresses the implication of chemokines and their receptors in the initial recruitment steps of blood monocytes, and provides an overview of recent research on these molecular controllers of inflammation.

Biomolecular Surfaces for the Capture and Reprogramming of Circulating Tumor Cells

Circulating Tumor Cells (CTC) have the potential to be used clinically as a diagnostic tool and a treatment tool in the field of oncology. As a diagnostic tool, CTC may be used to indicate the presence of a tumor before it is large enough to cause noticeable symptoms. As a treatment tool, CTC isolated from patients may be used to test the efficacy of chemotherapy options to personalize patient treatment. One way for tumors to spread is through metastasis via the circulatory system. CTC are able to exploit the natural leukocyte recruitment process that is initially mediated by rolling on transient selectin bonds. Our capture devices take advantage of this naturally occurring recruitment step to isolate CTC from whole blood by flowing samples through selectin and antibody-coated microtubes. Whole blood was spiked with a known concentration of labeled cancer cells and then perfused through pre-coated microtubes. Microtubes were then rinsed to remove unbound cells and the number of labeled cells captured on the lumen was assessed. CTC were successfully captured from whole blood at a clinically relevant level on the order of 10 cells per mL. Combination tubes with selectin and antibody coated surface exhibited higher capture rate than tubes coated with selectin alone or antibody alone. Additionally, CTC capture was demonstrated with the KG1a hematopoietic cell line and the DU145 epithelial cell line. Thus, the in vivo process of selectin-mediated CTC recruitment to distant vessel walls can be used in vitro to target CTC to a tube lumen. The biomolecular coatings can also be used to capture CTC of hematopoietic and epithelial tumor origin and is demonstrated to sensitivities down to the order of 10 CTC per mL. In a related study aimed at reducing the blood borne metastatic cancer load, we have shown that cells captured to a surface can be neutralized by a receptor-mediated biochemical signal. In the proposed method we have shown that using a combined selectin and TRAIL (TNF Related Apoptosis Inducing Ligand or Apo 2L) functionalized surface we are able to kill about 30% of the captured cells in a short duration of one hour whereas it took about 4 hours to kill the same proportion of cells without flow on a similarly functionalized surface. Here we have taken the approach a step further by showing that with very small doses of chemotherapeutic agents like bortezomib, we can increase the kill rate of CTC, thus allowing the device to function in scenarios where the patient is undergoing treatment. We show here that, with leukemic cells treated with bortezomib we are able to kill about 41% of the captured cells.

Vav1 Is Essential for Mechanotactic Crawling and Migration of Neutrophils out of the Inflamed Microvasculature

Mac-1-dependent crawling is a new step in the leukocyte recruitment cascade that follows LFA-1-dependent adhesion and precedes emigration. Neutrophil adhesion via LFA-1 has been shown to induce cytoskeletal reorganization through Vav1-dependent signaling, and the current study investigates the role of Vav1 in the leukocyte recruitment process in vivo with particular attention to the events immediately downstream of LFA-1-dependent adhesion. Intravital and spinning-disk-confocal microscopy was used to investigate intravascular crawling in relation to endothelial junctions in vivo in wild-type and Vav1(-/-) mice. Adherent wild-type neutrophils almost immediately began crawling perpendicular to blood flow via Mac-1 until they reached an endothelial junction where they often changed direction. This pattern of perpendicular, mechanotactic crawling was recapitulated in vitro when shear was applied. In sharp contrast, the movement of Vav1(-/-) neutrophils was always in the direction of flow and appeared more passive as if the cells were dragged in the direction of flow in vivo and in vitro. More than 80% of Vav1(-/-) neutrophils moved independent of Mac-1 and could be detached with LFA-1 Abs. An inability to release the uropod was frequently noted for Vav1(-/-) neutrophils, leading to greatly elongated tails. The Vav1(-/-) neutrophils failed to stop or follow junctions and ultimately detached, leading to fewer emigrated neutrophils. The Vav1(-/-) phenotype resulted in fewer neutrophils recruited in a relevant model of infectious peritonitis. Clearly, Vav1 is critical for the complex interplay between LFA-1 and Mac-1 that underlies the programmed intravascular crawling of neutrophils.

Golgi GDP-fucose Transporter-deficient Mice Mimic Congenital Disorder of Glycosylation IIc/Leukocyte Adhesion Deficiency II

Modification of glycoproteins by the attachment of fucose residues is widely distributed in nature. The importance of fucosylation has recently been underlined by identification of the monogenetic inherited human disease "congenital disorder of glycosylation IIc," also termed "leukocyte adhesion deficiency II." Due to defective Golgi GDP-fucose transporter (SLC35C1) activity, patients show a hypofucosylation of glycoproteins and present clinically with mental and growth retardation, persistent leukocytosis, and severe infections. To investigate effects induced by the loss of fucosylated structures in different organs, we generated a mouse model for the disease by inactivating the Golgi GDP-transporter gene (Slc35c1). Lectin binding studies revealed a tremendous reduction of fucosylated glycoconjugates in tissues and isolated cells from Slc35c1(-/-) mice. Fucose treatment of cells from different organs led to partial normalization of the fucosylation state of glycoproteins, thereby indicating an alternative GDP-fucose transport mechanism. Slc35c1-deficient mice presented with severe growth retardation, elevated postnatal mortality rate, dilatation of lung alveoles, and hypocellular lymph nodes. In vitro and in vivo leukocyte adhesion and rolling assays revealed a severe impairment of P-, E-, and L-selectin ligand function. The diversity of these phenotypic aspects demonstrates the broad general impact of fucosylation in the mammalian organism.

Radiation-induced intestinal inflammation

Radiation induces an important inflammatory response in the irradiated organs, characterized by leukocyte infiltration and vascular changes that are the main limiting factor in the application of this therapeutic modality for the treatment of cancer. Recently, a considerable investigative effort has been directed at determining the molecular mechanisms by which radiation induces leukocyte recruitment, in order to create strategies to prevent intestinal inflammatory damage. In these review, we consider current available evidence on the factors governing the process of leukocyte recruitment in irradiated organs, mainly derived from experimental studies, with special attention to adhesion molecules, and their value as therapeutic targets.

No endothelial L‐selectin ligand mediates leukocyte rolling in inflammation

The multistep process of leukocyte recruitment guides leukocyte trafficking and immune function. The leukocyte cell adhesion molecule (CAM) L-selectin is a key molecule in this process. Its role in inflammation has largely been attributed to the presence of an endothelial L-selectin ligand expressed on inflamed endothelium. However, the identity of this ligand(s) has been elusive. Here, we used intravital microscopy to show that the reduction of leukocyte rolling in inflammation following blockage of L-selectin is entirely dependent on loss of L-selectin/PSGL-1-dependent leukocyte-mediated secondary capture. Secondary capture initiates rolling mainly on endothelial E-selectin and function-inhibition of L-selectin or E-selectin thus blocks rolling of largely the same pool of rolling leukocytes. All rolling along endothelium in venules following six distinct treatment regimens were abolished after simultaneous blockage of P-selectin, E-selectin and VCAM-1 and no L-selectin ligand activity on endothelium was detected. These data show that there is no ligand for L-selectin mediating rolling along endothelium in inflamed venules. These findings may conclude the search for L-selectin ligands capable of mediating leukocyte rolling in inflammation.

Emerging roles for ectodomain shedding in the regulation of inflammatory responses

The multistep model of leukocyte recruitment to sites of inflammation has helped elucidate specific molecular cues for each of the individual steps. However, it is less clear how cells transition between the different steps and how the complex interactions are coordinately regulated. Once a leukocyte sticks to the endothelium, it only takes a few minutes to reach the subendothelial basement membrane, so the transitions and regulatory mechanisms must be rapid. We put forward the hypothesis that proteolytic shedding of cell surface proteins provides a mechanism to aid in the rapid transition of cells and coordinate the complex, multistep process of leukocyte recruitment in response to inflammatory stimuli. Support for this hypothesis is provided from analyses of disease states and from studies with protease inhibitors and genetically engineered mutations that prevent "ectodomain shedding" of cell surface proteins and consequently perturb the inflammatory response.

Effects of New Peritoneal Dialysis Solutions on Leukocyte Recruitment in the Rat Peritoneal Membrane

Objectives: Peritonitis remains a principal cause of dropout in peritoneal dialysis (PD). The physiological host response to a peritoneal infection involves a rise in numbers of circulating leukocytes to the peritoneal cavity. We evaluated the effects of (1) conventional peritoneal dialysis fluid (PDF), (2) bicarbonate-based PDF, low in glucose degradation products, and (3) non-glucose PDF on peritoneal leukocyte recruitment in response to an inflammatory stimulus using intravital microscopy. Methods: The visceral peritoneum was exposed to EBSS, conventional lactate-buffered and bicarbonate/lactate-buffered glucose-based PDF and three lactate-buffered non-glucose PDF – icodextrin, amino acid-based PDF and amino acid/glycerol-based PDF. The number of rolling, adhering and extravasated leukocytes and leukocyte rolling velocity was assessed at different time intervals after stimulation with lipopolysaccharide (LPS). Results: Exposure to LPS dissolved in EBSS dramatically increased the number of rolling, adhering and extravasated leukocytes and decreased leukocyte rolling velocity. Conventional PDF completely abolished LPS-induced leukocyte recruitment. Bicarbonate/lactate-buffered PDF only minimally affected the process of leukocyte recruitment, whereas icodextrin PDF resulted in partial inhibition of the immune response. The amino acid-based and the amino acid/glycerol-based PDF inhibited leukocyte recruitment to a similar extent as conventional PDF. Conclusions: Bicarbonate/lactate-buffered PDF has superior biocompatibility towards peritoneal host defense, in spite of its high glucose concentrations. Lactate-buffered non-glucose containing PDF has substantial inhibitory effects on leukocyte recruitment, indicating that the bioincompatibility of high lactate concentrations and/or low pH may not be underestimated.

Emerging Topics in the Regulation of Leukocyte Transendothelial Migration

This year marks the 50th Anniversary of the founding of the Microcirculatory Society. Since the formation of this society this field has witnessed tremendous progress in understanding the process of leukocyte recruitment during inflammation, injury, and immune reactions. This topic has been an important focus of many of the members of the Microcirculatory Society as well as our colleagues worldwide. The goal of this brief review is to bring attention to a few emerging topics in inflammation research. Here the focus is on one particular model of how one leukocyte type (PMN) can regulate the recruitment of a second different leukocyte type (T cell) and provide an outline of other aspects that bear on spatial and temporal behavior of specific leukocyte and endothelial cell adhesion molecules during leukocyte transmigration under dynamic shear flow in vitro.

Adhesion molecules and their role in vascular disease

A variety of recently discovered glycoproteins have been implicated in cell-cell interactions that are critical for normal hemostasis, immune surveillance, and vascular wall integrity. These cell adhesion molecules (CAM) are known to mediate blood cell (leukocyte, platelet)-endothelial cell interactions that can occur in all segments of the microvasculature under certain physiological (eg, hemostasis) and pathological (eg, inflammation) conditions. The multistep process of leukocyte recruitment illustrates how the coordinated and regulated expression of structurally and functionally distinct families of CAM can elicit a highly reproducible vascular response to inflammation. Selectins mediate the initial, low-affinity leukocyte-endothelial cell interaction that is manifested as leukocyte rolling. This transient binding results in further leukocyte activation and subsequent firm adhesion and transendothelial migration of leukocytes, both of which are mediated by interactions between members of the integrin and immunoglobulin superfamily of CAM. This CAM-regulated process of leukocyte recruitment often results in endothelial cell dysfunction, which can be manifested as either impaired endothelium-dependent vasorelaxation in arterioles, excess fluid filtration in capillaries, and enhanced protein extravasation in venules. Consequently, CAM have been implicated in a variety of vascular disorders (eg, ischemia/reperfusion, atherosclerosis, allograft dysfunction, and vasculitis) and an enhanced expression of these CAM has been invoked to explain the exaggerated microvascular dysfunction associated with some of the risk factors (hypertension, hypercholesterolemia, diabetes) for cardiovascular disease. Monoclonal antibodies and genetically engineered mice have proven to be valuable tools for defining the contribution of CAM to disease progression and provide hope for new diagnostic and therapeutic strategies for cardiovascular diseases.

Leukocyte adhesion and recruitment, and alpha-1-antitrypsin deficiency: a report from ATS 2001, May 18-23, San Francisco

The program at this year's American Thoracic Society international conference included over 300 scientific and clinical symposia. In this report I have reviewed the data presented on two important areas of lung inflammation, namely leukocyte recruitment and alpha-1-antitrypsin deficiency. Highlights included work from a number of groups identifying the contribution of specific leukocyte adhesion molecules (CD18, CD11a and vascular cell adhesion molecule-1) which varied according to the site and nature of the initial inflammatory stimulus. In addition work was presented examining the contribution of various chemoattractants to the process of leukocyte recruitment in chronic obstructive pulmonary disease, with leukotriene B4 in particular appearing to play a major role. In alpha-1-antitrypsin deficiency other molecules may also be important and work was presented demonstrating the pro-inflammatory potential of alpha-1-antitrypsin polymers in the lungs of these patients. These advances in the understanding of the basic mechanisms of inflammation will, in the future, allow the development of novel anti-inflammatory therapies for a variety of lung diseases.