Published online before print March 27, 2008
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William Harvey Research Institute, Barts and The London, London, United Kingdom
1Correspondence: William Harvey Research Institute, Barts and The London, School of Medicine and Dentistry, Charterhouse Square, London EC1M 6BQ, UK. E-mail: d.cooper{at}qmul.ac.uk
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Key Words: endothelial cells • inflammation • adhesion molecules
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Originally identified in organs of electric eel and termed electrolectin [4 ], Gal-1 now belongs to a family of 15 lectins, classified by their carbohydrate recognition domains and their affinity for β-galactoside. The anti-inflammatory/immunoregulatory nature of Gal-1 has been identified in various animal models of chronic inflammatory and autoimmune diseases. The administration of human recombinant (hr)Gal-1 in vivo prevents the development of chronic inflammation and ongoing disease in models of experimental autoimmune myasthenia gravis and experimental autoimmune encephalomyelitis [5 , 6 ]. In collagen-induced arthritis, i.p. injection of hrGal-1 or expression of mouse Gal-1 from engineered syngeneic fibroblasts attenuated the development of experimental arthritis. This effect was associated with induction of T cell apoptosis and a switch from a Th1- to a Th2-driven condition [7 ].
Pharmacological intervention with Gal-1 also exerts protective actions in models of tissue injury, e.g., acute hepatotoxicity following Con A administration [8 ], a mouse model of enterocolitis [9 ], and experimental autoimmune uveitis [10 ]. Again, the underlying mechanism was proposed to be inhibition of T cell activation and a shift from a Th1 to a Th2 lymphocyte profile [9 , 10 ]. Our own work has shown that hrGal-1 inhibits neutrophil chemotaxis and transmigration through endothelial monolayers and reduces leukocyte recruitment onto IL-1-treated, mesenteric vessels [11 ]. Here, we extend these findings by determining the potential of hrGal-1 to alter neutrophil adhesion molecule expression as well as the recruitment of this cell type to the endothelium under flow conditions. In addition, we complemented this analysis by addressing, for the first time, the role of endogenous Gal-1 in an inflamed microcirculation.
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Assessment of hrGal-1 binding to polymorphonuclear neutrophil by flow cytometry
Determination of cell-surface binding sites on neutrophils was assessed using biotinylated hrGal-1 (biotGal-1; using classical biochemical protocols, Pierce, Rockford, IL, USA). The local research ethics committee approved experiments with healthy volunteers. Informed consent was provided according to the Declaration of Helsinki. Blood was collected into 3.2% sodium citrate and diluted 1:1 in RPMI 1640 (Sigma-Aldrich, Poole, USA) before separation through a double density gradient as described previously [13
]. After neutrophil isolation and washing, contaminating erythrocytes were removed by hypotonic lysis. Neutrophils were incubated with or without platelet-activating factor (PAF; 10–9 M; C16 form: C26H54NO7P, Sigma-Aldrich) for 30 min at 37°C. Cells were then plated at a density of 2 x 105 cells per well in 96-well plates and incubated with biotGal-1 (4 µg/ml) for 1 h on ice. To determine whether Gal-1 binding was carbohydrate-dependent in nature, neutrophils were coincubated with Gal-1 in the presence of 30 mM thiodigalactoside or sucrose. Following three washes with FACS buffer (PBS containing 0.2% BSA and 1.3 mM CaCl2), cells were incubated with PE-conjugated streptavidin (Caltag, Burlingame, CA, USA) for 45 min on ice. Unstained controls were also prepared for accurate calibration of the FACS machine. Flow cytometry was performed using a FACScan II analyzer (Becton Dickinson, Cowley, UK) with an air-cooled, 100 mW argon laser tuned to 488 nm, connected to an Apple Macintosh G3 computer (Cupertino, CA, USA) running CellQuest II (Becton Dickinson, Franklin Lakes, NJ, USA). Gal-1 binding was recorded as units of fluorescence, where the median fluorescence intensity for 10,000 cells was measured in the fluorescence 2 (FL2) red channel (590 nm).
Assessment of adhesion molecule expression by flow cytometry
Peripheral blood neutrophils, isolated as for the Gal-1-binding studies, were incubated with or without hrGal-1 (0.04–4 µg/ml) or PAF (10–9M) for 30 min at 37°C. Cells were then plated at a density of 2 x 105 cells per well in 96-well plates and incubated with purified mAb: mouse anti-human L-selectin (20 µg/ml, clone FMC46, AbD Serotec, Oxford, UK), mouse anti-human CD11b (5 µg/ml, clone ICRF44, AbD Serotec), or mouse anti-human PE-conjugated P-selectin glycoprotein ligand 1 (PSGL-1; 10 µg/ml, clone KPL-1, BD PharMingen, Erembodegem, Belgium) for 1 h on ice, prior to staining with FITC-conjugated F(ab')2 goat anti-mouse IgG (1:200, AbD Serotec). Isotype and unstained controls were also prepared for accurate calibration of the FACS machine. Flow cytometry was performed as described above with the following exceptions: L-selectin and CD11b expression was recorded as units of fluorescence where the median fluorescence intensity for 10,000 cells was measured in the FL1 green channel (548 nm). In the case of the anti-PSGL-1 antibody, the red FL2 channel was used (590 nm).
Flow chamber assay
Confluent HUVEC (Glycotech, Gaithersburg, MD, USA) monolayers (up to passage 4) were stimulated with TNF-
(10 ng/ml, Sigma-Aldrich) for 4 h. Neutrophils were isolated as for flow cytometry experiments, diluted to 1 x 106/ml in Dulbecco’s PBS supplemented with Ca2+ and Mg2+, and incubated with or without hrGal-1 (0.04–4 µg/ml) for 10 min prior to flow at 37°C. The flow chamber assay was run as described previously [13
]. In brief, the chamber was placed under an Eclipse TE3000 microscope (Nikon, Melville, NY, ISA) with 40x magnification, and neutrophils (1x106/ml) were perfused over the endothelial monolayers at a constant rate of 1 dyne/cm2 using a syringe pump (Harvard Apparatus Inc., South Natick, MA, USA). After 8 min of perfusion, six random fields were recorded for 10 s each using a JVC TK-C1360B digital color video camera, ready for off-line analysis.
Video sequences were transferred to a computer and loaded into ImagePro-Plus software (Media Cybernetics, Wokingham, Berkshire). Neutrophils were manually tagged and their movements on the endothelium monitored. The total number of interacting cells was quantified as initial cell capture and further classified as rolling or firmly adherent (cells that remained stationary for the 10-s observation period) as described in the literature [14 ].
Knockdown of Gal-1 using small interfering (si)RNA
HUVEC were seeded 24 h before transfection at a density of 2 x 105 cells in antibiotic-free media. Transfections were performed with nontargeting or a pool of three Gal-1 target-specific siRNAs (Santa Cruz Biotechnology, Santa Cruz, CA, USA; sense strand 1: CAGCAACCUGAAUCUCAAA, sense strand 2: CCAGAUGGAUACGAAUUCA, sense strand 3: GUGUGGCCUUUGACUGAAA) with cells at 60–80% confluence, according to the manufacturer’s instructions. Knockdown of Gal-1 protein expression was monitored by Western blotting, as described previously using a rabbit anti-Gal-1 polyclonal antibody [11
]. Flow chamber experiments were performed as described above, 48 h post-transfection.
Animals
Breeding founders of the Gal-1 null mouse colony were received from the Consortium for Functional Glycomics, and a colony was established at B&K Universal (Hull, UK). These mice are on a homogenous C57Bl6 background, and age- and sex-matched wild-type (WT) mice were purchased from B&K Universal. All experiments were performed with male animals (body weight 25–30 g) strictly following the Home Office regulations (Guidance on the Operation of Animals, Scientific Procedures Act 1986).
Intravital microscopy
Intravital microscopy was used to observe IL-1β-induced leukocyte responses within the cremasteric microcirculation of Gal-1 null and WT mice. IL-1β was used for these studies rather than TNF-, as at least part of the adhesive response to TNF- within the cremasteric microcirculation results from a direct activation of neutrophils [15
]. IL-1β (30 ng in 400 µl saline) was injected intrascrotally as described previously [15
] at Time 0, and the microcirculation was observed at 2, 4, and 6 h post-injection. The cremaster was prepared for intravital microscopy as recently described [16
]. In brief, mice were anesthetized with a mixture of xylazine (7.5 mg/kg) and ketamine (150 mg/kg); the cremaster was then dissected free of skin and fascia, opened longitudinally, and pinned against the viewing platform of a plexiglass stage. The preparation was mounted on a Zeiss Axioskop "FS" microscope (original magnification, 40x, Carl Zeiss, Welwyn Garden City, UK) and transilluminated with a 12-V, 100-W halogen light source. To avoid drying out, the cremaster muscle was superfused with bicarbonate-buffered saline (pH 7.4, 37°C, gassed with 5% CO2/95% N2) at a rate of 2 ml/min.
Following a 30-min stabilization period, video recordings were made with a Hitachi charged-coupled device color camera (KPC571, Tokyo, Japan) and a S-VHS video-recorder (SVO-9500MDP) for subsequent off-line analysis. Leukocyte rolling flux, firm adhesion, and transmigration in post-capillary venules with a wall shear rate 
500 per s and diameter 20–40 µm were quantified as described previously [16
]. Briefly, rolling flux was quantified as the number of rolling leukocytes to pass a defined point on the venular wall per minute. Firmly adherent leukocytes were classified as those remaining stationary for 30 s within a given 100-µm vessel segment and transmigration as the number of leukocytes that had emigrated up to 50 µm on either side of a 100-µm vessel segment. In each animal, responses from several vessel segments (three to five) and multiple vessels (three to five) were quantified.
Statistical analyses
Statistical difference across the different treatments was analyzed by one-way ANOVA, followed if significant, by Bonferroni’s post-hoc test. Where two variables were analyzed, a Student’s t-test was used. All data are reported as mean ± SEM of n experiments performed for the in vitro analyses in duplicate. P < 0.05 was considered significant.
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Figure 1. Gal-1 binding to neutrophils. Isolated neutrophils (1x106/ml) were incubated in the presence/absence of PAF (10–9 M) for 30 min at 37°C prior to incubation with biotGal-1 (4 µg/ml) for 1 h on ice. Thiodigalactoside (TDG; 30 mM) or sucrose (Suc; 30 mM) was added to some samples at the same time as the Gal-1, and Gal-1 binding was assessed by flow cytometry. Histograms represent fluorescence intensity in the FL2 channel and are representative of separate experiments from four different donors.
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Figure 2. Effect of Gal-1 on neutrophil adhesion molecule expression. Isolated neutrophils (1x106/ml) were incubated with PAF (10–9 M) for 30 min at 37°C in the presence or absence of hrGal-1 (0.04–4 µg/ml). Neutrophils analyzed by flow cytometry for PSGL-1 (A), CD11b (B), and L-selectin (C) expression. Results are expressed as percentage of control. Experiments were performed in duplicate from three different donors. #, P < 0.05 vs. 4 µg/ml Gal-1; *, P < 0.05, versus Control (Ctrl);  , P < 0.05 vs. 0.04 µg/ml;  , P < 0.05 vs. 0.4 µg/ml.
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Figure 3. Exogenous Gal-1 inhibits neutrophil:HUVEC interactions under flow. Effects of hrGal-1 on neutrophil capture (A), rolling (B), and adhesion (C). Isolated neutrophils (1x106/ml) were incubated with Gal-1 (0.04–4 µg/ml) for 10 min at 37°C prior to perfusion over TNF- (10 ng/ml; 4 h)-stimulated HUVECs. Interactions were quantified from six random fields/treatment. Results are expressed as percentage of control of four independent experiments. *, P < 0.05, versus control; #, P < 0.05, versus 0.04 µg/ml Gal-1 and 0.4 µg/ml Gal-1, n = 4.
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50% at 48 h and 72 h post-transfection (Fig. 4B
), without affecting the expression of Gal-3 or the housekeeping gene β-actin, as detected by Western blotting (Fig. 4A)
. Forty-eight hours post-transfection (time-point chosen for optimum confluency for flow chamber assays), the attenuated endothelial Gal-1 expression led to a substantial increase (89%) in the initial capture of neutrophils to the endothelium; a prerequisite for further interactions (Fig. 5A
) with a subsequent increase in cell rolling also observed (Fig. 5B)
. No changes were observed with regards to firm adhesion of neutrophils (Fig. 5C)
.
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Figure 4. Selective decrease of endothelial Gal-1 protein expression. Knockdown of Gal-1, but not Gal-3, in HUVEC as determined by Western blotting (A). Cumulative data from greater than or equal to three individual experiments. Data are mean ± SEM; *, P < 0.05, versus 48 h nontransfected control value (B).
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Figure 5. Decreased endothelial Gal-1 enhances neutrophil:HUVEC interactions under flow. Knockdown of Gal-1 in HUVEC affects neutrophil capture (A), rolling (B), and adhesion (C), as determined 48 h post-transfection. Neutrophils were isolated as described in Materials and Methods and were perfused over TNF- (10 ng/ml; 4 h)-stimulated HUVECs. Interactions were quantified from six random fields/treatment. Results are expressed as percentage of control of greater than or equal to three independent experiments; *, P < 0.05, versus nontransfected control.
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Figure 6. Lack of endogenous Gal-1 leads to increased leukocyte emigration in vivo. Gal-1 null mice and their WT counterparts were injected with IL-1β intrascrotally for the time-points shown. Leukocyte flux (A), adhesion (B), and emigration (C) were quantified in three to five segments of three to five vessels per mouse by intravital microscopy of the cremaster muscle. Results are expressed as mean ± SEM of four to seven mice/group; *, P < 0.05, versus WT.
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The effects of Gal-1 on neutrophil function have been addressed in few studies. It has been demonstrated that although Gal-1 induces phosphatidylserine exposure on the neutrophil plasma membrane, it does not, in contrast to activated lymphocytes, induce neutrophil apoptosis [19 , 20 ]. This effect of hrGal-1 renders the cells sensitive to phagocytic recognition and removal [19 ]; hence, if confirmed in an in vivo setting, it would be a proresolving, anti-inflammatory signal. Gal-1 has also been demonstrated to induce NAD(P)H oxidase and subsequently, superoxide generation in exudated neutrophils in what could be described as a proinflammatory role for Gal-1 [21 ]. These effects, however, were only evident at high (40 µM) concentrations, which far exceed the maximal concentration used in this study (maximal concentration used of 275 nM). As NAD(P)H oxidase induction was only observed in primed neutrophils and coincided with granule mobilization, it was suggested that priming resulted in up-regulation of a receptor for Gal-1, which was not present on naïve neutrophils. A receptor(s) for Gal-1 on neutrophils has not been identified to date. In agreement with the studies by Almkvist et al. [21 ] and Dias-Baruffi et al. [19 ], who described an increase in Gal-1 binding to neutrophils collected from skin blister exudates or following treatment with fMLP, we have also demonstrated increased Gal-1 binding to neutrophils post-adhesion to the endothelium [11 ]. However, in the present study, we did not observe increased Gal-1 binding after stimulation with PAF, nor in our previous study following PMA stimulation [11 ], indicating that up-regulation of a receptor might not be a necessary prerequisite to unveil Gal-1 effects on the neutrophil; in line with this hypothesis, hrGal-1 produces an increase in intracellular calcium in naïve and activated neutrophils [20 ]. The Gal-1 binding to naïve neutrophils observed in the present study was diminished significantly by coincubation with thiodigalactoside, indicating that the binding to neutrophils is carbohydrate-dependent. Moreover, these data are in line with the abolition of the effects of Gal-1 in the flow chamber by thiodigalactoside.
In light of our previous studies in which hrGal-1 inhibited neutrophil chemotaxis and transmigration [11 ], we addressed the effect of hrGal-1 on neutrophil adhesion molecule expression as key determinants of neutrophil recruitment. The quantitative increase in CD11b expression on neutrophils in response to agonists such as PAF or fMLP, although not necessarily sufficient to support neutrophil adhesion, serves as an indication of neutrophil activation [22 , 23 ]. In conjunction with an increase in CD11b expression, neutrophil activation also results in L-selectin and PSGL-1 shedding [24 , 25 ]. Although L-selectin shedding is thought to limit neutrophil activation and thus adhesion during inflammation [26 , 27 ], the function of PSGL-1 shedding has still to be fully elucidated. Gal-1 did not have any effect on L-selectin levels on naïve or PAF-stimulated neutrophils; however, it did appear to enhance PAF-stimulated PSGL-1 shedding in a concentration-dependent manner. The mechanism responsible for PSGL-1 shedding is distinct from that of L-selectin shedding [24 ], which may account for the differing effects on these two adhesion molecules. Although the full functional impact of PSGL-1 shedding is not clear, it has been linked to a decrease in leukocyte rolling and adhesion [24 , 28 ]. The lack of an effect on PSGL-1 shedding in naïve neutrophils suggests that this is an unlikely mechanism for Gal-1 inhibition of neutrophil rolling in the flow chamber. The loss of the PAF-induced CD11b expression in response to Gal-1 suggests that Gal-1 may function to limit some aspects of neutrophil activation. These effects of Gal-1 are in contrast to another galectin, Gal-3, which has been shown to induce L-selectin shedding and IL-8 production in naïve and primed neutrophils [29 ]. These opposing effects are not limited to adhesion molecule expression; Gal-3 has also been demonstrated to promote neutrophil adhesion to endothelial monolayers in vitro [30 ] and to enhance neutrophil apoptosis [31 ]. The effects of Gal-1 on adhesion molecule expression were only apparent at the highest concentration of Gal-1 used (4 µg/ml), whereas its effects in the flow chamber were apparent at lower concentrations. Specific dose-dependent effects of Gal-1 are not unusual with numerous reports in the literature indicative of this [32 33 34 ]. It is difficult to directly compare the effects of Gal-1 on adhesion molecule expression in a static, single-cell system with those on cell recruitment under flow conditions. It may be that when exposed to shear stress, neutrophils are more sensitive to lower concentrations of Gal-1 than under static conditions.
With this study, we have highlighted another role for Gal-1 with regards to neutrophil recruitment in acute inflammation. These effects were observed at relatively low concentrations (2.75–275 nM) of Gal-1 in comparison with those used in other studies. However, we and others have previously demonstrated activity of Gal-1 at concentrations as low as 2.75 nM in inhibiting neutrophil transmigration [11
], T cell adhesion [35
], and IL-2 production by T cells [7
]. The present study is in line with others that suggest biphasic, concentration-dependent effects of Gal-1 [33
, 34
]. The lowest concentrations of Gal-1 used in the present study resulted in a significant reduction in all three parameters measured: neutrophil capture, rolling, and firm adhesion. However, these effects were lost at the highest concentration of Gal-1 used, with only a significant reduction in cell rolling apparent at the highest concentration of 4 µg/ml. Along with this reduction in neutrophil rolling, there was also an increase in firm adhesion at this highest concentration, suggesting that the decreased rolling is not a result of decreased neutrophil capture, as observed at lower concentrations, but a result of conversion from a rolling to adherent state, suggesting that high concentrations of Gal-1 may play a role in bridging neutrophils to the endothelium, an effect that has been observed for another galectin, Gal-3 [30
]. Gal-1 is known to exist in a monomer-dimer equilibrium with a Kd of 7 µM [36
]. At lower concentrations, the homodimeric protein spontaneously dissociates into a monomeric form but retains its carbohydrate-binding specificity [37
]. It is therefore likely that at the concentrations used in the present study, hrGal-1 was acting in monomeric form. As alluded to above, the effects of Gal-1 are often opposing at low versus high concentrations, as is the case with neutrophil recruitment: low concentrations inhibiting cell recruitment and high concentrations promoting recruitment. Low concentrations of Gal-1 have previously been shown to be mitogenic, whereas high concentrations inhibit cell growth and/or induce apoptosis [32
, 33
]. In an inflammatory context, high Gal-1 concentrations have been observed to trigger macrophage apoptosis and inhibit cytokine generation, and low concentrations decrease inflammatory macrophage activity without affecting viability in response to parasitic infection [34
].
It is becoming increasingly apparent that the effects of Gal-1 are complex, and its molecular mechanism of action is likely dependent on target cell, concentration applied, and carbohydrate dependency. From the present study, it can be concluded that the inhibitory effects of Gal-1 on neutrophil recruitment are apparent at low concentrations of Gal-1 and are carbohydrate-dependent in nature. The mechanism of action of Gal-1 at different concentrations has still to be elucidated; however, depending on the concentration of Gal-1 used, it is likely that it may act by inducing the cross-linking of proteins leading to inhibition or promotion of a cellular response or by enhancing or sterically hindering the binding of cell surface receptors with their ligands, as may be the case when it interacts with adhesion molecules such as CD43 [38 ]. With regards to the effects of Gal-1 on neutrophil recruitment, other than the implication of an effect in the study of Rabinovich et al. [39 ] and our previous data showing Gal-1 inhibits neutrophil chemotaxis and transmigration [11 ], this has not been addressed. In determining the effects of Gal-1 on neutrophil recruitment under flow, we have been able to observe that the specific steps of neutrophil rolling and firm adhesion are down-regulated by this mediator.
As endothelial cells, in contrast to neutrophils, express high amounts of Gal-1 [11
, 40
], it is attractive to hypothesize that endogenous Gal-1 presented by the endothelium can act to limit recruitment of this cell type (even more if primed) during an ongoing, inflammatory response. The expression of endothelial Gal-1 is increased upon activation by proinflammatory cytokines [40
] or exposure to tumor cell-conditioned medium [41
]. Little is known, however, about the function of endothelial cell-derived Gal-1 during inflammation. Overexpression of Gal-1, induced by conditioned medium from prostate cancer cells, reduces T cell migration across the endothelial monolayer, an effect that can be reversed by antiserum to Gal-1 [38
]. Our data presented here also suggest that endogenous Gal-1 limits neutrophil recruitment with higher numbers of cells recruited to HUVEC monolayers in which Gal-1 has been depleted. How knockdown of endothelial Gal-1 would augment neutrophil recruitment is not yet apparent and clearly warrants further investigation. We were unable to duplicate the effects of knocking down endothelial Gal-1 by pretreating endothelial monolayers with thiodigalactoside, suggesting that merely blocking exposed Gal-1 on the endothelial surface is not sufficient to promote neutrophil recruitment. As levels of endothelial Gal-1 are not increased upon short-term TNF- treatment (our unpublished observations), the levels of Gal-1 present in endothelial cells used for the flow assays are equivalent to basal and as such, will not reflect a more chronic situation where endothelial Gal-1 is increased [40
]; during such conditions, blocking surface Gal-1 may be more effective. The implication of a role for endogenous Gal-1 was corroborated further by the increased leukocyte adhesion and emigration observed in Gal-1 null mice in response to IL-1β. Lack of Gal-1 in endothelial cells in vitro or in Gal-1 null mice led to an enhanced cell recruitment, although different aspects of the leukocyte recruitment cascade were modulated in these two models. In vitro, a decrease in endothelial Gal-1 levels led to an increase in cell capture and rolling with no apparent effect on firm adhesion. However, in vivo, an increase in firm adhesion and emigration was observed with no apparent effect on the number of rolling cells. There are various explanations for these discrepancies. As the flow chamber system consists of just two cell types, and only one of these has been depleted of Gal-1 (in fact, human neutrophils express little if any detectable Gal-1), it can be deduced that a lack of endothelial Gal-1 results in an increase in the number of neutrophils captured and rolling on the endothelium. In the in vivo scenario, it is impossible to rule out the contribution of Gal-1 derived from cell types other than endothelial cells. It is possible that a lack of Gal-1, derived from macrophages, for example, may also affect leukocyte recruitment. As shown for other inflammatory mediators, such as NO, the source and amount of mediator produced have important bearings on its actions. Furthermore, it is difficult to directly compare the events observed in the in vitro setting of the flow chamber with those in vivo. It is well known that cells such as erythrocytes and platelets affect how leukocytes interact with the vessel wall under inflamed and noninflamed conditions; it cannot be ruled out therefore that in vivo, another cell type, such as platelets, is also involved in the increased recruitment of leukocytes to the vessel wall leading to an apparent effect on different aspects of the recruitment cascade. To the best of our knowledge, this is the first study investigating the vascular inflammatory response in Gal-1 null mice to date. Although a specific role for endothelial-derived Gal-1 cannot be derived from these results, they are a further indication that Gal-1 functions to negatively regulate leukocyte recruitment during acute inflammation, and further studies are clearly warranted.
In conclusion, we have revealed here a novel, endogenous, anti-inflammatory pathway centered on endothelial Gal-1 that targets neutrophil trafficking in an inflammatory context. Analyses of single-cell or dual-cell systems have shown, by large, an inhibitory function for hrGal-1 on neutrophil activation, although the variety of effects observed at distinct concentrations of the protein may indicate the involvement of multiple receptors and signaling circuits. Irrespective of a specific molecular mechanism(s), we propose that during inflammation, modulation of Gal-1 levels on endothelial cells would be part of a "negative check-point" aimed at limiting the influx of leukocytes into the surrounding tissues, thereby contributing to a moderation of the inflammatory response.
Received December 14, 2007; revised February 8, 2008; accepted February 25, 2008.
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in mouse cremasteric venules Br. J. Pharmacol. 137,1237-1246[CrossRef][Medline]2,3-sialylated and non-sialylated terminal N-acetyllactosamine units on surface-bound extended glycans J. Biol. Chem. 280,5549-5562This article has been cited by other articles:
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  L. V Norling, M. Perretti, and D. Cooper Endogenous galectins and the control of the host inflammatory response J. Endocrinol., May 1, 2009; 201(2): 169 - 184. [Abstract] [Full Text] [PDF]
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