Biomedical subjects

K Ley

Publications and source records attributed to K Ley.

At least 19 recordsLinked to original sources

PubMed1996

Absence of trauma-induced leukocyte rolling in mice deficient in both P-selectin and intercellular adhesion molecule 1.

Leukocyte recruitment during inflammation is achieved through a multistep paradigm that includes margination, selectin-mediated rolling, beta 2 integrin-mediated firm adhesion, emigration, and migration into the site of inflammation. We have used the mouse cremaster muscle as a model of trauma- and cytokine-induced inflammation to study the possible role of intercellular adhesion molecule (ICAM) 1 in leukocyte rolling using gene-targeted mice deficient in ICAM-1, P-selectin, and a combination of P-selectin and ICAM-1. Rolling flux and average leukocyte rolling velocity in ICAM-1-deficient mice was not different from wild-type mice, but P-selectin/ICAM-1-deficient mice showed a total absence of rolling for at least 2 h after surgical trauma. Rolling in both wild-type and ICAM-1-deficient mice 60-120 min after trauma was significantly inhibited by a P-selectin monoclonal antibody (mAb) (RB40.34). In contrast, an mAb (KAT-1) blocking ICAM-1 binding to leukocyte function-associated antigen 1 did not block residual rolling in P-selectin-deficient mice. TNF-alpha induced leukocyte rolling in P-selectin/ICAM-1-deficient mice, but the rolling flux fraction was significantly lower than in TNF-alpha-treated ICAM-1-deficient mice. Leukocyte rolling in P-selectin/ICAM-1-deficient mice treated with TNF-alpha for 3 h was completely blocked by an E-selectin mAb (9A9E3), and partially by an L-selectin mAb (MEL-14). This clearly demonstrates E-selectin-dependent rolling in vivo. Leukocyte rolling velocities were significantly reduced after TNF-alpha treatment and were similar in wild-type and gene-targeted strains. We conclude that the residual trauma-induced leukocyte rolling seen in P-selectin-deficient mice is completely abolished by concomitant ICAM-1 deficiency. This severe defect in leukocyte rolling may explain the absence of leukocyte recruitment into the inflamed peritoneal cavity of P-selectin/ICAM-1-deficient mice at early time points (< or = 4 h).

Animals↗

PubMed1995

Leukocyte rolling in vivo is mediated by P-selectin glycoprotein ligand-1.

Leukocyte rolling, an early and important step in the inflammatory response, is mediated by the selectin family of adhesion molecules. The selectins bind with low affinity to sialylated and fucosylated glycans such as sialyl Lewisx (sLex), but bind with high affinity to only a few specific glycoproteins on cell surfaces. One such glycoprotein is P-selectin glycoprotein ligand-1 (PSGL-1). The relative contributions of low- and high-affinity ligands to leukocyte rolling in vivo are unknown. We show here that a monoclonal antibody to PSGL-1 (PL1) dramatically reduces rolling of human polymorphonuclear neutrophils (PMN) and promyelocytic HL-60 cells in venules of acutely exteriorized rat mesentery. Control PMN and HL-60 cell rolling flux fractions were 39% +/- 3% and 33% +/- 5%, which were reduced by PL1 to 7% +/- 2% and 6% +/- 2%, respectively. Similar reductions were seen with F(ab) fragments of PL1. PL1-treated PMN rolled at significantly higher mean velocities than untreated PMN owing to intermittent rather that continuous interactions. These findings show that interaction of P-selectin with PSGL-1 is required for rolling of myeloid cells in mesenteric venules at physiologic shear stress in vivo.

Animals↗

PubMed1995

Leukocyte interactions with vascular endothelium. New insights into selectin-mediated attachment and rolling.

Among the earliest signs of inflammation is the capture of leukocytes from the blood stream and their subsequent rolling along the endothelium of postcapillary venules. This commentary summarizes recent insight into the molecular basis of leukocyte rolling gained from gene-targeted mice, Ab blocking studies, and in vitro and in vivo reconstitution assays. These data reveal how the selectins individually and collectively contribute to the process of leukocyte capture and subsequent rolling on vascular endothelium.

Animals↗

PubMed1995

Sialylated O-glycans and L-selectin sequentially mediate myeloid cell rolling in vivo.

Leukocyte rolling precedes firm adhesion and emigration in inflammatory cell recruitment. Both P-selectin, an endothelial lectin that binds to sialylated O-glycans containing sialyl-Lewisx (sLex) on the granulocyte surface, and leukocyte L-selectin have been shown to mediate leukocyte rolling in vivo. Here, we investigate rolling of isolated human neutrophils (PMN), HL-60 promyelocytes, and an L-selectin-transfected cell line (300.19-L) during trauma-induced inflammation in rat mesenteric venules. HL-60 cells, which express no L-selectin but abundant sLex, rolled effectively immediately after abdominal surgery. HL-60 cell rolling was almost completely abolished by pretreatment with sialidase or monoclonal antibody (MoAb) AM-3 recognizing sLex, and was reduced by about 80% by O-sialoglycoprotein-endopeptidase (OSGP). By contrast, 300.19-L cells rolled poorly immediately after surgery but rolled well between 40 and 120 minutes after surgery. Their rolling was completely inhibited by the blocking L-selectin MoAb LAM1-3, but not by a binding control MoAb. PMN express both L-selectin and clustered, sialylated glycoproteins including P-selectin glycoprotein ligand-1 (PSGL-1). PMN showed effective rolling at all times, which was abolished by sialidase or MoAb AM-3 pretreatment during the first 30 minutes after surgery, but not later, when PMN rolling was largely L-selectin-dependent. We conclude that in trauma-induced inflammation, a two-step mechanism accounts for most of myeloid cell rolling, which initially requires O-glycans and subsequently depends on L-selectin function.

Animals↗

PubMed1995

Flow-dependent regulation of arteriolar diameter in rat skeletal muscle in situ: role of endothelium-derived relaxing factor and prostanoids.

1. Arteriolar diameter in the resting rat spinotrapezius muscle was studied by intravital video microscopy before and after blockade of the L-arginine-EDRF (NG-nitro-L-arginine, L-NNA) or the cyclo-oxygenase-prostacyclin (indomethacin) pathway. Blockade of either pathway leads to a decrease of arteriolar diameter of 25-40%, while the combined blockade of both results in vasoconstriction of 50-60%. 2. Alteration of blood flow velocity elicited by partial micropipette occlusion induces corresponding changes of vessel diameter. The flow-dependent diameter response is reduced by about 80% by L-NNA. By contrast, blockade of prostanoid production shows no significant influence on vessel response to blood flow alteration in the range tested. 3. Transient overshooting vasodilatation is seen for about 1 min following the sudden restoration of flow velocity subsequent to occlusion. In contrast to the initial phase of this response, the late phase is blocked by L-NNA. 4. The findings suggest that basal release of endothelium-derived relaxing factor (EDRF) and prostanoids leads to additive and independent dilator effects, and that flow-dependent diameter changes are primarily mediated by EDRF. 5. If present data are compared with literature reports, it appears that arterial flow sensitivity is most pronounced in the smallest vessels. In such vessels, flow-dependent dilatation will amplify even small changes of volume flow by more than four times.

Animals↗

PubMed1995

Sequential contribution of L- and P-selectin to leukocyte rolling in vivo.

Leukocyte recruitment into inflammatory sites is initiated by a reversible transient adhesive contact with the endothelium called leukocyte rolling, which is thought to be mediated by the selectin family of adhesion molecules. Selectin-mediated rolling precedes inflammatory cell emigration, which is significantly impaired in both P- and L-selectin gene-deficient mice. We report here that approximately 13% of all leukocytes passing venules of the cremaster muscle of wild-type mice roll along the endothelium at < 20 min after surgical dissection. Rolling leukocyte flux fraction reaches a maximum of 28% at 40-60 min and returns to 13% at 80-120 min. In P-selectin-deficient mice, rolling is absent initially and reaches 5% at 80-120 min. Rolling flux fraction in L-selectin-deficient mice is similar to wild type initially and declines to 5% at 80-120 min. In both wild-type and L-selectin-deficient mice, initial leukocyte rolling (0-60 min) is completely blocked by the P-selectin monoclonal antibody (mAb) RB40.34, but unaffected by L-selectin mAb MEL-14. Conversely, rolling at later time points (60-120 min) is inhibited by mAb MEL-14 but not by mAb RB40.34. After treatment with tumor necrosis factor (TNF)-alpha for 2 h, approximately 24% of all passing leukocytes roll in cremaster venules of wild-type and P-selectin gene-deficient mice. Rolling in TNF-alpha-treated mice is unaffected by P-selectin mAb or E-selectin mAb 10E9.6. By contrast, rolling in TNF-alpha-treated P-selectin-deficient mice is completely blocked by L-selectin mAb. These data show that P-selectin is important during the initial induction of leukocyte rolling after tissue trauma. At later time points and in TNF-alpha-treated preparations, rolling is largely L-selectin dependent. Under the conditions tested, we are unable to find evidence for involvement of E-selectin in leukocyte rolling in mice.

Antibodies, Monoclonal↗

PubMed1995

The leukocyte integrin Mac-1 (CD11b/CD18) contributes to binding of human granulocytes to collagen.

Adhesion of polymorphonuclear granulocytes (PMN) to extracellular matrix proteins has been shown to be important for their migration in vitro and is thought to participate in PMN recruitment to sites of inflammation. Isolated human PMN stimulated with PMA were found to adhere best to microtiter wells coated with the novel ECM glycoprotein undulin (27 +/- 3% of PMNs added), followed by fibrinogen (25 +/- 2%), collagen type VI (18 +/- 2%), fibronectin (16 +/- 2%), and laminin (15 +/- 3%). PMN adhesion to other collagens ranged between 3 and 11%. Monoclonal antibodies recognizing CD18 and CD11b subunits of Mac-1 inhibited adhesion of PMN to collagens by an order of magnitude more effectively than to all noncollagenous substrates. F(ab')2 fragments of the anti-CD18 antibody were also able to block adhesion to collagens. Anti-LFA-1 (CD11a) and anti-CD44 antibodies did not significantly reduce adhesion. PMN adhesion was also inhibited by soluble collagens type II and VI (ID50 approximately 75 micrograms/ml). Binding of soluble radiolabeled collagens type II and VI to PMNs was specific and saturable with apparent dissociation constants of 2.2 and 1.9 nM, respectively, and specific binding of collagens type II and VI was almost completely inhibited by anti-CD18, but not by control antibodies. These data indicate that Mac-1 function is required for binding of human PMN to collagens.

Antibodies, Monoclonal↗

PubMed1995

Effect of oxygen tension on regulation of arteriolar diameter in skeletal muscle in situ.

Skeletal muscle arterioles are known to constrict upon elevation of ambient PO2. While several studies have shown that the endothelium plays an important role in this response, it is not clear how this response is mediated. We examined the oxygen-induced constriction of arterioles in the rat spinotrapezius muscle. Elevation of superfusion solution PO2 from about 15 to 150 mm Hg caused arteriolar constriction by 25% (+/- 3%, n = 18). Inhibition of prostaglandin synthesis by superfusion of indomethacin (30 microM) produced vasoconstriction by 28% (+/- 9.5%, n = 5), but left the PO2 response unaffected. Blockade of the synthesis of endothelium-derived relaxing factor (EDRF) by NG-nitro-L-arginine (L-NNA, 35 mg/kg i.v.) caused arteriolar constriction by 31% (+/- 8%, n = 8). During application of L-NNA, the constrictor response to PO2 elevation was reduced to 3 +/- 2%. Administration of superoxide dismutase (SOD, 80,000 U/kg i.v.) did not affect the PO2 response. It is concluded that in small arterioles of skeletal muscle both EDRF and prostanoids sustain a significant basal dilatation. The dilatory effects of EDRF but not of prostaglandins are strongly dependent on PO2. The vasoconstriction in response to high ambient PO2 is not due to EDRF breakdown during its diffusion from endothelial to smooth muscle cells.

Animals↗

PubMed1995

Gene-targeted mice in leukocyte adhesion research.

Physiologic and inflammatory leukocyte trafficking are controlled by adhesion molecules on leukocytes and endothelial cells. These adhesion molecules can be grouped into four major families: integrins, immunoglobulinlike molecules, selectins, and glycoproteins serving as selectin ligands. The recent advent of gene-targeting technology in embryonal stem cells has prompted the production of mutant mice that lack individual adhesion molecules or combinations thereof. Such gene-targeted mice permit studies into the roles of adhesion molecules in acute and chronic inflammation and of the regulation and interplay between different sets of adhesion receptors in vivo. Microcirculatory studies have been indispensable to our understanding of the importance of certain adhesion molecules for different steps of leukocyte recruitment in vivo. Targeting new genes and investigating mice with combined adhesion-molecule deficiencies will help to further clarify the molecular mechanisms of leukocyte trafficking in health and disease. This article reviews the insight gained through using adhesion molecule-deficient mice, emphasizing the role of microcirculatory studies in this research.

Animals↗

PubMed1994

Cross-linking of CD18 in human neutrophils induces an increase of intracellular free Ca2+, exocytosis of azurophilic granules, quantitative up-regulation of CD18, shedding of L-selectin, and actin polymerization.

Polymorphonuclear leukocytes (PMNs) exert most of their physiological functions while adherent to surfaces rather than in suspension. PMN adhesion is largely dependent on the function of the beta 2 integrins, CD11a,b,c/CD18. We mimicked engagement of beta 2 integrins by antibody cross-linking of CD18 on isolated human PMNs using both intact monoclonal antibody and F(ab')2 fragments. Within seconds of CD18 cross-linking, we observed a significant, transient rise of intracellular free Ca2+ concentration by 200-300 nM, which was largely due to Ca2+ mobilization from intracellular stores. The Ca2+ signal was blocked after pretreatment with phorbol myristate acetate, an activator of protein kinase C, but not with herbimycin A, a potent inhibitor of tyrosine kinases. In addition to the rise of intracellular free Ca2+ concentration, CD18 cross-linking induced exocytosis of azurophilic granules (release of 26% of total PMN elastase), which was significantly inhibited by herbimycin A. Moreover, 2.2-fold up-regulation of CD18 antigen and significant down-regulation of surface expression of the granulocyte adhesion molecule L-selectin were induced. Granulocyte F-actin content as measured by nitrobenzoxadiazole-phallacidin increased significantly 1 min after CD18 cross-linking. By contrast, CD18 cross-linking by soluble antibodies did not induce superoxide production, but PMNs bound to immobilized monoclonal antibodies against CD18 released significant amounts of superoxide. Initial signaling through beta 2 integrins does not appear to be mediated by a phospholipase C isoform activated through tyrosine phosphorylation, because the Ca2+ signal was not altered by herbimycin A. However, more complex cellular responses including exocytosis were found to require tyrosine phosphorylation. We show that engagement of beta 2 integrins provides an important stimulatory signal to PMNs inducing degranulation, modulation of L-selectin, and cytoskeletal changes.

Actins↗

PubMed1994

Lymphocyte homing and leukocyte rolling and migration are impaired in L-selectin-deficient mice.

L-selectin, a cell adhesion molecule expressed by leukocytes, mediates the attachment of lymphocytes to high endothelial venules (HEV) of peripheral lymph nodes and mediates the earliest interactions between leukocytes and activated vascular endothelium. Mice possessing a mutant L-selectin gene that results in the complete loss of cell surface receptor expression were generated by gene targeting. Lymphocytes from these mice did not bind to peripheral lymph node HEV and these mice had a severe reduction in the number of lymphocytes localized to peripheral lymph nodes. Short-term homing experiments demonstrated that L-selectin was also involved in lymphocyte migration to mucosal lymph nodes, Peyer's patches, and spleen. Furthermore, significant defects in leukocyte rolling and neutrophil migration into the peritoneum in response to an inflammatory stimulus were observed. Thus, L-selectin plays an essential role in leukocyte homing to lymphoid tissues and sites of inflammation.

Animals↗

PubMed1994

A role for the epidermal growth factor-like domain of P-selectin in ligand recognition and cell adhesion.

The selectin family of adhesion molecules mediates the initial interactions of leukocytes with endothelium. The extracellular region of each selectin contains an amino-terminal C-type lectin domain, followed by an EGF-like domain and multiple short consensus repeat units (SCR). Previous studies have indirectly suggested a role for each of the extracellular domains of the selectins in cell adhesion. In this study, a panel of chimeric selectins created by exchange of domains between L- and P-selectin was used to directly examine the role of the extracellular domains in cell adhesion. Exchange of only the lectin domains between L- and P-selectin conferred the adhesive and ligand recognition functions of the lectin domain of the parent molecule. However, chimeric selectins which contained both the lectin domain of L-selectin and the EGF-like domain of P-selectin exhibited dual ligand-binding specificity. These chimeric proteins supported adhesion both to myeloid cells and to high endothelial venules (HEV) of lymph nodes and mesenteric venules in vivo. Exchange of the SCR domains had no detectable effect on receptor function or specificity. Thus, the EGF-like domain of P-selectin may play a direct role in ligand recognition and leukocyte adhesion mediated by P-selectin, with the lectin plus EGF-like domains collectively forming a functional ligand recognition unit.

Animals↗

PubMed1994

Histamine can induce leukocyte rolling in rat mesenteric venules.

Rolling is a retarded movement of leukocytes that depends on the function of the selectin class of adhesion molecules. In venules of internal organs, rolling is rapidly induced on tissue exposure by unknown mediator(s). Rolling was investigated with intravital microscopy in venules of the exteriorized mesentery of anesthetized rats. Immediately after exteriorization, rolling leukocyte flux was very low (10 +/- 4 min-1) and increased rapidly to reach a peak of 76 +/- 10 min-1 at 30 min. Intraperitoneal pretreatment of rats with histamine induced near-maximal rolling in mesenteric venules immediately after exteriorization. Leukocyte rolling was significantly inhibited by intravenular microinfusion of monoclonal antibody PB1.3 that recognizes and functionally blocks human and rat P-selectin. The effect of histamine was blocked by pretreatment with ranitidine, an H2-receptor antagonist, but not with diphenhydramine, which blocks H1 receptors. However, ranitidine did not block the subsequent increase of rolling leukocyte flux, and rolling leukocyte flux was similar in all groups 20 min after exteriorization. Histological investigation revealed degranulation of mast cells, suggesting release of histamine and other mediators. These findings indicate that histamine can induce leukocyte rolling in vivo via H2 receptors, most likely by inducing endothelial expression of P-selectin. In addition, mediators other than histamine released from mast cells and/or other cells are likely to promote sustained rolling.

Animals↗

PubMed1993

Intravenous interleukin-8 inhibits granulocyte emigration from rabbit mesenteric venules without altering L-selectin expression or leukocyte rolling.

Injection (i.v.) of the granulocyte chemoattractant/activator IL-8 has been shown to reduce neutrophil recruitment into dermal inflammatory sites in vivo. To further investigate the mechanism of this phenomenon, we examined the effect of i.v. [Ser-IL-8]72 (12-20 micrograms/kg) on leukocyte rolling and chemoattractant-induced emigration in mesenteric venules of New Zealand White rabbits and on expression of L-selectin (mAb LAM1-3) and CD18 (mAb 60.3) on circulating rabbit granulocytes. Within 1 min of IL-8 i.v., granulocytes virtually disappeared from carotid blood samples for approximately 5 min. Concomitantly, the flux of rolling leukocytes in mesenteric venules fell from 83 +/- 21 to 2 +/- 1 leukocytes/min. Both rolling leukocyte flux and systemic granulocyte count returned to or exceeded control values within less than 30 min. The chemoattractant/activator FMLP (0.15 microgram/kg i.v.) produced similar results. A second i.v. injection of IL-8 or FMLP, 90 min after the first challenge, had equipotent effects. Local extravascular application of IL-8 via micropipette close to a venule induced adhesion and emigration of 63 +/- 21 leukocytes per site before, but only 26 +/- 9 leukocytes per site 50 to 75 min after i.v. IL-8, when systemic granulocyte count and rolling leukocyte flux had reached or exceeded control values. This was not due to agonist-specific desensitization, because a similar reduction of leukocyte emigration was seen after FMLP i.v. Rabbit granulocytes circulating in vivo uniformly expressed near-control levels of L-selectin at all times between 3 and 360 min after IL-8 i.v. CD18 expression transiently increased after IL-8 i.v. and returned to base line by 90 min. These findings show that IL-8 i.v. reduces granulocyte recruitment to inflammatory sites by inhibiting function(s) necessary for transmigration that are independent of L-selectin and subsequent to rolling.

Animals↗

PubMed1993

L-selectin can mediate leukocyte rolling in untreated mesenteric venules in vivo independent of E- or P-selectin.

Granulocyte recruitment during the acute inflammatory response is initiated by their rolling along the endothelial lining of postcapillary venules. To determine whether expression of L-selectin alone is sufficient for rolling, the murine pre-B lymphocytic cell line 300.19, which does not bind E- or P-selectin, was transfected with human L-selectin cDNA, which led to stable L-selectin expression at a level similar to that of blood lymphocytes. Fluorescent-labeled cells were infused retrogradely into a side branch of the superior mesenteric artery of anesthetized rats. In venules of the mesenteric membrane, leukocyte rolling occurs without intentional stimulation. On average, 17% +/- 6% of L-selectin transfectants rolled in the observed venules, while mock-transfected cells did not roll. Rolling of L-selectin transfectants began approximately 20 minutes after surgery and continued for at least 120 minutes. In contrast, HL-60 promyelocytes, which express sialyl-Lewis(x) tetrasaccharide (sLe(x)) but not L-selectin and that bind to E- and P-selectin in vitro, did not roll between 20 and 120 minutes, but some HL-60 cells rolled at very early (< 20 minutes) and late (> 2 hours) time points. Pretreatment with either of two function-blocking monoclonal antibodies recognizing the lectin domain of L-selectin completely blocked rolling of L-selectin transfectants and sharply reduced (by 70%) rolling of isolated human granulocytes. Taken together, these results show that L-selectin can mediate leukocyte rolling by virtue of its lectin activity.

Animals↗

PubMed1993

Regulation of leukocyte rolling and adhesion to high endothelial venules through the cytoplasmic domain of L-selectin.

L-selectin (leukocyte adhesion molecule 1/MEL-14), a member of the selectin family of cell adhesion molecules, mediates leukocyte rolling and leukocyte adhesion to endothelium at sites of inflammation. In addition, L-selectin mediates the binding of lymphocytes to high endothelial venules (HEV) of peripheral lymph nodes. The strong amino acid sequence conservation of the cytoplasmic domain of L-selectin between humans and mice suggests an important role for this region. Deletion of the COOH-terminal 11 amino acids from the approximately 17 amino acid cytoplasmic domain of L-selectin eliminated binding of lymphocytes to HEV in the in vitro frozen section assay, and also abolished leukocyte rolling in vivo in exteriorized rat mesenteric venules, but did not alter the lectin activity of L-selectin. Pretreatment of cells with cytochalasin B, which disrupts actin microfilaments, also abolished adhesion without affecting carbohydrate recognition. Therefore, the cytoplasmic domain of L-selectin regulates leukocyte adhesion to endothelium independent of ligand recognition, by controlling cytoskeletal interactions and/or receptor avidity.

Actin Cytoskeleton↗

PubMed1993

Fucoidin, but not yeast polyphosphomannan PPME, inhibits leukocyte rolling in venules of the rat mesentery.

Leukocyte rolling in venules is inhibited by several sulfated polysaccharides, by antibodies to the leukocyte adhesion receptor L-selectin (LECAM-1), and by recombinant soluble L-selectin. The sulfated fucose polymer fucoidin and the polyphosphomannan PPME bind to L-selectin and inhibit L-selectin-mediated lymphocyte adhesion to lymph node high endothelial venules (LN-HEV). We investigated whether fucoidin and PPME also inhibit leukocyte rolling. Rolling leukocyte flux was determined by intravital microscopy in 47 venules (diameter 21 to 50 microns) of the rat mesentery with and without micro-infusion of each reagent through 8-microns glass micropipettes. Micro-infusion (1 mg/mL) or intravenous (IV) injection (25 mg/kg) of fucoidin, but not vehicle, reduced leukocyte rolling by greater than 90%. The half-effective concentration was approximately 2.5 micrograms/mL. Stroboscopic fluorescence video microscopy showed that fucoidin decreased the fraction of rolling leukocytes from 44% of all leukocytes passing the venules in control to less than 1%. PPME micro-infusion (1 mg/mL) or IV injection (14 mg/kg) did not reduce leukocyte rolling. Hence, leukocyte rolling differs from lymphocyte homing with respect to the effect of PPME. This may be related to fucoidin binding to L-selectin with greater affinity than PPME. Alternatively, inflamed venular endothelium may express a ligand for L-selectin different from that constitutively expressed on LN-HEV.

Animals↗

PubMed1993

Molecular mechanisms of leucocyte rolling and adhesion to microvascular endothelium.

Leucocyte accumulation and activation can lead to tissue injury subsequent to ischaemic insults and reperfusion. Post ischaemic leucocyte recruitment requires the coordinated function of at least four sets of adhesion receptors. Leucocyte rolling in microvessels is mediated by the selectin family of adhesion molecules and their carbohydrate ligands, while firm adhesion and transendothelial migration requires binding of integrin molecules on leucocytes to molecules of the immunoglobulin superfamily expressed on endothelial cells. Adhesion processes are exquisitely regulated at the transcriptional level, but also by conformational changes of proteins and enzymatic modifications of carbohydrate ligands. This article reviews the current knowledge on the function and regulation of adhesion molecules pertinent to leucocyte recruitment.

Animals↗