Soluble L-selectin is present in human plasma at high levels and retains functional activity

Are circulating neutrophils intravascularly activated in patients with anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitides?

Vascular injury in vasculitis may be due to activation of circulating neutrophils resulting in their increased adhesiveness to locally activated endothelium (Shwartzman phenomenon). Previously, we demonstrated up-regulation of endothelial intercellular adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-1 (VCAM-1) in biopsies from patients with ANCA-associated vasculitis. In the present study, we investigated the expression of adhesion molecules (CD11b, ICAM-1, VLA-4, L-selectin) and activation markers (CD66b, CD64, CD63) on circulating neutrophils from patients with ANCA-associated vasculitis in comparison with their expression on cells from healthy volunteers and patients with sepsis. We related these findings to parameters of disease activity. Surface marker expression was determined by using a non-activating whole blood flow cytometric assay. The expression of activation markers, but not the expression of adhesion molecules, was increased on neutrophils from patients with active vasculitis. The expression of CD63 and CD66b on neutrophils correlated with disease activity as determined by the Birmingham Vasculitis Activity Score (BVAS). In contrast to patients with active vasculitis, patients with sepsis showed up-regulation of all markers, including adhesion molecules, suggesting that circulating neutrophils are fully activated in sepsis. We conclude that in ANCA-associated vasculitis, circulating neutrophils are not fully activated, since they do not express increased levels of adhesion molecules as sepsis or in the Shwartzman reaction. These findings are compatible with the concept that in vivo vascular damage in ANCA-associated vasculitides does not occur due to a Shwarzman-like reaction but only after ANCA-induced neutrophil activation at the endothelial cell surface.

Relationship Between Cleaved L-Selectin Levels and the Outcome of Acute Myeloid Leukemia

High plasma levels of the shed form of L-selectin (sL-selectin) are frequently detectable in acute myeloid leukemia (AML). sL-selectin can inhibit blast cell adhesion to vascular endothelium and may thereby influence the phenotype of AML. In this study, we have investigated the relationship between sL-selectin levels and clinical presentation or disease outcome in 100 patients with AML. Fifty-eight patients were found to have sL-selectin levels ≥3.12 μg/mL (≥3 SD above the mean of healthy controls: “increased”). Patients with extramedullary disease such as lymphadenopathies, splenomegaly, hepatomegaly, and/or muco-cutaneous infiltration had significantly increased sL-selectin levels (P < .001). sL-selectin levels were significantly heterogeneous in the French-American-British subtypes (P = .0003). Patients with “normal” sL-selectin levels had higher probability of achieving complete remission (CR) than with “increased” levels: 81% versus 64%, respectively (P = .06). When adjusting for clinically relevant covariates predictive for CR (sex, age, Auer rods), “normal” sL-selectin levels were significantly associated with CR (odds ratio, 3.08; 95% confidence interval [CI], 1.10 to 8.58;P = .03). Moreover, patients with “increased” sL-selectin levels (≥3.12 μg/mL) had shorter event-free survival (EFS) (median 7.3 v 12 months, P = .008) and overall survival (median 1 v 2.05 years, P = .03) than patients with sL-selectin <3.12 μg/mL. Multivariate statistical analysis (adjusted for age and presence of Auer rods) indicated that sL-selectin was an independent prognostic factor for EFS (hazard ratio [HR], 1.96; 95% CI, 1.21 to 3.17, P = .006) and overall survival (HR, 1.80; 95% CI, 1.09 to 2.98; P = .02). Thus, plasma sL-selectin may be a useful prognostic marker in the evaluation of AML at diagnosis.

© 1998 by The American Society of Hematology.

Adhesion molecules in common variable immunodeficiency (CVID)--a decrease in L-selectin-positive T lymphocytes

CVID is immunologically characterized by defective antibody production. Various additional immunological abnormalities have been reported, but little is known of the role of adhesion molecules in CVID. In 31 CVID patients serum levels of L-selectin (CD62L), vascular cell adhesion molecule-1 (VCAM-1) (CD106) and intercellular adhesion molecule-1 (ICAM-1) (CD54) were significantly elevated compared with controls. In 15 CVID patients investigated, the number of L-selectin-positive cells was significantly reduced in both CD4+ and CD8+ lymphocytes compared with controls, and these changes were observed in both CD45RA+ and CD45RO+ subsets. In CD19+ lymphocytes the percentage of ICAM-1+ cells was significantly increased compared with controls. Fifty percent of the patients had splenomegaly. These patients demonstrated even higher serum levels of adhesion molecules, a lower percentage of L-selectin-positive and a higher percentage of CD38+ cells in many T lymphocyte subsets compared with both other CVID patients and controls. Finally, in this patient group the percentage of L-selectin-positive CD19+ lymphocytes was significantly reduced compared with both other patients and controls. These findings indicate a state of ongoing T lymphocyte activation in CVID, especially in the subgroup of patients with splenomegaly, which may contribute to the impaired antimicrobial defence observed in these patients.

Levels of soluble Fc gammaRIII correlate with disease severity in sepsis

Neutrophil activation is thought to play a crucial role in the pathogenesis of sepsis. During activation, neutrophils adhere to and migrate through the endothelium. Therefore, the amount of circulating neutrophils does not adequately reflect the total amount of neutrophils that are involved in the pathophysiologic process of this condition. In this study we test the hypothesis that the severity of sepsis is associated with the total body mass of neutrophils as reflected in the plasma concentration of soluble Fc gamma receptor type III (sFc gammaRIII). Nineteen patients with sepsis (12 male, seven female, median age of 69 years, range 29-87 years) were included in this study. Ten healthy volunteers served as controls. Plasma sFc gammaRIII concentrations were measured by ELISA. Other parameters that were studied were leucocyte count, plasma concentrations of lactoferrin and soluble L-selectin, and surface expression of CD11b and CD66b on circulating neutrophils. Disease activity was measured using the Acute Physiology and Chronic Health Evaluation (APACHE) II score. Soluble Fc gammaRIII levels were elevated in sepsis patients whereas soluble L-selectin levels were moderately decreased compared with healthy controls. Markers of cell activation were significantly increased in sepsis patients. Soluble Fc gammaRIII correlated with disease severity as measured by the APACHE score (P<0.05, r=0.53), whereas the other parameters did not correlate with the APACHE score. In conclusion, this study demonstrates that soluble Fc gammaRIII is a useful marker for disease severity in patients with sepsis.

Relationship Between Cleaved L-Selectin Levels and the Outcome of Acute Myeloid Leukemia

High plasma levels of the shed form of L-selectin (sL-selectin) are frequently detectable in acute myeloid leukemia (AML). sL-selectin can inhibit blast cell adhesion to vascular endothelium and may thereby influence the phenotype of AML. In this study, we have investigated the relationship between sL-selectin levels and clinical presentation or disease outcome in 100 patients with AML. Fifty-eight patients were found to have sL-selectin levels ≥3.12 μg/mL (≥3 SD above the mean of healthy controls: “increased”). Patients with extramedullary disease such as lymphadenopathies, splenomegaly, hepatomegaly, and/or muco-cutaneous infiltration had significantly increased sL-selectin levels (P < .001). sL-selectin levels were significantly heterogeneous in the French-American-British subtypes (P = .0003). Patients with “normal” sL-selectin levels had higher probability of achieving complete remission (CR) than with “increased” levels: 81% versus 64%, respectively (P = .06). When adjusting for clinically relevant covariates predictive for CR (sex, age, Auer rods), “normal” sL-selectin levels were significantly associated with CR (odds ratio, 3.08; 95% confidence interval [CI], 1.10 to 8.58;P = .03). Moreover, patients with “increased” sL-selectin levels (≥3.12 μg/mL) had shorter event-free survival (EFS) (median 7.3 v 12 months, P = .008) and overall survival (median 1 v 2.05 years, P = .03) than patients with sL-selectin <3.12 μg/mL. Multivariate statistical analysis (adjusted for age and presence of Auer rods) indicated that sL-selectin was an independent prognostic factor for EFS (hazard ratio [HR], 1.96; 95% CI, 1.21 to 3.17, P = .006) and overall survival (HR, 1.80; 95% CI, 1.09 to 2.98; P = .02). Thus, plasma sL-selectin may be a useful prognostic marker in the evaluation of AML at diagnosis.

© 1998 by The American Society of Hematology.

Leukocyte adhesion molecule profiles and outcome after traumatic brain injury

Adhesion molecules have an important role in leukocyte migration into tissue after injury. We hypothesised that changes in ICAM-1 and L-selectin expression after traumatic brain injury would result in altered serum concentrations of these molecules, which would be related to injury severity and outcome. We investigated arterial and jugular venous concentrations of ICAM-1 and L-selectin in 22 patients. The Glasgow Coma Score and Injury Severity Score were recorded. Paired arterial and jugular venous blood samples were taken at designated times after brain injury: on admission, at 24 hours, 48 hours and 96 hours. Glasgow Outcome Scores at 6 months were obtained. Mean serum concentrations of ICAM-1 were normal on admission, but became significantly increased by 96 hours (p = 0.018). Mean L-selectin concentrations wre markedly below controls at all time points (p < 0.001). There were no significant differences between jugular venous and arterial concentrations of either ICAM-1 or L-selectin. Serum ICAM-1 was significantly related to neurological outcome (p < 0.001) and to the Glasgow Coma Score (p < 0.001). These changes in adhesion molecules expression may be important in the pathophysiology of secondary injury. The highly significant relationship between serum ICAM-1 and neurological outcome suggests that drugs which antagonize adhesion molecule activity may improve outcome after traumatic brain injury.

Inflammatory mediators in Escherichia coli O157:H7 hemorrhagic colitis and hemolytic-uremic syndrome

BACKGROUND

Recent experimental data suggest that the inflammatory response of the host to verotoxin and/or lipopolysaccharides of Escherichia coli is involved in the pathophysiology of verotoxin-producing E. coli (VTEC) infections.

METHODS

We measured the circulating concentrations of cytokines [TNF-alpha, interleukin (IL)-1-beta, IL-1 receptor antagonist (Ra), IL-6, IL-8, IL-10] and soluble leukocyte adhesion molecules (L-selectin, P-selectin, E-selectin, intracellular cell adhesion molecule-1, vascular cell adhesion molecule-1) by sandwich enzyme-linked immunosorbent assay among (1) normal controls (n = 12), (2) disease controls with hemorrhagic colitis (HC) not associated with VTEC infections (n = 57), (3) patients with uncomplicated HC caused by E. coli O157:H7 (n = 30), and (4) children with hemolytic-uremic syndrome (HUS) (n = 28). Patients with HUS were matched with children who presented an uncomplicated HC caused by E. coli O157:H7 for the time interval elapsed between the onset of HC and that of blood sample collection.

RESULTS

Concentrations of TNF-alpha and IL-1-beta were undetectable. Children with HUS were characterized by increased amounts of IL-6 and IL-8, lower values of soluble L-selectin as well as increased levels of IL-10 and IL-1Ra. The circulating concentrations of IL-1Ra were higher among children with O157:H7 HC who subsequently developed HUS.

CONCLUSIONS

Increased pro- and antiinflammatory cytokine responses are produced by the host during the development of HUS among children with VTEC infections. Further studies are needed to determine their relative contribution to the pathophysiology of classic HUS.

Circulating L-selectin levels and endothelial CD34 expression in inflammatory bowel disease

OBJECTIVE

Soluble L-selectin (sL-selectin) concentrations are positively correlated with disease activity in ulcerative colitis (UC) but not in Crohn's disease (CD). This difference in sL-selectin regulation could be due to a disease specific regulation of L-selectin ligands. The aim of this study was to compare levels of circulating sL-selectin, expression of the L-selectin ligand CD34 in the affected colon, and inflammatory bowel disease activity.

METHODS

Twenty-three patients with UC, 16 patients with CD, and 18 control subjects were included in the study. In blood samples concentrations of serum sL-selectin were determined by an ELISA technique. In colonoscopically obtained biopsies, CD34 expression was evaluated by immunohistochemical methods using monoclonal CD34 antibodies. Disease activity was determined by a clinical semiquantitative scale.

RESULTS

sL-selectin levels were found to be significantly increased along with increasing disease activity in UC (p < 0.001) but not in CD (p > 0.05) patients. UC patients with quiescent and severe disease activity had significantly lower (p < 0.005) and higher (p < 0.002) sL-selectin concentrations than controls, respectively. CD34 expression was found to be increased in both disease groups as compared with controls (p < 0.05).

CONCLUSION

A disease-specific regulation of CD34 was not found as an explanation for the distinction in sL-selectin regulation. In the light of recent reports on low sL-selectin in other diseases, it is suggested instead that ongoing neutrophil activation may be the reason for low sL-selectin concentrations during quiescent disease stages, whereas chemokine secretion could explain the increased levels of sL-selectin associated with severe disease activity.

Detection of soluble E-selectin, ICAM-1, VCAM-1, and L-selectin in the cerebrospinal fluid of patients after subarachnoid hemorrhage

OBJECT

The goal of this study was to explore whether the levels of soluble adhesion molecules were elevated in cerebrospinal fluid (CSF) after subarachnoid hemorrhage (SAH). This association was suggested by the known inflammatory response in vasospasm and the role of vascular adhesion molecules in regulating leukocytic adhesion to, and migration across, vascular endothelium.

METHODS

A prospective analysis was performed on CSF samples obtained in 17 patients who had suffered a recent aneurysmal SAH and in 16 control patients by using quantitative enzyme-linked immunosorbent assays for E-selectin, intercellular adhesion molecule-1 (ICAM-1), vascular adhesion molecule-1 (VCAM-1), and L-selectin. Levels of soluble forms of E-selectin (p=0.0013), ICAM-1 (p=0.0001), and VCAM-1 (p=0.048) were found to be elevated in the CSF of patients after SAH compared with levels in the CSF of norminal controls, patients with unruptured aneurysms, and patients tested months after SAH occurred. In addition, individual patients tested at the time of their initial ictus demonstrated a fall in adhesion molecule levels over time. Levels of E-selectin (p=0.044) were highest in patients who later developed moderate or severe vasospasm.

CONCLUSIONS

Adhesion molecules are known to be involved in white cell adherence to the endothelium and subsequent diapedesis and migration in which a role in initiation of tissue damage is postulated. The authors have demonstrated the elevation of three adhesion molecules, with severely elevated levels of E-selectin seen in patients who later develop vasospasm. A correlation with a role of vascular adhesion molecules in the pathogenesis of cerebral vasospasm is suggested.

Decreased soluble adhesion molecule L-selectin plasma concentrations after major trauma

BACKGROUND

Binding of the leukocyte glycoprotein L-selectin to ligands expressed by activated endothelium directs leukocyte recruitment to areas of acute inflammation. Sequestration by activated microvascular endothelium has been proposed to explain the low plasma concentrations of soluble L-selectin (sCD62L) observed early in patients with acute respiratory distress syndrome. We hypothesized that inflammatory endothelial activation may occur in trauma patients, leading to decreased sCD62L plasma concentrations.

METHODS

This study was a prospective analysis of sCD62L plasma concentrations in patients with isolated head injuries and multiple trauma patients without head injuries admitted to two tertiary-level intensive care units. sCD62L plasma concentrations were determined in 18 consecutive adult patients with isolated moderate and severe head injuries and in 13 multiple trauma patients without head injuries immediately upon admission to the intensive care unit and then daily for up to 10 days after trauma.

RESULTS

Compared with healthy adult controls (n=22), patient sCD62L plasma concentrations were significantly decreased upon admission (5.7+/-1.6 vs. 11.0+/-1.7 pmol/mL; p < 0.001). In all patients, sCD62L concentrations remained depressed throughout the study period. sCD62L concentrations did not differ significantly between patients with isolated head injuries and multiple trauma patients without head injuries, although repeated-measures analysis of variance showed significantly more depressed sCD62L concentrations associated with severe (n=14) compared with moderate head injuries (n=4) during the study period (p < 0.05).

CONCLUSION

Patients with major trauma present with a significant reduction of sCD62L plasma concentrations within the first 12 hours after trauma and during subsequent intensive care. This finding suggests widespread microvascular endothelial activation after trauma, which may be associated with increased neutrophil extravasation.

Changes in leucocyte counts and soluble intercellular adhesion molecule-1 and E-selectin during cardiopulmonary bypass in children

A consequence of cardiopulmonary bypass (CPB) in young children is postoperative capillary leak and associated pulmonary dysfunction. Neutrophils sequester in the lungs and may contribute to functional endothelial damage. The endothelial adhesion molecules, E-selectin and intercellular adhesion molecule-1 (ICAM-1), mediate sequential steps in adhesion by binding to leucocyte ligands. Circulating forms of these proteins have been identified. We studied changes in the plasma concentrations of soluble E-selectin and soluble ICAM-1 using fixed phase immunoassays, and associated leucocyte counts in 10 paediatric patients undergoing CPB. Concentrations of soluble L-selectin and soluble ICAM-1 consistently fell during CPB from preoperative levels of 89 +/- 17 ng/ml (mean +/- 2SEM) and 218 + 61 ng/ml, respectively, to 39 +/- 7 ng/ml and 84 +/- 24 ng/ml, respectively at the beginning of maximum hypothermia. The haemodilution that occurred during CPB largely explained this fall, but not the more marked decrease in white cell counts that also occurred over this period (6.7 +/- 1.1 to 1.7 +/- 0.5 x 10(9)/l) which may reflect increased leucocyte sequestration. By 24 h postoperatively, levels of both soluble adhesion molecules approached preoperative concentrations, as did lymphocyte counts. In marked contrast, neutrophil counts rose appreciably towards the end of CPB, and continued to rise to a maximum of 10.9 +/- 3.1 x 10(9)/l during the immediate postoperative period and remained at these elevated levels 24 h later. Major consistent changes in circulating leucocyte numbers which occur early in cardiopulmonary bypass may reflect changes in adhesion to the endothelium and consequent sequestration. Alterations in the levels of soluble adhesion proteins may influence these processes.

Poor diagnostic value of colonic CD44v6 expression and serum concentrations of its soluble form in the differentiation of ulcerative colitis from Crohn's disease

BACKGROUND

Increased expression of CD44v6 on colonic crypt epithelial cells in ulcerative colitis has been suggested as a diagnostic tool to distinguish ulcerative colitis from colonic Crohn's disease.

AIMS

To investigate colonic CD44v6 expression and serum concentrations of soluble CD44v6 (sCD44v6) in patients with ulcerative colitis and Crohn's disease.

METHODS

Colonic biopsy samples were obtained from 16 patients with ulcerative colitis, 13 with ileocolonic Crohn's disease, and 10 undergoing polypectomy. Serum samples were obtained from 15 patients with active ulcerative colitis, 20 with active Crohn's disease, and 20 healthy donors. Colonic CD44v6 expression was evaluated immunohistochemically by monoclonal antibody 2F10 and the higher affinity monoclonal antibody VFF18. Serum sCD44v6 concentrations were measured by ELISA.

RESULTS

2F10 stained colonic epithelium of inflamed ulcerative colitis and Crohn's disease samples in 80% and 40% of cases, respectively, and VFF18 in 95% and 87%, respectively. Both monoclonal antibodies displayed a sensitivity and specificity of 60% and 87% to differentiate ulcerative colitis from colonic Crohn's disease. Serum concentrations of sCD44v6 were lower in patients with ulcerative colitis (median 153 ng/ml; interquartile range (IQR) 122-211) compared with Crohn's disease (219; IQR 180-243) and healthy donors (221; IQR 197-241 (p = 0.002)). Its sensitivity and specificity to discriminate ulcerative colitis from Crohn's disease was 75% and 71%, respectively.

CONCLUSION

Colonic CD44v6 and serum sCD44v6 concentrations do not facilitate reliable differential diagnosis between ulcerative colitis and Crohn's disease.

Role of the leukocyte-adhesion molecule L-selectin in experimental autoimmune encephalomyelitis

L-selectin is an adhesion molecule expressed on T cells and monocytes. It mediates rolling--the initial step of transendothelial migration. In this study, we investigated the role of L-selectin in the pathogenesis of experimental autoimmune encephalomyelitis (EAE), an animal model of multiple sclerosis. EAE was induced in Lewis rats by active sensitization with myelin basic protein (MBP-EAE), or by adoptive transfer using MBP specific T cells (AT-EAE). Treatment with HRL3, a monoclonal antibody to L-selectin, and its F(ab')2 fragments efficiently suppressed MBP-EAE, and had a mild inhibitory effect on AT-EAE. Histological examination revealed a marked reduction of inflammatory infiltrates after treatment with HRL3. Administration of the control antibody HRL4 did not significantly alter the course of the disease. HRL3 caused T-cell depletion in the draining lymph nodes and spleen and a downregulation of L-selectin expression on T cells. We conclude that L-selectin-dependent mechanisms are involved in the pathogenesis of EAE. Modulation of L-selectin in vivo by antibodies or by competitive antagonists could be a novel therapeutic approach to autoimmune diseases of the central nervous system.

Methylprednisolone-induced neutrophil leukocytosis--down-modulation of neutrophil L-selectin and Mac-1 expression and induction of granulocyte-colony stimulating factor

The mechanisms underlying corticosteroid-induced neutrophil leukocytosis are not fully understood; however, leukocyte/endothelial cell adhesion molecule interactions are known to be key to the movement of neutrophils within and out of the vasculature. This study was designed to investigate the effects of corticosteroids on neutrophil adhesion molecules in relation to neutrophil leukocytosis. Circulating neutrophil counts, neutrophil L-selectin and Mac-1 expression (measured by flow cytometry), soluble L-selectin, and granulocyte-colony stimulating factor concentrations were determined in 15 multiple sclerosis patients receiving intravenous methylprednisolone prior to and at 6 and 24 h following the initial 500-mg dose. A follow-up sample was obtained 48 h after the 5-day therapeutic course. Neutrophil counts were elevated at 6 h (threefold) and 24 h (twofold). This was associated with a 40% reduction in L-selectin expression at 6 and 24 h and a 35% reduction in Mac-1 expression at 6 h. Serum granulocyte-colony stimulating factor levels were increased (6 h: threefold; 24 h: twofold), whereas soluble L-selectin concentrations were unaltered. All of the above parameters had returned to basal levels in the follow-up sample. Short-term in vitro cultures (6 and 24 h) of blood samples from untreated multiple sclerosis patients and controls with 0.01 mg/ml methylprednisolone resulted in minimal reductions in neutrophil L-selectin and Mac-1 and no change in soluble L-selectin. Granulocyte-colony stimulating factor induced Mac-1 expression in a dose-dependent manner, whereas L-selectin expression was unaffected or reduced at high concentrations. Reduction in neutrophil L-selectin and Mac-1 expression following methylprednisolone infusion may cause decreased adhesion of marginated neutrophils and/or reduced capacity of neutrophils to migrate from the vasculature. Additionally, the induction of granulocyte-colony stimulating factor may contribute to neutrophil production and release into the circulation.

Biomechanics of cell interactions in shear fields

Cellular interactions play a key role in diverse biological processes within the cardiovascular system. Targeting of leukocytes to sites of inflammation is viewed as a multistage process of sequential involvement of distinct adhesion molecules on the leukocyte and endothelial cell (EC) surface that is dictated by the local fluid dynamic environment. For neutrophils, the initial contact and rolling along the vessel wall are mediated primarily by selecting. Subsequent firm adhesion requires activation of neutrophil P, integrins and binding to their ligand ICAM-1 on the EC surface. The final step of this cascade of events includes neutrophil transmigration to extravascular tissue space. The neutrophil model of emigration in inflammation has been extended and refined to account for monocyte and T cell interactions with ECs. Platelet adhesion to thrombogenic surfaces (i.e. immobilized von Willebrand factor) under flow follows the general principles of leukocyte extravasation. More specifically, platelet glycoprotein (GP) Ib alpha appears to mediate an initial selectin-like tethering platelet-vWf interaction, followed by alpha II beta beta 3 integrin activation and firm adhesion. Some of the signaling mechanisms associated with cellular interactions in inflammatory and thrombotic processes are discussed. These basic principles are also discussed in the context of tissue engineering research.

Adenosine Triphosphate–Induced Shedding of CD23 and L-Selectin (CD62L) From Lymphocytes Is Mediated by the Same Receptor but Different Metalloproteases

CD23 is a transmembrane protein expressed on the surface of B-lymphocytes that binds IgE, CD21, CD11b, and CD11c. High concentrations of soluble CD23 and L-selectin are found in the serum of patients with B-chronic lymphocytic leukemia (B-CLL). Because extracellular adenosine triphosphate (ATP) causes shedding of L-selectin via activation of P2Z/P2X7 receptors expressed on B-CLL lymphocytes, we studied the effect of ATP on shedding of CD23. ATP-induced shedding of CD23 at an initial rate of 12% of that for L-selectin, whereas the EC50 for ATP was identical (35 μmol/L) for shedding of both molecules. Furthermore, benzoylbenzoyl ATP also produced shedding of CD23 and L-selectin with the same agonist EC50 values for both (10 μmol/L). Inactivation of the P2Z/P2X7 receptor by preincubation with oxidized ATP abolished ATP-induced shedding of both molecules. Moreover, KN-62, the most potent inhibitor for the P2Z/P2X7 receptor, inhibited ATP-induced shedding of both CD23 and L-selectin with the same IC50 (12 nmol/L). Ro 31-9790, a membrane permeant zinc chelator that inhibits the phorbol-ester-stimulated shedding of L-selectin, also inhibited shedding of CD23 from B-CLL lymphocytes. However, the IC50 for this inhibition by Ro31-9790 was different for L-selectin and CD23 (83 v 6 μmol/L, respectively). Although L-selectin was completely shed by incubation of cells with phorbol-ester, CD23 was not lost under these conditions. The data show that extracellular ATP induces shedding of L-selectin and CD23 from B-CLL lymphocytes by an action mediated by the P2Z/P2X7 receptor. However, different membrane metalloproteases seem to mediate the shedding of L-selectin and CD23.

© 1998 by The American Society of Hematology.

Adenosine Triphosphate–Induced Shedding of CD23 and L-Selectin (CD62L) From Lymphocytes Is Mediated by the Same Receptor but Different Metalloproteases

CD23 is a transmembrane protein expressed on the surface of B-lymphocytes that binds IgE, CD21, CD11b, and CD11c. High concentrations of soluble CD23 and L-selectin are found in the serum of patients with B-chronic lymphocytic leukemia (B-CLL). Because extracellular adenosine triphosphate (ATP) causes shedding of L-selectin via activation of P2Z/P2X7 receptors expressed on B-CLL lymphocytes, we studied the effect of ATP on shedding of CD23. ATP-induced shedding of CD23 at an initial rate of 12% of that for L-selectin, whereas the EC50 for ATP was identical (35 μmol/L) for shedding of both molecules. Furthermore, benzoylbenzoyl ATP also produced shedding of CD23 and L-selectin with the same agonist EC50 values for both (10 μmol/L). Inactivation of the P2Z/P2X7 receptor by preincubation with oxidized ATP abolished ATP-induced shedding of both molecules. Moreover, KN-62, the most potent inhibitor for the P2Z/P2X7 receptor, inhibited ATP-induced shedding of both CD23 and L-selectin with the same IC50 (12 nmol/L). Ro 31-9790, a membrane permeant zinc chelator that inhibits the phorbol-ester-stimulated shedding of L-selectin, also inhibited shedding of CD23 from B-CLL lymphocytes. However, the IC50 for this inhibition by Ro31-9790 was different for L-selectin and CD23 (83 v 6 μmol/L, respectively). Although L-selectin was completely shed by incubation of cells with phorbol-ester, CD23 was not lost under these conditions. The data show that extracellular ATP induces shedding of L-selectin and CD23 from B-CLL lymphocytes by an action mediated by the P2Z/P2X7 receptor. However, different membrane metalloproteases seem to mediate the shedding of L-selectin and CD23.

© 1998 by The American Society of Hematology.

Staphylococcal enterotoxin-A-induced in-vitro adhesion of HL-60 cells to endothelial cells involves both selectin and integrin families of cell adhesion molecules

In-vivo exposure to the bacterial superantigen Staphylococcal enterotoxin-A (SEA) induces an inflammatory response characterized by rapid extravasation of leucocytes and release of excessive amounts of cytokines. We have utilized an in-vitro adhesion assay to understand the molecular mechanisms responsible for SEA-induced extravasation of leucocytes. Stimulation of human umbilical cord endothelial cells (HUVEC) with increasing concentrations of recombinant SEA (rSEA) did not influence the in-vitro adhesion of HL-60 cells to HUVEC, whereas stimulation of HUVEC by interleukin (IL)-1beta supported adhesion of HL-60 cells. Increased adhesion of HL-60 cells to HUVEC was noted upon stimulation of endothelium with culture medium obtained from human peripheral blood mononuclear cells (PBM) stimulated with recombinant SEA for 24 (CM-SEA 24 h), 72 (CM-SEA 72 h) and 120 h (CM-SEA 120 h), but not after stimulation with culture medium obtained from control human peripheral blood mononuclear cells (CM), suggesting that soluble factors present in the supernatants play a major role in SEA-induced cell adhesion. While CM-SEA 24 and 72 h induced both a rapid (4 h) and delayed type of adhesion, CM-SEA 120 h only induced a delayed type of adhesion. Stimulation of PBM by SEA resulted in increased levels of IL-1beta, IL-2 and interferon (IFN)-gamma after 24h. Further stimulation for 72-120h resulted in a significant increase in the levels of IL-1beta, IFN-gamma and tumour necrosis factor (TNF). Stimulation of PBM with SEA also resulted in increased levels of soluble and L-selectin in the cell supernatants. Increased cell-surface expression of E-selectin, ICAM-1, HLA-DR and VCAM-1 was detected on HUVEC stimulated with CM-SEA media. While E-selectin and VCAM were induced on HUVEC within a few hours, induction of ICAM and HLA-DR required a longer induction period. Adhesion of HL-60 cells to HUVEC treated with CM-SEA was inhibited by monoclonal antibodies (MoAbs) against both the selectin and integrin families of cell adhesion molecules, suggesting that multiple pathways contribute to SEA-induced leucocyte extravasation. The results suggested that selectin-dependent adhesion was more prominent during the early phase while integrin-induced adhesion occurred at a later stage.

Circulating Form of Human Vascular Adhesion Protein-1 (VAP-1): Increased Serum Levels in Inflammatory Liver Diseases

Vascular adhesion protein-1 (VAP-1) is a dimeric 170-kDa endothelial transmembrane molecule that under normal conditions is most strongly expressed on the high endothelial venules of peripheral lymph nodes and on hepatic endothelia. It is a glycoprotein that mediates tissue-selective lymphocyte adhesion in a sialic acid-dependent manner. In this study, we report the detection of a soluble form of VAP-1 in circulation. We developed a quantitative sandwich ELISA using novel anti-VAP-1 mAbs and used it to determine the levels of soluble VAP-1 (sVAP-1) in the serum of healthy individuals and in patients with inflammatory diseases. In healthy persons, circulating sVAP-1 concentrations were 49 to 138 ng/ml. Immunoblotting studies revealed that the apparent molecular mass of dimeric sVAP-1 is slightly (∼10 kDa) higher than that of transmembrane VAP-1 under nonreducing conditions. In contrast, the electrophoretic mobilities of monomeric sVAP-1 and transmembrane VAP-1 were similar after reduction and boiling. Adhesion assays showed that the circulating sVAP-1 modulates lymphocyte binding to endothelial cells. Inflammation can cause an elevation of serum sVAP-1 levels, because sVAP-1 concentrations in patients with certain liver diseases were two- to fourfold higher than those in normal individuals. In contrast, rheumatoid arthritis and inflammatory bowel diseases were not associated with elevated levels of sVAP-1. These findings indicate that there is a functionally active, soluble form of VAP-1 in circulation and suggest that the serum level of sVAP-1 might be a useful marker of disease activity in inflammatory liver diseases.

Kinetics of circulating selectin levels during bone marrow aplasia

We have studied the kinetics of plasma levels of circulating (c)selectins in 8 patients undergoing bone marrow or stem cell transplantation to gain estimates for the distribution and half-life of (c)selectins and to potentially identify an endothelial source of cP-selectin in patients who are deprived of platelets and megakaryocytes. Blood was sampled just before conditioning treatment and immediately after, at 2 occasions under bone marrow aplasia (1 and 2 wk after BMT), on 2 separate days (3-8 d apart) before and at 60 min after platelet transfusion, and 30-72 d after BMT. All (c)selectins showed a strikingly parallel decrease during bone marrow aplasia: cP-selectin decreased by a median of 70% (range: 59-95%), cE-selectin by 63% (range: 27-78%), and cL-selectin by 75% (range: 66-90%) compared to baseline (p=0.012 for all comparisons). Estimates for plasma half-lives of all (c)selectins were obtained from individual time vs. concentration profiles of the maximal decreases and ranged from 2 to 4 d. cP-selectin increased by 23% (p=0.003), cE-selectin by 5% (p=0.041) and cL-selectin by 19% (p=0.009) 1 h after the platelet transfusions. Based on these results the calculated volume of distribution (Vd) of transfused (c)selectins was 2.5-fold higher than the plasma volume, which supports the concept of the in-vivo expression of binding sites, i.e. ligands, for cE-selectin and cL-selectin. In summary, while our study cannot provide any evidence for endothelial cells as a source of cP-selectin, we have found for the first time evidence for the existence of ligands for soluble cE-selectin and cL-selectin in humans.

Leukocyte L-selectin is up-regulated after mechanical trauma in adults

BACKGROUND

Infection and multiple organ failure remain the principal causes of late mortality after trauma despite advances in the resuscitation of injured patients. Because a better understanding of postinjury leukocyte trafficking is essential to the development of possible therapeutic measures aimed at preventing these complications, we have performed a study of one factor in the early posttrauma endothelial adhesion behavior of monocytes, lymphocytes, and neutrophils: their cell surface expression of L-selectin (CD62L). We have also studied the plasma levels of soluble L-selectin in these patients.

METHODS

Two venous blood samples were taken from each of 41 trauma patients at median times of 1 and 20 hours after injury. The study group included 16 patients with major (Injury Severity Score (ISS) > or = 16), 17 with moderate (ISS = 9-15), and 8 with minor (ISS < 9) trauma. Cell surface L-selectin was measured on leukocyte subsets by staining with specific fluorescent-labeled monoclonal antibodies to CD62L and using flow cytometry. Both the percentage of cells expressing the molecule and the mean channel fluorescence were measured. Levels of soluble L-selectin were measured in the plasma, sampled concurrently, by enzyme-linked immunosorbent assay.

RESULTS

Monocytes, lymphocytes, and neutrophils all showed an early increase in cell surface L-selectin expression as measured by mean channel fluorescence (p < 0.0001, p < 0.001, and p < 0.0001, respectively), and this persisted in later samples taken at a median 20 hours after injury (p < 0.0001,p < 0.0001, and p < 0.01). Only monocytes showed an increased percentage of cells expressing the molecule in the early phase (p < 0.02), and this remained in the later phase (p < 0.001). Monocytes also showed a further significant increase in mean channel fluorescence (p < 0.02) between the two periods. No significant changes in levels of plasma soluble L-selectin were found at either stage.

CONCLUSION

An increase in the expression of L-selectin on each of three leukocyte populations has been demonstrated in the early phase after trauma. This would tend to promote rolling behavior of leukocytes and increase their contact with the vascular endothelium. There were marked differences in the later responses of the three populations, which may represent differential control of their behavior.

Raised CSF levels of soluble adhesion molecules across the clinical spectrum of multiple sclerosis

Endothelial activation is considered an important step in multiple sclerosis (MS) lesion formation, elevated cerebrospinal fluid (CSF) and serum levels of certain adhesion molecules being associated with varying stages of disease activity and clinical course. CSF and serum sVCAM-1, sICAM-1, sE-selectin and sL-selectin were measured by ELISA in 16 primary progressive (PPMS), 16 secondary progressive (SPMS) and 43 relapsing-remitting MS patients (RRMS) and compared with 20 inflammatory (IND) and 46 non-inflammatory neurological disease (NIND) controls. CSF sVCAM-1 and sICAM-1 were increased in all MS groups vs. NIND with no significant differences between the MS groups. CSF sE-selectin (p = 0.007) and the sE-selectin index (p = 0.01) were elevated in PPMS vs. RRMS in relapse, whilst serum sE-selectin was significantly raised in PPMS compared to RRMS in remission (p = 0.005), RRMS in relapse (p = 0.004), NIND (p = 0.03) and IND (p = 0.05). Adhesion molecule levels in both progressive MS groups were similar. These results provide evidence for a distinct inflammatory component in PPMS and for immunological heterogeneity between the clinical subgroups of MS.

Gene-targeted mice reveal importance of L-selectin-dependent rolling for neutrophil adhesion

It has not been determined whether L-selectin-mediated rolling can promote leukocyte adhesion in vivo independent of P- and E-selectin. We used intravital microscopy of E- and P-selectin double-mutant mice (E-/P-) stimulated with tumor necrosis factor-alpha for 6-8 h to investigate the importance of L-selectin-dependent rolling in cremaster muscle venules. Rolling leukocyte flux in E-/P- mice was 9 +/- 2 cells/min compared with 77 +/- 17 cells/min in wild-type (WT) mice. Pretreatment with the L-selectin monoclonal antibody MEL-14 significantly reduced rolling in both E-/P- (by 89%) and WT mice (by 79%). L-selectin-dependent rolling in E-/P- mice resulted in leukocyte adhesion comparable to that seen in WT mice. MEL-14 pretreatment of E-/P- mice reduced leukocyte adhesion by 50%. The majority (approximately 80%) of intravascular leukocytes in both WT and E-/P- mice were neutrophils. We conclude that L-selectin can mediate rolling that results in sufficient leukocyte recruitment to account for the robust inflammatory response seen in E-/P- mice at later times.

Differential patterns of circulating adhesion molecules in children with bronchial asthma and acute bronchiolitis

The object of the study was to assess the levels of circulating forms of the cellular adhesion molecules ICAM-1, VCAM-1, E-selectin, L-selectin and P-selectin in young children with asthma and acute bronchiolitis. Thirty-nine children aged 12 to 84 months with mild or moderate asthma were studied at admission for acute asthma (n = 15) or in a stable phase (n = 24). Ten of the children with acute asthma were seen again after one month. Twenty-two children aged 1 to 17 months with acute bronchiolitis and nine non-atopic controls were also included in the study. In children with acute asthma, the mean concentration of circulating soluble ICAM-1 (sICAM-1) was increased compared to children with stable asthma (mean 442 micrograms/l versus 363 micrograms/l; p < 0.001) and to controls (363 micrograms/l; p < 0.05). The levels of sICAM-1 remained high at follow up. In children with stable asthma, the mean serum concentration of soluble L-selectin (sL-selectin) (2080 micrograms) was significantly higher than in the controls (1664 micrograms/l; p < 0.05). The levels of circulating cellular adhesion molecules were similar in atopic and non-atopic asthmatics. Children with acute bronchiolitis had increased serum levels of soluble VCAM-1 (sVCAM-1) (1637 micrograms/l versus 1019 micrograms/l in the controls; p < 0.01) and sL-selectin (2041 micrograms/l versus 1664 micrograms/l in the controls; p < 0.05). There was no difference between the levels of circulating cellular adhesion molecules in children with respiratory syncytial virus (RSV) positive and RSV negative bronchiolitis. Soluble E-selectin (sE-selectin) and soluble P-selectin (sP-selectin) in serum were not significantly increased in any of the groups studied. In conclusion, our data suggest differential patterns of circulating cellular adhesion molecules in young children with acute asthma, stable asthma, and acute bronchiolitis, which may reflect differences in the underlying inflammatory processes in these obstructive pulmonary diseases.

Soluble form of selectins in blood of patients with acute myocardial infarction and coronary intervention

Soluble (s) P-selectin, sE-selectin, sL-selectin and soluble intercellular adhesion molecule-1 (sICAM-1) levels were examined by monoclonal antibody-based enzyme immunoassay on serum samples taken from nine patients with acute myocardial infarction (AMI) and eight patients with stable angina pectoris (SAP) before and after the successful percutaneous transluminal coronary angioplasty (PTCA). In patients with acute phase of AMI, the levels (mean +/- SEM) of sP-selectin (110 +/- 18 ng/ml) and sE-selectin (54 +/- 15 ng/ml) before PTCA, were significantly higher than those in the SAP group, the values being 44 +/ 27 and 21 +/- 4 ng/ml (p < 0.05), respectively. After recanalization, the levels of sE-selectin and sL-selectin were significantly decreased (sE-selectin 54 +/- 15 to 42 +/- 11 ng/ml, sL-selectin 1104 +/- 106 to 891 +/- 59 ng/ml, P < 0.05, respectively). These findings suggest that the presence of activated and/or injured endothelial cells, which may be involved in the plaque disruption or intraluminal thrombosis in AMI region and that the inflammatory process may be altered after reperfusion therapy.

The relationship of soluble adhesion molecule concentrations in systemic and jugular venous serum to injury severity and outcome after traumatic brain injury

Adhesion molecules control the migration of leukocytes into tissue after injury. This may result in further cellular damage. We hypothesized that altered serum concentrations of soluble intercellular adhesion molecule (sICAM)-1 and soluble L-selectin (sL-selectin) after traumatic brain injury would correlate with injury severity and neurological outcome. We investigated serum concentrations of sICAM-1 and sL-selectin in 22 patients with traumatic brain injury admitted to the intensive care unit. The Glasgow Coma Scale (GCS) score and Injury Severity Score were recorded. Paired arterial and jugular venous blood samples were taken on admission and 24, 48, and 96 h after injury. Mean systemic and jugular venous concentrations of sICAM-1 were normal on admission but became significantly increased by 96 h (P = 0.018). sL-selectin concentrations of injured patients were markedly below those of controls at all time points (P < 0.001). There were no significant differences between jugular venous and arterial concentrations of either sICAM-1 or sL-selectin. Serum sICAM-1 was significantly related to neurological outcome (P < 0.001) and to the GCS score (P < 0.001). These changes in adhesion molecule expression after acute brain injury may be important in the pathophysiology of secondary injury. The highly significant relationship between serum sICAM-1 and neurological outcome suggests that the inflammatory response to injury may be detrimental. Drugs that antagonize the actions of the adhesion molecules may have a role in therapy after traumatic brain injury.

IMPLICATIONS

This observational study shows that there is a strong association between soluble intercellular adhesion molecule-1 in serum and poor neurological outcome after traumatic brain injury. This suggests that inflammation after brain injury may worsen the prognosis and that therapies directed against this inflammation may prove useful.

Endothelial activation in patients with chronic venous disease

OBJECTIVES

Leukocyte trapping due to leukocyte-endothelial activation has been implicated as the cause of lipodermatosclerosis and ulceration in patients with chronic venous disease. We investigated endothelial activity in normal controls and patients subjected to short-term venous hypertension.

METHODS

Twenty-five normal volunteers and 30 patients with chronic venous disease divided into two groups: varicose veins with skin changes (LDS, n = 15); and varicose veins without skin changes (VVs, n = 15) were studied. Blood samples were taken from a foot vein before and after experimental venous hypertension. Plasma levels of ELAM-1 (endothelial leukocyte adhesion molecule-1), ICAM-1 (intercellular adhesion molecule-1), VCAM-1 (vascular cell adhesion molecule-1), and von Willebrand factor (vWf) was measured by an ELISA.

RESULTS

There was a significant rise in the plasma concentration of ELAM-1, ICAM-1 and VCAM-1 in patients and normal controls in response to venous hypertension. Basal levels of plasma VCAM-1 and vWf were higher in patients with LDS compared to patients with VVs. The magnitude of rise of VCAM-1 was greater in patients with LDS compared to patients with VVs (p = 0.01, Mann-Whitney U-test). There was no difference in the basal levels or in the magnitude of change in plasma ICAM-1 and ELAM-1 between the two patient groups.

CONCLUSION

Venous hypertension results in endothelial activation which may aid endothelial-leukocyte adhesion. Patients with LDS exhibit increased VCAM-1, which is a counterligand for receptors expressed by monocytes and lymphocytes signifying that these cells may be more important in the development of skin changes.

Antibody to E- and L-selectin does not prevent lung injury or mortality in septic baboons

Recruitment of polymorphonuclear leukocytes (PMN) through upregulation of cellular adhesion molecules is a proposed mechanism of injury in sepsis and acute respiratory distress syndrome (ARDS). We hypothesized that pretreatment of baboons with a monoclonal antibody to human E- and L-selectin (EL-246) during sepsis would decrease PMN influx into tissues and result in less organ injury during gram-negative sepsis. We studied 14 anesthetized, ventilated adult baboons; six animals received 1 mg/kg of EL-246 before infusion of an LD100 of live Escherichia coli and six received the E. coli infusion without antibody therapy. Two other animals received 1 mg/kg of EL-246 intravenously without an infusion of bacteria. Intermittent measurements were made of circulatory pressures, cardiac output, urine output, arterial blood gases, ventilation:perfusion ratio (VA/Q), and hematologic status. The experiments were ended at 48 h or at the time of death. Tissues were harvested for pathology and biochemical measurements. The E. coli infusions were associated with a hyperdynamic state, pulmonary hypertension, systemic hypotension, decreased urine output (UOP), and metabolic acidosis. The antibody partly blocked PMN migration, but there were few significant physiologic or biochemical differences between the EL-246-treated and untreated animals. In the antibody-treated animals, UOP was decreased, metabolic acidosis was worsened, and median survival time was decreased significantly. We conclude that treatment with an antibody to E- and L-selectin in gram-negative sepsis does not improve gas exchange or protect against lung injury, and is associated with decreased survival time in primates.

Fever-Range Hyperthermia Enhances L-Selectin-Dependent Adhesion of Lymphocytes to Vascular Endothelium

The L-selectin leukocyte adhesion molecule plays an important role in controlling leukocyte extravasation in peripheral lymph nodes and at sites of tissue injury or infection. Although febrile responses during infection and inflammation are associated with enhanced immune activity, the contribution of fever-range temperatures to controlling lymphocyte recruitment to tissues has not been previously examined. In this report we provide evidence that direct exposure of lymphocytes to fever-range temperatures (38–41°C) in vitro for 9 to 24 h resulted in a &gt;100% increase in L-selectin-dependent adhesion of these cells to lymph node high endothelial venules (HEV). Moreover, culture of lymphocytes under hyperthermia conditions markedly enhanced the ability of these cells to traffic in an L-selectin-dependent manner to peripheral lymph nodes, mesenteric lymph nodes, and Peyer’s patches. In contrast, febrile temperatures did not increase LFA-1 function as assessed by measuring lymphocyte adhesion to ICAM-1–3T3 transfectants. Fever-range hyperthermia further did not increase L-selectin surface density on lymphocytes or L-selectin-dependent recognition of soluble carbohydrate substrates; however, a marked increase in ultrastructural immunogold-labeling of L-selectin was observed in response to thermal stimuli. These results suggest that elevated temperatures enhance L-selectin adhesion and/or avidity through the regulation of L-selectin conformation or organization in the plasma membrane. Finally, the observed thermal effects on L-selectin adhesion were attributed to soluble factors in the conditioned medium of heat-treated cells. Taken together, these data provide new insight into the potential physiologic role of the febrile response in enhancing lymphocyte recruitment to tissues through the regulation of L-selectin adhesion.

Granulocyte colony-stimulating factor administration increases serum concentrations of soluble selectins

In order to explore the possible role of granulocyte colony-stimulating factor (G-CSF) in the inflammatory process, we examined the serum concentrations of soluble selectins (sL-selectin, sE-selectin and sP-selectin) following in vivo administration of G-CSF to five healthy volunteers and 12 neutropenic patients with haematological malignancies. The serum concentrations of both sL-selectin and sE-selectin were slightly but significantly increased after G-CSF administration in the healthy volunteers. The serum concentrations of all three selectins were significantly increased after G-CSF administration in the neutropenic patients concomitant with an increase in their neutrophil counts. These findings suggest that G-CSF may participate in the leucocyte-endothelial cell interactions in vivo.

Elevated levels of soluble adhesion molecules in serum of patients with diffuse panbronchiolitis

STUDY OBJECTIVE

Adhesion molecules have been implicated in the pathogenesis of inflammatory diseases. This study was designed to determine whether soluble adhesion molecules in serum reflect the disease activity in diffuse panbronchiolitis (DPB).

PATIENTS AND METHODS

Using an enzyme-linked immunosorbent assay, we measured the serum levels of soluble L-, E-, and P-selectin (sL-, sE-, and sP-selectin), intercellular adhesion molecule-1, and vascular cell adhesion molecule-1 in 27 patients with DPB, 13 with bronchiectasis, and 15 normal adults. BAL was also performed, and the levels of interleukin (IL)-8 and IL-1 beta in BAL fluid (BALF) were measured.

RESULTS

The serum levels of these molecules were significantly elevated in DPB patients compared with the control subjects. DPB patients also had significant high levels of circulating sE- and sP-selectin compared with patients with bronchiectasis. There was a significant correlation between serum sE-selectin and the percentage of neutrophils in BALF in all patients. There was a significant inverse correlation between serum sE-selectin and percent vital capacity in DPB patients. In the same patients, the relationships between serum sE-selectin and BALF concentrations of IL-1 beta as well as between serum sL-selectin and BALF IL-8 were also significant. Treatment of DPB patients with macrolides significantly reduced the serum levels of these soluble adhesion molecules and BALF concentrations of IL-1 beta and IL-8.

CONCLUSIONS

Our results suggest that these soluble adhesion molecules, particularly selectins, may reflect the disease activity of DPB, and that their levels may be regulated by cytokines produced in the lungs.

Dexamethasone down-regulates the expression of L-selectin on the surface of neutrophils and lymphocytes in humans

OBJECTIVE

On the basis of previous animal studies, we hypothesized that dexamethasone may reduce the expression of L-selectin on neutrophils and lymphocytes in healthy men.

METHODS

A double-blind, randomized, placebo-controlled, and three-way crossover trial was conducted in nine healthy men. Every subject received four identical infusions of saline solution, 0.04 mg/kg dexamethasone, or 1.0 mg/kg dexamethasone during three observation periods of 48 hours each.

RESULTS

Dexamethasone time and dose dependently decreased the L-selectin expression on neutrophils and lymphocytes as measured by flowcytometry. This effect occurred with a time lag of 8 hours after start of treatment: the L-selectin binding index of neutrophils decreased by a maximum of -50% (confidence interval [CI], -37% to -63%) and that of lymphocytes by -26% (CI, -8% to -45%) at 32 hours after the start of treatment with high-dose dexamethasone (p < 0.016). Low-dose dexamethasone had only a transient effect on L-selectin expression of lymphocytes and a less pronounced effect on L-selectin expression of neutrophils.

CONCLUSION

Dexamethasone time and dose dependently decreases L-selectin expression on neutrophils and lymphocytes in health men, an effect that is less pronounced than that previously reported for animals.

L-selectin: a novel receptor for lipopolysaccharide and its potential role in bacterial sepsis

The activation of leukocytes by bacterial cell wall lipopolysaccharide (LPS) contributes to the pathogenesis of septic shock. It is well established that, in the presence of plasma LPS-binding protein (LBP), LPS binds with high affinity to CD14. The binding of LPS to CD14 has been associated with the activation of cells, although available evidence indicates that CD14 itself does not transduce intracellular signalling. The physiological function of this interaction is to promote host defense mechanisms of cells to combat the infection and clear LPS from the circulation. At higher concentrations of LPS, however, the activation of cells can take place in the absence of LBP and CD14, presumably through a distinct low-affinity signalling LPS receptor. On the evidence published by us and others, we propose that in neutrophils, and possibly other leukocytes, L-selectin can act as a low-affinity LPS receptor.

Soluble Markers of Leucocyte Adhesion in Patients with Venous Disease

Objective:

To measure soluble CD54 (ICAM-1) and CD62E (E-selectin) as markers of neutrophil adhesion in four groups of patients with varying severity of venous disease and compare the values obtained with those in age- and sex-matched control subjects.

Design:

Prospective study of patients with varicose veins compared with a group of control subjects with no history or clinical findings of varicose veins.

Setting:

The Middlesex Hospital Vascular Laboratory, London.

Patients:

Patients referred to the Middlesex Hospital Vascular Laboratory for investigation of venous disease. Neither patients nor controls had arterial disease, any other systemic illness, or were on any medication known to alter white cell activity.

Interventions:

Ten millimetres of blood taken from an arm vein into EDTA for a neutrophil count and soluble CD54 and CD62E, measured using an ELISA.

Results:

Similar levels of soluble CD54 and CD62E were found in all four groups of patients compared with their controls ( p = 0.71 for soluble CD54 for all patients compared with all controls, and p = 0.65 for soluble CD62E, Mann–Whitney U-test). There was no difference in the neutrophil count between the controls and patients in any group ( p = 0.74 for all subjects, Mann–Whitney U-test).

Conclusion:

This study shows no evidence of increased soluble CD54 or CD2E or CD62E in patients with venous disease, despite previous work showing increased CD54 and neutrophil degranulation in patients with venous disease. The reason for this is currently unknown.

L-Selectin--a signalling receptor for lipopolysaccharide

The activation of leukocytes by bacterial cell-wall lipopolysaccharide contributes to the pathogenesis of septic shock. We propose that in neutrophils, and possibly other leukocytes, L-selectin can act as a low-affinity lipopolysaccharide receptor. Inhibitors of L-selectin may therefore be of therapeutic value in treating this life-threatening condition.

Cellular adhesion molecules in neurology

The study of cellular adhesion molecules offers crucial understanding of cellular interactions. Their name implies an underestimation of their function, as intercellular glue. In fact, they play vital roles in tissue development and intra- and intercellular signaling. In neurology, cellular adhesion molecules are already providing welcome new insight into neurodevelopmental anomalies, autoimmune demyelination, and invasive tumours. Cellular adhesion molecule manipulation has led to several therapeutic options which are the subject of ongoing clinical investigation.

Lymphocyte-endothelial cell interactions in multiple sclerosis: disease specificity and relationship to circulating tumour necrosis factor-alpha and soluble adhesion molecules

This study addressed two questions; first, whether the supranormal adherence of blood lymphocytes from patients with multiple sclerosis (MS) to endothelial cell monolayers treated with tumour necrosis factor-alpha (TNF alpha) was a feature common to other inflammatory disorders; and second, whether the adherence properties of blood lymphocytes from MS patients were related to changes in disease activity and to levels of circulating TNF alpha and soluble adhesion molecules. In the first part of the investigation, lymphocytes from 14 patients with MS were more adherent to TNF alpha-treated endothelial cells (P < 0.01) than those from healthy controls, whereas the adherence properties of lymphocytes from 12 patients with rheumatoid arthritis, eight patients with psoriasis and ten patients with neurological diseases other than MS were normal. In the second phase of the work, measurement of the adhesive properties of lymphocytes isolated at monthly intervals from a further six MS patients over a 5-8 month period, found that changes in binding to TNF alpha-treated endothelial cells, directly paralleled changes in circulating levels of TNF alpha (r = 0.77; P < 0.001) and soluble vascular cell adhesion molecule-I (sVCAM-1) r = 0.67; P = 0.001). An increase in disease activity, measured by T2-weighted and gadolinium-enhanced magnetic resonance imaging of the central nervous system (CNS), occurred in two patients and was associated with heightened lymphocyte adhesiveness and a rise in serum TNF alpha levels. Further analysis of the 34 serum samples from the six MS patients revealed a direct relationship between the concentration of sL-selectin and soluble intercellular adhesion molecule-I (sICAM-I) (r = 0.65; P < 0.001) and between sL-selectin and sTNF alpha (r = 0.42; P < 0.02). These findings support the view that disease activity in MS is associated with an increased adhesive interaction of blood lymphocytes with vascular endothelium at inflammatory sites within the CNS.

Regulation of schistosome egg granuloma formation: host-soluble L-selectin enters tissue-trapped eggs and binds to carbohydrate antigens on surface membranes of miracidia

Immunogenic carbohydrate epitopes are prominent in soluble egg antigens (SEA) of Schistosoma mansoni and in vivo are released through ultramicroscopic pores in the eggshell. Previously, one immunogenic carbohydrate was identified as lacto-N-fucopentaose III (LNFPIII), which contains the biologically important trisaccharide Lewis(x) (Le(x)), a weak ligand for E-, L-, and P-selectins. Selectins are involved in various inflammatory reactions, including recruitment of granulocytes. Further, L-selectin molecules are shed from leukocyte cell surfaces upon activation. These independent observations suggest that selectins may play various roles in granuloma formation and/or regulation. We tested in situ for alterations in expression of host E-, L-, or P-selectin in murine liver tissue at various times postinfection with schistosome cercariae. We found that L-selectin was expressed on cells surrounding egg granulomas, but surprisingly we also found mouse L-selectin on the surface membranes of larval miracidia within the S. mansoni ova. In contrast, neither E- nor P-selectin was found within ova. Antibodies to human or rat L-selectin or 15 other distinct mouse leukocyte surface molecules did not bind to the miracidial surface. The anti-mouse L-selectin staining of miracidia could be inhibited by wash buffer containing sulfated carbohydrates such as sulfated Le(x), heparan sulfate, fucoidan, and carrageenan. The elution studies imply that the miracidial surface and, therefore, schistosomes express sulfated glycans. The binding of soluble L-selectin to miracidia was not restricted by the genetic background of the host, as mouse L-selectin was detected on the surface of S. mansoni miracidia in livers from BALB/C, CBA/J, C57BL/6, and outbred Swiss mice. We also detected soluble mouse L-selectin binding to Schistosoma japonicum miracidia, indicating that these observations can be generalized to all schistosome infections. On the basis of these observations we hypothesize that host-soluble L-selectin traverses through pores in the eggshell and binds to target ligands on the surface membranes of miracidia; this complex formation might ultimately impede the release of soluble antigens from the eggs. The intraovum binding of mouse L-selectin to immunogenic carbohydrate antigens is a novel role for selectins, and this model may, in part, explain the down-regulation in granulomatous pathology observed following the acute phase of the disease.

Serum levels of adhesion molecules and cytokines in patients with acute leukaemia

The cytokine network and the adhesion molecule system are intercellular signal pathways. The cytokine effects are modulated in vivo by soluble cytokine antagonists, whereas the cell to cell contact mediated by adhesion molecules and their ligands may be blocked by the soluble forms of the adhesion molecules. The cytokine network is important for proliferation and cytokine secretion by acute leukaemia blasts, and membrane-bound adhesion molecules are important for blast interactions with neighbouring cells of the in vivo microenvironment. Both these signal systems are operative during the period of cytopenia following intensive chemotherapy for acute leukaemia. In the present review, we discuss the influence of disease status, chemotherapy and complicating infections on serum levels of cytokines and soluble adhesion molecules in acute leukaemia patients. We have demonstrated increased serum levels of both cytokines and cytokine antagonists in acute leukaemia patients with complicating bacterial infections during chemotherapy-induced cytopenia. Serum levels of the selectin adhesion molecules were decreased during bacterial infections in leukopenic patients compared to healthy individuals. In contrast, the intercellular adhesion molecule-1 response and the cytokine/cytokine antagonist responses were qualitatively similar to responses seen in previously healthy individuals with serious bacterial infections.

Soluble L-selectin in peripheral arterial disease: relationship with soluble E-selectin and soluble P-selectin

Soluble L-selectin, E-selectin and P-selectin were measured in a small case control study of 42 patients with peripheral arterial disease and 42 age and sex matched controls. Levels of soluble L-selectin were 1204 +/- 221 ng/ml (mean +/- S.D.) in the patients compared to 1256 +/- 271 ng/ml in the controls (P = 0.37). There was also no difference in levels of soluble E-selectin (57 +/- 17 ng/ml versus 51 +/- 20 ng/ml, P = 0.15) but levels of soluble P-selectin were increased (249 +/- 101 ng/ml versus 198 +/- 98 ng/ml, P = 0.011). There were no significant correlations between any of the selectins and the risk factors for atherosclerosis or with any leucocyte index. The data point to different mechanisms of release of the soluble selectins in peripheral atherosclerosis and may have important implications for leukocyte/endothelial cell interactions.

Lymphocyte adhesive interactions with cultured parotid salivary gland epithelial cells from rats

Cellular interactions control lymphocyte localization within salivary gland tissues and contribute to the immune defense of oral surfaces. We examined lymphocyte adherence to cultured parotid cells using an in vitro assay and found good correlation with previously reported binding to parotid gland frozen sections. Thoracic duct lymphocytes (TDL) bound to parotid cells in greater numbers than thymocytes (74 vs 11 cells/mm2). B cells showed preferential adherence compared to T cells (75% vs 28%). TDL binding was inhibited by sodium azide or cytochalasin B (60% and 80%, respectively). EDTA inhibition (63%) was restored by replacing calcium (9%) but not magnesium (65%). Binding was inhibited by fucoidin or phosphomannan (approximately 70%). Fibronectin peptides had no effect. Culture supernatants were inhibitory for TDL adherence (60%), suggesting that molecules involved in lymphocyte localization may be shed and that parotid cell cultures will be useful for ligand isolation and characterization.

Differential regulation of leucocyte L-selectin (CD62L) expression in normal lymphoid and inflamed extralymphoid tissues

AIMS

To study tissue expression of L-selectin, a leucocyte cell surface molecule that is considered to be involved in adhesion to certain endothelia, particularly in peripheral lymph nodes and during inflammation, and is shed upon leucocyte activation.

METHODS

Leucocytes were examined by immunohistochemistry and double immunofluorescence staining in various lymphoid sites and normal and inflamed extralymphoid tissues.

RESULTS

L-selectin was present on mantle zone B lymphocytes in different lymphoid sites, including in intestinal lymphoid tissue, but was absent on germinal centre B cells. Splenic white pulp B cells also expressed L-selectin. The proportion of T lymphocytes expressing L-selectin depended on the site under study, being greatest in peripheral lymph nodes (mean 48% of T cells positive), and lower in mucosal lymphoid sites and spleen (9 and 11% positive, respectively). Non-lymphocytic L-selectin staining was observed on follicular dendritic cells in tonsils and on macrophages in thymus. L-selectin positive leucocytes were rare in normal extralymphoid tissues, and relatively few were seen in most inflammatory settings. However, in rejecting renal transplants, a higher proportion (30%) of leucocytes expressed L-selectin.

CONCLUSIONS

Overall, the results indicate how the degree of L-selectin expression by leucocytes in particular tissues may reflect a requirement for L-selectin expression for entry into those tissues and the activation state of leucocytes once localised there.

Soluble adhesion molecules and oral antigen feeding in infants

Oral administration of foreign proteins, e.g. cow's milk (CM) proteins, stimulates the immune system and induces humoral and cellular immune response against these antigens in infants. Up-regulation of adhesion molecules is known to be associated with activation of the immune system. The purpose of the study was to examine whether orally administered CM proteins induce elevation in soluble adhesion molecules, i.e. intercellular adhesion molecule-1 (ICAM-1) and L-selectin, in infants. In a double-blind trial, 10 infants received CM-based formula and 10 infants casein hydrolysate formula until the age of 9 mo. The infants of mothers with insulin-dependent diabetes mellitus (IDDM) were recruited into a pilot study of a trial for primary prevention of IDDM by elimination of CM proteins from the diet during early infancy. A cord blood sample and peripheral blood samples were taken at the ages of 3, 6, 9, and 12 mo of age. The levels of soluble ICAM-1 and L-selectin were measured by ELISA. The levels of soluble ICAM-1 were higher at the ages of 3, 6, 9, and 12 mo in infants who received CM-based formula than in infants who received hydrolyzed formula (p = 0.05). Instead, no difference was found in the the levels of soluble L-selectin. The levels of soluble ICAM-1 and L-selectin were higher in all infants when compared with the levels reported in adults or to the levels seen in cord blood. Orally fed CM proteins induce an elevation in soluble ICAM-1 in infants. This may reflect the generation of an immune response against these proteins, because ICAM-1 has an important costimulatory role in lymphocyte activation.

Alterations in circulating intercellular adhesion molecule-1 and L-selectin: further evidence for chronic inflammation in ischemic heart disease

Atherosclerosis is increasingly thought to be a chronic inflammatory disease. Inflammation requires transmigration of leukocytes from the circulation to the tissues. Adhesion of leukocytes to endothelial calls is the initial event in an inflammatory response and is mediated by expression of several adhesion molecules. In this study we characterize the contribution of intercellular adhesion molecules (ICAM-1) and L-selectin in patients with different coronary artery disease syndromes. Serum concentrations of cICAM-1 and sL-selectin were measured by enzyme-linked immunosorbent assay in 31 patients with stable angina, 30 patients with unstable angina, 18 patients with acute myocardial infarction and 20 healthy subjects in a control group. All patients underwent coronary angiography. Mean (+/-SE) cICAM-1 levels were higher (p < 0.05) in patients with stable angina (249 +/- 6 ng/ml), unstable angina (260 +/- 16 ng/ml), or acute myocardial infarction (261 +/- 24 ng/ml) compared with those in subjects in the control group (171 +/- 11 ng/ml). In contrast, levels of sL-selectin were lower (p < 0.01) in patients with stable angina (1.2 +/- 0.1 microg/ml), unstable angina (1.1 +/- 0.6 microg/ml), or acute myocardial infarction (1.1 +/- 0.1 microg/ml) compared with those in subjects in the control group (1.8 +/- 0.1 microg/ml). No difference was found in cICAM-1 or sL-selectin levels among patients with stable angina, unstable angina, or acute myocardial infarction. No correlation was seen between cICAM-1 or sL-selectin levels and extent (or severity) of coronary artery disease or leukocyte count. L-selectin expression was observed to be depressed in patients with severe angina compared with that in members of the control group. To examine the mechanism of reduction in sL-selectin levels and L-selectin expression on leukocytes, leukocytes from the control group were stimulated in vitro. Stimulation of leukocytes resulted in a rapid downregulation of surface L-selectin expression, measured by flowcytometry, similar to the suppressed expression of L-selectin found on leukocytes from patients with coronary artery disease. In conclusion, altered cICAM-1 and sL-selectin levels in patients with coronary artery disease reflect the presence of a chronic inflammatory process. This inflammatory process results in downregulation of leukocyte expression of L-selectin and thus lower circulating sL-selectin levels.