Endothelial adhesion molecules and their role in inflammation. (1993 Jul)
endothelial adhesion molecules and their role in inflammation . The emigration of leukocytes such as neutrophils into inflammatory sites requires adhesion to the endothelium of small venules . The initial adhesive event is margination characterized by rolling of neutrophils along the luminal surface of the endothelium . Each member of the selectin family of adhesion molecules has been shown to support neutrophil rolling under conditions of flow . E selectin is synthesized by endothelial cells following cytokine stimulation , P selectin is rapidly mobilized from weibel palade bodies to the endothelial cell surface following stimulation with agents such as histamine , and L selectin is constitutively expressed on the surface of leukocytes . Each selectin functions primarily as a lectin , recognizing carbohydrate structures on the leukocyte or endothelial cell surface . Once the marginated neutrophil forms a stationary adhesion with endothelial cells , it is stimulated by chemotactic factors to downregulate the selectin based adhesion and upregulate adherence dependent on beta 2 integrins , principally cd11a / CD18 ( LFA 1 ) and cd11b / CD18 ( Mac 1 ) . these adhesion molecules interact with intercellular adhesion molecule 1 ( ICAM 1 ) and possibly other structures on the endothelial cell , and the leukocyte rapidly emigrates into surrounding tissue . transendothelial migration in vitro is markedly inhibited by monoclonal antibodies against CD18 integrins or ICAM 1 . monoclonal antibodies against the selectins , CD18 , cd11a , cd11b , and ICAM 1 have all been shown to …

Platelet / endothelial cell adhesion molecule 1 ( pecam 1 ) expression by human brain microvessel endothelial cells in primary … (1997 Mar)
platelet / endothelial cell adhesion molecule 1 ( pecam 1 ) expression by human brain microvessel endothelial cells in primary culture . pecam 1 expression was investigated in primary cultures of human brain microvessel endothelial cells ( hbmec ) . hbmec constitutively express pecam 1 along their apical cell surface , advancing processes and on the basal surface at points of contact with the extracellular matrix . surface expression is not altered by cytokine or lipopolysaccharide treatment . This distribution may mediate cell cell contract and migration during angiogenesis and hbmec leukocyte interactions in CNS inflammation .

Role of intra cellular adhesion molecule 1 ( ICAM 1 ) and its soluble form ( sicam ) in chronic … (2004 Jun)
Role of intra cellular adhesion molecule 1 ( ICAM 1 ) and its soluble form ( sicam ) in chronic airway inflammation mucosal inflammation is the feature of both bronchial asthma and allergic rhinitis with evident of tissue eosinophilia , mast cells , eosinophils and T lymphocytes activation . The initial phase of cell recruitment is the margination and adhesion of leucocytes to the endothelium , prior to their transendothelial migration under a directed chemotactic stimulus . This adhesion occurs through specific ligand receptor couplets involving leucocyte endothelial adhesion molecules . One of these cell adhesion molecules is ICAM 1 , an important early marker of immune activation and response . Its ligand , leukocyte function associated antigen one ( LFA 1 ) is expressed on neutrophils , eosinophils and T cells . ICAM 1 was found to be expressed on epithelial and endothelial cells in rhinitis patients and in bronchial biopsies obtained from asthmatics also after allergen challenge . circulating forms of these adhesion molecules have been identified in the peripheral blood , bronchoalveolar lavage ( BAL ) fluid and nasal lavage in patients with asthma and rhinitis . systemic and local up regulation of sicam 1 suggests a function role for this soluble form of ICAM in the allergic inflammation .

Human / severe combined immunodeficient mouse chimeras. (1993 Apr)
human / severe combined immunodeficient mouse chimeras . An experimental in vivo model system to study the regulation of human endothelial cell leukocyte adhesion molecules . The ability of circulating white blood cells to enter inflamed tissues is mediated by specific cell adhesion molecules thought to be expressed in a programmed and sequential manner to form an adhesion cascade . because of the complexity of this process , it is becoming increasingly important to develop in vivo models . Two major problems have limited the utility of current animal models . The first is the inability of many of the antibodies developed against cell adhesion molecules in human cell culture models to cross react in animals . The second is the uncertainty in extrapolating animal ( particularly rodent ) findings to humans . To circumvent these problems , full thickness human skin grafts were transplanted onto immunodeficient ( severe combined immunodeficient ) mice . after 4 6 wk , the transplanted skin grafts closely resembled normal skin histologically and maintained their human vasculature as determined by immunohistochemical staining with human specific endothelial cell markers . intradermal injection of tumor necrosis factor alpha resulted in the reversible upregulation of the leukocyte endothelial adhesion molecules E selectin , vascular cell adhesion molecule 1 , and intercellular adhesion molecule 1 , and in an active inflammatory reaction with migration of murine leukocytes into cytokine injected areas . these results indicate that the severe combined immunodeficient mouse / human skin transplant model provides a …

Dynamic expression of L selectin in cell to cell interactions between neutrophils and endothelial cells in vitro. (1998 Sep)
dynamic expression of L selectin in cell to cell interactions between neutrophils and endothelial cells in vitro . neutrophil endothelial cell interactions are regulated by cell adhesion molecules and their cognate ligands . It has been proposed that L selectin and Mac 1 ( cd11b / CD18 ) , two neutrophil adhesion receptors , have sequential roles in neutrophil extravasation during inflammation . In this model , L selectin mediates rolling and initial adherence of neutrophils to endothelial cells , while Mac 1 strengthens this initial adherence and also facilitates migration of neutrophils through endothelial cells . L selectin and Mac 1 expression are known to be inversely regulated . Here an in vitro culture system has been developed to investigate in situ expression of L selectin during cell to cell interactions between neutrophils and endothelial cell monolayers by confocal immunofluorescence analysis . neutrophils underwent profound cell shape change from round to polarized cell morphology with pseudopod formation after 5 to 15 min coculture with IL 1 stimulated human endothelial cells . L selectin was redistributed to the pseudopod of the polarized neutrophils in correlation with such cellular changes . during initial cell attachment , neutrophils bound to IL 1 stimulated endothelial cells expressed a high level of L selectin in a polarized pattern . L selectin expression decreased over time during neutrophil endothelial cell interactions .

The route of antigen entry determines the requirement for L selectin during immune responses. (1997 Jan)
The route of antigen entry determines the requirement for L selectin during immune responses . L selectin , an adhesion molecule constitutively expressed on leukocytes , is important for primary adhesion and extravasation of lymphocytes at specialized high endothelial venules within lymph nodes and other leukocytes at sites of inflammation . We have generated L selectin deficient mice by targeted disruption , and have confirmed a previously reported phenotype which includes strikingly impaired contact hypersensitivity ( CHS ) responses to reactive haptens ( tedder , T . F . , D . A . steeber , and P . pizcueta . 1995 . J . Exp . Med . 181 : 2259 2264 ; Xu , J . C . , I . S . grewal , G . P . Geba , and R . A . flavell . 1996 . 183 : 589 598 . ) . since the mechanism of this impairment has not been clarified , we sought to define the stage ( s ) at which the CHS response is affected in L selectin deficient mice . We show that epidermal langerhans cells in L selectin deficient mice are normal in number , migrate to peripheral lymph nodes appropriately , and are functional in presenting allogeneic and haptenic antigens . moreover , T cells , as well as neutrophil and monocyte effector populations , are fully capable of entry into the inflamed skin sites in the absence of L selectin . Thus , antigen presentation …

Expression of cell adhesion molecules in the lungs of patients with idiopathic pulmonary fibrosis. (1995 Aug)
expression of cell adhesion molecules in the lungs of patients with idiopathic pulmonary fibrosis . idiopathic pulmonary fibrosis ( IPF ) is a chronic inflammatory disorder restricted to the lungs . leukocyte entry into the area of inflammation is regulated , at least partly , by endothelial expression of leukocyte selective cell adhesion molecules ( CAMs ) . To investigate the relevance of these CAMs to the accumulation of leukocytes in IPF , we examined the expression of E selectin ( endothelial leukocyte adhesion molecule 1 ; ELAM 1 ) , intercellular adhesion molecule 1 ( ICAM 1 ) , and vascular cell adhesion molecule 1 ( VCAM 1 ) by immunohistochemistry in lung tissue from nine patients with IPF and five nonsmoking normal subjects . The results demonstrated that in normal lungs , ICAM 1 was weakly expressed on endothelial cells , but neither E selectin nor VCAM 1 was detected . In the lungs of patients with IPF , E selectin expression on endothelial cells was restricted to honeycombing regions . endothelial expression of ICAM 1 was increased throughout the tissue , but VCAM 1 was not detected in IPF . The distribution of leukocytes in lungs with IPF consisted of mostly lymphocyte accumulation in the interstitium and neutrophil accumulation within the airspaces of honeycomb regions . these results suggest that E selectin may play a role in the recruitment of neutrophils in regions of honeycombing and that ICAM 1 may play a role in lymphocyte recruitment into …

Identification of L selectin binding heparan sulfates attached to collagen type xviii. (2005 Jul)
identification of L selectin binding heparan sulfates attached to collagen type xviii . L selectin is a C type lectin expressed on leukocytes that is involved in both lymphocyte homing to the lymph node and leukocyte extravasation during inflammation . known L selectin ligands include sulfated lewis type carbohydrates , glycolipids , and proteoglycans . previously , we have shown that in situ detection of different types of L selectin ligands is highly dependent on the tissue fixation protocol used . Here we use this knowledge to specifically examine the expression of L selectin binding proteoglycans in normal mouse tissues . We show that L selectin binding chondroitin / dermatan sulfate proteoglycans are present in cartilage , whereas L selectin binding heparan sulfate proteoglycans are present in spleen and kidney . furthermore , we show that L selectin only binds a subset of renal heparan sulfates , attached to a collagen type xviii protein backbone and predominantly present in medullary tubular and vascular basement membranes . As L selectin does not bind other renal heparan sulfate proteoglycans such as perlecan , agrin , and syndecan 4 , and not all collagen type xviii expressed in the kidney binds L selectin , this indicates that there is a specific L selectin binding domain on heparan sulfate glycosaminoglycan chains . using an in vitro L selectin binding assay , we studied the contribution of N sulfation , O sulfation , C5 epimerization , unsubstituted glucosamine residues , and chain length in L …

Role of P selectin in radiation induced intestinal inflammatory damage. (2001 Apr)
Role of P selectin in radiation induced intestinal inflammatory damage . The aims of our study were to characterize the dose and time dependent changes in endothelial P selectin expression and the role of this adhesion molecule as a mediator of radiation induced inflammation . For that purpose , endothelial P selectin expression was measured by the radiolabeled antibody technique in control and irradiated mice at 2 , 6 , and 24 hr following abdominal irradiation with 4 or 10 Gy ; leukocyte endothelial cell interactions were assessed using intravital microscopy in intestinal venules following irradiation at the aforementioned doses and times in c57bl / 6 and P selectin deficient mice . In wild type mice , radiation induced a time and dose dependent up regulation of P selectin and a significant increase in the flux of rolling leukocytes 2 hr after irradiation . irradiation induced a significant increase in leukocyte adhesion that was dose dependent . following irradiation , P selectin deficient mice did not show any increase in leukocyte rolling but did demonstrate a response in leukocyte adhesion similar to that of the wild type mice . radiation induced dose dependent histological inflammatory damage that did not differ between P selectin deficient and wild type mice . We conclude that P selectin is up regulated following irradiation and is a key molecular determinant of leukocyte rolling but not leukocyte adhesion in this inflammatory condition . therefore , isolated neutralization of this adhesion molecule is not an effective means …

Blocking endothelial adhesion molecules : a potential therapeutic strategy to combat atherogenesis. (2004 Sep)
blocking endothelial adhesion molecules : a potential therapeutic strategy to combat atherogenesis . purpose OF review : This review provides a concise update of the involvement of endothelial adhesion molecules in atherogenesis , an overview of current advances in the development of adhesion molecule blocking agents , as well as an insight into the potential of these molecules in cardiovascular therapy . recent findings : As endothelial adhesion molecules are deemed to play an important role in the development and progression of atherosclerotic lesions , they are interesting targets for therapeutic intervention in this process . In particular , P selectin and vascular cell adhesion molecule 1 are widely considered to hold promise in this regard . current research efforts centre on the design of agents that directly block the interaction of the receptor with its ligand ( e . g . soluble P selectin glycoprotein ligand 1 , blocking antibodies , EWVD based peptides ) or that interfere with their synthesis ( e . g . antisense oligonucleotides ) or their regulatory control by nuclear factor kappa B or peroxisome proliferator activated receptor gamma . furthermore , adhesion molecules have been exploited as a target for the specific delivery of drug carriers ( e . g . biodegradable particles with entrapped dexamethasone ) or therapeutic compounds ( e . g . dexamethasone ) to the plaque . All approaches have been shown to be effective in blocking adhesion molecule function in in vitro studies and in vivo models for …

Endothelial leukocyte adhesion molecules. (1993 May)
endothelial leukocyte adhesion molecules . One decade ago , vascular endothelium was commonly considered a non stick lining of blood vessels that functioned only to prevent blood coagulation and to separate the vascular space from tissues . By comparison to many other cell types , endothelial cells were thought to be less active , less complex , and less interesting . since that time , research concerning the endothelium has expanded dramatically and produced a new image of the vascular lining as an active participant in a wide variety of pathophysiological processes , including inflammation and immunity . nowhere has the excitement been more intense than in the study of the molecular mechanisms of leukocyte adhesion to endothelium . recent efforts resulted in the identification , characterization , and cloning of multiple endothelial cell surface glycoproteins that support adhesion through an interaction with specific ligands ( or counter receptors ) on leukocytes . The selectins , two of which are found on endothelium and one on leukocytes , support adhesion through the recognition of carbohydrates . endothelial members of the immunoglobulin superfamily including ICAM 1 and VCAM 1 / incam 110 bind to leukocyte cell surface integrins . In various combinations , these and other molecules support leukocyte adhesion to the vessel wall and extravasation , key steps in our response to infection and tissue injury .

Circulating soluble adhesion molecules in patients with giant cell arteritis. (1999 Jun)
circulating soluble adhesion molecules in patients with giant cell arteritis . correlation between soluble intercellular adhesion molecule 1 ( sicam 1 ) concentrations and disease activity . objective : To evaluate whether changes in concentrations of circulating adhesion molecules are related to disease activity in patients with giant cell arteritis ( GCA ) . methods : A sandwich elisa was used to measure soluble intercellular adhesion molecule 1 ( sicam 1 ) , sicam 3 , vascular cell adhesion molecule 1 ( svcam 1 ) , E selectin ( sE selectin ) , and L selectin ( sL selectin ) in serum and plasma samples from patients with GCA . A cross sectional study was performed on 64 GCA patients at different activity stages and on 35 age and sex matched healthy donors . thirteen of these patients were evaluated at the time of diagnosis and serially during follow up . results : At the time of diagnosis , sicam 1 concentrations were significantly higher in active GCA patients than in controls ( mean ( SD ) 360 . 55 ( 129 . 78 ) ng / ml versus 243 . 25 ( 47 . 43 ) ng / ml , p 0 . 001 ) . In contrast , sicam 3 , svcam 1 , sE selectin , and sL selectin values did not differ from those obtained in normal donors . With corticosteroid administration , a decrease in sicam 1 concentrations was observed , reaching normal values when …

Leucocyte endothelial cell adhesion in a model of intestinal inflammation. (1995 Dec)
leucocyte endothelial cell adhesion in a model of intestinal inflammation . leucocyte endothelial cell adhesion is modulated by a variety of adhesion glycoprotein expressed on the surface of leucocytes and endothelial cells . although in vitro studies show that these adhesion molecules mediate the decrease in leucocyte rolling velocity and the increase in leucocyte adherence and emigration associated with inflammation , there are few in vivo data to support this hypothesis . The aim of this study was to assess the role of leucocyte ( cd11b / CD18 ) and endothelial cell ( P and E selectin ) adhesion molecules in mediating the leucocyte endothelial cell adhesion elicited in rat mesenteric venules during a model of longlasting intestinal inflammation . indomethacin was injected 48 and 24 hours before the experiment . The mesenteric microcirculation was observed by intravital microscopy in animals treated with monoclonal antibodies ( MAb ) directed against either P selectin , E selectin , or cd11b / CD18 . leucocyte rolling velocity , and the number of adherent and emigrated leucocytes as well as vessel diameter and erythrocyte velocity were monitored in roughly 30 micron diameter postcapillary venules . indomethacin treatment resulted in mucosal ulceration and granulocyte infiltration , and a corresponding inflammatory response in the mesentery , which was characterised by an increase in the number of adherent ( eightfold ) and emigrated ( sixfold ) leucocytes and a reduction ( 80 ) in leucocyte rolling velocity . The indomethacin induced leucocyte endothelial cell adhesion in …

Reciprocal activation of leukocyte endothelial adhesion molecules in acute coronary syndromes. (2003 Sep)
reciprocal activation of leukocyte endothelial adhesion molecules in acute coronary syndromes . background : The acute coronary syndromes are associated with an intense inflammatory response and sustained leukocyte activation . This inflammatory state has been correlated with an adverse prognosis , but the source of this inflammation remains controversial , with evidence that it may arise either from the coronary vasculature or from the systemic endothelium . methods : levels of soluble cell adhesion molecules , and of their respective monocyte cell surface ligands , were measured in the peripheral serum of 21 patients presenting with acute coronary syndromes . soluble intercellular adhesion molecule 1 and soluble vascular cell adhesion molecule 1 were measured by enzyme linked immunosorbent assay and expression of the monocyte integrins cd11b ( Mac 1 ) and cd49d ( VLA 4 ) was measured by direct immunofluorescence using flow cytometry . results : High levels of the monocyte receptor cd11b ( 531 vs . 345 MFI , P 0 . 01 ) , and its soluble intercellular adhesion molecule 1 ( 329 vs . 232 ng / ml , P 0 . 01 ) , were noted in patients with acute coronary syndromes compared to healthy controls . conclusions : reciprocal activation of monocyte receptor ligands and endothelial adhesion molecules was found in the peripheral blood of patients with acute coronary syndromes . This may indicate a coordinated state of pro inflammatory upregulation with widespread activation of both leukocytes and endothelium and suggests a systemic rather …

Expression of the cutaneous lymphocyte antigen and its counter receptor E selectin in the skin and joints of patients with … (1997 Sep)
expression of the cutaneous lymphocyte antigen and its counter receptor E selectin in the skin and joints of patients with psoriatic arthritis . We have investigated whether the skin homing T lymphocytes identified by the cutaneous lymphocyte antigen ( CLA ) are increased in the synovial membrane of patients with psoriatic arthritis . twenty six synovial samples ( 13 psoriatic arthritis , seven rheumatoid arthritis , six osteoarthritis ) were obtained from involved knees . lesional skin biopsies were taken from nine of the patients with psoriatic arthritis and six patients with psoriasis alone . All samples were single and dual stained for CLA and CD3 ( to identify T lymphocytes ) using HECA 452 ( anti CLA ) and anti CD3 monoclonal antibodies . E selectin expression was also determined . The percentage of dual stained lymphocytes was significantly greater in psoriatic skin than in synovium ( P 0 . 001 ) and similar between psoriatic and rheumatoid synovium . there was no significant difference in the percentages of CLA positive cells in psoriatic skin in patients with psoriatic arthritis compared with psoriasis alone . The intensity of endothelial E selectin expression was significantly greater in skin psoriasis than in synovium ( P 2 x 10 ( 5 ) ) , and rheumatoid synovium had significantly greater expression than psoriatic synovium ( P 0 . 05 ) . however , there was no significant correlation between E selectin expression and the percentages of CLA positive lymphocytes . This study …

De novo expression of the cell adhesion molecule E selectin on gastric cancer endothelium. (1998 Aug)
De novo expression of the cell adhesion molecule E selectin on gastric cancer endothelium . background AND AIMS : angiogenesis and the molecular phenotype of the tumor vasculature determine tumor growth and metastasis . patients / methods : In a series of 58 gastric cancer patients , vascular density and the antigenic profile of endothelial cells in normal , inflamed and malignant gastric tissues were compared using immunohistochemistry . results : In both benign gastric mucosa and primary gastric cancer vascular density was inflammation independent . however , increased vascularity in primary tumors was positively associated with a high tumor cell density suggesting tumor induced angiogenesis ( P 0 . 00001 ) . P selectin was expressed in most of the gastric mucosa samples on a small fraction of vessels and increased in the presence of moderate to strong leukocyte infiltrate . VCAM 1 positive mucosal vessels were rare and showed no association with inflammation . E selectin and the EN 7 / 44 antigen defining budding vessels were absent on normal and inflamed endothelium . In contrast , in primary gastric cancer de novo expression of both E selectin and the EN 7 / 44 antigen was observed . E selectin positive vessels were preferentially found in vascular rich tumor areas ( P 0 . 0043 ) independently of leukocyte infiltration . upregulation of VCAM 1 on tumor associated endothelium was closely related to inflammation ( P 0 . 019 ) , while P selectin expression resembled that in …

Alterations in circulating intercellular adhesion molecule 1 and L selectin : further evidence for chronic inflammation in ischemic heart disease. (1996 Sep)
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 …

Adhesion molecules in inflammatory diseases : insights from knockout mice. (2002 Oct)
adhesion molecules in inflammatory diseases : insights from knockout mice . leukocyte / endothelial cell adhesion molecules are essential mediators of both immune and inflammatory responses . however , their specific roles in the initiation and progression of inflammatory diseases remain largely undefined . The focus of our laboratory is the identification of the adhesion molecule interactions that mediate leukocyte recruitment and tissue damage during the development of rheumatoid arthritis , systemic lupus erythematosus , and psoriasis . For these studies , we use a basic genetic approach in mice , analyzing different gene targeted adhesion molecule mutants , or knockouts , in murine disease models . Our findings suggest that loss of intercellular adhesion molecule 1 significantly inhibits the development of arthritis and glomerulonephritis , while selectin deficiency results in accelerated development of joint and kidney inflammation . Our results also indicate that the beta2 integrins may play a key role in regulating the initiation of psoriasiform skin diseases .

Synovial fluid levels of E selectin and intercellular adhesion molecule 1 : relationship to joint inflammation in children with chronic … (2002 Sep)
synovial fluid levels of E selectin and intercellular adhesion molecule 1 : relationship to joint inflammation in children with chronic arthritis . E selectin and intercellular adhesion molecule ( ICAM ) 1 are crucial to the inflammatory response in chronic inflammatory arthritis . soluble ( s ) levels of these molecules in sera and synovial fluid ( SF ) correlate with some clinical parameters and synovial tissue expression of the same molecules in rheumatoid arthritis . studies of sera from children with chronic inflammatory arthritis corroborate this information ; corresponding SF data are relatively lacking . We thus studied SF sE selectin and sicam 1 in 28 children with active juvenile rheumatoid arthritis or a spondyloarthropathy . levels were correlated with erythrocyte sedimentation rate ( ESR ) , SF leukocyte counts , duration of disease , and duration of response to concomitant intra articular corticosteroid injection . levels were compared according to use of methotrexate and / or sulfasalazine . synovial fluid sE selectin correlated with ESR and SF leukocyte counts . there was a trend toward lower sicam 1 in patients treated with sulfasalazine and / or methotrexate . We conclude that SF levels of sE selectin accurately reflect intra synovial inflammation . soluble ICAM 1 levels may reflect the effects of disease modifying agents .

L selectin expression enhances clonogenesis of CD34 cord blood progenitors. (1999 Aug)
L selectin expression enhances clonogenesis of CD34 cord blood progenitors . L selectin , a surface adhesion glycoprotein expressed on leukocytes , has a well established role in mediating inflammation and lymphocyte recirculation . recent evidence suggests that L selectin may also influence hematopoiesis . We observed that a greater proportion of CD34 cells express L selectin in cord blood compared with adult bone marrow , and we hypothesized that L selectin expression is associated with enhanced clonogenic properties . To test this , we compared CD34 / L selectin cells with CD34 / L selectin cells in hematopoietic clonogenic assays . From CD34 / L selectin cell cultures , we observed a 3 fold increase of d 12 14 colony forming unit granulocyte / macrophage and multipotent progenitor cells , and a 5 fold enhancement of primitive d 21 high proliferative potential colony forming cells compared with the progeny of CD34 / L selectin cells . We conclude that CD34 cord blood cells expressing L selectin are enriched in their clonogenic activity compared with cell fractions lacking L selectin expression .