Modification of P-selectin glycoprotein ligand-1 with a natural killer cell-restricted sulfated lactosamine creates an alternate ligand for L-selectin

Natural killer (NK) cells are components of the innate immune system that can recognize and kill virally infected cells, tumor cells, and allogeneic cells without prior sensitization. NK cells also elaborate cytokines (e.g., interferon-gamma and tumor necrosis factor-alpha) and chemokines (e.g., macrophage inflammatory protein-1alpha) that promote the acquisition of antigen-specific immunity. NK cell differentiation is accompanied by the cell surface expression of a mucin-like glycoprotein bearing an NK cell-restricted keratan sulfate-related lactosamine carbohydrate, the PEN5 epitope. Here, we report that PEN5 is a post-translational modification of P-selectin glycoprotein ligand-1 (PSGL-1). The PEN5 epitope creates on PSGL-1 a unique binding site for L-selectin, which is independent of PSGL-1 tyrosine sulfation. On the surface of NK cells, the expression of PEN5 is coordinated with the disappearance of L-selectin and the up-regulation of Killer cell Ig-like Receptors (KIR). These results indicate that NK cell differentiation is accompanied by the acquisition of a unique carbohydrate, PEN5, that can serve as part of a combination code to deliver KIR(+) NK cells to specific tissues.

Cyclosporine A and purinergic receptors in rat kidney

Previous reports have demonstrated that Cyclosporine A (CyA) chronically administered induces an increase in adenosine plasma concentration by inhibiting adenosine uptake by red blood cells (RBC). We hypothesized that this effect may modulate, by a down regulation, the mRNA expression of adenosine receptors in rat kidney. Since high blood pressure (HBP) is a classical side effect of CyA treatment, nicardipine, a dihydropyridine calcium channel blocker, is often associated with CyA in treatment. To distinguish between the effects of CyA-induced HBP and the effects of CyA by itself, we have evaluated the effects of CyA and/or nicardipine on the mRNA expression of A1 and A2a adenosine receptors. The study was performed on five groups of rats (n= 8) receiving during 21 days either serum saline (0.5 ml i.p), CyA (12 mg/kg/day, i.p), nicardipine (1.2 mg/kg i.p) or nicardipine + CyA. The last (or fifth) group was injected with vehicle (0.5 ml i.p). Blood samples for adenosine assay were collected in the renal artery at day 21, just before the rat kidneys were removed for quantitation of adenosine A1 and A2a mRNA concentration by RT-PCR. We make two conclusions :i) Nicardipine induces a decrease in mRNA expression of A1 but not of A2a adenosine receptors. However, because nicardipine lowered both blood pressure and A1 mRNA expression, it is not possible to conclude if A1 mRNA decrease is implicated in the nicardipine effects on blood pressure.ii) CyA induces an increase in renal artery adenosine concentration and a decrease in mRNA expression of A1 and A2a adenosine receptors.

Differences in levels of soluble E-selectin and VCAM-1 in malignant versus non malignant Mediterranean spotted fever

In the present study, we investigated the plasma levels of soluble adhesion molecules E-selectin, P-selectin, intercellular adhesion molecule- (ICAM- ) and vascular cell adhesion molecule-1(VCAM-1) in 24 patients with Mediterranean spotted fever (MSF), 6 of whom with a malignant form. Measurements were performed on blood samples collected before treatment (T1), then twice during treatment (T2 and T3). Before treatment, MSF patients taken as a whole presented elevated levels of sICAM-1 and sVCAM-1 and normal levels of sE-selectin and sP-selectin compared to healthy controls. We found that sICAM-1 was elevated both in mild and malignant MSF. sE-selectin and sVCAM-1 were elevated only in patients with the malignant form and allowed to discriminate the two clinical subgroups. Their levels decreased after treatment with sE-selectin reaching control values at T2 whereas sVCAM-1 remained higher over the course of the malignant form. In patients with mild MSF, sP-selectin steadily increased after treatment, whereas it did not present any modification at any of the two sampling times in patients with the malignant form. Raised plasma levels of sE-selectin and sVCAM-1 reflect endothelial activation in malignant rickettsial disease and may be sufficiently early markers to influence the therapeutic decision.

Localization of Na,K-ATPase alpha/beta isoforms in rat sciatic nerves: effect of diabetes and fish oil treatment

The localization of the Na,K-ATPase isoenzymes in sciatic nerve remains controversial, as well as diabetes-induced changes in Na,K-ATPase isoforms. Some of these changes could be prevented by fish oil therapy. The aim of this study was to determine by confocal microscopy the distribution of Na,K-ATPase isoforms (alpha1, alpha2, alpha3, beta1, and beta2) in the sciatic nerve, the changes induced by diabetes, and the preventive effect of fish oil in diabetic neuropathy. This study was performed in three groups of rats. In the first two groups, diabetes was induced by streptozotocin and rats were supplemented daily with fish oil or olive oil at a dosage of 0.5 g/kg of body weight. The third one was a control group that was supplemented with olive oil. Five antibodies against specific epitopes of Na,K-ATPase isoenzymes were applied to stained dissociated nerve fibers with fluorescent secondary antibodies. The five isoenzymes were documented in nonspecific regions, Schwann cells (myelin), and the node of Ranvier. The localization of the alpha1, alpha2, and beta1 isoenzymes was not affected by diabetes. In contrast, diabetes induced a decrease of the alpha2 subunit (p < 0.05) and an up-regulation of the beta2 subunit (p < 0.05). These modifications were noted in both regions for alpha2 and were localized at the myelin domain only for the beta2. Fish oil supplementation prevented the diabetes-induced changes in the alpha2 subunit with an additional up-regulation. The beta2 subunit was not modified. A phenotypic change similar to nerve injury was induced by diabetes. Fish oil supplementation partially prevented some of these changes.

In vitro generation of endothelial microparticles and possible prothrombotic activity in patients with lupus anticoagulant

Microparticles (MPs) resulting from vesiculation of platelets and other blood cells have been extensively documented in vitro and have been found in increased numbers in several vascular diseases, but little is known about MPs of endothelial origin. The aim of this study was to analyze morphological, immunological, and functional characteristics of MPs derived from human umbilical vein endothelial cells (HUVECs) stimulated by TNF, and to investigate whether these MPs are detectable in healthy individuals and in patients with a prothrombotic coagulation abnormality. Electron microscopy evidenced bleb formation on the membrane of TNF-stimulated HUVECs, leading to increased numbers of MPs released in the supernatant. These endothelial microparticles (EMPs) expressed the same antigenic determinants as the corresponding cell surface, both in resting and activated conditions. MPs derived from TNF-stimulated cells induced coagulation in vitro, via a tissue factor/factor VII-dependent pathway. The expression of E-selectin, ICAM-1, alphavbeta3, and PECAM-1 suggests that MPs have an adhesion potential in addition to their procoagulant activity. In patients, labeling with alphavbeta3 was selected to discriminate EMPs from those of other origins. We provide evidence that endothelial-derived MPs are detectable in normal human blood and are increased in patients with a coagulation abnormality characterized by the presence of lupus anticoagulant. Thus, MPs can be induced by TNF in vitro, and may participate in vivo in the dissemination of proadhesive and procoagulant activities in thrombotic disorders.

Direct evidence of endothelial injury in acute myocardial infarction and unstable angina by demonstration of circulating endothelial cells

Circulating endothelial cells (CECs) have been detected in association with endothelial injury and therefore represent proof of serious damage to the vascular tree. Our aim was to investigate, using the technique of immunomagnetic separation, whether the pathological events in unstable angina (UA) or acute myocardial infarction (AMI) could cause desquamation of endothelial cells in circulating blood compared with effort angina (EA) and noncoronary chest pain. A high CEC count was found in AMI (median, 7.5 cells/mL; interquartile range, 4.1 to 43.5, P <.01 analysis of variance [ANOVA]) and UA (4.5; 0.75 to 13.25 cells/mL, P <.01) within 12 hours after chest pain as compared with controls (0; 0 to 0 cells/mL) and stable angina (0; 0 to 0 cells/mL). CEC levels in serial samples peaked at 15.5 (2.7 to 39) cells/mL 18 to 24 hours after AMI (P <.05 repeated measures ANOVA), but fell steadily after UA. Regardless of acute coronary events, the isolated cells displayed morphologic and immunologic features of vascular endothelium. The CECs were predominantly of macrovascular origin. They did not express the activation markers intercellular adhesion molecule (ICAM)-1, vascular cell adhesion molecule (VCAM)-1, and E-selectin, although some were positive for tissue factor. CECs failed to exhibit characteristics of apoptosis (TUNEL assay) excluding this event as a possible mechanism of cell detachment. The presence of CECs provides direct evidence of endothelial injury in AMI and UA, but not in stable angina, confirming that these diseases have different etiopathogenic mechanisms.

Differential regulation of killer cell Ig-like receptors and CD94 lectin-like dimers on NK and T lymphocytes from HIV-1-infected individuals

NK and T lymphocytes share various cell surface receptors, including NK receptors for MHC class I molecules (NKR). NKR include killer cell Ig-like receptors (KIR) and lectin-like dimers which are composed of the invariant CD94 associated with a variety of NKG2 molecules. The combination of KIR and CD94/NKG2 dimers expressed on NK and T cell subsets defines a repertoire of MHC class I recognition. Engagement of NKR by cognate MHC class I molecules governs T and NK cell activation. We investigated the NKR distribution on NK and T cell subsets from uninfected and HIV-infected individuals, according to the clinical status, the absolute numbers of CD4+ T cells as well as the plasmatic viral load of the patients. We show that the KIR distribution on NK cells is not affected by HIV-1 infection, whereas the absolute numbers of T cells expressing specific KIR members (CD158b, p70) transiently increase in early stages of HIV infection. By contrast, the percentages of NK and T cells which express CD94 dimers increase in parallel with the disease. These results document a differential regulation of KIR and CD94 lectin-like dimers during the course of a chronic viral infection in humans and further suggest that both types of NKR are independently regulated.

Cholesterol and omega-3 fatty acids inhibit Na, K-ATPase activity in human endothelial cells

We have investigated the effects of cholesterol and omega-3 fatty acids eicosapentaenoic acid (EPA) and docosahexenoic acid (DHA) on Na, K-ATPase activity in human endothelial cells (HUVEC). Cultured HUVEC were incubated for 18 h with pure egg phosphatidylcholine (PC), or cholesterol-enriched liposomes (4 mg PC/ml). EPA and DHA alpha-tocopherol-acetate were emulsified with PC and incubated with HUVEC (10 mM). Na, K-ATPase and 5'-nucleotidase activities were determined using the coupled assay method on microsomal fractions obtained from cultured cells using non treated cells as control. Cholesterol enrichment significantly reduced both Na, K-ATPase and 5'-nucleotidase activities by a similar level (- 40%), whereas pure phospholipid liposomes inhibited this activity only by 22%. The dose-response curves of Na, K-ATPase activity were all biphasic assuming the presence of two independent sites exhibiting different affinities for ouabain of nM and microM respectively. The cholesterol induced inhibitory effect was greater for low affinity sites (-54%) as compared to that of the high affinity sites (-24%) whereas omega-3 fatty acids reduced the activity of both sites by 22%. Short term effects of EPA and DHA on Na, K-ATPase activity were determined by incubating microsomal fractions from untreated cells with various concentrations of free fatty acids (from 1 to 200 microM) for 20 min. Both EPA and DHA significantly reduced Na, K-ATPase activity but inhibition by EPA seems to be more effective than DHA. These results suggest that cholesterol and omega-3 fatty acids reduce Na, K-ATPase activity in HUVEC.

Evidence for the expression of urokinase-type plasminogen activator by human venous endothelial cells in vivo

Endothelial cells (ECs) in culture synthesize and secrete urokinase-type plasminogen activator (u-PA), but the normal vascular endothelium is believed to synthesize only tissue plasminogen activator (t-PA), which is thought to be responsible for intravascular fibrinolysis. More recently, animal studies have shown that the biological role of u-PA in fibrinolysis has been underestimated, prompting a re-examination of its synthesis by the endothelium. In this study, we investigated whether u-PA was synthesized by non-atherosclerotic endothelial cells in vivo by testing ECs dislodged by venipuncture from 12 normal volunteers and 17 patients admitted for plasmapheresis. The ECs were isolated with an anti-endothelial monoclonal antibody coupled to immunomagnetic beads and characterized by morphology and by labelling for vWF, CD31, and UEA-1 binding. U-PA antigen was found in 50% of the ECs from the normal subjects and in 60% of those from patients. U-PA enzymatic activity on zymograms was detected in 50% of the normal samples and 60% of the patient samples, with the latter being more frequently and more strongly positive. U-PA mRNA was found in all the normal and patient samples tested. The results indicate that u-PA is synthesized by the venous endothelium in vivo but that its expression is highly variable.

A case report: CD8 expression in B-cell chronic lymphocytic leukemia (B-CLL). Prognostic significance of the aberrant CD8 expression

The human CD8 molecule is usually expressed on T lymphocytes or natural killer cells but not on normal B cells. Over a course of 5 years, we followed a case of B-CLL which aberrantly expressed the CD8 molecule. During this period, the clinical and hematological conditions of the patient were stable. This B-CLL presented a typical immunophenotype (HLA DR+, CD19+, CD5+, CD23+) with monotypic expression of surface immunoglobulin light chain kappa. We confirmed the CD8 expression on these leukemia cells by using double labelling and different antibodies directed against this antigen. We measured the quantitative expression of the CD8 molecule. The number of CD8 molecules per cell was clearly lower on these malignant B cells than on normal T lymphocytes. In order to evaluate the prognostic significance of this CD8 expression, we quantitated in parallel other markers such as CD5, CD23, CD22, CD11c. During 5 years, this aberrant CD8 expression persisted and was associated with an increase of the CD23 and a decrease of CD22 levels, known to correlate with a good prognosis in agreement with the karyotype analysis. Altogether our results led us to conclude that the aberrant CD8 expression in this case of B-CLL may correlate with a non-aggressive form of lymphoproliferative disorder.

Activation of human endothelial cells via S-endo-1 antigen (CD146) stimulates the tyrosine phosphorylation of focal adhesion kinase p125(FAK)

S-Endo-1 antigen (CD146), a transmembrane receptor also known as MUC18/MCAM, is a member of the immunoglobulin superfamily and belongs to a group of cell adhesion molecules. CD146 is highly expressed on the whole vascular tree. We demonstrate here that engagement of CD146 on human endothelial cells isolated from cord blood results in tyrosine phosphorylation of a large panel of cellular proteins, although no tyrosine phosphorylation of CD146 was detected. In particular, CD146 cross-linking induces the tyrosine phosphorylation of the protein tyrosine kinase p125(FAK) as well as p125(FAK) association with paxillin, both events being inhibited by cytochalasin D. No direct association of CD146 with p125(FAK) was observed. Consistent with these data, CD146 associates with p59(fyn), a Src family kinase known to phosphorylate p125(FAK). The identification of a signaling pathway initiated by CD146 engagement and which includes p59(fyn), p125(FAK), and paxillin indicates that CD146 participates in outside-in signaling in endothelial cells.

Adenosine and the nervous system: pharmacological data and therapeutic perspectives

1. Adenosine acts on a family of G-protein-coupled receptors called purinoreceptors. 2. Four subtypes have been cloned and pharmacologically characterized. 3. The principal pharmacological data and structure-function relations for agonist interactions with P1 receptors are presented. 4. We conclude that the potent role of adenosine in the nervous system may be interesting for the development of drugs targeted at purines and their receptors.

Role of Kaposi's sarcoma cells in recruitment of circulating leukocytes: implications in pathogenesis

OBJECTIVE

We sought to identify and characterize mechanisms of interaction between Kaposi's sarcoma cells and circulating leukocytes leading to leukocyte migration into the lesion.

STUDY DESIGN/METHODS

By using static and dynamic adhesion models, we measured the ability of late-stage KSY1 cells to support adhesion and transmigration of peripheral blood lymphocytes (PBL).

RESULTS

We showed that resting as well as TNF-alpha- or PMA-activated KSY1 cells supported adhesion and transmigration of PBL with a higher efficiency compared with normal endothelial cells. The LFA1/ICAM1 pathway was totally involved in PBL adhesion to resting or TNF-alpha-activated KSY1 cells and partially responsible for adhesion to PMA-activated KSY1 cells. No inhibition of adhesion was observed by blockage of the VLA4 pathway. Under flow conditions, PBL/KSY1 cell interaction was totally dependent on L-selectin.

CONCLUSION

Our data indicate that KS cells mimic an endothelium-like structure by regulating extravasation of lymphocytes into lesions.

Evidence that human endothelial cells express different isoforms of Na,K-ATPase

BACKGROUND

The catalytic alpha and smaller beta subunits of the plasma membrane Na,K-ATPase occur in various molecular forms (alpha1, alpha2, alpha3, beta1 and beta2). The alpha isoforms of the enzyme have varying affinities for ouabain and exist in different tissues with particular distribution patterns.

OBJECTIVE

To document the existence of isoforms of the Na,K-ATPase in cultured human umbilical vein endothelial cells.

METHODS

Microsomal fractions were prepared by differential ultracentrifugation from primary cultures of human umbilical vein endothelial cells and from such cells obtained after three passages. Na,K-ATPase activity was assayed using the coupled assay method and sensitivity to ouabain was determined in the presence of varying concentrations of ouabain. Specific antibodies for the various Na,K-ATPase isoforms were used to label these different proteins by immunocytochemistry in endothelial cells and by Western blotting in isolated membranes.

RESULTS

In plotting the dose-response curves for Na,K-ATPase activity in response to ouabain we assumed the existence of two independent sites exhibiting different affinities for ouabain (in the micromol/l and the nmol/l ranges). The contribution of low-affinity sites was threefold that of high-affinity sites. After three passages in culture, a specific increase in Na,K-ATPase activity of the high-affinity sites was observed compared with that of cells from primary cultures. Confocal microscopy revealed the existence of beta1, beta2, and alpha1 subunit proteins in human umbilical endothelial cells. Staining for alpha3 isoform was less pronounced and no obvious alpha2 was detected.

CONCLUSION

These findings suggest that human umbilical vein endothelial cells contain beta1, beta2, a large amount of alpha1 isoform with an apparently low affinity for ouabain, and a lesser amount of high-affinity sites, which may correspond to the alpha3 protein.

CD146: biosynthesis and production of a soluble form in human cultured endothelial cells

We previously identified the S-Endo 1-associated antigen (CD146), an endothelial member of the immunoglobulin superfamily with a characteristic V-V-C2-C2-C2 Ig domain structure. In cultured human endothelial cells, we investigated its biosynthesis by immunoprecipitation and pulse-chase labeling. CD146 was synthesized as a 100 kDa precursor form, which was processed into a 120 kDa mature form. In the culture media of endothelial cells, we observed a CD146 soluble form that was about 10 kDa smaller than cell-associated CD146. In parallel with soluble forms of other members of the immunoglobulin superfamily, soluble CD146 could modulate and control the functions of the molecule.

Interactions between cyclosporine A and adenosine in kidney transplant recipients

Adenosine is involved in a large number of physiological processes including immune response and vasomotor function. But its precise involvement in renal physiology is poorly understood. We have investigated the putative relationships between cyclosporine A (CsA) and adenosine (ADO) metabolism in kidney transplant recipients (KTR). We first compared ADO plasma levels in three groups of patients and in 10 controls: the first group (N = 14) was composed of CsA-treated KTR; the second group (N = 5) was KTR not treated with CsA, and the third (N = 6) was chronic kidney failure patients. We also measured ADO plasma level in two KTR treated with FK506, a CsA analog. ADO plasma levels in CsA-treated KTR were significantly higher (mean 0.76 microM +/- 0.27) than in the control group (mean 0.31 +/- 0.13; Mean-Whitney test, S = 8.5; P = 2.1 x 10(-4)) and than in the chronic kidney failure group (0.37 +/- 0.16, Mann-Whitney, S = 5.5; P = 1.6 x 10(-3)). In CsA-treated KTR, CsA and ADO plasma levels were significantly correlated (Spearman's, r = 0.8, P = 1.9 x 10(-3)). No significant differences in ADO plasma levels were found between patients with chronic kidney failure and controls (P < 0.05). ADO plasma levels in KTR not treated with CsA were in the same range as those in controls. Finally, the ADO plasma level was increased in the two FK506-treated patients. We also investigated the action of CsA on ADO plasma degradation and uptake by erythrocytes in vitro. No interaction between adenosine deaminase and CsA was found because CsA, in the presence of adenosine deaminase, did not modify the plasma half-life of ADO. Conversely, in the presence of CsA (500 and 1000 ng/ml), the uptake of ADO by erythrocytes was significantly decreased in adenosine deaminase-free samples (analysis of variance, P = 1.8.10(-3) and 1.2 x 10(-4), respectively). We conclude that ADO plasma levels are significantly elevated and correlate with CsA blood level in CsA-treated KTR, and that these high levels are due to CsA inhibition of ADO uptake by red cells. Since ADO and metabolites have well known immunosuppressive and vascular effects, ADO is likely to participate in the immune defect and in the vasoconstriction induced by CsA.

Effect of uremia and hemodialysis on soluble L-selectin and leukocyte surface CD11b and L-selectin

Leukocyte Mac-1 (CD11b/CD18) and L-selectin (CD62L) are implicated in leukocyte adhesion to endothelial cells. In this study, L-selectin and CD11b expression on leukocytes and soluble L-selectin (sL-selectin) serum levels were investigated in 17 nondialyzed patients with chronic renal failure (CRF), in 28 chronic hemodialysis patients before hemodialysis (basal state), and in 32 healthy subjects. These parameters were also monitored during hemodialysis with cuprophane and cellulose diacetate membranes in a crossover study in five patients. Granulocytes from CRF patients displayed lower expression of L-selectin and higher expression of CD11b than granulocytes from healthy subjects. On the other hand, baseline expression of L-selectin and CD11b on leukocytes from hemodialysis patients did not differ from that of healthy subjects. In CRF and hemodialysis patients, sL-selectin levels were significantly lower than in healthy subjects. During hemodialysis, cuprophane membrane induced an upregulation of granulocyte CD11b, a decrease in granulocyte L-selectin, and an increase in sL-selectin serum levels. Conversely, cellulose diacetate caused only a transient increase in granulocyte CD11b and did not modify granulocyte L-selectin and sL-selectin serum levels. High CD11b and low L-selectin expression on granulocytes in CRF patients suggests an activation state, which was not found in hemodialysis patients at the basal state. The lack of activation in hemodialysis patients could reflect the elimination of a uremic toxin by dialysis or a loss of granulocyte responsiveness because of the repetitive stimulation by hemodialysis treatment. The low serum levels of sL-selectin in CRF and hemodialysis patients also suggest granulocyte dysfunction.

[Endothelium and infections]

Endothelial cells control vascular homeostasis by regulating haemostasis, inflammatory and immune response, vascular tone or angiogenesis. The endothelium is the target of infectious agents capable of altering this equilibrium. Such alterations may result from a direct cytopathic effect with disruption of endothelial integrity, or from an indirect effect due to unregulated activation leading to vascular dysfunction. The endothelium is both the target and the effector of human vascular diseases associated with infection such as atherosclerosis, vasculitis, neuropaludism or graft rejection. A better comprehension of endothelial alterations is these diseases should have biological and therapeutic implications.

Thrombosis in congenital deficiencies of AT III, protein C or protein S: a study of 44 children

Congenital deficiency in coagulation inhibitors is a cause of hereditary thrombotic disease. The severity of symptoms is variable and depends on the type of deficit. In this paper, 44 children suffering from deep venous thrombosis, with a mean age of 5 years, were studied. A search for Lupus anticoagulant (LA) and coagulation inhibitor deficiency showed: 3/44 cases (6.8%) had protein S deficiency, 2/44 cases (4.5%) had protein C deficiency, 1/44 cases (2.3%) had deficiencies in both protein C and S; no cases of AT III deficiency and LA was positive in 2/44 cases (4.5%). Only 1 case of APC resistance out of 13 studied was found. Four family studies were performed and confirmed the congenital origin of the disorder.

Immunologic phenotype of cultured endothelial cells: quantitative analysis of cell surface molecules

Endothelial cells express a wide spectrum of surface molecules involved in multiple vascular functions. We quantitatively determined an extensive immunologic phenotype of endothelial cells through a large panel of antibodies directed against i) well-known endothelial molecules CD31, CD34, CD49b, e, f, CD51, CD54, CD55, CD62E and P, CD105, CD106, HLA class I and HLA class II; ii) molecules defined by monoclonal antibodies newly clustered during the 6th workshop of Human Leukocyte Differentiation Antigen (HLDA) CD109, CD140b, CD141, CD142, CD143, CD144, CDw145, CD146 and CD147; iii) molecules defined by unclustered monoclonal antibodies. The expression of these molecules was quantified on human umbilical vein endothelial cells (HUVEC) cultured in resting conditions and after stimulation with IL-1beta (10 U/ml), TNF-alpha (10 ng/ml) and phorbol myristate acetate (60 ng/ml). Some molecules were constitutively expressed, and others were negative, which served to determine the basal phenotype. After cell stimulation, the molecules showed weak or strong expression modulation, leading to the definition of an activated phenotype. Changes in the kinetics and the amplitude of expression served to characterize poorly defined molecules and may be useful to determine their physiologic role. Also, we compared the phenotypes of endothelial cell lines EA.hy 926 and ECV 304 to that of HUVEC to assess their reliability as an endothelial cell model. Each cell line displayed a specific repertoire of molecules expressed at different levels, which could have significant implications for cell line behavior as endothelial cells.

Quantitative analysis of leukocyte membrane antigen expression on human fetal and cord blood: normal values and changes during development

We studied the antibody binding capacity (ABC) of various cell-surface antigens in normal human fetuses and term neonates on lymphocyte, monocyte, and polymorphonuclear (PMN) cells by quantitative flow cytometry also designated by quantimetry. Analysis of changes of expression level on these leukocytes during the developmental process was also investigated. The results indicated that the ABC values of most studied markers change during the maturational process. The ABC of lymphocyte-associated antigens studied such as CD5 and CD7 showed only a decrease from fetus to adult, whereas according to the type of molecule on monocyte and PMN there was either an increase or a decrease of ABC values dependent on the stage of the developmental process, from fetus to neonate or from neonate to adult. However, the ABC values of leukocyte membrane antigens such as CD16, CD46, and CD55 on all leukocytes and CD11b, CD11c, and CD35 on myeloid cells did not change. Their expression level was already mature in fetuses compared with adult cells. In addition, in this quantimetric approach, the analysis of the results for CD11a and CD8 suggested that the changes of CD11a expression level on lymphocyte subsets can depend on one mechanism, whereas there are probably at least two for CD8. Furthermore, the expression patterns of CD5, CD7, and CD11a change during maturation. We concluded that, even if the neonate response pattern to immunological challenge differs from an adult and this is based primarily on the relative numbers and functional activity of lymphocyte T subsets (especially TH1/TH2) and their cytokine profiles, these quantitative and qualitative phenotypical differences might also contribute to explain the functional peculiarities of leukocyte fetal and cord blood cells. All these findings support the notion of immaturity and maturity of ABC expression.

Rickettsia conorii infection enhances vascular cell adhesion molecule-1- and intercellular adhesion molecule-1-dependent mononuclear cell adherence to endothelial cells

Leukocyte adherence to the endothelium is an essential component of the inflammatory response during rickettsial infection. In vitro, Rickettsia conorii infection of endothelial cells enhances the expression of adhesive molecules E-selectin, intercellular adhesion molecule-1 (ICAM-1), and vascular cell adhesion molecule-1 (VCAM-1) in a time- and dose-dependent manner. Rickettsial lipopolysaccharide does not seem to be involved, because polymyxin B does not reduce their expression. The intracellular presence of the organism and de novo host protein synthesis are required for expression of cell adhesive molecules, since rickettsial inactivation by formol and pretreatment of cells with cycloheximide inhibits an increase in expression. The contribution of interleukin-1alpha (IL-1alpha) to this endothelial adhesive phenotype was shown by inhibitory experiments 8 and 24 h after infection with IL-1 receptor antagonist and IL-1alpha blocking antibodies. Enhanced adherence of mononuclear cells to infected endothelial cells involved VCAM-1- and ICAM-1-dependent mechanisms at the late phase of the inflammatory response. This endothelial adhesive phenotype may constitute a key pathophysiologic mechanism in R. conorii-induced vascular injury.

Evaluation of sensitivity and specificity of a standardized procedure using different reagents for the detection of lupus anticoagulants. The Working Group on Hemostasis of the Société Française de Biologie Clinique and for the Groupe d'Etudes sur I'Hémostase et la Thrombose

This study was designed to test the sensitivity and specificity of a combination of 3 phospholipid-dependent assays performed with various reagents, for the detection of lupus anticoagulant (LA). Plasmas containing an LA (n = 56) or displaying various confounding pathologies [58 intrinsic pathway factor deficiencies, 9 factor VIII inhibitors, 28 plasmas from patients treated with an oral anticoagulant (OAC)] were selected. In a first step, the efficiency of each assay and reagent was assessed using the Receiving Operating Characteristic (ROC) method. Optimal cut-offs providing both sensitivity and specificity > or = 80% were determined. The APTT assay and most of the phospholipid neutralization assays failed to discriminate factor VIII inhibitors from LA. In a second step, using the optimal cut-offs determined above, the results of all the possible combinations of the 3 assays performed with 4 different reagents were analyzed. Thirteen combinations of reagents allowed > or = 80% of plasmas of each category (LA, factor deficiency or OAC) to be correctly classified (3/3 positive test results in LA-containing plasmas and 0/3 positive results in LA-negative samples).