Platelet deposition in remote cardiac regions after coronary occlusion.

BACKGROUND: Activated platelets might contribute to endothelial dysfunction in non-ischaemic territories during acute myocardial infarction. We assessed platelet deposition, coronary flow reserve and contractile function in remote cardiac regions after transient coronary occlusion and their association with systemic platelet activation. MATERIALS AND METHODS: In 10 pigs (series A) subjected to 48-min occlusion of the left anterior descending coronary artery (LAD), 99mTc-platelet content in the right coronary artery (RCA) and its dependent myocardium was counted after reflow. In 10 pigs (series B) receiving the same occlusion of the RCA, the hyperaemic response at the LAD and systolic shortening in LAD-dependent myocardium were monitored after reperfusion. P-selectin expression on circulating platelets was assessed in both series by flow cytometry. RESULTS: In series A, platelet counts in the RCA and non-ischaemic myocardium were correlated with platelet content, polymorphonuclear leukocyte infiltration and infarct size in the reperfused zone, as well as with the percentage of P-selectin-positive platelets after reflow. In series B, a transient reduction in peak hyperaemic response in the LAD and sustained contractile dysfunction in non-ischemic myocardium were observed after releasing the RCA occlusion, these changes being also correlated with platelet activation status. CONCLUSIONS: Ischaemic injury triggers macro- and microvascular platelet deposition and causes an impairment in coronary flow reserve and contractile function in distant regions of the heart, which are related to activation of circulating platelets.

CD84 functions as a homophilic adhesion molecule and enhances IFN-gamma secretion: adhesion is mediated by Ig-like domain 1.

CD84 is a member of the CD2 subset of the Ig superfamily of cell surface molecules. Its cytoplasmic tail binds to Src homology 2 domain-containing protein 1A (signaling lymphocytic activation molecule-associated protein), a protein encoded by the X-linked lymphoproliferative disease gene. It is preferentially expressed on B lymphocytes, monocytes, and platelets. We show that it is also expressed on thymocytes and T cells. CD84 was positive on CD4-CD8- thymocytes, and its expression decreased with cell maturation. It is expressed on mature T cells preferentially on CD45RO+. To identify the CD84 ligand, we generated a soluble Ig fusion protein containing the human CD84 extracellular domains (CD84-Ig). Because receptor-ligand interactions occur between several members of this subfamily, we assayed CD84-Ig binding with all members of the CD2 family. CD84-Ig bound to CD84-transfected cells, whereas no binding was detected with cells expressing other CD2 subfamily receptors, showing that CD84 binds to itself. Anti-CD84 mAbs recognizing epitopes wholly within domain 1 of CD84 blocked the binding of the CD84-Ig fusion protein to CD84-transfected cells and platelets. Data from CD84 domain human/mouse chimeras further revealed that only the first extracellular domain of the molecule is involved in the ligand receptor recognition. The CD84-CD84 interaction was independent of its cytoplasmic tail. Finally, concurrent ligation of human CD84 with mAbs or CD84-Ig and CD3 enhanced IFN-gamma secretion in human lymphocytes. Thus, CD84 is its own ligand and acts as a costimulatory molecule.

Neutrophil adhesion is impaired in the mesentery but not in the liver sinusoids of portal hypertensive rats.

Altered leukocyte/cytokine response to inflammation has been observed in human and experimental portal hypertension. The aim of this study was to characterize leukocyte adhesion in portal hypertensive (PPVL) rats stimulated with endotoxin. Leukocyte rolling, adhesion, and migration assessed by intravital microscopy were impaired in mesenteric venules after lipopolysaccharide administration (150 microg/kg) in PPVL vs. sham-operated rats. Analysis of leukocyte L-selectin expression and soluble L-selectin showed that this defective adhesion was related to increased L-selectin shedding. In vitro experiments using isolated leukocytes treated with phorbol 12-myristate 13-acetate showed that monocytes and neutrophils but not lymphocytes were hyperreactive to cell activation, as measured by CD11b overexpression and increased L-selectin shedding in PPVL rats. However, neutrophil emigration in liver sinusoids and in the lung 3 h after endotoxin injection were similar in both groups of animals. Thus the alterations in leukocyte activation and adhesion molecule expression observed in this study may contribute to a better understanding of the higher susceptibility and severity of bacterial infections in cirrhotic patients with portal hypertension.

Molecular characterization and expression of a novel human leukocyte cell-surface marker homologous to mouse Ly-9.

Ly-9 is a mouse cell-surface glycoprotein that is selectively expressed on thymocytes and on mature T and B lymphocytes. Ly-9 belongs to the CD2 subset of the immunoglobulin superfamily, an emerging family of cell signaling receptors. Recently, a partial human Ly-9 complementary DNA (cDNA) sequence has been described. Full-length cDNA clones were isolated that included the initiation codon, the sequence encoding the full signal peptide, and 14 amino acids more in the cytoplasmic domain than in the previously reported clone. The predicted extracellular domain of human Ly-9 contains 4 immunoglobulinlike domains, similar to those in mouse Ly-9. Northern blot analysis revealed that the human Ly-9 messenger RNA (2.6 kb) is expressed predominantly in lymph node, spleen, thymus, and peripheral blood leukocytes. Four monoclonal antibodies (mAbs) were raised against human Ly-9 by immunizing mice with the pre-B-cell line 300.19 stably transfected with human Ly-9 full-length cDNA. These mAbs strongly stained the surfaces of cells transfected with human Ly-9 cDNA but not of untransfected cells. Human Ly-9 expression was restricted to T and B lymphocytes and thymocytes, with the highest levels of expression on CD4(+)CD8(-) and CD4(-)CD8(+) thymocytes. Monocytes, granulocytes, platelets, and red blood cells were uniformly negative for Ly-9. These mAbs immunoprecipitated major polypeptides of 120 kd from the transfected cells and 120 kd and 100 kd from B-cell line Daudi, probably because of the cell-surface-expressed isoforms. These data demonstrate that human Ly-9 is a new marker for the study of normal and malignant leukocytes. (Blood. 2001;97:3513-3520)

Effects of blood volume restitution following a portal hypertensive-related bleeding in anesthetized cirrhotic rats.

The aim of this study was to investigate the influence of different strategies of blood volume restitution in the outcome of portal hypertension-related bleeding in anesthetized cirrhotic rats. Gastrointestinal hemorrhage was induced by sectioning a first order branch of the ileocolic vein in 38 cirrhotic rats (common bile duct ligation and occlusion). The subsequent hypovolemic shock was treated with no transfusion (n = 17), moderate transfusion (50% of expected blood loss, 5 mL, n = 11), and total transfusion (100% of expected blood loss, 10 mL, n = 10). At the end of the blood transfusion period (minute 15), mean arterial pressure (MAP) partially recovered in rats receiving moderate transfusion or no transfusion but decreased in the 10-mL transfusion group ( downward arrow 12 +/- 43%, P < .05 vs. no transfusion and 5 mL transfusion). After transfusion, groups given no or 5 mL transfusion remained hemodynamically stable. However, rats receiving 10 mL transfusion continued to deteriorate with persistent bleeding and progressive fall in MAP ( downward arrow 65 +/- 12%; P < .05 vs. no transfusion and 5 mL transfusion). Collected blood loss was significantly greater in the 10-mL group (20.0 +/- 1.5 g) than in groups given 5 mL (15.9 +/- 2.8 g; P < .05) or no transfusion (13.2 +/- 2.1 g; P < .05 vs. 10 mL and 5 mL transfusion). Survival in the no transfusion group was 47%. Rats given 5-mL transfusion had 64% survival. The worst survival was observed in the 10-mL transfusion group (0% survival; P < .05). We concluded that a transfusion policy aimed at completely replacing blood loss worsens the magnitude of bleeding and mortality from portal hypertensive-related bleeding in cirrhotic rats. On the contrary, moderate blood transfusion allowed hemodynamic stabilization and increased survival.

Expresión de CD150 en leucocitos humanos. producción y caracterización de un nuevo anticuerpo monoclonal contra la molécula CD150 / Expression of CD150 on human leukocytes. Production and characterisation of a new CD150 monoclonal antibody

CD150, también conocido como Signaling Lymphocyte Activation Molecule (SLAM), es una molécula expresada en la superficie celular que se halla implicada en procesos de activación. Su región intracelular se une con elevada afinidad a SAP/SH2D1A, proteína codificada por el gen responsable de XLP (X-linked lymphoproliferative disease). En el presente trabajo describimos la producción y caracterización de un nuevo anticuerpo monoclonal (AcMo) contra la molécula CD150 (SLAM.4). Este AcMo murino (SLAM.4) fue producido utilizando células transfectadas con el cDNA que codifica para la molécula CD150 humana. Los experimentos de bloqueo demostraron que SLAM.4 se une a un epítopo distinto pero solapado al reconocido por el AcMo IPO-3. Además, los estudios funcionales demostraron que SLAM.4 inducía secreción de IFN- en linfocitos de sangre periférica preactivados vía CD3. SLAM.4 fue utilizado para analizar la distribución de la molécula CD150 diferentes poblaciones leucocitarias. Monocitos, granulocitos, eritocitos y plaquetas no expresaban CD150. Sin embargo, monocitos activados in vitro expresaban niveles elevados de CD150. CD150 se encontraba expresado en los primeros estadios de maduración de los linfocitos T ya que los timocitos inmaduros (CD4-C D 8-) expresaban una cantidad significativa de CD150. Los niveles de expresión mayores los encontramos en timocitos CD4+C D 8+, decreciendo a medida que maduran hacia CD4+ o CD8+. Los niveles de CD150 en linfocitos B de sangre periférica eran superiores que en células T. CD150 diferenciaba dos tipos de subpoblaciones tanto en células CD4+ como CD8+ pero especialmente estas últimas. Los linfocitos CD4 y CD8 más positivos para el CD150 expresaban grandes niveles de CD45RO+indicando que podrían corresponder a linfocitos T memoria/efectores. Nuestros resultados muestran la utilidad del AcMo SLAM.4 para realizar estudios funcionales de la molécula CD150 y revelan algunas características novedosas de su distribución celular (AU)

Differential role of selectins in experimental colitis.

BACKGROUND AND AIMS: The role of selectins in experimental colitis remains unknown. The aims of this study were to characterize the time-course expression of selectins in trinitrobenzene sulfonic acid (TNBS)-induced colitis, the functional role of selectins in colonic leukocyte-endothelial cell interactions, and the therapeutic usefulness of selectin blockade in this model. METHODS: Control and TNBS-induced colitic rats were studied. Expression of P- and E-selectin was assessed by the radiolabeled antibody technique, and L-selectin by flow cytometry. Leukocyte-endothelial cell interactions were studied in colonic venules by using intravital microscopy under basal conditions and after P-, E-, or L-selectin immunoblockade. Additional groups of animals were treated with anti-P-selectin antibody, a nonbinding antibody, or dexamethasone, for 7 days. RESULTS: P-selectin and E-selectin expression were markedly up-regulated in colitic rats. Increased leukocyte rolling was abrogated by anti-P-selectin, but only attenuated by anti-E- or anti-L-selectin antibodies. Only pretreatment with anti-P- selectin decreased leukocyte adhesion. Animals chronically treated with dexamethasone, but not with anti- P-selectin, had significantly lower macroscopic and histologic damage scores, colon weight, and myeloperoxidase (MPO) activity than those treated with nonbinding antibody. CONCLUSIONS: P-selectin plays a key role on leukocyte rolling and its blockade attenuates leukocyte adhesion in TNBS-induced colitis. However, treatment with an anti-P-selectin antibody does not significantly improve colitis.

Production and characterization of monoclonal antibodies against conserved epitopes of P-selectin (CD62P).

P-selectin (CD62P) is an adhesion molecule expressed on the activated endothelium and activated platelets that is involved in the initial attachment of leukocytes to inflamed vascular endothelium. Blocking monoclonal antibodies (mAbs) and P-selectin-deficient mice have shown that P-selectin is a potential target in anti-inflammatory therapy. Most mAbs against P-selectin do not bind to conserved epitopes, including the ligand-binding region, since P-selectin from mammalian species shares high amino acid sequence homology. The aim of this study was to generate a novel panel of anti-P-selectin mAbs against the conserved epitopes present in several animal species. To produce these mAbs, P-selectin-deficient mice were immunized with a pre-B-cell line transfected with human P-selectin cDNA. Twelve mouse mAbs that recognize human P-selectin were obtained. Individual mAbs that bound to human, rat, mouse, rabbit and pig activated platelets were characterized by flow-cytometry, immunohistochemistry, adhesion assays and immunoprecipitation. Four of these mAbs (P-sel.KO.2.3, P-sel.KO.2.4, P-sel.KO.2.7 and P-sel.KO.2.12) cross-reacted with human, rat and mouse P-selectin. Another three mAbs (P-sel.KO.2.2, P-sel.KO.2.11 and P-sel.KO.2.12) blocked the attachment of HL60 cells to P-selectin-transfected COS cells, demonstrating that these mAbs inhibit P-selectin-mediated adhesion. MAb cross-blocking experiments showed that these three mAbs bind to very close and overlapping epitopes. An ELISA assay using mAbs P-sel.KO.2.3 and P-sel.KO.2.12 was designed to measure soluble rat, mouse and human P-selectin. These anti-P-selectin mAbs are unique since they recognize common epitopes conserved during mammalian evolution and they may be useful for studying P-selectin function in inflammatory models in various species.

Gene structure of the mouse leukocyte cell surface molecule Ly9.

The Ly9 glycoprotein is a member of the immunoglobulin (Ig) superfamily, which is expressed on the cell surface of B and T lymphocytes. With two alleles (Ly9.1 and Ly9.2), it was first described as an alloantigenic marker of lymphocyte differentiation. Ly9 consists of four Ig-like domains with the structural features of the CD2 subfamily, which includes CD2, CD48, CD58, 2B4, CD84, and CDw15O (SLAM). Here, we report the isolation and characterization of the Ly9 gene, which encompasses at least 19 kb and contains ten separated exons, with sizes ranging from 54 to 355 bp. Each Ig-like domain is encoded by an individual exon. Sequence analysis of a 1.5-kb fragment upstream from the start translational codon revealed the absence of appropriately located TATA and CAAT boxes. However, potential binding sites for the transcription factors PU.1, Ikaros, AP-1, GATA-2, NF-GMa, NFAT-1, and Oct-2, which are involved in the early development and maturation of lymphocytes, were found. To further characterize the two allotypes of Ly9, cDNA of Balb/C and C57BL/6 mouse strains were sequenced and the predicted polypeptides compared. Nine discrepancies were found, four of them in the first Ig-like domain. The characterization of the genomic organization of Ly9 presented in this paper may improve understanding of the molecular mechanisms that regulate Ly9 expression, and the production of a construct to disrupt the Ly9 gene in ES cells in order to produce deficient mice.

The role of portal pressure in the severity of bleeding in portal hypertensive rats.

The aim of this study was to investigate the role of portal hypertension determining the severity of bleeding in portal hypertensive rats. The effects of section of branches of the ileocolic vein were studied in sham-operated (SO), partial portal vein-ligated (PPVL), and common bile duct-ligated (CBDL) rats. The ensuing hemorrhage was compared with that caused by section of femoral vein, where the portal hypertensive factor is excluded. In PPVL rats, section of branches of increasing size (divided into fourth, third, second, and first order) resulted in increasingly severe bleeding (arterial pressure: / +/- 4%, / 6 +/- 12%, / /15 +/- 8%, and / 28 +/- 13%; P <.005; hematocrit / 4 +/- 2%, / 6 +/- 1%, / 7 +/- 2%, and / 10 +/- 4%; P <.005). Bleeding from first-order branches was mild in SO, moderate in PPVL, and severe in CBDL rats, as shown by increasing changes in arterial pressure (/ 3 +/- 3%, / 12 +/- 16% and, / 43 +/- 23%; P <.01), hematocrit (/ 4 +/- 1%, / 12 +/- 2%, and / 32 +/- 19%; P <.01), and mortality (0%, 0%, and 56%; P <.001). Greater blood loss in CBDL rats was associated with higher portal pressure (16.6 +/- 2.7 vs. 13. 1 +/- 1.1 mm Hg in PPVL; P <.01) and more prolonged bleeding time (70 +/- 4 vs. 35 +/- 3 seconds in PPVL; P <.001). Vessels were similarly dilated in CBDL and PPVL (0.7 +/- 0.2 and 0.7 +/- 0.1 vs. 0.4 +/- 0.1 mm in SO; P <.05). Section of femoral vein caused equal blood loss in SO, PPVL, and CBDL rats, assessed by falls in hematocrit (/ 8 +/- 2%, / 7 +/- 1%, / 8 +/- 1%, respectively; NS) and by the blood loss (3.6 +/- 0.7, 3.5 +/- 0.9, and 3.8 +/- 0.7 g; NS). The study shows that the degree of portal pressure elevation is a major determinant of the severity of portal hypertension-related bleeding in PPVL and CBDL rats.

Circulating concentrations of soluble L-selectin (CD62L) in patients with primary Sjögren's syndrome.

OBJECTIVE: Serum concentrations of soluble (s) L-selectin (CD62L) were measured in patients with primary Sjögren's syndrome (SS) to relate these concentrations to clinical and immunological features of SS. METHODS: The study included 40 consecutive patients (38 women and two men) with a mean age of 61 years (range 24-78) who fulfilled four or more of the preliminary diagnostic criteria for SS proposed by the European Community Study Group in 1993, and 33 healthy blood donors from the hospital blood bank. A sandwich enzyme linked immunosorbent assay (ELISA) was used to detect the soluble form of human sL-selectin (CD62L). RESULTS: The mean (SEM) values of sL-selectin (CD62L) were 861 (66) microg/ml for patients with SS and 986 (180) microg/ml for healthy blood donors, but there was no significant difference. In patients with primary SS, serum sL-selectin (CD62L) concentrations were significantly higher in patients with Raynaud's phenomenon (1275 (112) microg/ml versus 789 (69) microg/ml, p=0.007), autoimmune thyroiditis (1162 (113) microg/ml versus 787 (69) microg/ml, p=0.02) and rheumatoid factor (993 (95) microg/ml versus 684 (70) microg/ml, p=0.01) when compared with patients without these features. CONCLUSION: The presence of Raynaud's phenomenon, autoimmune thyroiditis and rheumatoid factor is associated with higher concentrations of circulating sL-selectin (CD62L) in the sera of patients with primary SS.

Enhanced monocyte activation and hepatotoxicity in response to endotoxin in portal hypertension.

BACKGROUND/AIMS: Septic shock is a systemic response to infection, and it causes a high mortality rate in cirrhotic patients. The mechanisms responsible for this susceptibility in cirrhosis are poorly understood. The aim of this study was to investigate whether monocyte activation and hepatic function are altered in portal hypertension after endotoxin administration. METHODS: Portal-hypertensive and sham-operated rats were used. Plasma levels of tumor necrosis factor-alpha after lipopolysaccharide stimulation (both in vivo and in vitro) were measured by ELISA. CD11b/CD18 integrin expression on leukocyte membrane was measured by flow cytometry. Plasma transaminase activities were also determined. RESULTS: The levels of tumor necrosis factor-alpha in plasma and the expression of CD11b/CD18 on leukocytes in portal-hypertensive rats was similar to that in sham-operated rats. Injection of 150 microg/kg of lipopolysaccharide produced a 9-fold increase in plasma levels of tumor necrosis factor-alpha in portal-hypertensive compared with sham-operated rats, together with a significant up-regulation of CD11b/CD18 expression on monocytes and an elevation in plasma transaminase activity. Blood leukocytes incubated in vitro with lipopolysaccharide (0.5 microg/ml) induced a hypersecretion of tumor necrosis factor-alpha in portal-hypertensive rats, as compared to sham-operated rats. CONCLUSIONS: This study shows that monocytes from portal-hypertensive rats have an enhanced response to endotoxin, leading to hepatotoxicity.

Increased serum levels of soluble L-selectin (CD62L) in patients with active systemic lupus erythematosus (SLE).

The adhesion molecule L-selectin (CD62L) mediates lymphocyte recirculation and leucocyte rolling on vascular endothelium at sites of inflammation. Serum levels of soluble L-selectin (sL-selectin) were measured in patients with SLE in order to relate these levels to clinical activity and immunological parameters. An ELISA was used to detect the soluble form of human L-selectin (CD62L) in 42 patients with SLE and in 33 healthy individuals. The mean +/- s.e.m. values of sL-selectin were 1285 +/- 121 ng/ml for patients with SLE and 986 +/- 180 ng/ml for healthy blood donors, but there was no significant difference. When patients with active SLE were analysed, higher levels of circulating sL-selectin were found when compared with patients without activity (1497 +/- 167 ng/ml versus 941 +/- 150 ng/ml; P = 0.028). We found a significant correlation between the levels of sL-selectin and of dsDNA antibodies (r = 0.36, P = 0. 044) and between levels of sL-selectin and SLE Disease Activity Index (SLEDAI) score (r = 0.42, P = 0.003). Patients with active SLE studied cross-sectionally showed significant elevations of sL-selectin (CD62L) compared with controls. Thus, the levels of this soluble adhesion molecule correlated with active disease and levels of anti-dsDNA antibodies.

Impaired mesenteric leukocyte recruitment in experimental portal hypertension in the rat.

Increased incidence of septic complications in human and experimental portal hypertension has been documented. Because development of an inflammatory response is essential in defense against infectious agents, the aim of this study was to assess leukocyte-endothelial cell interactions in an experimental model of portal hypertension. Intravital microscopy studies showed that under baseline conditions, leukocyte rolling, adhesion, and emigration in mesenteric venules were similar in control, sham operated (SO), and partial portal vein ligated (PPVL) rats. Compared with either control or SO rats, PPVL animals exhibited a markedly reduced recruitment of rolling, adherent, and emigrated leukocytes in response to leukotriene B(4) (LTB(4)) stimulation. Similarly, platelet-activating factor (PAF) superfusion, which induced a large increment in leukocyte rolling and adherence in control and SO rats, was without any effect in PPVL animals. Endothelial P-selectin expression in control rats, as measured by the double radio-labeled monoclonal antibody (mAb) technique, was not modified by LTB(4), but significantly increased in response to PAF. PPVL rats had a significantly lower expression of P-selectin after stimulation with PAF. Neutrophils isolated from PPVL rats exhibited increased L-selectin shedding and CD11b up-regulation in response to PAF and LTB(4), compared with neutrophils isolated from SO rats. These observations indicate that portal hypertension is associated with a defective inflammatory response, which is manifested as a decreased recruitment of rolling leukocytes, and subsequently reduced adhesion/emigration. This defect appears to result from a reduced endothelial P-selectin up-regulation and increased L-selectin shedding.

Molecular cloning, characterization, and chromosomal localization of the mouse homologue of CD84, a member of the CD2 family of cell surface molecules.

CD84 is a member of the immunoglobulin gene superfamily (IgSF) with two Ig-like domains expressed primarily on B lymphocytes and macrophages. Here we describe the cloning of the mouse homologue of human CD84. Mouse CD84 cDNA clones were isolated from a macrophage library. The nucleotide sequence of mouse CD84 was shown to include an open reading frame encoding a putative 329 amino acid protein composed of a 21 amino acid leader peptide, two extracellular immunoglobulin (Ig)-like domains, a hydrophobic transmembrane region, and an 87 amino acid cytoplasmic domain. Mouse CD84 shares 57.3% amino acid sequence identity (88.7%, considering conservative amino acid substitutions) with the human homologue. Chromosome localization studies mapped the mouse CD84 gene to distal chromosome 1 adjacent to the gene for Ly-9, placing it close to the region where other members of the CD2 IgSF (CD48 and 2B4) have been mapped. Northern blot analysis revealed that the expression of mouse CD84 was predominantly restricted to hematopoietic tissues. Two species of mRNA of 3.6 kilobases (kb) and 1.5 kb were observed. The finding that the pattern of expression was restricted to the hematopoietic system and the conserved sequence of the mouse CD84 homologue suggests that the function of the CD84 glycoprotein may be similar in humans and mice.

CD84 leukocyte antigen is a new member of the Ig superfamily.

cDNA isolated from a human B-cell line Raji library was analyzed and shown to encode the full-length cDNA sequence of a novel cell-surface glycoprotein, initially termed HLy9-beta. The predicted mature 307-amino acid protein was composed of two extracellular Ig-like domains, a hydrophobic transmembrane region, and an 83-amino acid cytoplasmic domain. The extracellular Ig-like domains presented structural and sequence homology with a group of members of the Ig superfamily that included CD2, CD48, CD58, and Ly9. Northern blot analysis showed that the expression of HLy9-beta was predominantly restricted to hematopoietic tissues. Chromosome localization studies mapped the HLy9-beta gene to chromosome 1q24, where other members of this Ig superfamily (CD48 and HumLy9) have been mapped. CD84 monoclonal antibodies (MoAbs) were shown to react with cells transfected with the cloned cDNA. These MoAbs were further used to show that CD84 is expressed as a single chain cell-surface glycoprotein of Mr 64,000 to 82,000, which was highly glycosylated. CD84 had a unique pattern of expression, being found predominantly on lymphocytes and monocytes. Thus, the glycoprotein HLy9-beta is recognized by MoAbs previously clustered as CD84 and represents a newly identified member of the Ig superfamily that may play a significant role in leukocyte activation.

Platelet activation In mice and human Helicobacter pylori infection.

Extracts of Helicobacter pylori (HP) have been shown to induce leukocyte adhesion in mesenteric venules, but the effects of HP infection on gastric microvessels are unknown. Inflammatory cell interactions in the gastric microcirculation were studied by intravital videomicroscopy in mice inoculated with either saline or fresh isolates of HP. Platelet aggregates were detected and quantified in murine portal blood, while endothelial P-selectin expression was determined using the dual radiolabeled mAb technique. Platelet activation and aggregation were studied in HP-infected patients and controls by measuring the platelet-aggregate ratio and platelet P-selectin expression. HP infection induced a marked increase in the flux of rolling leukocytes and the appearance of platelet and leukocyte- platelet aggregates in murine gastric venules. The HP-induced rolling and platelet aggregate formation was abrogated by mAbs against L- or P-, but not E- selectin. Endothelial cell expression of P-selectin was not altered, but platelet P-selectin expression was enhanced in HP-infected mice. Circulating platelet aggregates and activated platelets were also detected in HP-infected patients. These findings indicate that platelet activation and aggregation contribute to the microvascular dysfunction and inflammatory cell recruitment associated with HP infections.

L-selectin-deficient mice have impaired leukocyte recruitment into inflammatory sites.

L-selectin, a cell surface adhesion molecule that is expressed by most leukocytes, mediates leukocyte rolling along vascular endothelium at sites of inflammation. The contribution of L-selectin to leukocyte migration in models of chronic inflammation was assessed by using mice that lack cell surface L-selectin expression. Significant inhibition of neutrophil (56-62%), lymphocyte (70-75%), and monocyte (72-78%) migration into an inflamed peritoneum was observed 24 and 48 h after administration of thioglycollate, an inflammatory stimulus. L-selectin-deficient mice were also significantly impaired in delayed-type hypersensitivity reactions. Footpad swelling in response to sheep red blood cell challenge was reduced 75% in L-selectin-deficient mice compared with wild-type mice. Ear swelling in a model of contact hypersensitivity induced by oxazolone challenge was also reduced by 69% compared to wild-type mice. Consistent with L-selectin-mediating leukocyte migration into diverse vascular beds during inflammation, L-selectin-deficient mice were significantly resistant to death resulting from lipopolysaccharide (LPS)-induced toxic shock. LPS administration resulted in a 90% mortality rate in control mice after 24 h, while there was a 90% survival rate in L-selectin-deficient mice. These results demonstrate that L-selectin plays a prominent role in leukocyte homing to nonlymphoid tissues during inflammation and that blocking this process can be beneficial during pathological inflammatory responses.

Effects of continued NO inhibition on portal hypertensive syndrome after portal vein stenosis in rat.

The present study investigated whether chronic nitric oxide (NO) inhibition prevents the hyperdynamic circulatory syndrome that appears in rats after partial portal vein ligation (PPVL). N omega-nitro-L-arginine methyl ester (L-NAME; 30 micrograms.kg-1.min-1, n = 17), a NO biosynthesis inhibitor, or vehicle (n = 17) was infused continuously from PPVL through subcutaneously osmotic pumps. Studies were performed, in ketamine-anesthetized Sprague-Dawley rats, in one-half of the animals at 4 days and in the remaining one-half at 8 days from PPVL. At 4 days, PPVL rats treated with L-NAME had higher mean arterial pressure (MAP), systemic vascular resistance (SVR), and splanchnic arteriolar resistance (SAR) and lower cardiac output and portal venous inflow (PVI) than PPVL rats treated with vehicle (P < 0.05). Similarly, at 8 days PPVL rats treated with L-NAME had higher MAP and SVR and lower cardiac output (P < 0.05) than PPVL rats treated with vehicle. In contrast, PVI and SAR were similar. At 4 days plasma volume and mesenteric-systemic shunting were lower, although nonsignificantly, in PPVL rats treated with L-NAME. This trend completely disappeared at 8 days. L-NAME did not change portal pressure at either 4 or 8 days. After 4 days of continuous treatment with L-NAME, nonportal hypertensive control rats had a significantly higher MAP, lower cardiac index and PVI, and higher SVR and SAR than nonportal hypertensive rats treated with vehicle. Contrary to PPVL rats, these effects were maintained after 8 days of treatment. The present study shows that NO contributes to the systemic disturbances of portal hypertension. However, NO inhibition delayed but did not prevent the splanchnic vasodilation that appears after PPVL, suggesting that other factors could also be involved.

Neonatal capsaicin treatment does not prevent splanchnic vasodilatation in portal-hypertensive rats.

It has been suggested that the peripheral sensory neurons are involved in the splanchnic hemodynamic changes of portal hypertension. Therefore the influence of permanent ablation of sensory neurons by neonatal capsaicin pretreatment (50 mg/kg, subcutaneously) on the development of the hyperdynamic splanchnic circulation in portal-hypertensive rats was studied. In adulthood, portal hypertension was induced with partial portal vein ligation. In study 1, systemic and splanchnic hemodynamics were measured by means of a radiolabeled-microsphere technique in portal-hypertensive rats, under ketamine anesthesia, pretreated with capsaicin or vehicle. Mean arterial pressure, heart rate, cardiac index, systemic and splanchnic vascular resistance, portal pressure, portal venous inflow, portal-collateral resistance and portal-systemic shunting were not significantly different between capsaicin-pretreated and vehicle-pretreated rats. In study 2, gastric mucosal blood flow, measured by means of hydrogen gas clearance, and the hemoglobin and oxygen content of the gastric mucosa, as assessed with reflectance spectrophotometry, were not significantly different in the two groups of anesthetized portal-hypertensive rats pretreated with capsaicin or vehicle. In study 3, we confirmed the effectiveness of neonatal capsaicin pretreatment by measuring calcitonin gene-related peptide content of the gastric corpus wall. Capsaicin pretreatment caused a depletion of calcitonin gene-related peptide by at least 98% compared with that in vehicle-pretreated rats. These results do not support a role of capsaicin-sensitive sensory neurons that innervate the gastrointestinal tract in the development of the splanchnic vasodilatation characteristically observed in chronic portal hypertension.