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O Spertini

Publications and source records attributed to O Spertini.

33 records · Page 2Linked to original sources
PubMed1992

Tissue-specific migration pathways by phenotypically distinct subpopulations of memory T cells.

A proportion of T cells recirculate in a tissue-selective manner. Recent studies which showed that the skin-tropic subset of T cells was of memory/activated type, led us to examine whether the preferential homing of T cells to the gut also involved memory T cells, and if so whether these memory T cells were phenotypically distinct from other memory T cells. Lymphocytes migrating through the gut and the skin of sheep was collected by cannulating the lymphatic ducts draining these tissues. Both naive and memory T cells were found to recirculate through the gut, although only memory T cells migrated through the skin. However, when T cells from the gut were labeled with fluorescein isothiocyanate and assessed for their migration back to the gut, it was the memory population which showed a tropism for the gut. Gut-tropic memory T cells migrated poorly through the skin, indicating that these cells were distinct from skin-tropic memory T cells. This was confirmed by phenotypic analysis. Gut memory T cells expressed very low levels of the alpha 6 and beta 1 integrins, in contrast to skin memory T cells which expressed high levels. There was no evidence for heterogeneity within the naive T cell population, which migrated preferentially to lymph nodes. This migration pattern could be explained in part by the high expression of the L-selectin (lymph node homing receptor, LAM-1) on naive T cells, in contrast to memory T cells from gut or skin which were mostly L-selectin negative. These results in sheep indicate that subsets of alpha/beta memory T cells show tissue-selective migration patterns, which probably develop in a particular environment following encounter with antigen.

Animals↗
PubMed1992

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

L-selectin expressed by granulocytes, lymphocytes, and monocytes is responsible for initial leukocyte attachment to inflamed endothelium and high endothelial venules of peripheral lymph nodes. After leukocyte activation in vitro, L-selectin is rapidly shed from the cell surface. In this study, shed L-selectin (sL-selectin) from both lymphocytes and neutrophils was demonstrated to be present in high levels in human plasma by Western blot analysis and using a quantitative ELISA. In serum from normal human blood donors, a mean sL-selectin level of 1.6 +/- 0.8 micrograms/ml (n = 63) was found by ELISA. In addition, semipurified sL-selectin from plasma inhibited L-selectin-specific attachment of lymphocytes to cytokine-activated endothelium in a dose-dependent manner. L-selectin-dependent leukocyte attachment was completely inhibited at sL-selectin concentrations of 8-15 micrograms/ml, while physiological concentrations of sL-selectin caused a small but consistent inhibition of lymphocyte attachment. sL-selectin in plasma also inhibited anti-L-selectin mAb (2-5 micrograms/ml) binding to the surface of leukocytes. Interestingly, one epitope present within the EGF-like domain of L-selectin was lost in sL-selectin, suggesting a conformational change in the structure of the receptor after shedding. The presence of serum sL-selectin with functional activity indicates a potential role for sL-selectin in the regulation of leukocyte attachment to endothelium.

Blotting, Western↗
PubMed1991

Leukocyte adhesion molecule-1 (LAM-1, L-selectin) interacts with an inducible endothelial cell ligand to support leukocyte adhesion.

The human lymphocyte homing receptor, LAM-1, mediates the adhesion of lymphocytes to specialized high endothelial venules (HEV) of peripheral lymph nodes. We now report that LAM-1 is also a major mediator of leukocyte attachment to activated human endothelium. In a novel adhesion assay, LAM-1 was shown to mediate approximately 50% of the adhesion of both lymphocytes and neutrophils to TNF-activated human umbilical vein endothelial cells at 4 degrees C. The contribution of LAM-1 to leukocyte adhesion was only detectable when the assays were carried out under rotating (nonstatic) conditions, suggesting that LAM-1 is involved in the initial attachment of leukocytes to endothelium. In this assay at 37 degrees C, essentially all lymphocyte attachment to endothelium was mediated by LAM-1, VLA-4/VCAM-1, and the CD11/CD18 complex, whereas neutrophil attachment was mediated by LAM-1, endothelial-leukocyte adhesion molecule-1, and CD11/CD18. Thus, multiple receptors are necessary to promote optimal leukocyte adhesion to endothelium. LAM-1 also appeared to be involved in optimal neutrophil transendothelial migration using a videomicroscopic in vitro transmigration model system. LAM-1-dependent leukocyte adhesion required the induction and surface expression of a neuraminidase-sensitive molecule that was expressed for at least 24 h on activated endothelium. Expression of the LAM-1 ligand by endothelium was optimally induced by LPS and the proinflammatory cytokines TNF-alpha and IL-1 beta, whereas IFN-gamma and IL-4 induced lower levels of expression. The LAM-1 ligand on HEV and cytokine treated endothelium may be similar carbohydrate-containing molecules, because phosphomannan monoester core complex from yeast Hansenula hostii cell wall blocked binding of lymphocytes to both cell types, and identical epitopes on LAM-1-mediated lymphocyte attachment to HEV and activated endothelium. Thus, LAM-1 and its inducible endothelial ligand constitute a new pair of adhesion molecules that may regulate initial leukocyte/endothelial interactions at sites of inflammation.

Antibodies, Monoclonal↗
PubMed1991

Function and evolutionary conservation of distinct epitopes on the leukocyte adhesion molecule-1 (TQ-1, Leu-8) that regulate leukocyte migration.

The leukocyte adhesion molecule-1 (LAM-1, TQ=1, Leu-8) in humans, like its murine homologue, MEL-14, is the principal receptor that mediates the binding of leukocytes to high endothelial venules (HEV) of peripheral lymph nodes. In this study, several regions of the protein which mediate receptor function were identified by using a large panel of murine mAb reactive with LAM-1. Individual mAb reacted with LAM-1+ cells with characteristic intensities of immunofluorescence staining, and each bound both lymphocytes and neutrophils. Lymphocyte attachment to HEV was significantly inhibited by the binding of five mAb. In contrast, only two of these mAb were able to completely block the binding of phosphomannan monoester core complex from the yeast Hansenula holstii cell wall (PPME), a phosphomannan monoester core polysaccharide that serves as a soluble model of the natural ligand of LAM-1. Interestingly, the binding of two anti-LAM-1 mAb to cells induced a significant increase in PPME binding, reminiscent of the increase in receptor affinity observed after leukocyte activation. Antibody cross-blocking studies indicated that many of the functionally important epitopes were spatially distinct, and domain mapping indicated that they recognized distinct domains of LAM-1. The expression and function of these epitopes were further assessed by using a variety of animal species to further characterize the functionally relevant epitopes defined in these studies. At least some anti-LAM-1 mAb reacted with leukocytes from monkey, cow, rabbit, sheep, dog, cat, pig, and goat, but not from chicken, rat, or mouse. The reactivity of anti-LAM-1 mAb in several animal species correlated with the ability of leukocytes to bind PPME, and mAb that inhibited lymphocyte binding to HEV in man could also inhibit this function in rhesus monkey and dog. Thus, several LAM-1 epitopes are structurally and functionally well conserved throughout recent mammalian evolution, emphasizing an important role for LAM-1 in the regulation of leukocyte traffic.

Animals↗
PubMed1991

Regulation of leukocyte migration by activation of the leukocyte adhesion molecule-1 (LAM-1) selectin.

A central feature of host defence is the ability of leukocytes to enter tissues in response to immune or inflammatory stimuli. The leukocyte adhesion molecule-1 (LAM-1) regulates the migration of human leukocytes by mediating the binding both of lymphocytes to high endothelial venules of peripheral lymph nodes and of neutrophils to endothelium at inflammatory sites. As lymphocytes and neutrophils express the same LAM-1 protein, it is not clear how lineage-specific differences in leukocyte migration are controlled. We now report that the affinity of LAM-1 for a carbohydrate-based ligand, PPME, is dramatically increased following lymphocyte and neutrophil activation by lineage-specific stimuli. In addition, activation of lymphocytes by physiological stimuli enhanced LAM-1-dependent binding to high endothelial venules. Thus, transient changes in LAM-1 affinity after leukocyte stimulation probably directly influence leukocyte migration.

Antibodies, Monoclonal↗
PubMed1991

Dysmegakaryopoiesis predicting response to therapy in acute myeloid leukaemia. A histologic and clinical study.

With standard induction therapy between 50 to 85% of patients with Acute Myeloid Leukaemia (AML) achieve Complete Remission (CR). We investigated whether any morphological feature of bone marrow (BM) plastic embedded biopsies could predict failure of therapy. We reviewed BM plastic embedded biopsies from 54 adult patients presenting with untreated AML. The main histologic parameters analysed were cellularity, dysmegakaryopoiesis (DysM), percentage of marrow blasts and fibrosis. CR was obtained in 34 of 49 treated patients (69%). The rate of CR was significantly lower in the group of patients presenting with DysM: CR was achieved in 54% of the 28 treated patients with DysM and in 90% of the 21 treated patients without DysM (p less than 0.02). Patients with DysM had a significantly lower blood count and bone marrow blasts at presentation. Median age was not significantly different in the 2 groups. Cellularity and fibrosis were not predictive. DysM may be the hallmark of an AML subgroup with distinct clinical behaviour and lower rate of CR with conventional therapy. DysM should be carefully looked for on BM marrow biopsies and aspirate from AML patients at diagnosis.

Acute Disease↗
PubMed1991

Molecular mapping of functional domains of the leukocyte receptor for endothelium, LAM-1.

The human lymphocyte homing receptor LAM-1, like its murine counterpart MEL-14, functions as a mammalian lectin, and mediates the binding of leukocytes to specialized high endothelial cells in lymphoid organs (HEV). LAM-1 is a member of a new family of cell adhesion molecules, termed selectins or LEC-CAMs, which also includes ELAM-1 and PAD-GEM (GMP-140/CD62). To localize the regions of LAM-1 that are involved in cell adhesion, we developed chimeric selectins, in which various domains of PAD-GEM were substituted into LAM-1, and used these chimeric proteins to define the domain requirements for carbohydrate binding, and to localize the regions recognized by several mAb which inhibit the adhesion of lymphocytes to lymph node HEV. The binding of PPME or fucoidin, soluble complex carbohydrates that specifically define the lectin activity of LAM-1 and MEL-14, required only the lectin domain of LAM-1. The LAM1-1, LAM1-3, and LAM1-6 mAb each strongly inhibit the binding of lymphocytes to HEV in the in vitro frozen section assay, and defined three independent epitopes on LAM-1. Blocking of PPME or fucoidin binding by LAM1-3 indicated that this site is identical, or in close proximity, to the carbohydrate binding site, and analysis of the binding of LAM1-3 to chimeric selectins showed that the epitope detected by LAM1-3 is located within the lectin domain. Although the LAM1-6 epitope is also located in the lectin domain, LAM1-6 did not affect the binding of PPME or fucoidin. The LAM1-1 epitope was located in, or required, the EGF domain, and, importantly, binding of LAM1-1 significantly enhanced the binding of both PPME and fucoidin. These results suggest that adhesion mediated by LAM-1 may involve cooperativity between functionally and spatially distinct sites, and support previous data suggesting a role for the EGF domain of LAM-1 in lymphocyte adhesion to HEV.

Amino Acid Sequence↗
PubMed1991

An activated CD8+ lymphocyte appears in lymph nodes of rhesus monkeys early after infection with simian immunodeficiency virus.

Although alterations in T lymphocyte subset distribution and function in the peripheral blood of HIV-infected humans are well defined, the extent to which these reflect changes in other lymphoid compartments is unclear. We have characterized the coincident changes in PBL and lymph nodes (LN)1 after simian immunodeficiency virus of macaques (SIVmac) infection of rhesus monkeys. Whereas no consistent change in CD8+ PBL was noted during the first 60 d after infection, CD8+ lymphocytes increased significantly in number in LN. These CD8+ LN lymphocytes exhibited an increased expression of MHC class II and a decreased expression of leukocyte adhesion molecule-1, suggesting that they were activated, but interestingly did not express CD25 (IL-2 receptor). Moreover, there was no evidence that these CD8+ LN cells were proliferating, suggesting that they had migrated to the LN. These changes in the LN CD8+ lymphocyte population preceded any detectable change in the light microscopic appearance of the LN. When SIVmac-specific effector T cell responses were assessed, the magnitude of virus-specific effector activity was nearly identical in the PBL and LN of each monkey studied. However, the presence of SIVmac-specific effector cells in the LN did not correlate with the presence of CD8+, MHC class II+ cells. These findings suggest that this numerically important CD8+ lymphocyte subpopulation may serve a regulatory function.

Animals↗
PubMed1991

Regulation of leukocyte adhesion molecule-1 (TQ1, Leu-8) expression and shedding by normal and malignant cells.

The human leukocyte adhesion molecule-1 (LAM-1, TQ1, Leu-8) is involved in the binding of human leukocytes to high endothelial venules (HEV) of peripheral lymph nodes (LN). The regulation of LAM-1 expression is unique in that leukocyte stimulation induces a rapid down-modulation of LAM-1 from the cell surface. In this study, the regulation and function of LAM-1 was studied in detail in normal lymphocytes and compared with the LAM-1 of malignant leukocytes. Modulation of LAM-1 from the cell surface occurred concomitantly with the appearance of LAM-1 in the culture medium indicating that LAM-1 is cleaved from the cell surface. Shedding of LAM-1 was decreased in the presence of protein kinase C (PKC) inhibitors. As with normal lymphocytes, cells transfected with the LAM-1 cDNA and chronic lymphocytic leukemia (CLL) cells also shed LAM-1 following phorbol myristate acetate (PMA) exposure. CLL cells expressed the same Mr LAM-1 protein as normal lymphocytes and LAM-1+ CLL cells were able to specifically bind to HEV. In addition, normal lymphocytes and LAM-1+ CLL cells were capable of binding polyphosphomonester core polysaccharide (PPME) derived from yeast cell wall, a carbohydrate which mimics an essential component of the natural ligand for LAM-1, and PPME and HEV binding was specifically blocked by a new monoclonal antibody (mAb) reactive with LAM-1. The expression of LAM-1 and other adhesion molecules was examined on cells of 118 hematopoietic malignancies. LAM-1 was most frequently expressed on CLL and follicular or diffuse small cleaved cell lymphomas, whereas most other malignancies were LAM-1-. Thus, most CLL cells and some non-Hodgkin's lymphoma cells express a functionally active LAM-1 molecule which may correlate with their capacity to migrate through the circulation and disseminate into peripheral LN.

Cell Adhesion Molecules↗
PubMed1990

Granulocyte-macrophage colony-stimulating factor and other cytokines regulate surface expression of the leukocyte adhesion molecule-1 on human neutrophils, monocytes, and their precursors.

There is increasing evidence that cytokines such as granulocyte-macrophage (GM)-CSF can profoundly affect the adhesion, aggregation, and mobility of neutrophils both in vitro and in vivo. However, the mechanisms whereby these factors might alter the adhesive properties of neutrophils are incompletely understood. A new family of cellular adhesion molecules has recently been identified by cDNA cloning. The members of this family include human leukocyte adhesion molecule-1 (LAM-1), the human endothelial-leukocyte adhesion molecule, and the mouse leukocyte homing receptor for high endothelial venules, MEL-14. LAM-1 is the human homologue of murine MEL-14, and is believed to mediate binding of leukocytes to human high endothelial venules. LAM-1 can be identified by mAb TQ-1, Leu 8, or anti-LAM1.1. The expression and regulation of LAM-1 on granulocytes, monocytes, and their precursors was investigated using flow cytometry and the anti-LAM-1.1 mAb. Neutrophils, eosinophils, monocytes, marrow myeloid cells, granulocyte/macrophage colony-forming unit, and burst-forming unit for erythroid cells were LAM-1+ by flow microfluorimetry. The regulation of LAM-1 expression was tested by treating various cell populations with cytokines or other stimuli for 0-90 min. Exposure of neutrophils, monocytes, and marrow myeloid cells to GM-CSF induced rapid and complete loss of LAM-1 from the cell surface, but had no effect on LAM-1 expression by lymphocytes. The loss of LAM-1 was temporally correlated with up-regulation of CD11b (Mo1), an adhesion molecule involved in neutrophil aggregation. Several other factors known to activate neutrophils also caused down-regulation of LAM-1 and up-regulation of CD11b, including TNF, FMLP, and leukotriene B4. Interestingly, granulocyte-CSF and IFN-gamma had minimal effects on neutrophil LAM-1 expression. Similar results were observed on monocytes and myeloid precursor cells. Thus, exposure of neutrophils to GM-CSF results in a profound change in surface expression of adhesion molecules, with coordinated up-regulation of CD11b and down-regulation of LAM-1. These changes in adhesion proteins are likely to alter aggregation and mobility of both mature myeloid cells and their precursors in patients receiving certain types of cytokine therapy.

Antibodies, Monoclonal↗
PubMed1990

Structure of the gene encoding the human leukocyte adhesion molecule-1 (TQ1, Leu-8) of lymphocytes and neutrophils.

The leukocyte adhesion molecule-1 (LAM-1, TQ1, Leu-8), expressed by human lymphocytes, neutrophils, monocytes, and their precursors, is a member of the selectin family of cellular adhesion/homing receptors which play important roles in leukocyte-endothelial cell interactions. These cell surface molecules contain an amino-terminal lectin-like domain followed by an epidermal growth factor-like domain and a variable number of short consensus repeat sequences similar to those found in C3/C4 binding proteins. In this report, the structure of the lyam-1 gene that encodes the LAM-1 protein was determined by isolating overlapping genomic DNA clones that hybridized with a LAM-1 cDNA probe. The lyam-1 gene spans greater than 30 kilo base pairs of DNA and is composed of at least 10 exons. The 5' end of the LAM-1 mRNA was mapped by primer extension analysis revealing a single initiation region for transcription. Exons II through X contain translated sequences; exon II encodes the translation initiation codon; exon III, the leader peptide; IV, the lectin-like domain; V, the epidermal growth factor-like domain; VI and VII, the short consensus repeat units; exon VIII, the transmembrane region; exon IX encodes seven amino acids containing a potential phosphorylation site; and exon X encodes the five remaining amino acids of the cytoplasmic tail and the long 3' untranslated region. Sequencing of LAM-1 cDNA clones derived from neutrophils revealed that the protein expressed by neutrophils would be identical in sequence with the protein expressed by lymphocytes and cDNAs that would encode different isoforms of LAM-1 protein were not detected. In addition, the level of LAM-1 expression by lymphocytes and neutrophils from two patients with paroxysmal nocturnal hemoglobinuria, a disorder in which linkage of phosphatidylinositol anchors to proteins is defective, was similar to that of normal controls. Therefore, the usage of exons II through X results in the generation of a single major LAM-1 protein product expressed by lymphocytes and neutrophils.

Base Sequence↗
PubMed1986

Biophysical properties and morphology of purified antigen associated with non-A, non-B hepatitis.

The antigen from a non-A, non-B antigen-antibody system previously described was purified and, when tested by immunodiffusion, was shown to produce patterns of identity with all antigen-positive sera of the system. The sedimentation coefficient S20,w of the antigen was estimated by rate zonal ultracentrifugation to be 48. Isopycnic ultracentrifugation in CsCl gradient of non-A, non-B antigen generated a single sedimentation peak at the density of 1.28. SDS-polyacrylamide-agarose gel electrophoresis showed that I125-labelled antigen migrated as a single band (molecular weight 3.0 X 10(6)); in addition, labelled material also migrated to the albumin region. With SDS-PAGE under reducing conditions, the antigen was shown to consist of seven polypeptides. Spherical particles of 23 nm in diameter, demonstrated by electron microscopy, could be aggregated by purified non-A, non-B antibody. They probably represent the antigen and not a complete viral particle. The characteristics of this antigen associated with non-A, non-B hepatitis appear therefore to be close to those of hepatitis B surface antigen.

Antigens, Viral↗
PubMed1982

Demonstration of a single antigen-antibody system in 26 patients with non-A, non-B viral hepatitis.

26 patients with viral hepatitis were selected on the basis of negative responses to serological tests for hepatitis B virus and hepatitis A virus infections. The illness was acute in 19 patients and chronic persistent in the remaining 7. Immunodiffusion tests showed a single antigen-antibody system in the sera of all 26 patients. Each patient had at least one serum sample positive for antigen or antibody. In 1 post-transfusion case, the corresponding immunological marker was found in the donor. This system was considered specific for the disease, since the markers could not be detected in sera from patients with other liver conditions or immune complex diseases, or in sera from healthy blood donors without a history of hepatitis. The antigen could be separated from contaminating serum proteins. The purified preparation showed immunological identity with all our antigen-containing sera and with samples of a study already published. These results suggest the existence of an antigen associated with non-A, non-B, viral hepatitis and probably related to an infectious agent responsible for all the cases in this study.

Adult↗
PubMedDate not supplied

Immune response to purified non-A, non-B hepatitis-related antigen demonstrated by leukocyte migration inhibition in patients recovering from the infection.

Eight patients, convalescent from acute hepatitis, all negative for HBsAg, anti-HBc, anti-HA-IgM, anti-CMV and anti-EB, and all positive for non-A, non-B related antigen and/or antibody in at least one sample during the course of disease, were investigated. Their specific cell-mediated immunity was tested using the leukocyte migration inhibition test in presence of a previously described non-A, non-B related antigen. A control group consisted of ten individuals (two normal subjects, six patients recovering from acute hepatitis B and two with autoimmune chronic active hepatitis). Leukocyte migration was inhibited by the antigen in seven of the eight patients. The test was negative in all control subjects. It is thus demonstrated that after recovery, patients with non-A, non-B viral hepatitis develop a cellular immune response specific for purified non-A, non-B related antigen. The association between the described antigen and viral hepatitis non-A, non-B can now be established not only by immunoprecipitation, but also by a cellular test.

Adult↗