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Results for “Immunologic Capping”

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At least 163 records · Page 9Linked to original sources
PubMed1978

Concanavalin A receptors on the surface membrane of lymphocytes from patients with Burkitt's lymphoma, other malignant lymphomas, leukaemia and lymphoma cell lines.

Lymphocytes isolated from the peripheral blood and tumour tissues of patients with African Burkitt's lymphoma (BL) showed a reduced cap-forming ability and increased agglutinability by concanavalin A (con A) compared to normal lymphocytes. Lymphocytes from the blood of patients with chronic lymphocytic leukaemia, Hodgkin's disease and other malignant lymphomas showed a similar reduction in cap formation and increase in agglutination compared to normal lymphocytes, lymphocytes from patients with carcinoma, and lymphocytes from patients with non-malignant disorders. The cap formation of lymphocytes from a healthy donor or a lymphoma patient was independent of the source from which the cells were isolated, e.g., lymph-node, spleen or blood. Lymphoma cell lines established from tumours of BL patients and lymphoblastoid cell lines originating from other sources also exhibited an increased agglutination and reduced cap formation with con A. Further studies indicated that EBV-carrying human lymphoid lines had a reduced cap-forming ability compared to EBV-negative lines.

Burkitt Lymphoma↗
PubMed1980

Cytoskeletal control of redistribution of surface membrane receptors in hairy cells.

The redistribution of surface membrane immunoglobulin (SmIg) and concanavalin A (Con-A) was studied in peripheral mononuclear cells of three patients who had hairy cell leukemia. Fluorescein-labeled polyvalent goat antihuman immunoglobulin and fluoresceinated Con-A were used as ligands. The capping of ligand-receptor complexes was temperature-dependent and was more prominent at 37 C. A significant drop in the percentages of SmIg and Con-A capping was observed when cytochalasin B was added. In contrast, no decline in the percentages of SmIg and Con-A capping was seen in the presence of colchicine. The inhibitory action of cytochalasin B on the capping of SmIg and Con-A receptors in hairy cells suggests that these receptors are integral macromolecules of the plasma membrane and their redistribution is regulated by cytoskeletal structures.

Cell Membrane↗
PubMed1985

Basophil immunoglobulin receptors in asthmatics under immunoscanning electron microscopy.

Immunolatex particles were used as markers for IgE receptors on basophils using electron-microscope scanning. These particles appeared to bind specifically to basophils. Basophils from atopic asthma patients showed greater binding to latex particles than those from intractable asthma patients or healthy subjects. Cap and patch formations on IgE receptors were frequently found in basophils of atopic asthmatics, and cap formation was observed only on basophils that were pear-shaped. The redistribution of IgE receptors, such as that by cap formation, may be a significant triggering mechanism for basophil activation. The latex density on basophils pre-treated with anti-human IgG was much greater in intractable asthmatics than in atopic asthmatics or healthy subjects, and almost all basophils with increased immunolatex particles were pear-shaped, suggesting the presence of some IgG receptors on the surface, and such receptors may play an important role in intractable asthma.

Asthma↗
PubMed1981

Detection of radiolabelled bone marrow cells bearing surface immunoglobulins by combined autoradiography and immunoperoxidase.

A method is described for the simultaneous detection of radiolabelled bone marrow cells bearing surface immunoglobulins by combined autoradiography and immunoperoxidase. Bone marrow cells from normal CBA mice prelabelled in vivo with 125IUDR or exposed in vitro to [3H] thymidine were incubated with rabbit anti-mouse immunoglobulins under capping conditions, washed, cytocentrifuged and treated with methanol and hydrogen peroxide to destroy endogenous peroxidase. Cells were then covered with peroxidase-conjugated goat anti-rabbit immunoglobulins, washed, treated with diaminobenzidine and hydrogen peroxide and finally covered with autoradiographic stripped film and exposed for different times. Peroxidase-positive cells were typically capped and those radiolabelled had autoradiographic silver grains overlying the nucleus.

Animals↗
PubMed1981

Dimethyl sulfoxide inhibits capping of surface receptors.

The microfilaments of cellular slime mold cells are known to be dislocated from their attachment to the plasma membrane by 10% dimethyl sulfoxide (DMSO). We report here that 10% DMSO inhibited capping of lentil lectin receptors on the surface of vegetative cells of the cellular slime mold, Dictyostelium mucoroides. When the DMSO was washed from the cells, capping took place. Capping of surface immunoglobulin of mouse lymphocytes was also reversibly inhibited by 10% DMSO.

Animals↗
PubMed1985

A T-lymphoma transmembrane glycoprotein (gp180) is linked to the cytoskeletal protein, fodrin.

A major mouse T-lymphoma surface glycoprotein (gp180) has been identified by labeling cells with 125I and [3H]glucosamine. After ligand-induced receptor patching and/or capping, the amount of gp 180 in the membrane-associated cytoskeleton fraction increases in direct proportion to the percentage of patched/capped cells. There is a parallel increase in the amount of fodrin in the membrane-associated cytoskeleton fraction. Evidence is presented that gp180 is the same as or very similar to the T-lymphocyte-specific glycoprotein T-200. An immunobinding assay of Nonidet P-40-solubilized plasma membrane selectively co-isolates gp180 and fodrin. After induction of receptor rearrangement, double-label immunofluorescence reveals that fodrin accumulated directly beneath gp180 patches and caps. Membrane extraction with Triton X-114 followed by sucrose gradient centrifugation permits isolation of a gp180-fodrin complex with a 1:1 molar ratio and sedimentation coefficient(s) of approximately 20. This complex remains stable during isoelectric focusing and exhibits a pl in the range of 5.2-5.7. On the basis of our results we conclude that gp180, an integral membrane glycoprotein, and fodrin, a component of the membrane-associated cytoskeleton, are closely associated into a complex. Furthermore, we contend that, through fodrin's association with actin, this complex is of functional significance in ligand-induced patching and capping of gp180. We also propose that, through lateral interactions in the plane of the membrane, the gp180-fodrin complex might be responsible for linking other surface receptors to the intracellular microfilament network during lymphocyte patching and capping.

Animals↗
PubMed1980

Role of coated vesicles, microfilaments, and calmodulin in receptor-mediated endocytosis by cultured B lymphoblastoid cells.

Cell surface receptor IgM molecules of cultured human lymlphoblastoid cells (WiL2) patch and redistribute into a cap over the Golgi region of the cell after treatment with multivalent anti-IgM antibodies. During and after the redistribution, ligand-receptor clusters are endocytosed into coated pits and coated vesicles. Morphometric analysis of the distribution of ferritin-labeled ligand at EM resolution reveals the following sequence of events in the endocytosis of cell surface IgM: (a) binding of the multivalent ligand in a diffuse cell surface distribution, (b) clustering of the ligand-receptor complexes, (c) recruitment of clathrin coats to the cytoplasmic surface of the cell membrane opposite ligand-receptor clusters, (d) assembly and (e) internalization of coated vesicles, and (f) delivery of label into a large vesicular compartment, presumably partly lysosomal. Most of the labeled ligand enters this pathway. The recruitment of clathrin coats to the membrane opposite ligand-receptor clusters is sensitive to the calmodulin-directed drug Stelazine (trifluoperazine dihydrochloride). In addition, Stelazine inhibits an alternate pathway of endocytosis that does not involve coated vesicle formation. The actin-directed drug dihydrocytochalasin B has no effect on the recruitment of clathrin to the ligand-receptor clusters and the formation of coated pits and little effect on the alternate pathway, but this drug does interfere with subsequent coated vesicle formation and it inhibits capping. Cortical microfilaments that decorate with heavy meromyosin with constant polarity are observed in association with the coated regions of the plasma membrane and with coated vesicles. SDS-polyacrylamide gel electrophoresis analysis of a coated vesicle preparation isolated from WiL2 cells demonstrates that the major polypeptides in the fraction are a 175-kdalton component that comigrates with calf brain clathrin, a 42-kdalton component that comigrates with rabbit muscle actin and a 18.5-kdalton minor component that comigrates with calmodulin as well as 110-, 70-, 55-, 36-, 30-, and 17-kdalton components. These results clarify the pathways of endocytosis in this cell and suggest functional roles for calmodulin, especially in the formation of clathrin-coated pits, and for actin microfilaments in coated vesicle formation and in capping.

B-Lymphocytes↗
PubMed1982

Association of myosin light chain kinase with lymphocyte membrane-cytoskeleton complex.

A specific antibody against myosin light chain kinase (MLCK) was used to identify the presence of a Ca2+-calmodulin-activated MLCK in mouse 1-lymphoma cells. With a double immunofluorescence technique, MLCK was determined to be accumulated directly under Con A-capped structures in a manner similar to that of previously described accumulation of actomyosin. The lymphocyte MLCK was phosphorylated in the uncapped cell and, by immunoprecipitation with a specific MLCK antibody, was shown to possess a Mr of 130,000. The MLCK was also found to constitute a major fraction of the phosphoproteins present in the plasma membrane associated-cytoskeleton. Myosin light chain kinase catalyzed the phosphorylation of both endogenous lymphocyte myosin light chains and those from smooth and skeletal muscle. The enzyme activity was dependent on the presence of Ca2+-calmodulin and was inhibited by the calmodulin-binding drug, trifluoperazine. These data suggest that the membrane-cytoskeleton-associated MLCK activity may be important in regulation of the actinmyosin contraction which is believed to be required for the collection of surface receptors into capped structures.

Animals↗
PubMed1984

Endocytosis: relation to capping and cell locomotion.

Most mammalian cells, such as fibroblasts, continuously internalize part of their surface membrane by endocytosis, and then later return it to the cell surface. This cyclical process is initiated by coated pits in the plasma membrane. These pits collect specific receptors plus lipid for internalization, but exclude other proteins. On a motile cell, the sites of endocytosis (randomly located on the cell) and those of membrane return (located at the front of the cell) are not coincident. This causes a bulk flow of lipid plus receptors in the plasma membrane, away from the front of the cell. Large objects on the cell surface are swept to the rear of the cell by this flow, a process called capping. Cells may use this polarized endocytic cycle to move.

Antigens, Surface↗
PubMed1984

Alterations of the capping phenomenon on lymphocytes from aged and Down's syndrome subjects.

The redistribution with the time of concanavalin A (Con A) receptors at one pole of the cell after addition of FITC-Con A - so-called capping - in the peripheral blood lymphocytes from 13 aged subjects (mean: 84 +/- 1 years old), and of 16 noninstitutionalized patients affected by a syndrome of precocious aging, such as Down's syndrome (mean: 17 +/- 2 years old), was studied and compared with a group of 15 normal young people (mean: 23 +/- 2 years old). An opposite alteration in the percentage of capped cells, i.e. a decrease in aged subjects and an increase in Down's syndrome patients, was observed. A derangement of lymphocyte membrane fluidity appears to be present in both groups even if the underlying biochemical defect may be different. However, a similar alteration of the kinetics of the phenomenon was present either in aged or in Down's syndrome subjects. Both groups did not show any significant increase with time of the percentage of capped cells, suggesting that they were lacking a lymphocyte subpopulation(s) which start capping later.

Adolescent↗
PubMed1988

Cytoskeletal involvement in the sequential capping of rat thymocyte surface glycoproteins.

The independent capping of the three major rat thymocyte glycoproteins, the leucocyte-common (L-C) antigen, the leucocyte sialoglycoprotein (LSGP) and Thy-1, was investigated using specific monoclonal antibodies. The capping of each antigen did not require redistribution of the other major surface glycoproteins, and was accompanied by a partial co-capping of the cytoskeletal proteins fodrin and actin, but not of tubulin. A study of the ability of a cell that already possesses one glycoprotein cap to cap a second different glycoprotein showed that this was possible in all cases to varying degrees, the second cap always forming at the same position on the cell surface as the first. Colchicine failed to perturb this observed sequential capping polarity, indicating that microtubules did not direct this second capping event.

Actins↗
PubMed1985

Capping of immune complexes by sporozoites of Eimeria tenella.

Sporozoites of Eimeria tenella were incubated for 10, 20, or 30 min with parasite-specific monoclonal IgG antibody 3D3II from mice and then rinsed in a Tris-buffered glucose saline solution (TBGS). Some sporozoites were then incubated for 10, 20, or 30 min with ferritin- or colloidal gold-conjugated goat anti-mouse IgG antibody and then fixed in 2.5% glutaraldehyde and prepared for transmission (TEM) or scanning (SEM) electron microscopy. Other sporozoites that had been previously exposed to monoclonal antibody were prefixed with 0.25% glutaraldehyde, incubated with ferritin- or colloidal gold-conjugated anti-mouse IgG antibody and then fixed and prepared for TEM or SEM. Control preparations consisted of sporozoites exposed only to TBGS, monoclonal antibody 3D3II or to ferritin- or colloidal gold-conjugated anti-mouse IgG antibody. Capping of immune complexes occurred only on the surface of those sporozoites exposed to monoclonal antibody 3D3II followed by ferritin- or gold-conjugated antibody. Immune complexes moved laterally and posteriorly on the outer surface of the parasite plasma membrane to form a cap at the posterior end of the sporozoite. Capping did not occur in TBGS controls nor in sporozoites treated with monoclonal antibody 3D3II and prefixed in 0.25% glutaraldehyde before exposure to ferritin- or gold-conjugated antibody. Thus, capping of surface antigens did not occur in the presence of monoclonal 3D3II antibody only, whereas specimens exposed to both monoclonal and ferritin- or colloidal gold-conjugated antibodies were able to cap immune complexes.

Antibodies, Monoclonal↗
PubMed1983

Ligand-induced association of rat lymphocyte membrane proteins with the detergent-insoluble lymphocyte cytoskeletal matrix.

There are two classes of membrane protein capping on the basis of ligand requirements. Surface immunoglobulin (Slg), the prototype of the first class, requires a single ligand for cap induction. RT1 (rat histocompatibility proteins) requires two antibodies for cap induction. The lateral mobility of Slg is relatively restricted compared with RT1. These differences may be due to differential interaction with the cytoskeleton. After ligand binding 71% of Slg becomes detergent insoluble and is associated with the lymphocyte cytoskeletal matrix. The insolubilization occurs at 4 degrees C and is not inhibited by sodium azide or cytoskeleton-active drugs. The insolubilized ligand-receptor complex can be solubilized by a cytoskeleton destabilizing buffer. In contrast, only 20% of RT1 becomes associated with the lymphocytic cytoskeleton after ligand binding. The ligand-induced receptor-cytoskeleton interaction influences capping behavior and may play a role in cell activation.

Animals↗