PubMed Health⌕ Search

Biomedical subjects

I S Trowbridge

Publications and source records attributed to I S Trowbridge.

At least 109 records · Page 6Linked to original sources
PubMed1980

Human homologue of murine T200 glycoprotein.

We report the identification of the human homologue of murine T200 glycoprotein. Peptide-mapping experiments suggest that the structure of the glycoprotein is highly conserved between the two species. Many of the properties of human T200 homologue are similar to those of murine T200 glycoprotein: it is broadly distributed within the hematopoietic system but is not detectable on nonhematopoietic cells; there are also structural differences between the forms of the glycoprotein found on T and B lymphoblastoid cell lines. These results suggest the homologous glycoproteins may play similar functional roles in both species.

Antibody Formation↗
PubMed1980

Human cell-surface glycoprotein with unusual properties.

We report here the identification of human cell-surface glycoprotein with unusual and interesting properties. We initially detected this glycoprotein on the surface of cultured human haematopoietic cell lines by means of a monoclonal antibody. Although it is expressed on all cultured human haematopoietic cell lines tested, including the inducible promyelocytic tumour cell line HL-60 (ref. 1), it is not present in readily detectable amounts on most normal or leukaemic human haematopoietic cells. HL-60 cells, on exposure in vitro to appropriate chemical inducers, undergo morphological and functional differentiation along the granulocytic pathway or into macrophage-like cells. One consequence of in vitro induction in the specific loss of the glycoprotein from the surface of HL-60 cells. The molecule does not, however, seem to be a highly tissue-specific differentiation antigen because it is also found on human tumour cell lines derived from non-haematopoietic tissues. Rather, its expression seems to be related to cell proliferation. Preliminary chemical characterization suggests that the glycoprotein maybe identical to the abnormal glycoprotein previously reported by Bramwell and Harris to be associated with malignancy.

Cell Cycle↗
PubMed1980

T200 cell surface glycoprotein of the mouse. Polymorphism defined by the Ly-5 system of alloantigens.

The cell line BW5147, and a mutant T200-negative cell line derived from BW5147, were studed by immunoprecipitation and peptide mapping, with xenogeneic monoclonal anti-T200 serum and with Ly-5 alloantiserum. It appears that the Ly-5 system defines a structural polymorphism of the cell surface glycoprotein T200, and that the monoclonal anti-T200 serum defines a feature of T200 that is common to mice of both Ly-5a and Ly-5b genotypes and may be invariable in the species.

Animals↗
PubMed1980

Disposition of T200 glycoprotein in the plasma membrane of a murine lymphoma cell line.

T200 glycoprotein, a major cell surface component of murine hematopoietic cells, is a phosphorylated transmembrane glycoprotein. Two distinct regions of the molecule can be defined by radiolabeling with a variety of metabolic precursors or by lactoperoxidase-catalyzed iodination, in combination with protease treatments, immunoprecipitation techniques, and peptide "mapping" analysis. A relative protease-resistant domain, which is exposed on the cell surface and contains the antigenic site recognized by a monoclonal anti-T200 antibody known to react with the exterior cell surface, contains most if not all of the mannose-containing oligosaccharide units of the glycoprotein and all of the amino acid residues labeled by lactoperoxidase-catalyzed iodination of intact viable cells. This protease-resistant fragment migrates with an apparent molecular weight of approximately 100,000 in sodium dodecyl sulfate-polyacrylamide gels. The remaining portion of the molecule contains a region, extensively digested by trypsin, which is exposed on the cytoplasmic side of the plasma membrane and contains phosphoserine residues which can be labeled with 32PO4 in vivo. A 125I-labeled tryptic peptide derived from this region of the molecule was obtained if membrane preparations from cells disrupted by nitrogen cavitation were labeled by lactoperoxidase-catalyzed iodination.

Animals↗
PubMed1979

Abnormal lipid-linked oligosaccharides in class E Thy-1-negative mutant lymphomas.

The glycosylation defect of Thy-1-mutant lymphomas of the class E complementation group has been identified as a block in the synthesis of the lipid-linked oligosaccharide precursor of the asparagine-linked oligosaccharides of glycoproteins. Two major lipid-linked oligosaccharides were isolated from the mutant cells. Both oligosaccharides were smaller than the lipid-linkid oligosaccharides of wild-type lymphomas and, in contrast to the lipid-linked oligosaccharides isolated from wild-type cells, both were resistant to digestion with endoglycosidase H. The oligosaccharides of newly synthesized polypeptides in class E Thy-1-cells were also resistant to endoglycosidase H digestion, providing strong evidence that they are derived from the abnormal lipid-linked oligosaccharides.

Animals↗
PubMed1978

Interspecies spleen-myeloma hybrid producing monoclonal antibodies against mouse lymphocyte surface glycoprotein, T200.

A cell hybrid has been selected from fusion of a mouse myeloma and rat spleen cells immunized against mouse lymphoma cells that produces monoclonal antibody against the mouse lymphocyte surface glycoprotein, T200. Antibody binding assays employing the monoclonal antibody show that there are about 50,000-100,000 molecules of T200 glycoprotein on mouse thymocytes and that similar antigens are present on spleen and bone marrow but not detected on nonlymphoid tissues. Examination of the labeled molecules precipitated from detergent extracts of spleen cells and thymocytes iodinated by the lactoperoxidase technique by SDS-PAGE confirm that there are structural differences between the antigens found on B and T lymphocytes. The B-cell glycoprotein consists of at least one component of apparent mol wt 220,000 on SDS-PAGE, while the T-cell glycoprotein has an apparent mol wt of about 190,000.

Animals↗
PubMed1978

Expression of Thy-1 glycoprotein on lectin-resistant lymphoma cell lines.

Lectin-resistant mutants with specific defects in glycosylation have been selected from the mouse lymphoma cell line, BW5147 (Thy-1+). The quantitative expression of cell surface glycoproteins on the mutant cells has been studied. The results show that some glycosylation defects that confer resistance to the cytotoxic effects of concanavalin A block the expression of Thy-1 glycoprotein on the cell surface. However, some changes in the oligosaccharides of Thy-1 glycoprotein generated by glycosylation defects found in PHAR mutant cells and restricted to the termini of complex-type oligosaccharides have no effect on the ability of Thy-1 to reach the cell surface. No glycosylation defects were found that interfered with the expression of either gp 69, 71 or H-2 on the surface of the mutant cells. It is concluded that aberrant biosynthesis of Thy-1 oligosaccharides can interfere with its expression on the cell surface, but that specific changes in oligosaccharide structure are necessary to block transport to the cell surface and integration into the plasma membrane.

Antigens, Surface↗
PubMed1978

The synthesis and properties of T25 blycoprotein in Thy-1-negative mutant lymphoma cells.

The synthesis and properties of T25 glycoprotein which bears the serological specificity Thy-1 have been studied in mutants of cultured mouse lymphoma cells that do not express Thy-1 on their surface. Five complementation classes of mutant cells were previously characterized by somatic genetic analysis. Synthesis of abnormal T25 glycoproteins was detected in four classes of mutants. Each of these aberrant products was degraded move rapidly than T25 glycoprotein of wild-type cells. Defects in the oligosaccharide units of T25 glycoprotein were demonstrated in three classes of mutants. In one of these mutant classes, evidence for a general defect in glycosylation of cell surface glycoproteins was obtained. These data indicate that normal glycosylation of T25 glycoprotein is probably essential for the molecule to be incorporated into the plasma membrane and expressed on the cell surface.

Cell Line↗
PubMed1977

Preliminary characterization of two thymus-dependent xenoantigens from mouse lymphocytes.

Preliminary characterization of two mouse thymus-dependent (T) lymphocyte xenoantigens, T25 and T200, which are selectively labelled by lactoperoxidase-catalysed iodination of T-cells, is described. Both molecules are membrane-bound glycoproteins. Fractionation of membrane vesicles prepared from BW5147 lymphoma cells by sedimentation through sucrose density gradients show that antigens T25 and T200 are in fractions enriched with plasma membrane. Moreover antigen T200 is partially degraded when viable cells are treated briefly with low concentrations of trypsin. Both molecules are efficiently solubilized in buffers containing sodium deoxycholate or Nonidet P-40, as measured by failure to sediment at 100000g for 60min. However, gel filtration on Sepharose 6B showed the presence of aggregated material in Nonidet P-40 extracts which was not found in deoxycholate-solubilized membranes. After solubilization in detergent, antigens T25 and T200 bind to, and may be specifically eluted from, columns of pea lectin--Sepharose or concanavalin A--Sepharose. Both molecules are heterogeneous when examined by polyacrylamide-gel electrophoresis in the presence of sodium dodecyl sulphate. As judged by its binding to columns of pea lectin, at least part of the heterogeneity of mouse thymocyte antigen T25 resides in its carbohydrate moiety.

Animals↗
PubMed1977

Human B cell line deficient in the expression of B cell-specific glycoproteins (GP 27,35).

A human B lymphoid cell line, P3HR-1, expresses only low levels of the 27 000 and 35 000 mol.wt. B cell-specific glycoproteins (GP 27,35). Indirect antibody-binding and quantitative absorption tests with a xenoantiserum against the antigens showed that P3HR-1 cells have on their surface about 1% of the amount found on other human B lymphoblastoid cell lines. The deficit of the glycoproteins on the surface of P3HR-1 cells could be accounted for by a reduced rate of synthesis in these cells. A simple relationship between the reduced expression of GP 27,35 on P3HR-1 cells and their inability to bind Epstein-Barr virus (EBV) or express complement receptors was excluded because other B lymphoid cells which expressed neither virus-binding sites nor complement receptor had normal amounts of GP 27,35 on their surface. However, antibodies against GP 27,35 could block the absorption of EBV by EBV receptor-positive B cells.

B-Lymphocytes↗
PubMed1976

Immunological properties of murine thymus-dependent lymphocyte surface glycoproteins.

The immunological properties of two murine thymus-dependent (T) lymphocyte surface glycoproteins, T200 and T25, were investigated. T200 is a lymphocyte-specific antigen with a high degree of species specificity. It shares antigenic determinants with molecules present on thymus-independent (B) lymphocytes. T25 has antigenic determinants which cross-react with antigens on mouse brain, rat thymocytes and rat brain. An antiserum against a purified rat brain glycoprotein which carries Thy-1.1 reacts with T25. Absorption of this antiserum with BALB/c thymocytes or brain homogenate produces a Thy-1.1 specific serum which reacts with T25 from AKR/J thymocytes but not with T25 from AKR/Cum thymocytes. These results confirm that T25 is the molecule on the surface of mouse T cells which carries the Thy-1 antigen. T25 also carries antigenic determinants, recognized by anti-thymocyte serum (ATS), which were found on secondary mouse embryo fibroblasts and untransformed fibroblast cell lines but which were not detected on fibroblast cell lines transformed with murine sarcoma virus (MSV) or with Simian virus 40 (SV40).

Animals↗
PubMed1976

Surface molecules of cultured human lymphoid cells.

Cell surface molecules of cultured human lymphoid cells were selectively labeled by lactoperoxidase-catalyzed iodination and examined by polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate. Two major iodinated species with apparent mol. wts. of 27 000 and 35 000 daltons were detected on autoradiographs of the labeled proteins of human lymphoid cell lines believed to be of thymus-independent (B) cell origin. Neither molecule was detected on putative thymus-dependent (T) lymphoid cell lines. Metabolic labeling studies showed that both molecules are glycoproteins. Rabbit antisera against cultured B lymphoid cells made specific by absorption for B cells reacted with several labeled species from iodinated B cells including the 27 000 and 35 000 mol. wt. glycoproteins. These molecules were also detected on tonsillar lymphocytes but not on peripheral blood lymphocytes. Reciprocal absorption with B cells of rabbit antisera against cultured T cells gave antisera specifically cytotoxic for T cells. However, these sera did not precipitate iodinated proteins from Nonidet P-40 lysates of T cells.

Antigens↗
PubMed1975

Thy-1 variants of mouse lymphomas: biochemical characterization of the genetic defect.

The surface proteins of Thy-1 positive mouse lymphomas and Thy-1 negative variants were labeled by lactoperoxidase-catalyzed iodination and characterized by polyacrylamide gel electrophoresis in the presence of sodium dodecylsulphate and by immunological studies. The loss of the serologically defined Thy-1 antigenic determinant correlated with the absence of a radioactive band corresponding to a T lymphocyte-specific surface glycoprotein, T25, on autoradiographs of the iodinated proteins of Thy-1 negative variants. Reexpression of Thy-1 on hybrid cells dervied from fusions of complementary Thy-1 negative variants correlated with the reappearance of T25. Quantitative absorption studies using an antiserum which specifically recognized T25 confirmed that the Thy-1 negative variants have no detectable T25 (less than 0.03 of that of the Thy-1 positive lines) on their surface. Biosynthetic labeling studies revealed that none of the Thy-1 negative variants synthesized T25. However, synthesis of an immunologically cross-reactive molecule could be detected in two variants. On the basis of these results, we propose a model which describes a possible structure of the Thy-1 antigenic determinant and explains the biochemical nature of the genetic lesions leading to the loss of Thy-1 in these variants.

Animals↗
PubMed1975

Differences in the surface proteins of mouse B and T cells.

We have selectively labeled the surface of mouse thymus-dependent (T) and thymus-independent (B) lymphocytes by means of lactoperoxidase-catalyzed iodination. Examination of the labeled proteins by electrophoresis in the presence of sodium dodecylsulfate followed by autoradiography revealed differences in the cell surface proteins of B and T cells. Proteins from labeled thymocytes, T cell lymphomas, and both normal and activated peripheral T cells give a broad band of radioactivity corresponding to at least two protein components with apparent molecular weights of 170,000 to 190,000. This band is absent from autoradiographs of iodinated B cell proteins, which instead have another band corresponding to a protein with an apparent molecular weight of about 220,000. We have shown that these T and B cell marker proteins are synthesized by the cell and are not serum components selectively bound to the cell surface. We have also established that these proteins are the major iodinated species precipitated from Nonidet P-40 cell lysates by rabbit anti-mouse lymphocyte serum, suggesting that they are the major antigens recognized by rabbit antibodies to mouse lymphocytes.

Animals↗