Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0023418 (leukemia)
 93,477 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Aggregating agents including phorbol esters which activate protein kinase C induce the rapid phosphorylation of a Mr = 47,000 cytosolic protein in blood platelets (P47 or pleckstrin). This protein is well resolved by analytical 16-BAC----SDS two-dimensional PAGE and was purified from platelets by preparative 16-BAC----SDS PAGE. Polyclonal antibodies were raised to the protein in mice and rabbits. These antisera detected a single protein with the migration of P47 on Western blots of platelet extracts, and the rabbit antisera immunoprecipitated 32P-labelled P47 from platelet cytosol. The presence of P47 in other haematopoietic cells was determined by prelabelling them with 32P and observing increased 32P incorporation into the location of P47 on autoradiographs of 16-BAC----SDS analytical PAGE of cells exposed to phorbol ester. The identity of the phosphoprotein found in this location was further established by probing Western blots of SDS PAGE gels of cultured cell lines with the P47 antisera. P47 was detected in peripheral blood lymphocytes, monocytes and granulocytes (including the granulocytes of two unrelated patients with X-linked chronic granulomatous disease). P47 was also found in HL-60 promyelocytes (especially after differentiation with retinoic acid), U937 histiocytes, HEL leukaemia cells, and Raji 'B' lymphoblasts. It was not detected in normal erythrocytes, K562 leukaemic cells, MOLT-3 'T' lymphoblasts, or in wide range of non-haematopoietic cell lines. We conclude that P47 is a major target for the action of phorbol ester induced phosphorylation in platelets, normal leucocytes and some haematopoietic cell lines. These cells have as their common feature the ability when stimulated to develop adhesive functions on their plasma membranes.
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PMID:P47 phosphoprotein of blood platelets (pleckstrin) is a major target for phorbol ester-induced protein phosphorylation in intact platelets, granulocytes, lymphocytes, monocytes and cultured leukaemic cells: absence of P47 in non-haematopoietic cells. 231 54

A monoclonal antibody (MAb-HB55) directed against a HLA class II antigen (Ia), was purified by DE-52 chromatography. The purified MAb contained less than 5% impure protein detected by SDS-PAGE. Ricin was conjugated with the MAb via a disulfide bond to construct an immunotoxin (ricin-HB55). The concentration causing fifty percent growth inhibition (IC50) was 2 x 10(-11)M for the Raji cells. In contrast, the IC50 for Molt-4 and K562 cells was 100 times higher than that for the Raji cells. B lymphocytes separated from peripheral blood lymphocytes by nylon wool were selectively killed by the conjugate, but T lymphocytes were not apparently affected. Our results demonstrate that the immunotoxin is selectively cytotoxic to Raji cells and B-cells, and may have potential for purging malignant cells from bone marrow of patients with B-cell leukemia and lymphoma.
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PMID:Selective killing of tumor cells in vitro by an immunotoxin composed of ricin and monoclonal antibody against Ia antigen. 232 15

Pokeweed antiviral protein (PAP-s) was prepared from seeds of Phytolacca americana. Monoclonal antibody against human pan-T lymphocyte Wu71 was linked to PAP-s by a disulfide bond. The results of SDS-PAGE, double immunodiffusion of active monoclonal antibody and PAP-s showed that the conjugate was highly cytotoxic to the human T-leukemic cell line CEM, but not to antigen-negative cell line SP2/O. At a concentration of 10(-9) mol/L, 76.4% of the target cells were killed, as compared with 10.1% at 10(-9) mol/L of free PAP-s. Treatment of the CEM cells with conjugate at 10(-9) mol/L reduced their rate of protein synthesis by 72.4%, as determined with 14C-leucine incorporation. The immunotoxin may be useful for the in-vitro eradication of leukemic cells in autologous bone marrow transplantation to leukemia patients.
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PMID:Monoclonal anti-human T cell antibody and PAP-s conjugate--preparation and selective cytotoxic properties on leukemic cell. 234 83

Murine splenocytes immune to influenza virus-activated human T-cells were fused with SP2/0 cells, selected in chemically defined HAT media, and subcloned to yield a monoclonal antibody (MAb) termed 7G7/B6. 7G7/B6 binds to lectin- and antigen-activated T-cells, but not resting T-cells or B-lymphoblastoid lines from the same donor. 7G7/B6 immunoprecipitates a 50-55 kD band from cell surface iodinated PHA-activated T-cells or the T-cell leukemia line HUT 102B2, as shown on SDS-PAGE. Cross-clearing studies demonstrate that 7G7/B6 binds the same cell surface molecule(s) as anti-Tac, a MAb which has been shown previously to recognize the human receptor for IL-2. 35S-methionine pulse chase experiments in HUT 102B2 cells reveal that 7G7/B6 binds to an early (less than 30 min) 35-37 kD and late (greater than 4 h) 50 kD protein. Sequential immunoprecipitations demonstrate that these are identical to the molecules identified by anti-Tac under similar conditions. However, only anti-Tac coprecipitates a higher molecular band at 110 kD. 7G7/B6 and anti-Tac do not competitively inhibit the binding of each other to PHA-activated T-cells. Functional studies reveal that in contrast to anti-Tac, 7G7/B6 has almost no inhibitory effect in vitro on IL-2-driven proliferation of IL-2-dependent T-cell lines, or alloimmune cytotoxic T-cell generation (however, once generated, these cytotoxic T-cells were both 7G7/B6 and anti-Tac positive). Finally, IL-2 does not inhibit the binding of 7G7/B6 to activated T-cells under conditions which result in up to 75% inhibition of anti-Tac binding. Therefore, 7G7/B6 is another MAb recognizing the human IL-2 receptor, but binding to an epitope distinct from that recognized by either IL-2 or anti-Tac.
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PMID:A monoclonal antibody 7G7/B6, binds to an epitope on the human interleukin-2 (IL-2) receptor that is distinct from that recognized by IL-2 or anti-Tac. 240 92

The expression of the antigenic determinant identified by the B54.2 rat monoclonal antibody on four populations of mouse mast cells has been quantified, and the epitope-bearing surface antigen and its biosynthesis have been characterized. As assessed by indirect immunofluorescence staining and flow cytometric analysis, B54.2 antibody bound to serosal mast cells (S-MC), bone marrow culture-derived mast cells (BM-MC), fetal liver culture-derived mast cells (FTL-MC), and Abelson murine leukemia virus-transformed FTL-MC (ABFTL-MC). However, the intensity of cell surface fluorescence exhibited by ABFTL-MC was approximately eightfold less per cell compared with nontransformed, culture-derived mast cells. Immunoprecipitation of B54.2 antibody-binding molecules from each population of mast cells labeled intrinsically with [35S]methionine and analysis by SDS-PAGE demonstrated that the B54.2 epitope was expressed in each case on two noncovalently associated proteins of 110,000 Mr and approximately 130,000 Mr, but that the percentage of radiolabel in the latter species was approximately threefold less in ABFTL-MC than in BM-MC. As assessed by pulse-chase analysis with [35S]methionine, the 110,000 Mr protein was a precursor of the 130,000 Mr molecule ("B54.2 antigen") synthesized by BM-MC. Labeling of BM-MC with [35S]methionine in the presence of tunicamycin followed by immunoprecipitation and SDS-PAGE of B54.2 antibody-binding material revealed a single species of 93,000 Mr, indicating that the native molecules contained N-linked carbohydrate. Endoglycosidase H treatment of the glycoproteins precipitated by B54.2 antibody from BM-MC reduced the Mr of the 110,000-Mr molecule to 93,000 Mr without an appreciable change in the 130,000-Mr species. These data indicate that the 110,000-Mr precursor form is a "high mannose" type glycoprotein and the 130,000-Mr membrane surface B54.2 antigen is a "complex" type glycoprotein, and that the epitope recognized by the B54.2 antibody on the surface of the mouse mast cell populations is located on the 93,000-Mr peptide core.
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PMID:Biochemical characterization of a mast cell plasma membrane antigen shared by mouse serosal, culture-derived, and virally transformed mast cells. 243 44

We have characterized a set of 15 monoclonal antibodies to p19gag, one of the internal proteins of avian sarcoma and leukaemia viruses. All the antibodies work in immune precipitations as well as in immunoblotting, though with different efficiencies. We have developed a simple epitope mapping technique, which uses partial chemical cleavages at methionine or tryptophan residues followed by immunoblotting from SDS-polyacrylamide gels, to localize the epitopes of nine of these antibodies. The epitopes fall into at least four classes. The mapping procedure should also be useful for other antigens of known primary structure.
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PMID:Epitope mapping of monoclonal antibodies to gag protein p19 of avian sarcoma and leukaemia viruses. 244 26

Monoclonal antibodies 50B4 and 50E6 recognize two distinct epitopes of human p85 glycoprotein (CDw44). Both epitopes are destroyed by reduction of the purified glycoprotein as demonstrated by inhibition of cellular radioimmunoassay and Western blot analysis. Endoglycosidase F treated p85 glycoprotein, with an apparent molecular weight of 73,000, is still reactive with both monoclonal antibodies. Thus both epitopes are conformational determinants of the polypeptide chain. A rabbit antibody produced against purified native p85 glycoprotein also reacted only with the non-reduced form of p85. Repeated immunizations with SDS-dissociated and reduced p85 yielded a polyclonal antibody reactive by Western blot analysis with reduced and non-reduced forms of p85 glycoprotein. When a HOON leukemia cell line cDNA expression library was screened with this polyclonal antibody, two cDNA clones were isolated which reacted specifically with the antiserum and not with the control non-immune serum. Preliminary characterization of these clones indicates that they are p85-related.
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PMID:Several epitopes of p85 glycoprotein (CDw44) are dependent on intact disulphide bonds. Isolation of cDNA clones requires a polyclonal antibody raised against the reduced protein. 246 Dec 31

Derivatives of the antiallergic drug cromolyn [disodium 5,5'-[(2-hydroxy-1,3-propanediyl)-bis(oxy)]bis [4-oxo-(4H-1-benzopyran)-2- carboxylate]], which can be conjugated covalently at the propane 2-position to macromolecules and to insoluble matrices, were synthesized. Conjugates of these derivatives with macromolecules were examined for their binding to cells of the rat basophilic leukemia line RBL-2H3, which is widely employed as a model for immunologically induced mast cell degranulation. Only those drug-protein conjugates in which the cromolyn analogue with an amino group at the propane 2-carbon instead of the hydroxyl was linked to the carrier by glutaraldehyde were found to exhibit specific and saturable binding to these cells. Analysis of the binding data for these conjugates yielded an apparent binding constant of 3.8 +/- 0.2 X 10(8) M-1 and an apparent number of binding sites for the probe of 4000-8000 per cell. The conjugates found to bind specifically to the cells were also immobilized on agarose matrices and employed in an affinity-based isolation of the membrane component responsible for the observed binding. A single labeled polypeptide was eluted from these columns, onto which either whole cell lysates or solubilized purified plasma membranes of surface-radioiodinated RBL-2H3 cells had been adsorbed. This membrane protein appears on autoradiograms of nonreducing SDS-PAGE as a single broad band of approximately 110,000 daltons (Da) apparent molecular mass. On autoradiograms of reducing gels, the only band detected has an apparent mass of approximately 50,000 Da and appears narrower. Elution of the columns with the drug and disulfide-reducing agents or with the latter alone resulted in significantly higher yields of the 50-kDa polypeptide. Both the intact and reduced proteins bind strongly to immobilized concanavalin A and less so to immobilized wheat germ agglutinin, suggesting that the isolated intact protein is probably a dimer of two glycosylated subunits of similar molecular mass. Treatment of the reduced protein with endoglycosidase F leads to a decrease in its apparent molecular mass by approximately 12 kDa, suggesting that the extent of glycosylation of this polypeptide is approximately 25%. As shown in the following paper, the intact protein constitutes a Ca2+ channel that is activated upon IgE-Fc epsilon receptor aggregation.
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PMID:Isolation and purification of an Fc epsilon receptor activated ion channel from the rat mast cell line RBL-2H3. 246 4

We have determined the organization and nucleotide sequence of the gene encoding the human T cell surface glycoprotein CD8 alpha. This gene spans approximately 8 kb and is organized into six exons which encode separate functional domains of the protein. Exon 1 encodes the 5' untranslated region and leader peptide, exon II the Ig V-like region, exon III the hinge-like region, exon IV the transmembrane domain, and exons V and VI the cytoplasmic tail. Alternative splicing that excludes nucleotide sequences from exon IV results in a transcript which encodes a secreted form of the protein. This transcript accounts for approximately 15% of the total CD8 alpha mRNA in human T cell leukemia lines and in normal human tissues. Secreted CD8 alpha protein can be detected in culture supernatants of T cell leukemia lines and PHA-stimulated PBMC by immunoprecipitation with the anti-CD8 alpha mAb OKT8 or with a polyclonal rabbit antiserum specific for the 28 amino acid cytoplasmic domain of CD8 alpha. The secreted CD8 alpha protein forms homodimers; when analyzed by SDS-PAGE, the protein migrates with an apparent molecular mass of 27 or 54 kDa under reducing or non-reducing conditions, respectively. Human secreted CD8 alpha may serve an immunoregulatory role for the interactions of T cells with their targets in vivo.
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PMID:Alternatively spliced mRNA encodes a secreted form of human CD8 alpha. Characterization of the human CD8 alpha gene. 249 67

We have found that preparations of rate-zonal purified Moloney murine leukemia virus originally obtained from the National Cancer Institute Resources Program, when separated by SDS-PAGE in the absence of mercaptoethanol (beta-MSH), exhibited a doublet envelope glycoprotein band of approximately 69/67 kD. When the same samples were run in the presence of beta-MSH, a single band at 70 kD (gp70) was observed. Western blot analysis with polyclonal antiserum identified both the 69- and 67-kD bands as envelope gene products. Tryptic peptide mapping of each of the gp67 and gp69 bands confirmed the serological data, with each showing conserved as well as unique peptides. These results imply that the Moloney murine leukemia virus samples examined above contain two structurally different envelope gene products. Western blot analysis using ecotropic and dualtropic specific sera suggest that gp69 is derived from an ecotropic virus, while gp67 is from a dualtropic virus. This is consistent with the results of an earlier study which showed that the majority of the cysteines (4/5) in dualtropic gp70 are lost by a single deletion relative to the ecotropic gp70 species. This would account for the difference in mobility observed in the SDS-PAGE profile in the absence of beta-MSH. It would indicate that the cysteines play an important role in defining structural differences that separate the ecotropic and dualtropic gp70s.
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PMID:Reduction-modifiable properties of Moloney murine leukemia virus gp70 as an indicator of envelope glycoprotein heterogeneity. 252 96


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