PubMed Health⌕ Search

Biomedical subjects

B B Cohen

Publications and source records attributed to B B Cohen.

At least 55 records · Page 3Linked to original sources
PubMed1983

Methods of detecting mature human Ia-like antigen and their metabolic precursors.

Ia antigens were shown to be present in the cell almost exclusively as mature alpha beta dimers which split into separate alpha and beta chains after boiling in SDS. In contrast metabolically labelling the cells with [35S]methionine resulted in only free alpha and beta chains being labelled. It is concluded that this widely used type of labelling, although useful for studying intermediate synthesis, should not be used for labelling mature cell surface molecules.

Carbon Radioisotopes↗
PubMed1983

Detection of Ia epitopes by monoclonal antibody blotting.

Monoclonal antibodies directed against human Ia alpha- and beta-subunit chains have been used as probes to detect polypeptides carrying recognized antigenic determinants or epitopes following two-dimensional PAGE separation. Approximately 4 sets of components differing in isoelectric point but not in molecular weight are recognized by each antibody. The anti-alpha-chain, McAb, reacts weakly with spots designated as epsilon but neither antibody recognizes Im, Ii or delta determinants under the conditions tested.

Antibodies, Monoclonal↗
PubMed1983

Analysis of the murine sperm surface with monoclonal antibodies.

Hybridomas secreting monoclonal antibodies reactive with murine spermatozoa were produced by fusion of myeloma cells with spleen cells from C57BL/6J mice immunized with spermatozoa from mice of the same strain. All antisperm antibodies were of the mu (mu) immunoglobulin heavy chain class; only one (MS-1) bound S. aureus protein A. Antibody MS-1 recognized an antigen present on the sperm acrosomal cap, on the surface of cells from liver and kidney and from some cultured cell lines. The subunit molecular weight (69000) of the polypeptide reactive with MS-1 was determined by SDS-PAGE analysis of sperm membrane proteins followed by their electrophoretic transfer to nitrocellulose.

Animals↗
PubMed1983

Biochemical variation of human Ia like antigens detected with monoclonal antibodies.

Four mouse monoclonal antibodies to human B cell surface determinants previously described as being directed against Ia like (MHC class II) antigens, have been shown to precipitate Ia alpha and beta chains. Electrophoretic transfer experiments showed one antibody to be directed against Ia alpha chains and two others to be against Ia beta chains. The antibodies were then used to analyse a range of cell types and a large number of lymphoblastoid and lymphoma cell lines. Ia antigens could not be detected on peripheral blood T cells, cord endothelium or T cell lines but their presence was confirmed on activated T cells and peripheral blood non-T cells. There was both qualitative and quantitative variation of Ia like antigen expression on B cell lines, including an apparent genetic polymorphism in alpha chain structure unrelated to DR allotypes and a single instance of a beta chain of abnormally high molecular weight.

Antibodies, Monoclonal↗
PubMed1982

Differential expression and serologically distinct subpopulations of human Ia antigens detected with monoclonal antibodies to Ia alpha and beta chains.

Studies with two monoclonal antibodies (DA6.147 and DA6.231) which react, respectively, with isolated human Ia alpha and beta chains are reported. Both antibodies detect epitopes expressed on all DR-heterozygous and DR-homozygous cell lines tested (n = 17) and bind to the Epstein-Barr virus-negative cell line Ramos. Ia subunit specificity of the antibodies was determined by an adaptation of an electroblot technique which transfers separated Ia chains from polyacrylamide gels to nitrocellulose paper. In radioimmunobinding assays, peripheral blood B cell-enriched fractions, phytohemagglutinin-activated T cells and pokeweed mitogen-activated cells gave strong reactions with DA6.231 (anti-Ia beta). In contrast, DA6.147 (anti-Ia alpha) reacted only weakly, if at all, with peripheral B cells, pokeweed mitogen blasts and activated T cells. However, both antibodies bound to isolated Ia from activated T cells and peripheral B cells after Nonidet-P40 solubilization of the cells and DA6.147+ antigens could be found in the cytoplasm of activated T cells by indirect immunofluorescence techniques. Results of serological inhibition procedures following fractionation of lymphoblastoid cell lysates on monoclonal antibody affinity columns showed that the DA6.147 alpha chain epitope is carried on only a minor subpopulation of human Ia.

Antibodies, Monoclonal↗
PubMed1982

Influence of monoclonal anti-Ia like antibodies on activation of human lymphocytes.

Four monoclonal antibodies directed against human DR antigens were examined for their effects on lymphocyte activation in vitro. Two (DA6.121 and DA6.231) were serologically and biochemically indistinguishable and recognized a common determinant on the DR beta chain. One, DA6.164, reacted with an epitope probably on the beta chain of a subset of DR molecules while the fourth, DA6.147 was directed against an alpha chain determinant. All four produced measurable inhibition of lymphocyte activation. Responses to PHA or PWM were generally reduced by less than 30% and those to autochthonous or to allogeneic lymphoid cells by more than 30% some being completely abolished. DA6.121 and 231 were the most consistently effective antibodies and behaved in an identical manner. There was no additive effect when different monoclonal reagents were mixed. Reduction in the level of activation occurred when the responding population consisted almost entirely of T lymphocytes, suggesting that ADCC was not involved. The presence or absence of complement had a profound effect on the level of lymphocyte mitogenesis but responses were depressed by anti-DR monoclonals under both conditions. The results indicate that both the alpha and the beta chain of DR play some part in lymphocyte activation. It is suggested that the continuous regeneration of DR antigens on the surface of stimulator cells may be important in eliciting MLR.

Adult↗
PubMed1981

Serological distinction between DR antigens and lymphocyte activating determinants.

The Burkitt lymphoma (BL)-derived, HLA-DR antigen positive B cell line, EB1, is a consistently low stimulator in MLC. A rabbit antiserum raised against the strongly stimulating BL line DAUDI, after appropriate absorption with EB1, inhibits MLC stimulation by both B cell lines and allogeneic lymphocytes, whilst lectin-induced proliferation is not significantly affected. Indirect immunofluorescence and 125I-staphylococcal protein A binding to cells pre-incubated with this antiserum suggest that the antigen is present on both peripheral B and T cells, as well as on B lymphoblastoid and myeloma lines. We suggest that this antiserum is directed against lymphocyte activating determinant(s) (LADs) and that these are distinct from the serologically defined DR antigens.

Animals↗
PubMed1976

Template activity of unfixed metaphase chromosomes.

Unfixed metaphase and non-metaphase cells were tested for their template activity with RNA polymerase. A device was used which disrupts the cell membrane by centrifugation, and which also ensures that the cells do not continue with their mitotic cycle during the transcription process. The template activity of acid/methanol fixed cells was also tested. None of the unfixed metaphase cells transcribed RNA whereas most of the non-metaphase cells did. In contrast, using fixed cells both classes of cells were transcribed equally well and to a much greater extent. It was concluded that metaphase chromosomes in vivo cannot act as templates for RNA synthesis.

Cell Line↗
PubMed1976

Ribonuclease inhibitors from mouse ascites cells.

Ribonuclease inhibitors were found to be present attached to mouse ascites ribosomes and in the post-ribosomal supernatant. Both inhibitors inhibited pancreatic RNAses A and B and two endonucleases prepared from ascites cells but did not inhibit RNAses T1 or N1. Both inhibitors had the same sedimentation coefficient and this taken with the results above suggest that they are identical. The inhibitor was shown to interact directly with the RNAse itself.

Animals↗
PubMed1969

Two fractions required for cell-free protein synthesis with components from rabbit reticulocytes.

An extract was prepared from rabbit reticulocyte ribosomes after treatment with potassium chloride as described by Miller, Hamada, Yang, Cohen & Schweet (1967). This extract has been shown to convert monoribosomes into polyribosomes during protein synthesis in vitro (Cohen, 1968). The nature of this extract was studied in greater detail. Centrifugation of the extract through a sucrose density gradient separated the activity into a fast-sedimenting fraction. The two fractions were shown to have different functions in stimulating cell-free protein synthesis and their active components were shown to be protein or partly protein in nature. Each fraction was analysed by electrophoresis and in the analytical ultracentrifuge. It was concluded that the active component in the fast-sedimenting fraction had a sedimentation coefficient of 15.5s and that of the slow-sedimenting fraction 10.5s.

Animals↗
PubMed1968

A factor converting monoribosomes into polyribosomes during protein synthesis in vitro.

An extract was prepared from rabbit reticulocyte ribosomes after treatment with potassium chloride as described previously (Miller, Hamada, Yang, Cohen & Schweet, 1967). The participation of the extract in cell-free protein synthesis was studied. Purified polyribosomes were isolated and converted into monoribosomes by incubation in the cell-free protein-synthesis system. The monoribosomes were isolated and found to be unable to synthesize protein in the cell-free system. The addition of the ribosomal extract to the system stimulated protein synthesis. This was accompanied by the conversion of some of the monoribosomes into polyribosomes. The active component or components of the extract were shown to be protein.

Animals↗