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J M McCune

Publications and source records attributed to J M McCune.

83 records · Page 5Linked to original sources
PubMed1987

Indirect induction of radiation lymphomas in mice. Evidence for a novel, transmissible leukemogen.

The transmission of a lymphomagenic agent(s) from the bone marrow of irradiated mice to thymic target cells has been demonstrated by: (a) the induction of T cell lymphomas in nonirradiated thymic grafts implanted in irradiated, Thy-l-congenic mice, (b) the induction of T cell lymphomas of host origin in mice infused with bone marrow from irradiated, Thy-l-congenic donors. The latter procedure also yields an appreciable number of pre-B cell lymphomas of uncertain origin. The results confirm Kaplan's theory that radiation induces thymic lymphomas in mice by an indirect mechanism. However, the previously described radiation leukemia virus is clearly not involved in the majority of transferred lymphomas. We propose that the mediating agent in radiation lymphomagenesis is a novel, transmissible agent induced in the bone marrow, but exerting its transforming activity on cells in the thymus. The nature and mode of action of the agent are under investigation.

Animals↗
PubMed1981

J chain biosynthesis in pre-B cells and other possible precursor B cells.

Human cell lines that resemble precursors in the B cell lineage have been found to synthesize J chain. In vivo pulse labeling, together with in vitro translation of total cellular RNA in a wheat germ cell-free system, detected the synthesis of J chain in immunoglobulin-secreting cell lines, in a cell line with only surface IgM, as well as in the pre-B-like cell line Josh 4 and the round cell lines Josh 7 and KLM 2. The primary translation products of J chain from all of these cell lines were found to be indistinguishable from one another by serologic criteria, by relative mobility on sodium dodecyl sulfate-polyacrylamide gel electrophoresis, by charge as judged by alkaline-urea gel electrophoresis, and by peptide mapping. These findings suggest that the onset of J chain biosynthesis represents a relatively early event in B cell ontogeny, occurring before the development of immunoglobulin polymer-secreting cells. Its role may, consequently, be fundamental to the biosynthesis of all immunoglobulins, at different stages of B cell differentiation.

Animals↗
PubMed1981

Biogenesis of membrane-bound and secreted immunoglobulins. II. Two forms of the human alpha chain translated in vitro and processed in vivo as distinct polypeptide chains.

Structural differences between alpha m (ther heavy chain of membrane IgA) and alpha s (the heavy chain of secretory IgA) were investigated. Messenger RNA from the human B lymphoblastoid line 32a.1, expressing both membrane and secretory IgA, was translated in a wheat germ cell-free system, resulting in the synthesis of two primary translation products for the alpha chain, that differed in molecular weight. In vivo pulse and pulse-chase experiments demonstrated that two early biosynthetic forms of the alpha chain were subsequently modified to yield three intracellular forms. As shown by endo-beta-N-acetylglucosaminidase H (endo H) treatment, these forms represent two alpha polypeptide chains, with varying compositions of N-linked oligosaccharides. Of the two forms of the alpha chain remaining after endo H treatment, only the form with the lowest molecular weight was associated with cells after long chase periods. The possible significance of this difference from the results with mu and delta chains is discussed. These results indicate that alpha m is distinguished from an alpha s by a difference in both primary structure and intracellular processing. The functional consequences of this distinction, previously shown for the heavy chain of membrane IgM (micrometer) and heavy chain of secretory IgM (microseconds), may reflect a principle common to the secretory and membrane forms of all immunoglobulin heavy chain classes.

B-Lymphocytes↗
PubMed1981

Biogenesis of membrane-bound and secreted immunoglobulins: two primary translation products of the human delta chain, differentially N-glycosylated to four discrete forms in vivo and in vitro.

Structural differences between the heavy chain of membrane IgD (delta m) and the heavy chain of secreted IgD (delta s) were investigated by using a human lymphoblastoid cell line that expresses idiotypically identical IgM and IgD. In a wheat germ cell-free system, mRNA from this cell line was shown to encode two distinct delta chains that differed in molecular weight. When translated in vitro in the presence of dog pancreatic microsomal membranes or when synthesized in vivo, these two delta chains were processed to four discrete glycosylated forms, all of which shared idiotypic determinants, C region determinants, and light chain linkage. As shown by digestion with endo-beta-N-acetylglucosaminidase H, these four delta forms represent two delta polypeptide chains that are differentially N-glycosylated. Pulse-chase experiments demonstrated that, after endo-beta-N-acetylglucosaminidase H treatment, delta m has a higher molecular weight than delta s. After integration into dog pancreatic microsomal membranes in vitro, delta m was found not to have a large cytoplasmic domain exposed to proteolytic digestion. The finding that delta m and delta s differ in primary structure is analogous to previous work with the corresponding heavy chains of IgM (mu m and mu s) from the same cell line. Thus, this cell line produces four Ig heavy chains (mu m, mu s, delta m, and delta s), with the same idiotype. The observation of differential N-glycosylation, apparently unique for the delta class, is discussed.

B-Lymphocytes↗
PubMed1981

Ig biosynthesis in a human pre-B cell line.

Ig synthesis was investigated in a human Epstein-barr virus transformed pre-B-like lymphoblastoid line, Josh 4. Translation of total extracted cellular RNA in a wheat germ cellfree system showed that the transcripts for both micrometer (the heavy chain of membrane IgM) and micros (the heavy chain of secreted IgM) were present in approximately equal proportions. Pulse-labeling of cells with 35S-methionine in culture followed by immunoprecipitation and endo-N-acetylglucosaminidase digestion of the precipitates demonstrated that each of these chains were synthesized and glycosylated intracellularly. No light chain synthesis was detected in either system. In addition, both mu-chains were found to be secreted. Hybrids formed between Josh 4 and 2 light chain-producing lymphoblastoid lines, RPMI-8866P (IgG kappa) and 32a1 (IgA lambda), were found to express surface IgM. Thus the provision of light chains permitted membrane expression of chains which might otherwise be degraded. These findings were discussed in relation to normal B cell development.

B-Lymphocytes↗
PubMed1980

Pre-B cells and other possible precursor lymphoid cell lines derived from patients with X-linked agammaglobulinemia.

A group of unique Epstein-Barr virus-containing cell lines was derived from the bone marrow of three patients with X-linked agammaglobulinemia. Efforts to obtain cell lines from the peripheral blood of these patients were uniformly unsuccessful. Immunofluorescence analyses as well as biosynthetic studies with [(35)S]methionine indicated unusual patterns of Ig synthesis in many of these bone marrow derived lines. Seven of the lines were of particular interest in that two produced no Ig of any type; two others showed no Ig by fluorescence but small amounts by [(35)S]methionine labeling; one expressed only cytoplasmic mu chains without any evidence of light chain synthesis, and two produced primarily mu chains with only slight amounts of light chains. One of the lines without membrane or cytoplasmic Ig studied in detail grew like a typical lymphoid line and was carried in intermittent culture over a period of 2 yr without Ig expression. One line grew quite differently and resembled the round cell type described previously, which has been obtained from a variety of sources. The cell line with cytoplasmic mu chains and no light-chain expression had the characteristic properties of pre-B cells. Three normal type Ig-producing cell lines also were obtained from the patients. The accumulated evidence obtained in the present study indicates that these unusual cell lines represent normal precursor cells of the B-cell lineage; these grew out in these cases because of the virtual absence of mature B cells that ordinarily overgrow the culture system. However, the possibility that in certain instances they reflect abnormal Ig synthesis characteristic of the disease has not been ruled out.

Agammaglobulinemia↗
PubMed1980

Biogenesis of membrane-bound and secreted immunoglobulins. I. Two distinct translation products of human mu-chain, with identical N-termini and different C-termini.

Structural differences between the heavy chain of membrane-bound IgM (mu m) and the heavy chain of secreted IgM (mu s) were investigated. The primary translation products of the mu-chain, free of posttranslational modifications, were synthesized in a wheat-germ cell-free system, programmed with messenger RNA derived from human lymphoblastoid cell lines positive for both membrane-bound and secreted IgM. Encoded in this sytem were two mu-chains, which shared N-terminal signal peptides and which differed both in molecular weight and in C-terminal amino acid sequence. In vivo pulse labeling of cells confirmed that, as intermediates in the rough endoplasmic reticulum, these two forms expressed the same idiotype and maintained their difference in molecular weight and in C-terminal sequence. By correlation with pulse-chase kinetics and with immunofluorescence, one form of mu-chain represents mu m, and the other, mu s. Because the molecular weight difference between the two is manifest at the level of their primary translation products, these studies demonstrate that mu m is distinguished from mu s by a difference in primary structure, at least in part at the C-terminus.

Amino Acid Sequence↗
PubMed1980

Two types of Ia-positive T cells. Synthesis and exchange of Ia antigens.

Two distinct types of Ia-positive T cells have been described. One type represents a blastoid T cell responding from stimulation by mitogens, antigens, and in allogeneic and autologous mixed lymphocyte culture reactions. This is a large cell that is strongly positive for Ia antigens as measured by a variety of different antisera. The other general type is a smaller cell with a lower expression of Ia antigens that is found at low levels in normal peripheral blood and is markedly elevated in various pathological states. It also rises rapidly after inoculation with tetanus toxoid and PPD in sensitized individuals. This cell does not incorporate thymidine and is enriched in the Tgamma fraction; it can be markedly concentrated from normal lymphocytes, and current evidence indicates that it is a T cell. The marked elevation of this cell in the blood of patients with rheumatoid arthritis is of special interest. Considerable evidence indicates that, at least in certain instances, the Ia antigens are synthetized by the cells that carry them. Incorporation of labeled amino acid experiments and the in vitro translation results presented above indicate this. However, the ready exchange of Ia antigens between cells in the experiments described indicates that uptake from other cells may be a significant source.

Histocompatibility Antigens Class II↗
PubMed1976

Isolation and immunologic characterization of a human. B-lymphocyte-specific, cell surface antigen.

In addition to HL-A antigens, another cell surface protein complex has been obtained from membranes of the human B-lymphoblast cell line IM-1. This complex which was solubilized with papain, consisted of polypeptides of 23,000 and 30,000 daltons (p23, 30). Rabbit antisera to this material precipitated from [35S]methionine-labeled detergent-solubilized cells, three proteins of 39,000, 34,000, and 29,000 daltons. These antisera were specifically cytotoxic for B lymphocytes of peripheral blood, for B-lymphoblast cell lines, and for EAC rosette receptor-positive surface Ig-negative (Null) lymphocytes. The p23,30 complex was not present on T lymphocytes, EAC rosette receptor-negative Null lymphocytes, or platelets. In addition, the p23,30 complex from several cell lines inhibited alloantisera from multiparous Amish women which had been shown to recognize non-HL-A, B-lymphocyte antigens. Some other properties of the anti-p23,30 sera antisera were described.

Antigen-Antibody Reactions↗
PubMed1975

Enhanced representation of HL-A antigens on human lymphocytes after mitogenesis induced by phytohemagglutinin or Epstein-Barr virus.

The amount of HL-A antigens present on the peripheral blood lymphocytes of a single human donor was increased about 11-fold after stimulation with phytohemagglutinin and 36-fold after transformation with Epstein-Barr virus. This increase applied to all four HL-A specificities of these cells. The response to phytohemagglutinin was dependent on dose and was first observed at 12 hr of incubation. Measurements of the amount of surface membranes by geometry, by radioiodinatable surface proteins, and by 5'-nucleotidase (5'-ribonucleotide phosphohydrolase, EC 3.1.3.5) assay all indicated that the enhanced representation of HL-A antigens after stimulation by phytohemagglutinin or transformation by Epstein-Barr virus must be due to an increase in the density of these antigens on the cell surface.

Binding Sites↗