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Biomedical subjects

E A Havell

Publications and source records attributed to E A Havell.

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

Endotoxin-induced interferon synthesis in macrophage cultures.

Pure cultures of murine bone marrow-derived macrophages produce interferon (IFN) after exposure to endotoxin. The levels of endotoxin-induced IFN were enhanced 5- to 20-fold by pretreating (priming) macrophages with murine interferons produced by either NDV-induced L cells, which consisted of a mixture of IFN alpha and IFN beta, or IFN gamma produced by spleen cells stimulated with phytohemagglutinin. Studies conducted on the kinetics of IFN release from endotoxin-induced macrophages demonstrated that peak synthesis occurred within 2-4 hr and was completed 6 hr after the start of treatment. The addition of actinomycin D to macrophages, up to 1 hr after exposure to endotoxin, completely inhibited release of interferon, thus indicating that gene transcription was required for interferon synthesis. The inclusion of cycloheximide in the medium of endotoxin or Poly(I) X Poly(C)-induced macrophages, although inhibiting 90% of protein synthesis, resulted in a superinducing effect, in that induced macrophages treated with cycloheximide produced higher levels of IFN than macrophages not treated with the inhibitor of protein synthesis. Antigenic characterization of macrophage IFNs revealed that endotoxin-induced IFN was neutralized to a higher degree than virus-induced IFNs derived from either macrophages or L cells.

Animals↗
PubMed1982

Enhanced production of murine interferon gamma by T cells generated in response to bacterial infection.

Spleen cell cultures derived from animals infected 6 d earlier with Listeria monocytogenes produced 10-20-fold more murine interferon gamma (MuIFN gamma) than spleen cells from nonimmune mice in response to stimulation with T cell mitogens. A striking temporal association was found between the enhanced synthesis of MuIFN gamma and the development of anti-Listeria immunity in that both the potential for increased MuIFN gamma production and the generation of Listeria-protective T cells developed and then decayed in unison. Treatment of spleen cells with monoclonal anti-Thy-1.2 plus complement virtually abolished the ability of cells from Listeria-immune mice to synthesize MuIFN gamma. The T cells producing MuIFN gamma were found to be more susceptible to complement-mediated lysis with monoclonal anti-Lyt-1.2 than with monoclonal anti-Lyt-2.2. The production of MuIFN gamma was not affected by treating spleen cells with anti-IgG antisera or with a monoclonal antibody directed against I-A specificities. MuIFN gamma was detected 4 h after the beginning of mitogenic stimulation of spleen cell cultures, and peak levels of MuIFN gamma were reached by 18 h. The IFN synthesized by mitogen-induced spleen cells derived from Listeria-immune mice were relatively labile at pH 2.0 and neutralized by a rabbit anti-MuIFN gamma serum but not by an antiserum having specificities for MuIFN alpha and MuIFN beta. The apparent molecular weight of the MuIFN gamma, as estimated by molecular sieving on a Bio-gel P-60 column, was estimated to be 38,000, and the isoelectric point as determined by chromatofocusing was extremely heterogeneous, ranging between pH 5.0 and pH 7.0.

Animals↗
PubMed1980

Antibody neutralization studies of the antiviral activities of human leukocyte interferon on different cells.

Human leukocyte and fibroblast interferons were titrated by inhibition of a single cycle of virus replication on different cells which vary in sensitivities to the action of human interferons. The interferon dose response curves were found to be regularly sigmoidal, exhibit similar slopes, and reflect the relative sensitivities of each cell type to the antiviral activities of the human interferons. The degree and pattern of antibody neutralization for a constant quantity of leukocyte interferon was determined on the various cell types by virus yield assays. The antibody neutralization curves reveal the quantity of antibody required to neutralize the antiviral activity of the leukocyte interferon on each of the different cells. Because of the high degree of sensitivity of the assay system, the presence of very low levels of antigenically distinct interferons in the preparation can be detected.

Antibodies↗
PubMed1978

Selection of new human foreskin fibroblast cell strains for interferon production.

The aim of this work has been to isolate and characterize new diploid cell strains, suitable for large-scale production of human fibroblast interferon. Twenty cell strains were isolated from individual neonatal foreskins obtained with the informed consent of the donors' parents. The techniques employed for the isolation of the cell strains were aimed at obtaining the highest possible yield of normal diploid cells, free of contaminating microorganism and viruses. The bulk of the cell yield has been frozen at a low population doubling level. Each of the isolated cultures was tested for interferon producing characteristics with poly(I)-poly(C) under a number of different conditions including "superinduction" with metabolic inhibitors. Most of the newly established cell strains produced lower interferon yields than the reference FS-4 cell strain. However, some new cell strains produced similar interferon yields as the FS-4 cells on superinduction. Five cell strains, designated FS-30, FS-35, FS-44, FS-48 and FS-49, identified as the highest interferon producers among the new cells, were selected for further testing. Of these, three cell strains (FS-35, FS-48 AND FS-49) produced similar interferon yields as FS-4 cells after superinduction. Cell strains FS-48 and FS-49 were found to have stable interferon producing characteristics over a wide span of population doubling levels. The interferon produced in these new cell strains had the antigenic and biological characteristics of human fibroblast interferon.

Cell Line↗
PubMed1978

Characteristics of human lymphoblastoid (Namalva) interferon.

Interferon derived from the human lymphoblastoid cell line, Namalva, was fractionated by antibody affinity chromatography into two antigenically distinct interferon subspecies. At least 13% of the total Namalva interferon activity possessed the F antigenic determinant found on human interferon derived from fibroblast cultures, while the bulk of the Namalva interferon activity had the Le antigenic determinant characteristic for human leukocyte interferon. The separated Le and F subspecies of Namalva interferon differed in the degree of their heterospecific activities on bovine cells. The Le moiety resembled crude leukocyte interferon in that it was highly active in bovine cells. The F component of Namalva interferon showed a lower degree of activity in bovine cells, thus resembling crude fibroblast interferon. When analysed by sodium dodecyl sulphate-polyacrylamide gel electrophoresis and by isoelectric focusing, crude Namalva interferon qualitatively resembled crude leukocyte interferon.

Burkitt Lymphoma↗
PubMed1977

Altered molecular species of human interferon produced in the presence of inhibitors of glycosylation.

The inhibitors of glycosylation, 2-deoxy-D-glucose or D-glucosamine, inhibit the synthesis of biologically active interferon in human FS-4 fibroblast cultures stimulated with polyinosinate-polycytidylate. Interferon synthesized in the presence of partially inhibitory concentrations of 2-deoxy-D-glucose or D-glucosamine were found to differ from interferons made in control cultures in some physical properties. Interferons synthesized in the presence of either inhibitor had a diminished charge heterogeneity demonstrable by iso-electric focusing. On sodium dodecyl sulfate-polyacrylamide gel electrophoresis, control interferon activity formed a single peak with the apparent molecular weight of 20,000, whereas interferons from cultures treated with either inhibitor could be resolved into two distinct molecular weight components, one of which was smaller than the interferon synthesized in control cultures.

Cells, Cultured↗
PubMed1977

De novo cell-free synthesis of human interferon.

Biologically active human interferon was synthesized de novo in a cell-free mouse extract stimulated with messenger RNA from induced human fibroblasts. The identity of the antiviral activity as human interferon was demonstrated by its antigenic and species specificity. Some characteristics of the cell-free synthesis were described.

Animals↗
PubMed1977

Induction and decay of human fibroblast interferon mRNA.

Polyadenylylated interferon mRNA, obtained from induced human fibroblasts, was quantitatively assayed by synthesis of biologically active human interferon in Xenopus laevis oocytes. The assay for interferon mRNA was used to distinguish between various hypotheses relating to interferon induction and biosynthesis. The data demonstrate that on induction with poly(I-poly(C) human fibroblasts accumulate interferon mRNA for 1-1.5 hr, after which time the mRNA is rapidly degraded with a half-life (t 1/2) of 18 min. Treatment of cells with cycloheximide prolongs the period of accumulation to 3 hr and decreases the rate of mRNA inactivation (t 1/2 = 49 min). Treatment with actinomycin D decreases the rate of inactivation still further (t 1/2 = 68 min). A comparison of cellular interferon synthesis with the relative amounts of interferon m RNA after simple induction or inductionin the presence of the inhibitors (superinduction) indicated a general correlation. Thus, on induction, the genes for interferon are activated to produce a transcript for a short time. The superinducing treatments prolong the period of accumulation and decrease the rate of degradation of this transcript.

Animals↗