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R Devos

Publications and source records attributed to R Devos.

At least 37 records · Page 2Linked to original sources
PubMed1985

Recombinant interleukin 2 induces immunoglobulin secretion in Staphylococcus aureus Cowan strain I activated human B-cells.

Human B-cells, exhaustively depleted for T-cells, were activated with Staphylococcus aureus Cowan strain I (SAC) and responded to recombinant human interleukin 2 (rIL2) by secretion of immunoglobulin (Ig), as measured by a protein A hemolytic plaque assay. The rIL2, however, had to be present early, since addition later than 24 h after SAC-activation of the B-cells reduced the response to background levels. No clear dose response was observed and Ig-secreting cells (ISC) could be induced even with rIL2 at 0.5 U/ml. The monoclonal antibody anti-TAC prevented the rIL2-promoted induction of ISC. Ig production could be induced in SAC-activated cultures with supernatants of Xenopus laevis oocytes injected with sucrose-gradient-fractionated poly(A+) RNA derived from a stimulated human spleen cell culture. This activity coincided with the IL2 mRNA activity and was well separated from the interferon-gamma mRNA activity. Our results suggest that IL2 is not only a B-cell growth factor but also promotes the differentiation of activated human B-cells towards Ig secretion.

Antibody-Producing Cells↗
PubMed1985

Characterization of antibodies against recombinant HuIFN-gamma produced by hybridoma cells.

Balbc/c mice were immunized with purified recombinant E. coli-derived human gamma-interferon (HuIFN-gamma). Their spleen cells were fused with a mouse myeloma cell line (Sp2/0). Hybridomas producing antibodies reacting with HuIFN-gamma were screened by a soluble-phase radioimmunoassay using pure 125I-labeled cloned IFN-gamma as antigen, and tested for their ability to neutralize the antiviral activity of IFN. Three hybridomas S1-1, S1-2, and S1-3, were cloned and subcloned and remained stable. Although the antibodies produced by clones S1-1 and S1-2 were both able to neutralize specifically the antiviral activity of natural and recombinant HuIFN-gamma, they appeared to recognize different epitopes on the HuIFN-gamma molecule. The antibodies produced by the S1-3 clone failed to neutralize the antiviral activity of either interferon. The antibodies from all three clones were characterized as IgG1 subclass. Their affinity constants were determined from competitive inhibition curves and ranged from 1 to 4.3 X 10(8) M-1.

Animals↗
PubMed1985

Binding of unglycosylated and glycosylated human recombinant interferon-gamma to cellular receptors.

Recombinant human interferons (IFNs), either unglycosylated produced in E. coli (rIFN-gamma) or glycosylated produced in CHO cells (g-rIFN-gamma), were labeled with 125I to similar specific activities to study their interaction with cell-surface receptors. When analyzed by gel electrophoresis, rIFN-gamma run as a single polypeptide of Mr 15,000-17,000, whereas g-rIFN-gamma separated into three components of Mr 20,000, 22,000, and 43,000, which corresponded to the known size of the two monomeric and one dimeric forms of glycosylated natural IFN-gamma. The binding of the two species of 125I-IFN-gamma was competed equally by rIFN-gamma in competition displacement experiments with Daudi cells, indicating that these IFNs bind with similar high affinity to the same receptors. KD values of 1.25 X 10(-10) and 2.5 X 10(-10) M were determined for g-rIFN-gamma and rIFN-gamma, respectively. This relatively small difference in KD does not apparently result in a detectable difference in biological activity, as measured by the increase in 2',5'-oligo(A) synthetase activity in IFN-treated HeLa and A549 cells. These results indicate that glycosylation of IFN-gamma does not play a significant role in its interaction with cellular receptors and in the induction of a biological response.

2',5'-Oligoadenylate Synthetase↗
PubMed1985

Interferon-gamma modulates HLA class II antigen expression on cultured human thymic epithelial cells.

Cultures of human thymic epithelial cells (TEC) were tested for the expression of HLA class I (A, B, C) and class II (DR and DC) antigens by indirect immunofluorescence. The epithelial nature of the cells was proven by using an antikeratin antiserum. A high level of expression (close to 100% positive cells) of HLA class I antigens was observed on TEC at the beginning of the culture and remained unchanged for up to 12 days. In contrast, HLA class II antigen expression (85% DR+ and 75% DC+ cells on day 2) decreased gradually and reached very low levels (less than 5% DR+ or DC+) by day 7 of culture. This loss of class II antigen expression was not seen when cultures were performed in the presence of supernatants from activated T cells containing interferon-gamma (IFN-gamma). Furthermore, the presence of recombinant IFN-gamma (rIFN-gamma) in the medium from the onset of culture maintained HLA-DR and DC antigen expression on a high number of cells (comparable to that observed on day 2 of culture). A large percentage of rIFN-gamma-treated cells also showed intracytoplasmic HLA-DR antigen expression. Addition of rIFN-gamma at various times after the onset of the culture led to a reinduction of DR and DC antigen expression. This effect of rIFN-gamma was observed in 48 hr with concentrations as low as 10 IU/ml and was apparently specific for this IFN species, in that rIFN-alpha was unable to modify HLA class II antigen expression at concentrations up to 1000 IU/ml. The increased expression of HLA class II antigen was truly due to induction in individual TEC, rather than selection of class II-positive cells, because induction under the influence of IFN-gamma was reversible and occurred in the absence of proliferation in mitomycin-treated or gamma-irradiated cultures. Our results indicate that synthesis and membrane expression of class II HLA antigens are enhanced by IFN-gamma in TEC cultures. This finding raises the possibility that IFN-gamma participates in the mechanisms that assure the permanent expression of DR and DC antigens observed in TEC in vivo, with potentially important functional consequences in terms of education for self recognition.

Cell Survival↗
PubMed1978

The 3'-Terminal nucleotide sequence of encephalomyocarditis virus RNA.

Poly(A)-containing encephalomyocarditis virus RNA functions as an excellent template for cDNA synthesis in vitro with an RNA-dependent DNA polymerase in the presence of an oligothymidylate primer. Under appropriate conditions, discrete transcripts of increasing chain length were obtained, suitable for sequence analysis. A limited cDNA fragment of 36 nucleotides, primer (dT)10 included, was synthesized when dGTP was omitted from the reaction mixture and its primary structure was elucidated using direct DNA-sequencing methods. The complement corresponds to the 3' end of encephalomyocarditis RNA. The hexanucleotide (5'-3')(A-A-U-A-A-A) found in this sequence is also present in all 3' non-coding regions of poly(A)-containing eukaryotic mRNAs studied until now, in nearly identical positions relative to the poly(A) tail. The possible biological significance of this structural homology is discussed.

Base Sequence↗
PubMed1976

Addition by ATP: RNA adenylyltransferase from Escherichia coli of 3'-linked oligo(A) to bacteriophage Qbeta RNA and its effect on RNA replication.

An oligo(A) or poly(A) segment was added in a stepwise fashion to the 3'-end of bacteriophage Qbeta-RNA with the aid of ATP : RNA adenylyltransferase from Escherichia coli. Nearly all RNA molecules, present in the reaction mixture, could be polyadenylated. For tail lengths not exceeding 200 nucleotide residues, the physical properties of Qbeta-RNA-poly(A) were found to be only slightly different from those of the original RNA. The polyadenylated RNA was purifed by affinity chromatography. The properties of Qbeta-RNA with oligo(A) tails of different average lengths were investigated in the in vitro replication reaction. Almost complete abolishment of template activity, even by short oligo(A) stretches, was found. Furthermore, polyadenylated Qbeta-RNA inhibited the normal replication reaction of Qbeta-RNA by removal of host factor HFI, in the same way as does free poly(A).

Adenosine Monophosphate↗
PubMed1976

The enzymic addition of poly(A) to the 3'-end of RNA using bacteriophage MS 2 RNA as a model system.

ATP : RNA adenyltransferase, purified from Escherichia coli, was used to add a series of adenosine residues to the 3'-end of MS2RNA. Incubations of the order of a few minutes at 37 degrees C were sufficient for synthesis of a short poly(A) chain that did not appreciably alter the hydrodynamic or electrophoretic properties of MS2 RNA. The size of the poly(A) tails was estimated by gel electrophoresis after prior hydrolysis of the primer RNA with pancreatic ribonuclease. These results were in good agreement with the values calculated on the basis of the relative amount of incorporated AMP. After the addition of a short poly(A) tail, approximately 50% of the treated material binds specifically to an oligo(dT)-cellulose column. The majority of the recovered poly(a)-containing RNA was still intact, as shown by analysis on polyacrylamide gel. After incubations beyond 6 min, slowly sedimenting material, also showing reduced electrophoretic mobility, was formed. Presumably this material corresponds to RNA chains to which long poly(A) tails are linked.

Centrifugation, Zonal↗
PubMed1975

Readenylation of polyadenylate-free globin messenger RNA restores its stability in vivo.

Using an ATP:RNA adenyltransferase from Escherichia coli, a polyadenylic sequence was resynthesized onto rabbit globin mRNA from which the poly (A) segment had been previously removed. Conditions for obtaining a homogenous reconstituted globin mRNA preparation containing 30 adenylic residues per message molecule were determined. The reconstituted globin mRNA was microinjected into Xenopus laevis oocytes. Its stability was very similar to that of native mRNA.

Adenine Nucleotides↗