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Biomedical subjects

A Meager

Publications and source records attributed to A Meager.

At least 127 records · Page 7Linked to original sources
PubMed1986

IL-2- and IFN gamma-enhanced natural cytotoxic activity: analysis of the role of different lymphoid subsets and implications for activation routes.

To elucidate the immunoregulatory mechanisms by which human recombinant interleukin 2 (r.IL-2) and human recombinant interferon (IFN)-gamma influence natural cytotoxic activity of human peripheral blood lymphocytes (PBL), experiments were performed in which we studied: the kinetics of augmentation of natural cytotoxic activity by IL-2 and IFN-gamma; the phenotypes of the natural cytotoxic precursor cells acted upon by IL-2 and IFN-gamma; the role of IL-2-induced IFN-gamma in the natural cytotoxic activity enhancing effects of IL-2 and (d) the surface phenotypes of the natural cytotoxic cells activated by IL-2 or IFN-gamma. Three phenotypical distinct precursor cells can be identified. The phenotypes of the precursor cells sensitive to r.IFN-gamma are T3-, Leu 7+or-, FcR-gamma+. The phenotypes of the precursor cells sensitive to r.IL-2 are T3-, Leu 7-, FcR-gamma+or-. It appears that during prolonged culture relatively more of the FcR-gamma- precursor cells acquire natural cytotoxic activity upon stimulation with r.IL-2. Antibodies to IFN-gamma, known to neutralize both recombinant and natural IFN-gamma, completely inhibited the IFN-gamma-induced augmentation of natural cytotoxic activity but only slightly affected the IL-2-mediated augmentation. This indicates that only part of the augmenting effect of r.IL-2 is mediated through IL-2-induced IFN-gamma. This implies that r.IL-2 augments natural cytotoxic activity predominantly through an IFN-gamma-independent pathway. The phenotype of the effector cells expressing natural cytotoxic activity after a 4-day culture period with IL-2 or IFN-gamma was analyzed by depletion experiments. Virtually all the cells that exerted the IFN-gamma-enhanced natural cytotoxic activity are FcR-gamma+, whereas a portion of the cells that exerted the IFN-gamma-enhanced natural cytotoxic activity are FCR-gamma-. Both natural killer cells and lymphokine-activated killer cells contribute to natural cytotoxic activity. The relative contributions of both activities to the natural cytotoxic activity augmented by IL-2, respectively, IFN-gamma, is discussed.

Hematopoietic Stem Cells↗
PubMed1986

Studies of the enhancement of natural cytotoxicity by the streptococcal immunopotentiator OK432.

The immunopotentiator OK432, a product of Streptococcus pyogenes A3, enhanced the natural killer (NK) activity of unseparated human peripheral blood mononuclear cells (PBM) and separated, nonadherent lymphocytes (PBL) containing less than 0.5% contamination with monocytes. Following treatment with OK432, both unseparated and non-adherent cell preparations produced interferon (IFN) alpha and gamma and low levels of interleukin-2 (IL-2). However, in the presence of neutralising amounts of anti-IFN alpha and gamma antisera, the NK enhancing effect of OK432 was not fully inhibited. Filtered supernatants derived from OK432-treated PBM or PBL also enhanced the NK activity of fresh PBM. In this instance, in most experiments, the NK enhancing effect of supernatants (from non-adherent cells) was fully inhibited by anti-IFN antisera. However, in some experiments, enhancement of NK activity by anti-IFN antisera-treated supernatants was still found. It is suggested that the presence of IL-2 or, possibly, other as yet uncharacterized factors secreted following OK432 treatment, account for this residual enhancement of NK activity.

Antibodies↗
PubMed1986

Antigenic characteristics of glycosylated natural and unglycosylated recombinant human gamma-interferon.

Neutralizing polyclonal antibodies raised in rabbits against glycosylated natural human gamma-interferon (nIFN-gamma) and unglycosylated recombinant IFN-gamma (rIFN-gamma) were tested for their ability to bind to several polypeptides spanning the entire amino acid sequence of the rIFN-gamma molecule. Antibodies raised in four rabbits against rIFN-gamma all bound efficiently to relatively large polypeptides whose sequences started from the amino-terminus, rIFN-gamma 1-48, 1-59, 1-80, and the internal polypeptide IFN-gamma 81-120. These antibodies bound poorly or not at all to the following polypeptides: IFN-gamma 1-20, 24-59, 36-59, 87-96, 121-137, 121-146, 138-146. In contrast, antibodies raised in four rabbits against nIFN-gamma in general bound less well to IFN-gamma 1-48, 1-59, 1-80, and 81-120. In addition, all the other polypeptides cited above were recognized to some degree by anti-nIFN-gamma antibodies. These results suggest that the oligosaccharide side-chains of nIFN-gamma cover or perturb the structure of antigenic sites present in rIFN-gamma and thus significantly modify the antigenic properties of the IFN-gamma molecule.

Amino Acid Sequence↗
PubMed1986

Epitope localization of a monoclonal antibody, LO-22, with broad specificity for interferon-alpha subtypes.

A murine monoclonal antibody, LO-22, with broad cross-reactivity to human interferon-alpha (HuIFN-alpha) subtypes and some animal IFN-alpha species was found to bind less efficiently to IFN-alpha A (IFN-alpha 2a). In contrast, LO-22 bound strongly to IFN-alpha 2 (IFN-alpha 2b) and IFN-alpha 2C (IFN-alpha 2c) which differ by one or two amino acids, respectively, from IFN-alpha A; the latter has lysine at position 23 whereas the other closely related IFNs have arginine. LO-22 also bound efficiently to IFN-alpha D which is only 83% related to IFN-alpha A, but which also has arginine at position 23. These results strongly suggest that LO-22 recognizes a conserved epitope among IFN-alpha subtypes in which arginine at position 23 is involved. The specificity of a second monoclonal antibody, MT4/E4, is also reported and compared to that of LO-22.

Animals↗
PubMed1986

Human interferon alpha and gamma production by lymphocytes during the generation of influenza virus-specific cytotoxic T lymphocytes.

We analysed the production of interferons (IFN)-alpha and -gamma during the generation of human influenza-virus specific cytotoxic T lymphocyte (CTL) responses using monoclonal antibodies in a specific radioimmunoassay. The results showed that the peripheral blood mononuclear cells (PBM) of all donors tested produced IFN-gamma and had influenza A virus-specific CTL activity after stimulation. The amount of IFN-gamma produced and the level of CTL activity were significantly correlated. The PBM of some donors also produced IFN-alpha. The level of IFN-gamma produced was low during the first few days and increased subsequently, but IFN-alpha, when it was detected, was produced on day 1. The kinetics of the increase in IFN-gamma correlated with the increase in CTL activity. We also observed an increased percentage of cells bearing interleukin-2 receptors, which may have been a response to the production of IFN-gamma. The T cells active in lysing influenza A virus-infected target cells and in producing IFN-gamma were determined after separating effector cells with monoclonal antibodies. The CTL effector cells were mainly in the T8+ subset, but IFN-gamma-producing cells were found in both T4+ and T8+ subsets. These results suggest that influenza virus-specific T8+ CTL produce IFN-gamma in response to virus, and that T4+ cells which are not CTL effectors also produce IFN-gamma after restimulation with influenza A virus-infected cells.

Antibodies, Monoclonal↗
PubMed1986

Induction of interferon alpha and gamma from human lymphocytes by dengue virus-infected cells.

Human peripheral blood lymphocytes (PBL) of non-immune donors produced interferon (IFN) when cultured with dengue virus-infected cells. IFN was detected as early as 2 h after exposure of PBL to dengue virus-infected cells, and the titres reached a maximum by 16 h of incubation. Dengue virus-infected cells treated with glutaraldehyde, which produced no infectious dengue virus, also induced IFN. These results indicate that PBL produce IFN in response to dengue virus-infected cells and that the production of IFN by PBL is due to stimulation of PBL by dengue virus-infected cells. Characterization of IFN-producing PBL with monoclonal antibodies demonstrated that the predominant producing cells were contained in M1+ and T3- subsets, and that the Leu11+ subset contains some IFN-producing cells. The IFNs that were produced by the PBL exposed to dengue virus-infected cells were analysed by radioimmunoassay employing monoclonal antibodies specifically to detect IFN-alpha or IFN-gamma. IFN-gamma as well as IFN-alpha was produced by PBL exposed to dengue virus-infected cells. Both IFN-alpha and IFN-gamma were predominantly produced by PBL contained in M1+ and T3- subsets. The observation that PBL of non-immune donors produced IFN-gamma as well as IFN-alpha in response to dengue virus-infected cells is of interest in view of the immunoregulatory roles of IFNs and the hypothesis that the complications of dengue virus infection (haemorrhagic fever and shock) may be due to immunopathology.

Antibodies, Monoclonal↗
PubMed1986

Natural cytotoxic activity in multiple sclerosis patients: defects in IL-2/interferon gamma-regulatory circuit.

In order to determine the factors underlying the impaired natural cytotoxic (NC) activity in multiple sclerosis (MS) patients, we have analysed the interleukin 2 (IL-2)-interferon gamma-(IFN gamma)-NC activity regulatory circuit in 40 MS patients and 40 matched healthy controls. Exogenous recombinant IFN gamma (rIFN gamma) enhanced NC activity in peripheral blood lymphocytes (PBL) derived from MS patients and controls equally well. In contrast, PBL from MS patients showed a significantly lower increase of NC activity in response to IL-2 than healthy controls. This defect in responsiveness was independent of the dose of IL-2. Even at the highest dose of rIL-2 (1000 U/ml), MS patients showed a decreased response. PBL from MS patients required a 2 to 10 times higher dose of IL-2 to reach NC activity levels comparable to controls. In healthy individuals IL-2 can act upon both Fc gamma R+ and Fc gamma R- NC precursor cells. The decreased responsiveness to IL-2 is not confined to one subpopulation of IL-2-responsive precursor cells because depletion of Fc gamma R+ cells before culture in the presence of IL-2 revealed no significant differences in the contribution of Fc gamma R+ precursor cells to the IL-2 enhanced NC activity between MS patients and controls. Also the number of IL-2-responsive precursor cells appeared to be normal since the number of Fc gamma R+ cells in MS patients and controls was comparable. PBL from MS patients produced significantly lower amounts of IFN gamma upon stimulation with IL-2. Analysis of the different parameters of the regulatory circuit at the population level showed, both for patients and controls, a significant correlation between IFN gamma production and increase of NC activity induced by IL-2. Also the endogenous NC activity and IFN gamma production, both in patients and controls, were correlated. At the individual level, defects in NC activity could not be linked to another parameter of the regulatory circuit.

Adult↗
PubMed1986

Development of interferon-specific monoclonal antibody for in vitro interferon assays.

In this study, monoclonal antibodies (MABs) to human interferon alpha (HuIFN alpha) were evaluated for their suitability for the quantification of different HuIFN alpha preparations by conventional immunoassay methods. The results obtained using four different MABs were compared and suggest that whilst immunoassays can be highly sensitive and reproducible to perform, calibration of antigen content in relation to units of biological activity remains a problem, particularly because of the molecular and biological heterogeneity of HuIFN alpha preparations. Nevertheless, the judicious selection of MABs specific for an individual HuIFN alpha subtype has indicated that immunoassays may be accurately calibrated in units of biological activity for potency estimations of that HuIFN alpha subtype.

Antibodies, Monoclonal↗
PubMed1985

Ricin-resistant human T-cell hybridomas producing interferon gamma.

Ricin-resistant variants of the SH9 T-cell line were selected after growth of this line in medium containing toxic amounts of ricin, a lectin derived from Ricinus communis. The ricin-resistant SH9 lines, SH9.R0 and SH9.R1, were demonstrated to be deficient in cell surface ricin-binding sites, but otherwise had the cellular phenotype of SH9 cells. Ricin-resistant T-cell hybridomas were prepared by fusion of SH9.R0 and SH9.R1 with activated T-lymphocytes. The presence of ricin in the selection medium rapidly killed unfused T-lymphocytes and prevented cell transformation by human T-cell leukaemia virus type 1 (HTLV-1) which is shed by the SH9.R0 and SH9.R1 cells. This ensured that the cells growing out were indeed hybridomas. Ricin-resistant T-cell hybridomas were characterised and also shown to lack cell surface receptors for ricin. Analysis of T-cell surface markers indicated that the T-cell hybridomas could be the result of fusions between SH9.R1 cells and T-helper lymphocytes or T-suppressor lymphocytes. All of the T-cell hybridomas prepared in this study spontaneously produced interferon gamma (IFN gamma).

Cell Line↗
PubMed1985

Interferon gamma produced by mitogen-activated T lymphocytes does not directly mediate lymphoproliferation.

Human interferon gamma (IFN-gamma) endogenously produced during mitogenic stimulation of human peripheral blood mononuclear cells or human T lymphocyte-enriched cultures was neutralized in situ by the addition of a polyclonal antiserum (anti-L) raised in a rabbit against partially purified natural IFN-gamma derived from peripheral blood mononuclear cells. Small decreases in mitogen-induced [3H]thymidine incorporation (lymphoproliferation) were demonstrated under these conditions. However, an antiserum (anti-G) raised in a sheep against highly purified recombinant IFN-gamma (E. coli-derived) which strongly neutralized the antiviral effect of IFN-gamma either had little effect on mitogen-induced lymphoproliferation or caused slight enhancement of mitogenesis. The interleukin 2 responsiveness of activated T lymphocytes following mitogenic stimulation was not found to be different in the presence of anti-G to that of control cultures incubated in the presence of normal sheep serum. These results suggest that IFN-gamma is not a direct requirement for lymphoproliferation.

Antibodies↗
PubMed1985

Antibodies to synthetic polypeptides corresponding to hydrophilic regions of human interferon gamma.

Synthetic polypeptides corresponding to hydrophilic regions of human interferon gamma (HuIFN gamma) based on the amino acid sequence of HuIFN gamma inferred from its cDNA sequence were used to produce antibodies in rabbits which reacted with the polypeptides and which might also be expected to recognise native HuIFN gamma. Groups of 3 or 4 rabbits were immunised with synthetic polypeptides corresponding to HuIFN gamma amino acid sequences 1-20, 1-59, 24-59, 36-59 and 87-96 which included major hydrophilic domains of the IFN gamma molecule. All the rabbits produced antibodies which recognised the polypeptide immunogen, but to date only 1 of 4 rabbits immunised with polypeptide 24-59 and 1 of 3 rabbits immunised with polypeptide 1-59 have produced antibodies which also recognise native HuIFN gamma. The positively reacting antiserum from the rabbit immunised with polypeptide 24-59 could only be shown to weakly bind to HuIFN gamma, whereas the positively reacting antiserum from the rabbit immunised with polypeptide 1-59 was shown to both weakly bind to HuIFN gamma and weakly neutralise its in vitro antiviral effect. The results so far obtained suggest that the amino acid sequences close to the N-terminus are important for biological activity.

Amino Acid Sequence↗
PubMed1984

Detection of hybridomas secreting monoclonal antibodies to human gamma interferon using a rapid screening technique and specificity of certain monoclonal antibodies to gamma interferon.

An immunoprecipitation technique, which uses radiolabeled human gamma interferon (HuIFN-gamma) and a sheep anti-mouse F(ab')2 serum, is described for the rapid detection of mouse monoclonal antibodies to IFN-gamma in hybridoma culture supernatants. This technique which can be performed in 4 h detects both neutralizing and nonneutralizing antibodies to IFN-gamma. Certain monoclonal antibodies prepared against natural (glycosylated) IFN-gamma which neutralized the antiviral activity of natural IFN-gamma bound strongly to rDNA (unglycosylated) IFN-gamma derived from E. coli, but failed to neutralize its antiviral activity.

Animals↗
PubMed1984

A comparison of the neutralizing properties of monoclonal and polyclonal antibodies to human interferon alpha.

Specific polyclonal antisera to human interferon-alpha 1 (HuIFN-alpha 1), human interferon-alpha 2 (HuIFN-alpha 2) and human lymphoblastoid interferon (HuIFN-alpha Ly Namalwa) have been raised in rabbits and sheep. The antisera raised against HuIFN-alpha 1 and HuIFN-alpha 2 strongly neutralized the antiviral activity of their homologous IFN-alpha subtypes, but were less active against the heterologous IFN-alpha subtypes and preparations containing mixtures of IFN-alpha subtypes, e.g. human leukocyte interferon (HuIFN-alpha Le). Antisera raised against HuIFN-alpha Ly Namalwa strongly neutralized the antiviral activity of all IFN-alpha-containing preparations and showed weak cross-reactivity with human interferon-beta (HuIFN-beta). Neither anti-HuIFN-alpha 1 nor anti-HuIFN-alpha 2 could be demonstrated to neutralize the antiviral activity of HuIFN-beta. A number of monoclonal antibodies to HuIFN-alpha 2 have been prepared and these were found to neutralize HuIFN-alpha 2 antiviral activity to varying degrees, but not to neutralize the heterologous subtype HuIFN-alpha 1, preparations containing mixtures of IFN-alpha subtypes or HuIFN-beta.

Antibodies, Monoclonal↗
PubMed1984

The preparation of interferon gamma-producing T-cell hybridomas from jacalin-stimulated T lymphocytes and the SH9 T-cell line.

Jacalin, a lectin(s) extracted from the seeds of Artocarpus integrifolia (Jackfruit), was shown to induce the production of gamma interferon (IFN gamma) in human peripheral blood mononuclear cells (PBMC) and human T-lymphocyte cultures. The amount of IFN gamma produced was enhanced in the presence of mezerein, a phorbol ester derivative. Fusion of jacalin stimulated T lymphocytes with the SH9 T-cell line resulted in the formation of T-cell hybridomas which spontaneously secreted IFN gamma. The spontaneous production of IFN gamma by T-cell hybridomas was not influenced by the presence of jacalin, although significant enhancement of production was observed when the cells were cultured in the presence of mezerein.

Animals↗
PubMed1983

Expression of the human interferon-beta gene cloned in phage M13 mp7.

The single-stranded DNA phage, M13 mp7 was used in the construction of an expression vector containing the coding sequence for mature interferon-beta (IFN-beta). Two clones expressed a fused polypeptide showing the biological and physicochemical properties of IFN-beta, despite the fact that the N-terminal amino acid sequence had been changed; 10(6) I.U./l of culture were produced with a molecular weight of 20 000.

Amino Acid Sequence↗
PubMed1982

Production of human alpha- and beta- interferons by human-rodent hybrids.

Attempts were made to demonstrate human alpha interferon production in virally induced human-rodent cell hybrids. In all hybrids investigated human beta-interferon production was detected when the relevant human chromosomes were retained, but only low levels of human alpha interferon could ever be detected even when human chromosome 9, which contains at least eight alpha-interferon genes, was present in the hybrid. The detection of human alpha interferon was made possible only by the use of specific antisera to human alpha and beta interferon and the sensitive virus yield-inhibition assay. Evidence is presented for independent regulatory mechanisms governing the expression of human alpha and beta interferons in human-rodent hybrids.

Animals↗
PubMed1982

The effect of hypertonic salt on interferon and interferon mRNA synthesis in human MG63 cells.

After infection with Sendai virus or Newcastle disease virus (NDV) strain F, human osteosarcoma MG63 cells produced large amounts of interferon-beta. Both interferon production and overall protein synthesis were strongly inhibited by hypertonic salt. Interferon mRNA synthesis, however, was little affected by hypertonic salt up to twice normal salt concentrations, although cellular RNA synthesis was inhibited under these conditions. The results are compared to those obtained with polyriboinosinic acid: polyribocytidylic acid copolymer [poly(rI) . poly(rC)] inductions of MG63 cells.

Cell Line↗