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Biomedical subjects

A G Morris

Publications and source records attributed to A G Morris.

At least 73 records · Page 4Linked to original sources
PubMed1989

Interaction of v-Ki-ras oncogene and interferon-gamma in the control of histocompatibility antigen expression in mouse fibroblasts.

C3H10T1/2 fibroblasts when transformed with Kirsten murine sarcoma virus lose the ability to be induced to express class II major histocompatibility complex antigens when induced with interferon-gamma (IFN-gamma). Sublines were derived from transformed lines by cell sorting after treatment with IFN-gamma, sorting for low or high expression of H-2Ak. These sublines remained stably noninducible or inducible for class II antigen for several passages after sorting. In all other respects tested, viz, sensitivity to IFN-gamma for the generation of an antiviral state or the induction of class I antigen, content of ras gene products, the sorted sublines were very similar. We conclude that ras oncogene expression in these cells can influence the induction of class II antigen but that because ras expression in the sorted lines is similar the effect of ras expression is indirect and presumably involves interaction with other cellular factors.

Animals↗
PubMed1989

Instability of expression of major histocompatibility antigens in fibroblasts expressing activated ras oncogene: constitutive and interferon-gamma induced class I and class II antigens in a series of clonal isolates of murine fibroblasts transformed by v-Ki-ras.

We have examined the expression of major histocompatibility complex (MHC) antigens, constitutive or induced with interferon gamma (IFN-gamma), in a line of C3H mouse embryo fibroblasts (C3H 201) transformed with a helper-virus-free preparation of the Kirsten strain of murine sarcoma virus. C3H 201 cells expressed some class I antigen (H-2Kk) in the absence of added interferon, unlike the parental C3H 10T1/2 cells from which they were derived. However, this declined with (in vitro) passage level after transformation. Treatment with IFN-gamma induced very high expression of H-2Kk at all passage levels. There was no constitutive expression of class II antigen (I-Ak); however, this could be induced by IFN-gamma. Inducibility of I-Ak was found also to be related to the number of passages after transformation; at early passage levels after transformation more I-Ak was induced than after the cells had been allowed to grow for several passages, until at high passage levels little or no I-Ak was induced. This was not due to the presence of a subpopulation of untransformed cells since when the cells were cloned shortly after infection all the resulting clones were transformed. In addition, IFN-gamma at any passage level induced clearly less I-Ak than was found in C3H 10T1/2 cells, in which I-Ak inducibility was high and stable. Twenty-one clones were derived from C3H 201 cells at early passage (less than 8) either from soft agar or from liquid culture. These clones showed a wide variation in MHC antigen phenotype. Many expressed H-2Kk in the absence of IFN-gamma, and all were strongly inducible for H-2Kk. None showed I-Ak in the absence of IFN-gamma. All but two expressed I-Ak after IFN-gamma treatment but, with four exceptions, clearly less than the untransformed line. Four clones derived at late passage (40) resembled the late passage line. The expression of the ras oncogene and tumorigenicity was studied in representative clones; there was no obvious correlation with MHC phenotype, nor with the method of cloning. We conclude from these studies that the expression of MHC antigens by fibroblasts expressing the v-Ki-ras oncogene, either with or without exposure to interferon gamma, is unstable, varying with the number of cell generations from transformation and from clone to clone.

Animals↗
PubMed1989

Assessment of the functional activity of antigen-bearing dendritic cells isolated from the lymph nodes of contact-sensitized mice.

The immunostimulatory properties of dendritic cells (DC) which rapidly accumulate within the draining lymph nodes of mice topically exposed to contact allergens have been assessed as a function of their ability to initiate proliferative responses by sensitized lymph node cells (LNC) in vitro. A proportion of such DC bear antigen which is in a highly immunogenic form. Thus, at low stimulator:responder ratios, DC-enriched populations prepared from the draining nodes of mice exposed to the skin-sensitizing fluorochrome fluorescein isothiocyanate (FITC) induced significant proliferative responses by FITC-primed responder lymphocytes. Under the same experimental conditions, unfractionated or DC-enriched LNC isolated from naive mice and coated with at least equivalent amounts of FITC in vitro were without effect. The influence of DC populations on lymphocyte proliferation was largely, but not wholly, antigen-specific in nature. Dendritic cell fractions isolated 18 h following topical exposure to high concentrations of FITC or oxazolone induced a marked proliferative response by lymphocytes sensitized to the homologous chemical and a significantly less vigorous response by lymphocytes primed to unrelated haptens. In contrast DC isolated from the nodes of mice sensitized with 2,4-dinitrochlorobenzene (DNCB) caused proliferation only of DNCB-primed lymphocytes. The relative potential of DC populations prepared from FITC- and oxazolone-primed mice to induce antigen-specific and non-specific stimulation was dependent upon both the concentration of chemical used for sensitization and the period of exposure.

Animals↗
PubMed1989

Interactions of interferons in the induction of histocompatibility antigens in mouse fibroblasts and glial cells.

The interactive effects of interferons (IFN) in the induction of class II major histocompatibility complex (MHC) antigens in a murine fibroblast line and murine glial cells (primary astrocytes and an oligodendroglioma line) were examined. It was found that IFN-alpha and -beta were additive with IFN-gamma in the induction of class I antigens but that both IFN-alpha and -beta down-regulated the induction of class II antigens by IFN-gamma. This was most clear cut when the IFN-alpha or -beta was present in large excess in terms of anti-viral activity. Recombinant IFN-alpha 2 was found weakly to induce class II antigens, unlike natural IFN-alpha. The results imply that IFN-alpha and -beta may be important in the control of class II antigen expression in vivo although not by themselves inducing class II antigens.

Animals↗
PubMed1989

Regulation of IFN-gamma-induced host cell MHC antigen expression by Kirsten MSV and MLV. I. Effects on class I antigen expression.

We have reported previously that the Kirsten murine sarcoma virus (Ki-MSV) that carries the v-Ki-ras oncogene prevents C3H10T 1/2 fibroblasts from being able to respond to interferon-gamma (IFN-gamma) with the expression of the class II major histocompatibility complex (MHC) antigen, H-2A. In this report we investigate further as to whether MSV or its parent virus Kirsten murine leukaemia virus (Ki-MLV) is able to reduce host class I MHC antigen expression. The results demonstrate that class I expression is diminished in MSV-infected cells over a time-course of 7 days after exposure to IFN-gamma and over a range of IFN-gamma concentrations. The optimal concentration of IFN-gamma for maximal class I expression remained unchanged. Cells infected with Ki-MLV, which failed to abolish the induction by IFN-gamma of class II antigens, also expressed lower levels of class I antigens, similar to those for cells infected with Ki-MSV, after exposure to IFN-gamma. It is likely therefore that the inhibition of class I induction is due to genetic material shared between the viruses, principally in the long terminal repeats (LTR), and hence that the mechanism of action is distinct from that responsible for the abolition of class II induction by Ki-MSV alone. Since class I antigens are required for CD8+ T cells (mainly cytotoxic T cells) to recognize (foreign) antigen this reduction in class I expression might lead to reduced visibility of infected cells to T cells and thus might contribute to the tumorigenicity of Ki-MSV-infected cells.

Animals↗
PubMed1989

Regulation of IFN-gamma-induced host cell MHC antigen expression by Kirsten MSV and MLV. II. Effects on class II antigen expression.

We have reported previously that the Kirsten murine sarcoma virus (Ki-MSV), which carries the v-Ki-ras oncogene, prevents the induction of the class II MHC antigen H-2A and reduces the induction of class I MHC antigens by interferon-gamma (IFN-gamma) on C3H10T 1/2 fibroblasts. It is here shown that the abolition by the virus of H-2A expression extends also to class II antigen H-2E and that this is maintained for at least 7 days after IFN treatment. In addition no concentration of IFN-gamma tested, including supra-optimal concentrations for class I antigen expression, induced class II antigens on MSV-infected cells. Thus MSV inhibits the induction by IFN-gamma of class II MHC antigens by a mechanism other than via a change in kinetics of response to, or in the sensitivity of the cells to, IFN. The possibility that transformation by MSV could result in the (selective) outgrowth of cells unresponsive to IFN was refuted by the observation that clones of C3H10T 1/2, when infected with Ki-MSV, expressed no or dramatically reduced levels of H-2A or H-2E. One C3H10T 1/2 clone chosen for high class II expression, when transformed with Ki-MSV, did express low levels of class II antigens at optimal concentrations of IFN-gamma, suggesting that the degree of the reduction of class II expression varies with the cells that are infected. Comparison with mechanisms whereby other viruses inhibit MHC antigen display revealed an interesting possibility: IFN response sequences (IRS) identified in the virus genomes might act in trans to (down) regulate MHC antigen expression. This could be an important mechanism determining the tumourigenicity of, and immune evasion by, Ki-MSV and other viruses.

Animals↗
PubMed1988

Kirsten murine sarcoma virus abolishes interferon gamma-induced class II but not class I major histocompatibility antigen expression in a murine fibroblast line.

The effect of infecting fibroblasts with Kirsten murine sarcoma virus/murine leukemia virus (Ki-MSV/MLV) on constitutive and IFN-gamma-induced H-2 antigen expression was investigated. The fibroblasts used were two established cell lines (C3H10T1/2 and BALB/c3T3) and fresh embryo fibroblasts from C3H mice. Class I antigens were expressed constitutively by BALB/c3T3; infection with MLV, MSV or the two together had little effect on this constitutive expression. Class I antigens (H-2K, H-2D) were strongly induced on all three types of fibroblast by rIFN-gamma, and infection had little effect on this. None of the fibroblasts expressed constitutively detectable levels of class II antigen; however, C3H10T1/2 fibroblasts could be induced for both H-2A and H-2E by IFN-gamma. Infection of C3H10T1/2 with helper-free Ki-MSV, or MSV together with MLV, completely abolished this induction of class II antigens, while infection with MLV alone had little effect, implying that the abolition of class II induction was due to genomic regions of Ki-MSV not shared with Ki-MLV, probably the v-Ki-ras gene.

Animals↗
PubMed1988

Interferons.

Interferon (IFN)-alpha and -beta are produced by virus-infected cells; IFN-gamma is produced as a primary response of T lymphocytes to mitogenic stimulation, IFN-gamma gene activation being brought about by changes in Ca2+ and phosphatidyl inositol metabolism. IFNs act by binding to cell surface receptors and triggering activation of IFN-responsive genes, probably via specific base sequences located in the 5' non-coding region of such genes, resulting in changes in cell function. Important genes activated in this way are the MHC antigen genes; class I induced by all IFNs, class II by IFN-gamma only. This MHC activation may have important consequences for lymphocyte function.

Animals↗
PubMed1988

Role of interferon-gamma in T-cell responses to Semliki Forest virus-infected murine brain cells.

Primary brain cell cultures prepared from newborn C3H mice were infected with Semliki Forest virus (SFV) or treated with a beta-propiolactone-inactivated preparation of SFV (BPL-SFV). The effects of recombinant interferon-gamma (IFN-gamma) treatment on SFV replication, SFV antigen display, major histocompatibility complex (MHC) class I and class II antigen expression, susceptibility to lysis by SFV-specific cytotoxic T lymphocytes (CTL) and the ability to stimulate SFV-specific T lymphocytes to release IFN-gamma were determined. The IFN-gamma treatment prevented replication of SFV, as determined by incorporation of [3H]uridine into SFV-RNA, and reduced expression of SFV antigens on the cell surface, as determined by lysis with antibody and complement or indirect immunofluorescence. BPL-SFV-treated brain cells expressed no SFV antigen detectable by lysis with antibody and complement or indirect immunofluorescence. IFN-gamma increased expression of MHC class I and class II antigens, measured by indirect immunofluorescence, susceptibility to killing by alloreactive T-cell lines and ability to stimulate an allogeneic mixed lymphocyte reaction (MLR). Brain cells infected with SFV or treated with BPL-SFV were susceptible to killing by the CTL. The killing was MHC restricted and neither uninfected nor untreated cells were killed. IFN-gamma treatment prior to SFV infection or BPL-SFV treatment resulted in an augmentation of lysis by the CTL, indicating that even where SFV antigen expression is reduced or present at very low levels, in the context of enhanced MHC class I expression cells remain susceptible to CTL killing. Brain cells treated with BPL-SFV stimulated SFV-specific T cells to release IFN-gamma. Pretreatment of brain cells with IFN-alpha beta or IFN-gamma prior to BPL-SFV treatment markedly increased the ability of the cells to stimulate the SFV-specific T cells to release IFN-gamma. Release of IFN-gamma was MHC restricted and brain cells untreated with BPL-SFV did not stimulate IFN-gamma release. IFN-gamma released by T cells stimulated with BPL-SFV-treated brain cells increased class II MHC expression by brain cells as assessed by indirect immunofluorescence.

Animals↗
PubMed1987

The induction of IFN-gamma production and m-RNAs of interleukin 2 and IFN-gamma by phorbol esters and a calcium ionophore.

Human peripheral blood mononuclear leukocytes were found to produce large amounts of interferon-gamma in response to the calcium ionophore A23187 combined with the phorbol ester mezerein. This effect was synergistic since A23187 and mezerein separately did not induce significant interferon-gamma levels. A23187 plus mezerein induced high levels of interleukin-2 and interferon-gamma mRNAs. The presence of cyclohexamide, which inhibits protein synthesis by greater than 99%, had no effect on the induction by A23187 plus mezerein of mRNA from either gene, indicating that synthesis of proteins such as interleukin-2 is not required for activation of either gene. In addition, using different protocols of stimulation of lymphocytes it was shown that both interleukin-2 and interferon-gamma mRNA steady state levels varied in concert. We conclude that interferon-gamma and interleukin-2 genes are coordinately expressed and activation of transcription of these genes is a primary event of T cell activation independent of production of other proteins.

Calcimycin↗
PubMed1987

Rapid intracellular calcium changes in U937 monocyte cell line: transient increases in response to platelet-activating factor and chemotactic peptide but not interferon-gamma or lipopolysaccharide.

The dye fura-2, a potentially more sensitive successor to quin2 for measuring intracellular free calcium ion concentrations [(Ca2+]i), has been applied here to investigate the possible involvement of early changes in [Ca2+]i in the stimulation of the human monocyte-macrophage-like cell line U937. The calcium ionophores A23187 and ionomycin, known pharmacological stimuli for macrophages, were found to cause sharp rises in [Ca2+]i as expected. Responses analogous to those reported for a murine macrophage cell (J774) were obtained on stimulation of U937 cells with ATP which caused rapid, but transient, increases in [Ca2+]i (from resting levels of about 70 nM to peaks of about 200 mM). In addition to ATP, several agents known to activate macrophages were used as stimuli. In particular, platelet-activating factor (PAF; 1-0-alkyl-2-acetyl-sn-glycero-3-phosphocholine) was found to cause rapid, but transient, increases in [Ca2+]i (from resting levels of about 70 nM to peaks of about 400 nM) even at concentrations as low as 10(-10) M. This contrasts with responses to ATP that were markedly reduced at 10(-6) M compared with 10(-5) M or above, suggesting that PAF is a highly potent stimulus for intracellular calcium mobilization in macrophages. Similar responses were obtained with chemotactic peptide (N-formyl-methionyl-leucyl-phenylalanine). On the other hand, two agents known to be potent activators of macrophages, interferon gamma and lipopolysaccharide, had no rapid effect on [Ca2+]i. This may reflect differences in the kinetics of signal-response coupling or alternatively a different mechanism of action by-passing the need for rapid elevation of [Ca2+]i.

Adenosine Triphosphate↗
PubMed1986

The regulation of gamma-interferon production by interleukins 1 and 2.

Purified interleukins 1 and 2 (IL-1 and IL-2) were used to investigate their role in the production of gamma-interferon (gamma-IFN). Macrophage depletion from human peripheral blood mononuclear leukocytes (PBML) inhibited gamma-IFN production. Addition of purified IL-1 partially restored IFN production of macrophage-depleted PBML induced by three T cell mitogens (phytohemagglutinin, PHA; concanavalin A, con A; and staphylococcal enterotoxin A, SEA), but had no effect on induction of IFN production by undepleted PBML. Therefore endogenous IL-1 production by macrophages is probably one of the mechanisms by which they act as accessory cells for IFN production by lymphocytes. A monoclonal antibody 9.6 which binds to the sheep erythrocyte (E) receptor found on human T cells inhibited IFN production. Addition of IL-2, but not IL-1, was found to reverse this inhibition. Prostaglandin E2, a macrophage product, inhibited gamma-IFN production induced by PHA, Con A, and OKT3 but usually not SEA. This inhibitory effect was reversible by the addition of IL-2 but not IL-1. In the absence of mitogen IL-1 alone rarely induced any IFN production, although some IFN was produced by PBML from a small minority of donors. Without mitogen IL-2 induced IFN production only at very high concentrations and the added presence of IL-1 did not enhance this induction.

Dinoprostone↗
PubMed1986

On the sexual intercourse drawings of Leonardo da Vinci.

Leonardo da Vinci's marvellous anatomical drawings have been praised by both artists and medical historians over the centuries. Specific reference is made here to Leonardo's drawings of the act of sexual intercourse. It is shown that his illustrations are not based purely on original observation. Rather, they are an attempt to illustrate and clarify anatomy and physiology as presented in the textbooks of the time.

Anatomy, Artistic↗
PubMed1986

Gamma-interferon production by human low-density lymphocytes induced by T-cell mitogens.

Low-density lymphocytes prepared by Percoll fractionation of human peripheral blood mononuclear leucocytes were found to produce large amounts of interferon-gamma (IFN-gamma) in response to different T-cell mitogens in the absence of macrophages, whilst higher density lymphocytes were strongly dependent on the presence of macrophages for significant IFN-gamma production. The addition of macrophages to the low-density lymphocytes made little difference to their IFN-gamma production. Subsets of the low-density lymphocytes prepared by rosetting with sheep red blood cells produced markedly less IFN-gamma than did the original population; IFN-gamma production could be largely restored by recombining the two low-density fractions. This suggests that IFN-gamma production by low-density lymphocytes whilst macrophage-independent does require co-operation between different cell types. The low-density lymphocytes were enriched for cells bearing the Leu 11 and OKM1 antigens, and for natural killer cell activity. The rosetting fraction was enriched for OKT3 antigen-bearing cells, and the non-rosetting fraction was enriched for Leu 11, OKM1 antigen-bearing cells. Depletion of B cells (surface Ig-positive) by nylon-wool chromatography had no effect on IFN-gamma production by low-density lymphocytes.

Concanavalin A↗
PubMed1985

Interferon gamma mRNA "superinduction" in human lymphocytes.

Human peripheral blood mononuclear lymphocytes produce interferon gamma (IFN-gamma) in response to stimulation by mitogens. Previous studies on the kinetics of IFN-gamma mRNA production upon mitogen induction, showed that steady-state levels of mRNA increased to a maximum at 12-24 h post-induction after which they declined to levels not detectable by the assay used. We show here that in mitogen induced peripheral blood lymphocytes, inhibition of protein synthesis using three different inhibitors (cycloheximide, puromycin, pactamycin) resulted in an increase in the steady-state levels of IFN-gamma mRNA. The levels of mRNA in cells treated with inhibitor 16 h post-induction were up to 3-fold higher than in untreated cells. Superinduction was possible up to 40 h post-induction after which the steady-state levels of mRNA had declined to limits below detection; IFN-gamma mRNA was not superinduced by cycloheximide in the presence of actinomycin D.

Cells, Cultured↗