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Biomedical subjects

A Kelso

Publications and source records attributed to A Kelso.

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

The myelopoietic inducing potential of mouse thymic stromal cells.

The thymus has generally been considered as being solely involved in T cell maturation. In this study we have demonstrated that mouse thymic stroma can also support myelopoiesis. Bone marrow from mice treated with 5-fluorouracil was depleted of cells expressing Mac-1, CD4, and CD8 and incubated on lymphocyte-free monolayer cultures of adherent thymic stromal cells. After 7 days there was a marked increase in nonadherent cells, the majority of which were Mac-1+, FcR+, and HSA+. These proliferating bone marrow cells also expressed markers (MTS 17 and MTS 37) found on thymic stromal cells. Such cells were not found in thymic cultures alone, in bone marrow cultured alone, or on control adherent cell monolayers. Supernatants from the cultured thymic stroma, however, were able to induce these cell types in the bone marrow precursor population. Incubation of normal thymocytes with a monolayer of these in vitro cultivated Mac-1+, MTS 17+, MTS 37+ myeloid cells leads to selective phagocytosis of CD4+ CD8+ cells. Hence, this study demonstrates that the thymic adherent cells can induce myelopoiesis in bone marrow-derived precursor cells and provide a form of self-renewal for at least one population of thymic stromal cells. Furthermore, these induced cells are capable of selective phagocytosis of CD4+ CD8+ thymocytes and may provide one mechanism for the selective removal of such cells from the thymus.

Animals↗
PubMed1989

GM-CSF expression is preferential to multi-CSF (IL-3) expression in murine T lymphocyte clones.

The expression of the lymphokines GM-CSF and Multi-CSF (IL-3) has been studied in three IL-2-dependent CD4+ T lymphocyte clones. By contrast with the widely held view that lymphokine genes are coordinately expressed, the present study revealed a marked preference for GM-CSF compared with Multi-CSF expression. Preferential expression of GM-CSF was evident in a number of situations: early after stimulation via the T cell antigen receptor; in a proportion of low-producing cells of a clone; and in response to IL-2. There was a clear hierarchy of the three clones studied, each being ranked in the same order in all situations, suggesting that a common mechanism underlies each phenomenon. The possibility that the GM-CSF gene is responsive to lower doses of intercellular signal than the Multi-CSF gene was rendered unlikely, since in only one clone was GM-CSF preferentially expressed at low doses of stimulus. Since GM-CSF expression occurred more rapidly after stimulation, the possibility that Multi-CSF expression is dependent upon that of GM-CSF was considered. However, GM-CSF production was neither necessary nor sufficient for Multi-CSF expression: A retroviral construct expressing a GM-CSF cDNA was introduced into one of the clones, leading to constitutive GM-CSF expression, but Multi-CSF expression was not induced. The possibility is discussed that Multi-CSF expression is dependent on transcriptional activation of the GM-CSF locus and that positive feedback occurs between these two tightly linked genes at the chromosomal level.

Animals↗
PubMed1989

Differential inhibition by cyclosporin A reveals two pathways for activation of lymphokine synthesis in T cells.

Two pathways for the activation of lymphokine synthesis in murine T cell clones and polyclonal T cell blast populations were identified. One was induced by ligands of the T cell receptor (TCR) and led to high production of GM-CSF, IFN-gamma, and IL-3. The other was induced by IL-2 and led to production of lower levels of GM-CSF and IFN-gamma with relatively little IL-3 synthesis. Cyclosporin A (CsA) markedly inhibited TCR-independent production of lymphokine mRNA and protein at concentrations where IL-2-dependent stimulation of lymphokine production and proliferation was unaffected. Stimulation of lymphokine synthesis by phorbol myristate acetate (PMA) and the Ca2+ ionophore ionomycin, or by ionomycin alone, mimicked the TCR-dependent response. PMA on its own was a preferential stimulus for GM-CSF production, but, whereas CsA did not inhibit PMA stimulation of polyclonal T cell blasts, T cell clones displayed a biphasic response in which CsA only inhibited stimulation by high PMA concentrations. The data suggest that Ca2(+)-independent (CsA-resistant) T cell activation induces synthesis of GM-CSF and IFN-gamma but is a poor stimulus for IL-3 production. On the other hand, when Ca2(+)-dependent (CsA-sensitive) pathways are activated by TCR binding or by a Ca2+ ionophore, production of high levels of all three lymphokines can be induced.

Animals↗
PubMed1988

The role of CD4 in antigen-independent activation of isolated single T lymphocytes.

The membrane molecule CD4 (L3T4) is thought to facilitate activation of Class II H-2-restricted T cells by binding to Ia determinants on antigen-presenting cells. Recent reports suggest that CD4 can also contribute to antigen-independent activation by anti-T cell receptor (TCR) antibodies. An assay which measures the secretion of two lymphokines, granulocyte-macrophage colony-stimulating factor and interleukin 3 (IL-3), by single T cells activated with an anti-TCR antibody, F23.1, was used to analyze the effects of anti-CD4 antibodies on antigen-independent T cell activation. Single cells of a CD4+F23.1+ clone were micromanipulated into wells to which F23.1 had been immobilized, and their lymphokine secretion was measured 24 hr later. The frequency of lymphokine-secreting cells was consistently reduced up to 10-fold in the presence of soluble anti-CD4 antibody (GK1.5) but only up to 2.5-fold by an antibody to the cell adhesion molecule, LFA-1. In both bulk and single-cell cultures, responses to suboptimal concentrations of F23.1 were more susceptible to inhibition by GK1.5 than responses to optimal F23.1. The failure of GK1.5 to inhibit IL-2-stimulated lymphokine synthesis in bulk cultures suggested that CD4 ligation did not deliver a negative signal to the clone. By contrast, when either anti-CD4 or anti-LFA-1 was immobilized on the same surface as F23.1, the frequency of lymphokine-secreting cells could be increased up to 10-fold. It is concluded that anti-CD4 antibodies can act directly on the responding T cell to affect TCR-dependent activation, in the absence of interaction with antigen-presenting cells or any other cell type.

Antibodies, Monoclonal↗
PubMed1988

Production of two hemopoietic growth factors is differentially regulated in single T lymphocytes activated with an anti-T cell receptor antibody.

A method has been developed to measure the production by single activated T lymphocytes of two hemopoietic growth factors, granulocyte-macrophage CSF (GM-CSF) and multipotential CSF (multi-CSF or IL-3). When individual cells of the L3T4 (CD4)+ F23.1+ T cell clone E9.D4 were transferred by micromanipulation into wells coated with the monoclonal anti-T cell receptor antibody F23.1, up to 90% of cells produced CSF as detected by CSF-dependent hemopoietic cell lines. Production occurred in the absence of proliferation and did not require the addition of accessory cells or IL-2. Both the frequency of CSF-producing cells and the average production per positive cell depended on the density of the immobilized stimulating ligand, indicating that the response of each cell is not an all-or-none phenomenon but varies with the strength of stimulation. Individual cells of the clone varied over a 100-fold range in their total CSF titer with a mean value of about 0.05 U/cell. They also varied in their relative production of GM-CSF and multi-CSF. Thus, low producing cells secreted only GM-CSF whereas high producing cells also secreted multi-CSF. The failure of low producing cells to secrete multi-CSF was not genetically based since such cells could give rise to progeny that synthesized multi-CSF. These results suggest that the synthesis of these two lymphokines can be differentially regulated at the level of the single cell.

Antibodies, Monoclonal↗
PubMed1988

Coexpression of granulocyte-macrophage colony-stimulating factor, gamma interferon, and interleukins 3 and 4 is random in murine alloreactive T-lymphocyte clones.

Lymphokine gene expression was examined in a panel of 116 short-term murine T-lymphocyte clones derived by single-cell micromanipulation from allogeneic mixed leukocyte cultures. About 30% of clonable T cells, including both CD4+ CD8- and CD4- CD8+ cells, could be expanded for assay at an average of 22 days after cloning. By RNA blot-hybridization analysis, most clones (85-96%) expressed detectable granulocyte-macrophage colony-stimulating factor, interleukin 3, and gamma interferon mRNAs, and 11% expressed interleukin 4 mRNA. Although no differences were noted between CD4+ and CD8+ clones in the combinations of lymphokines produced, CD4+ clones on average transcribed and secreted higher levels. When the frequencies of coexpression of any pair of lymphokine mRNAs were determined, all were found to correspond to the values predicted for random assortment of the individual frequencies. For example, among 13 interleukin 4-positive clones, 11 also transcribed gamma interferon, giving the frequency of double-positive clones expected for random association (9.6% versus 10.8%). Therefore, expression of the four lymphokine genes segregated independently among the clones and did not allow the division of T cells into subsets with distinct patterns of lymphokine synthesis.

Animals↗
PubMed1988

Production of colony-stimulating factors (CSFs) during infection: separate determinations of macrophage-, granulocyte-, granulocyte-macrophage-, and multi-CSFs.

After infection of mice with Listeria monocytogenes, elevated levels of colony-stimulating factors (CSFs) in the serum were quantitated by six different assays: ability to stimulate colony formation, the proliferation of 2 suspension of bone marrow cells (both measuring total colony-stimulating activity), a radioimmunoassay for macrophage-CSF (CSF-1), the WEHI-3B differentiation assay for granulocyte-CSF, and proliferation of 32D-c1-3 and FDC-P1 cell lines (specific for multi-CSF and either multi- or granulocyte-macrophage-CSFs, respectively). The great bulk of serum colony-stimulating activity represented macrophage- and granulocyte-CSFs, with small but measurable amounts of granulocyte-macrophage-CSF. The degree of elevation of serum CSF depended on the infecting dose used and the numbers of bacteria growing in the spleens and livers of the two mouse strains compared, i.e., L. monocytogenes-resistant C57BL/10 and susceptible BALB/cJ. The increase in serum CSFs occurred before the peak in bone marrow granulocyte-macrophage progenitors and before the reduction in bacterial numbers which follows the onset of specific cell-mediated immunity.

Animals↗
PubMed1988

Interleukin 2 inhibitor in synovial fluid.

Since evidence for the presence of IL-2 activity in rheumatoid synovial fluid is conflicting, we have assayed IL-2 activity in synovial fluid from patients with rheumatoid arthritis (RA) and other articular diseases (OAD). Using the IL-2-dependent murine T cell line CTLL, IL-2 activity was not demonstrable in synovial fluid tested at concentrations ranging from 50% to 0.02%. There was an inhibitory effect on IL-2 activity in the bioassay of synovial fluid from 16 of the 22 patients with RA and 15 of the 16 with OAD. This inhibitory activity was heat-labile, precipitable by ammonium sulphate, reversible with excess IL-2 and was not significantly altered by preincubation of synovial fluid with CTLL. The mean inhibitory activity of synovial fluid from patients with RA was significantly reduced in comparison with that of synovial fluid from patients with OAD. Sera also had an inhibitory effect on IL-2 activity; however sera from patients with RA were less inhibitory than control sera but were more inhibitory than sera from patients with systemic lupus erythematosus. The deficiency in synovial fluid of an inhibitor of IL-2 activity may be relevant to the pathogenesis of RA.

Adult↗
PubMed1987

Molecular cloning and expression of cDNA encoding a murine myeloid leukaemia inhibitory factor (LIF).

Leukaemia inhibitory factor (LIF) can induce macrophage differentiation in M1 murine myeloid leukaemic cells and suppress their proliferation in vitro. It does not stimulate the proliferation of normal progenitor cells and is apparently distinct from known colony-stimulating factors. We have used oligo-nucleotides complementary to partial amino acid sequence of LIF to isolate a LIF clone from a T lymphocyte cDNA library. When this cDNA was coupled to a yeast expression vector (YEpsec1) and introduced into yeast cells, a molecule with the biological properties characteristic of native LIF was secreted into the growth medium. The amino acid sequence of LIF established it to be a unique molecular entity, distinct from the other known haemopoietic growth factors. Since LIF is encoded by a unique gene, two biochemically separable forms of LIF probably represent post-transcriptional or posttranslational variants of the same gene product. In contrast to several other haemopoietic regulators, the 0.8- to 1-kb LIF mRNA was expressed constitutively in two murine T lymphocyte cell lines examined, and its abundance was not enhanced by stimulation with concanavalin A. Cloning, sequencing and expressing LIF has resolved several discrepancies in the literature concerning the identity of factors capable of inducing differentiation of murine myeloid leukaemic cells in vitro.

Amino Acid Sequence↗
PubMed1987

Transgenic mice expressing a hemopoietic growth factor gene (GM-CSF) develop accumulations of macrophages, blindness, and a fatal syndrome of tissue damage.

Transgenic mice carrying the murine granulocyte-macrophage colony stimulating factor (GM-CSF) gene expressed from a retroviral promoter exhibit elevated levels of GM-CSF in the serum, urine, peritoneal cavity, and eye. The eyes of transgenic mice are opaque, contain accumulations of macrophages, and develop retinal damage. Similarly, lesions containing macrophages develop in striated muscle. The mice also display an accumulation of large, often multinucleate, activated macrophages in the peritoneal and pleural cavities. The transgene is transcribed in peritoneal cells, as well as in eyes and infiltrated striated muscle. A high proportion of transgenic mice die with muscle wasting when aged 2-4 months, possibly because of macrophage activation resulting from the high levels of GM-CSF.

Animals↗
PubMed1987

Expression of genes transferred to haemopoietic stem cells by recombinant retroviruses.

We have compared several recombinant retroviruses carrying the selective marker NeoR for gene delivery to murine haemopoietic stem cells. Provirus content and expression was assessed in animals reconstituted with infected bone marrow cells. With viruses bearing only a NeoR gene, viral RNA was readily detectable both in spleen colonies and in the haemopoietic tissues of long-term reconstituted mice. Thus, the progeny of infected primitive multipotential cells are competent to express integrated proviruses. The level of expression was significantly greater for proviruses carrying a modified long terminal repeat in which the Moloney enhancer had been replaced with that from the myeloproliferative sarcoma virus. With viruses bearing the c-myc gene in addition to NeoR, however, no viral RNA could be detected in spleen colonies harbouring proviral inserts, even though these viruses are expressed in vitro within haemopoietic cells. The implications of these results for gene transfer to haemopoietic stem cells are discussed.

Animals↗
PubMed1986

An assay for colony-stimulating factor (CSF) production by single T lymphocytes: estimation of the frequency of cells producing granulocyte-macrophage CSF and multi-lineage CSF within a T lymphocyte clone.

The frequency of cells producing hemopoietic colony-stimulating factors (CSF) in a murine T lymphocyte clone has been determined by using a simple microassay that does not require clonal expansion or the addition of accessory cells. When stimulated with concanavalin A (Con A), the clone LB3 produced both granulocyte-macrophage CSF (GM-CSF) and multi-lineage CSF (Multi-CSF), which could be detected by using the cell line FDC-P1, whose proliferation is dependent on the presence of either of these factors. Limiting dilution analysis of Con A-stimulated LB3 cells indicated a requirement for cell-cell contact for optimal production of CSF, which could be bypassed by preincubation of the cells at high density with Con A for 4 hr before dilution in the assay. Limiting dilution estimates of the frequency of CSF-producing cells among Con A-pretreated LB3 cells ranged from 20 to 50%. Direct measurement of CSF production by single Con A-pretreated cells isolated by micromanipulation revealed that 10 to 20% could secrete detectable CSF. However, when isolated Con A-pretreated two-cell and three-cell aggregates were assayed, 50 to 99% were positive, indicating that 30 to 80% of the cells in the aggregates secreted CSF. Assay of the supernatants from single cells and two-cell aggregates on both FDC-P1 cells and another cell line, 32D c13, which responds only to Multi-CSF, demonstrated that many cells produced GM-CSF only, and others varied in the relative quantities of GM-CSF and Multi-CSF produced.

Animals↗
PubMed1986

Independent regulation of granulocyte-macrophage colony-stimulating factor and multi-lineage colony-stimulating factor production in T lymphocyte clones.

When murine T lymphocyte clones were cultured with purified recombinant IL 2, a dose-dependent increase in the production of granulocyte-macrophage colony-stimulating factor (GM-CSF) was observed. Whereas these clones produced both GM-CSF and multi-lineage CSF (multi-CSF) when cultured with concanavalin A, IL 2 induced the production of GM-CSF in the virtual absence of detectable multi-CSF. In addition, IL 2 synergistically enhanced the production of both GM-CSF and multi-CSF by some antigen- or Con-A-stimulated clones. Like Con-A-induced CSF production, GM-CSF production in the presence of IL 2 required protein synthesis but could occur in the absence of proliferation by the clone. Analysis of dose-response curves for stimulation of CSF production by Con A in the presence and absence of IL 2 suggested that Con A and IL 2 activated GM-CSF synthesis by different mechanisms. These results indicate that the coordinate production of two factors by a single T cell clone stimulated with Con A can be dissociated when the clone is stimulated with IL 2.

Animals↗
PubMed1985

Clonal heterogeneity in colony stimulating factor production by murine T lymphocytes.

A panel of 55 alloreactive murine T-lymphocyte clones was screened for the production of granulocyte-macrophage colony stimulating factor (GM-CSF), multilineage CSF (multi-CSF), human-active eosinophil CSF (human-active EO-CSF), and interleukin 2 (IL-2) in response to stimulation with the lectin concanavalin A. Many clones were also characterized for cytolytic specificity and expression of the T-cell antigen receptor-associated surface markers Lyt-2 and L3T4, which reflect their specificity for Class I (H-2K, H-2D) or Class II (H-2l, Mls) histocompatibility antigens, respectively. Eighty percent of the clones secreted detectable quantities of at least one of the four factors measured. Of the factor-producing clones, all appeared to secrete GM-CSF and half also secreted multi-CSF. A subpopulation of multi-CSF producers also released human-active EO-CSF. More than half of the factor-producing clones secreted detectable IL-2; whereas the IL-2-producing clones included some that did not secrete multi-CSF, IL-2 production was always associated with concomitant synthesis of GM-CSF. Comparison of the range and quantities of factors secreted by Lyt-2+ and L3T4+ clones indicated that more L3T4+ clones produced measurable titers of the four factors; on average, this group also secreted 10- to 100-fold higher titers of both the hemopoietic regulators and IL-2 than Lyt-2+ clones. Cells of the L3T4+ phenotype would therefore be expected to account for the majority of CSF and IL-2 secretion by polyclonal populations of activated T lymphocytes.

Animals↗
PubMed1985

Stimulator requirements for primed alloreactive T cells: macrophages and dendritic cells activate T cells across all genetic disparities.

The cellular requirements for stimulating primed alloreactive T cells have been investigated. In vitro-primed secondary alloreactive cells, long-term lines, and Ly 1+2- noncytolytic clones which reacted with allo-H-2K, D, or Mls (M locus) antigens were tested. The data indicated that a specialized antigen-presenting cell such as a macrophage or a dendritic cell was required for stimulating primed alloreactive cells across all the genetic disparities tested. B and T lymphocytes were ineffective stimulators. The stimulator requirement for secondary and Ly 1+2- clone responses was heterogeneous, since both macrophages and dendritic cells were effective stimulators. Thus, the allostimulator requirement for inducing proliferation and mediator secretion by the primed T-cell populations closely paralleled the requirement for stimulating unprimed populations. The only exception found was the peritoneal washout population, which did not stimulate a primary response but did stimulate secondary responses. The failure of peritoneal macrophages to stimulate a primary response was shown to be due to an inhibitory pathway which did not occur when the responding population was alloantigen primed.

Animals↗