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L Takacs

Publications and source records attributed to L Takacs.

At least 19 recordsLinked to original sources
PubMed2000

Human sphingosine kinase: molecular cloning, functional characterization and tissue distribution.

Sphingosine-1-phosphate (SPP), the product of sphingosine kinase, is an important signaling molecule with intra- and extracellular functions. The cDNA for the mouse sphingosine kinase has recently been reported. In this paper we describe the cloning, expression and characterization of the human sphingosine kinase (huSPHK1). Sequence analysis comparison revealed that this kinase is evolutionarily very conserved, having a high degree of homology with the murine enzyme, and presenting several conserved regions with bacteria, yeast, plant, and mammalian proteins. Expressed huSPHK1 cDNA specifically phosphorylates D-erythro-sphingosine and, to a lesser extent, D, L-erythro-dihydrosphingosine, and not at all the 'threo' isoforms of dihydrosphingosine; hydroxy-ceramide or non-hydroxy-ceramide; diacylglycerol (DAG); phosphatidylinositol (PI); phosphatidylinositol-4-phosphate (PIP); or phosphatidylinositol-4, 5-bisphosphate (PIP(2)). huSPHK1 shows typical Michaelis-Menten kinetics (V(max)=56microM and K(m)=5microM). The kinase is inhibited by D,L-threo-dihydrosphingosine (K(i)=3microM), and by N, N-dimethyl-sphingosine (K(i)=5microM). Northern blots indicate highest expression in adult lung and spleen, followed by peripheral blood leukocyte, thymus and kidney, respectively. It is also expressed in brain and heart. In addition, database searches with the stSG2854 sequence indicate that huSPHK1 is also expressed in endothelial cells, retinal pigment epithelium, and senescent fibroblasts.

Amino Acid Sequence↗
PubMed1994

An alternative Fc gamma-receptor ligand: potential role in T-cell development.

Fetal pre-T cells express low-affinity receptors for IgG (Fc gamma R) at a developmental stage prior to the rearrangement and expression of immunoglobulin genes. The present studies investigated the possible functional significance of Fc gamma R on fetal pre-T cells. Between 13 and 17 days of fetal development a subpopulation of T-cell receptor-, Thy-1+ thymocytes express for gamma R. The same cells contain mRNA for several forms of Fc gamma R (Fc gamma RII beta 1, beta 2, and Fc gamma RIII). Concurrently, a Pgp-1-, Thy-1-, surface-immunoglobulin- fetal thymic cell binds recombinant soluble Fc gamma R. In principle this cell can interact with the pre-T cells through this counter-receptor. To test this possibility anti-Fc gamma RII/III antibody (2.4G2) was injected into pregnant mice and then into their offspring for 6 wk postpartum. The injected antibody induced a slight increase in the proportion of CD4 or CD8 single-positive, alpha/beta T cells in the thymus. However, in fetal thymic cultures in the presence of 2.4G2 or the recombinant soluble Fc gamma R there was an accelerated differentiation of thymocytes to single-positive, CD3-bright, heat-stable antigen-dull, alpha/beta T cells. These experiments show that Fc gamma Rs are present on pre-T cells during early fetal thymic development, and that a non-IgG ligand of the Fc gamma R is expressed concurrently on Thy- fetal thymocytes. Furthermore, the presumed interaction of Fc gamma R and the alternative ligand(s) influences T-cell development. IgG binding could be an adapted function of Fc gamma Rs, and, as shown for many members of the Ig super family, these receptors may have originally served as cell-cell recognition/interaction molecules required for hematopoietic development.

Animals↗
PubMed1993

Inducible accessory function of a macrophage cell line.

Costimulatory molecules in addition to occupancy of the T-cell antigen receptor, are required to induce T-cell proliferation. Previous work suggested that membrane molecules responsible for costimulatory activity were not constitutively expressed on the antigen presenting cell (APC) surface. In the present study, we have identified a cloned macrophage cell line (FLJ2) with inducible APC function. The unactivated FLJ2 line could not induce T-cell proliferation. FLJ2 could present alloantigen, and stimulate proliferation of either a T-cell clone or normal resting T cells following activation with IFN gamma or unexpectedly with lipopolysaccharide (LPS)-Activated FLJ2 cells could be fixed and APC function was preserved. The relevant inducible molecules required for APC function appeared distinct from Ia and IL1. The expression of ICAM-1 and LFA-1 was increased during activation and anti-LFA-1 antibody blocked APC function. This suggests that one important feature of the activation process may be improvement of cellular adhesion.

Animals↗
PubMed1991

CD8 gamma delta cells: presence in the adult rat thymus and generation in vitro from CD4-/CD8- thymocytes in the presence of interleukin 2.

Three to fifteen percent of peripheral T cells in adults express the recently described gamma delta T-cell antigen receptor (TcR) heterodimer. A small subpopulation of gamma delta cells express the CD8 accessory molecule. In this study, we analyzed the potential of highly purified CD4-/CD8-, double negative (DN) rat precursor thymocytes to give rise to gamma delta cells. We observed that in the presence of interleukin 2 (IL-2) and concanavalin A (ConA), both DN and CD8 cells expressing the gamma delta TcR were generated in vitro. We then examined the rat thymus for these cells and confirmed the presence of a previously undescribed CD8 TcR-alpha beta- subset in the rat thymus, expressing high levels of TcR-gamma and delta messages with no detectable TcR-alpha transcripts, similar to the cells generated in vitro in the presence of IL-2 and ConA.

Animals↗
PubMed1990

A role for cytokines in antigen presentation: IL-1 and IL-4 induce accessory functions of antigen-presenting cells.

Fixation of APC with 1-ethyl-3-(3-dimethylamino-propyl)carbodiimide (ECDI) eliminates their ability to stimulate proliferation of alloreactive T cells or the D10 T cell clone, although a partial response, IL-4 production, was measured. However, if APC were activated before fixation, they could be ECDI-fixed and retain the ability to induce T cell proliferation. IL-1, IL-4 or LPS were capable of activating APC in this way, whereas IFN-gamma was not. This activation step occurred in 6 h, required protein synthesis, and was distinct from increases in Ia or IL-1. This suggests resting APC lack structures that are essential for inducing T cell proliferation.

Animals↗
PubMed1990

Growth of immature (double negative) rat thymocytes in the presence of IL-1.

It is unclear which growth factors, if any, are involved in the growth and differentiation of immature T cells in the thymus. Because IL-1 has been previously implicated in thymocyte proliferation, we examined the effects of IL-1 on precursor thymocytes, the CD4-CD8- or double-negative (DN) cells. We show that IL-1 (together with Con A) is a growth factor for DN, TCR- alpha beta-cells in vitro. After 5 days of culture in IL-1 and Con A, a number of phenotypic changes were observed and two subsets of DN cells were distinguished. One subset expressed full length TCR-alpha and -beta mRNA and surface alpha beta TCR, the other expressed low levels of full length TCR-gamma together with high levels of full length TCR-delta mRNA. Thus, DN cells are induced by IL-1 and Con A to proliferate and express TCR without parallel acquisition of CD4 or CD8 markers. These data suggest that IL-1 drives early steps of intrathymic T cell differentiation.

Animals↗
PubMed1990

Direct evidence for an intracellular role for tumor necrosis factor-alpha 1. Microinjection of tumor necrosis factor kills target cells.

TNF-alpha is a small peptide cytokine produced primarily by activated macrophages. One of the many biologic activities of TNF is the killing of diverse types of tumor cells. We considered the possibility that killing was mediated by TNF itself at an intracellular site, subsequent to receptor-mediated endocytosis. To test this hypothesis, we microinjected TNF into various murine normal cells and cell lines, some of which were killed by TNF given by the usual extracellular route, and others that were not. Cytotoxic effects of microinjected TNF were observed in several cell types 2 to 4 h after injection. L929 fibroblasts were killed by either extracellular or intracellular TNF. A TNF-resistant subline of L929 was insensitive to either extracellular or intracellular TNF. L6 fibroblasts were found to be resistant to high doses of TNF given either extracellularly or microinjected. Normal macrophages and the J774 macrophage-like cell line were not killed by extracellular TNF, but were rapidly killed by microinjected TNF. Thus, TNF, an extracellular peptide ligand, has an intracellular activity, suggesting that internalization of this ligand may have important intracellular biochemical roles.

Animals↗
PubMed1987

IL 1 induction by murine T cell clones: detection of an IL 1-inducing lymphokine.

T cell activation is widely believed to depend on interleukin 1 (IL 1) provided by antigen (Ag)-presenting cells (APC). Because IL 1 is not a constitutive product of APC, we examined the features of its production during the interaction of murine T cell clones and APC. We observed that IL 1 was detectable in supernatants of most myoglobin-specific T cell clones grown with APC and Ag. Two of these T cell clones induced exceptionally high levels of IL 1 in their supernatants, and these same clones demonstrated the unusual restriction to I-Ek, which is a low responder type for sperm whale myoglobin. One of these clones was characterized additionally as to the mechanism of IL 1 induction. This clone rapidly stimulated IL 1 production in the APC population (detectable at 4 hr of co-culture) or in macrophages (M phi) or a M phi-like cell line. IL 1 induction was Ag dependent and H-2 restricted. Induction was radioresistant, both on the part of the T cell and of the IL 1 producer. The IL 1-induction process was attributable to a lymphokine produced by the T cell clone. This lymphokine was distinct from IFN-gamma, TNF and CSF-1 and may account for a principal mechanism of T----APC signalling. The induced IL 1 was the same in size, co-mitogenicity, and pyrogenicity as lipopolysaccharide-induced IL 1.

Animals↗
PubMed1987

Cortical thymocyte differentiation in thymomas: an immunohistologic analysis of the pathologic microenvironment.

Four monoclonal antibodies (BH11, T2/30, AG3, and BC3) were produced against different epithelial components of the normal thymus. An immunohistologic study was performed on 13 thymomas by the use of these and other stromal and lymphocyte-specific reagents. The aim of this study was to find possible relationships between the proliferating thymoma epithelial cell type and the T cell composition of thymomas. Our results indicate that cortical T cell differentiation is present in thymomas, and that this differentiation is induced in the absence of detectable levels of MHC class II antigens on the epithelial component in most cases. The role of the MHC class II antigens cannot be excluded, however, because these antigens were always present on macrophages. Analysis of the selected group of thymomas, each of which contained epithelial cells homogeneously stained by at least one of the described monoclonal antibodies, showed that the cortical type T cell inducer capacity of thymomas is independent of the epithelial type predominant in the tumor.

Antibodies, Monoclonal↗
PubMed1987

The ontogeny of the interleukin 2 receptor expression and of the interleukin 2 responsiveness in the rat thymus.

The ontogeny of the interleukin 2 receptor (IL 2 R) expression and of the IL 2 responsiveness has been investigated in the rat thymus. In tissue sections, IL 2 R-bearing cells were first detected at day 16 of gestation using the anti-IL 2 R mAb ART-18. In contrast to mice, IL 2 R-bearing cells of the rat are localized mainly in the thymic medulla from the first day of the corticomedullary compartimentalization, and not in the cortex. They are found in regions with a high expression of MHC class II antigens. The proportion of IL 2 R-bearing cells increases during gestation, reaches a peak at the first day after birth and declines to the adult level in the following weeks. The appearance of medullary localized IL 2 R-bearing cells is paralleled with the capacity of the thymocytes to proliferate in response to IL 2 without any additional stimuli.

Animals↗
PubMed1986

T cell clone producing an IL 1-like activity after stimulation by antigen-presenting B cells.

We have analyzed the involvement of IL 1 in a cellular interaction during which murine B cells serve as antigen-presenting cells for a T cell clone (D10.G4.1). This T cell clone was chosen for study because it is highly dependent on exogenous IL 1 for concanavalin A (or anti-receptor antibody)-induced proliferation. We observed that B cells presented either self I-Ak plus nominal antigen or allogeneic I-Ab, and consequently induced proliferation of this T cell clone without any requirement for exogenous IL 1. After an overnight co-culture with allogenic B cells, we detected an IL 1-like activity in lysates of the cell mixture, but were unable to detect a similar activity in the culture medium. This IL 1-like activity was induced in a MHC-restricted manner. We determined that this intracellular IL 1-like activity was derived from the D10.G4.1-responding T cells, rather than from the antigen-presenting B cells. Moreover, we were unable to detect an IL 1-like activity in murine B cells after a variety of stimuli including LPS, anti-Ig, activated T cell supernatants, or combinations of these stimuli. Hybridization of cytoplasmic RNA with an oligonucleotide probe for human IL 1-alpha confirmed the T cell source of the biological activity. The IL 1-like factor derived from the cell culture mixture lysate showed two broad peaks of activity after gel filtration, one in the 10,000 to 20,000 dalton range and the second in the 35,000 to 45,000 dalton range. This first description of IL 1 activity produced by a T cell may introduce a new element to the early events leading to T cell activation and proliferation.

Animals↗
PubMed1986

The p150,95 molecule is a marker of human mononuclear phagocytes: comparison with expression of class II molecules.

A new monoclonal antibody (mAb), named 3.9, is described that is specific for the p150,95 molecule, a member of the LFA-1, CR3, p150,95 family of human leukocyte differentiation antigens. The LFA-1 molecule participates in a variety of T cell interactions and the CR3 molecule is the receptor for the complement component iC3b, but little is known about the p150,95 molecule. Here we show that the expression of p150,95 is confined to myeloid cells. mAb 3.9 reacts variably with neutrophils, more strongly with monocytes and is most strongly expressed on tissue macrophages. Using this mAb and others, we have examined the heterogeneity of tissue macrophages. Cells such as Langerhans' cells, dendritic reticulum cells and osteoclasts failed to react with these mAb and thus, probably do not belong to the mononuclear phagocyte lineage. Using a new double-labeling technique, we investigated lymphoid tissue for dendritic cells bearing class II molecules which might function in interactions with T cells. In T cell areas macrophages expressing class II markers were seen but there was no evidence for other types of dendritic or interdigitating cells which expressed class II molecules but not macrophage epitopes. The conclusion from this survey was that the most prominent cell with dendritic morphology found in the T cell areas of lymphoid tissue was a macrophage.

Antibodies, Monoclonal↗
PubMed1986

Cells reacting with the monoclonal anti-IL-2 receptor antibody AMT-13 in the regenerating thymus of irradiated mice.

The proportion and anatomical localization in murine thymus of T cell subpopulations, including those which are defined by the monoclonal anti-interleukin 2 (anti-IL-2) receptor antibody AMT-13, were studied by flow cytofluorometry and by immunohistochemical methods, both in irradiated and in normal mice. As a consequence of irradiation the proportion of AMT-13 positive cells and that of Lyt-1 positive cells were markedly enhanced, while the proportion of Lyt-2 positive cells was reduced. The vast majority of the AMT-13 positive cells both in normal and in irradiated thymi were located in the subcapsular area of the thymic cortex, whereas the irradiation resistant Lyt-1 positive cells were located in the medulla. These findings are compatible with the view that, similar to the developing thymus in the mouse embryo, in the regenerating adult thymus, AMT-13+ cells include the activated pro-thymocytes that repopulate the irradiated thymus.

Animals↗
PubMed1985

Dynamics of T cells of L3T4 and Ly 2 phenotype within granulomas in murine listeriosis.

Monoclonal antibodies anti-Ly 1, anti-Ly 2 and GK1.5 were applied to determine phenotypes of T cells within granulomas formed as a result of infection of mice with the facultative intracellular bacterium Listeria monocytogenes. Early in granuloma formation, equal numbers of Ly 1+, Ly 2+ and L3T4+ cells were found, T cells of different phenotypes being evenly distributed over the lesions. In mature granulomas, numbers of Ly 1+ and L3T4+ cells about doubled as compared to incipient granulomas, Ly 2+ cells, however, remained constant. Whereas Ly 1+ and L3T4+ cells within mature granulomas still were evenly distributed, Ly 2+ cells were predominantly localized in the periphery of the lesions. The data indicate that both, specific Ly 2+ and L3T4+ T cells, display characteristic dynamics within granulomas: Ly 2+ T cells which most likely mature from Ly 1+2+ T cells over time locate to the periphery. Concomitantly, L3T4+ T cells are enriched maintaining their distribution all over the lesions.

Animals↗
PubMed1985

Immunohistochemical localization of cells reacting with monoclonal antibodies directed against the interleukin-2 receptor of murine, rat and human origin.

Recently, species specific monoclonal antibodies, directed against the interleukin-2 (IL-2) receptor of murine, rat and human origin, have been produced. In this study we demonstrate with immunohistological methods that cells reacting with these antibodies are present in normal primary and secondary lymphatic organs. The cells are exclusively localized in T cell-dependent areas, and their number increased as a result of immunization.

Animals↗