Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:2.7.7.49 (reverse transcriptase)
31,746 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The mesothelium is a flat epithelial lining of serous cavities that could gate the traffic of molecules and cells between the circulation and these body compartments. The present study was designed to elucidate the capacity of mesothelial cells to express adhesion molecules and chemoattractant cytokines, two fundamental mechanisms of regulation of leukocyte recruitment. Cultured human mesothelial cells express appreciable levels of intercellular adhesion molecule 1 (ICAM-1) and vascular cell adhesion molecule 1 (VCAM-1), and these were increased by in vitro exposure to tumor necrosis factor (TNF), interferon gamma (IFN-gamma), or TNF and IFN-gamma. Interleukin 1 (IL-1) was a less consistent stimulus for adhesion molecule expression in vitro. Unlike endothelial cells, used as a reference cell population, resting or stimulated mesothelial cells did not express E-selectin and ICAM-2, as assessed by flow cytometry. Analysis of VCAM-1 mRNA by reverse transcriptase and polymerase chain reaction using appropriate primers revealed that mesothelial cells expressed both the seven- and the six-Ig domain transcripts, with predominance of the longer species. Monocytes bound appreciably to "resting" and, to a greater extent, to stimulated mesothelial cells. Monocytes exposed to IFN-gamma and lipopolysaccharide, used as prototypic activation signals, showed increased capacity to bind mesothelial cells. Anti-CD18 monoclonal antibody significantly inhibited binding of monocytes to mesothelial cells, and this blocking effect was amplified by anti-very late antigen 4. Mesothelial cells were able to express the chemotactic cytokines IL-8 and monocyte chemotactic protein 1 at the mRNA and protein levels. These results indicate that mesothelial cells can express a set of adhesion molecules (ICAM-1 and VCAM-1) overlapping with, but distinct from, that expressed in vascular endothelium (ICAM-1, ICAM-2, VCAM-1, E-selectin), and that these are functionally relevant for interacting with mononuclear phagocytes. The regulated expression of adhesion molecules and chemotactic cytokines by mesothelial cells is probably important in inflammatory and immune reactions that involve serous cavities, such as the long-known macrophage appearance and disappearance reactions.
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PMID:Expression of adhesion molecules and chemotactic cytokines in cultured human mesothelial cells. 138 76

We studied the effect of human immunodeficiency virus (HIV) infection on the surface-marker expression of the human promonocytic cell line U937. U937 cells persistently produced HIV as detected by reverse transcriptase activity in culture supernatant. Expression of HLA class II antigens on U937/HIV cells was decreased 2- to 10-fold, depending on the Mab used. Class II expression of U937/HIV cells increased approximately two-fold by treatment with r-interferon-gamma. Whereas noninfected U937 cells expressed moderate amounts of lymphocyte function-associated antigen-1 (LFA-1) (CD11a) and minimal amounts of the C3bi receptor (CD11b) and p150/95 (CD11c), U937/HIV cells expressed moderate amounts of C3bi receptor and p150/95 and showed elevated expression of LFA-1 alpha (CD11a) and -beta (CD18) chains. Expression of these adhesion molecules resulted in strongly enhanced phorbolester-induced aggregation of U937/HIV cells compared with the noninfected U937 cells. In addition, almost all U937/HIV cells, but not noninfected U937 cells, intensely stained for cytoplasmic nonspecific esterase activity. The effects of HIV infection on U937 cells strikingly resemble the effects of differentiation-inducing agents, such as PMA and DMSO, on the U937 phenotype. Our finding suggests that HIV infection, apart from down regulating class II expression, induces differentiation of U937 cells.
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PMID:Human immunodeficiency virus infection down-regulates HLA class II expression and induces differentiation in promonocytic U937 cells. 310 23

Human umbilical vein endothelial cells have recently been shown to respond to C5a with increases in intracellular Ca2+, production of D-myo-inositol 1,4,5-triphosphate and superoxide anion generation. In the current studies, C5a had been found to cause in a time- and dose-dependent manner rapid expression of endothelial P-selectin, secretion of von Willebrand factor, and adhesiveness for human neutrophils. The effects of C5a in P-selectin expression and adhesiveness of neutrophils were similar to the effects of histamine and thrombin on endothelial cells. The adhesiveness of C5a-stimulated endothelium for neutrophils was blocked by anti-P-selectin, but not by antibodies to intercellular adhesion molecule 1, E-selectin, or CD18. A cell-based ELISA technique has confirmed upregulation of P-selectin in endothelial cells exposed to C5a. Binding of C5a to endothelial cells has been demonstrated, with molecules bound being approximately 10% of those binding to neutrophils. By a reverse transcriptase-PCR technique, endothelial cells have been shown to contain mRNA for the C5a receptor. These data suggest that C5a may be an important inflammatory mediator for the early adhesive interactions between neutrophils and endothelial cells in the acute inflammatory response.
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PMID:C5a-induced expression of P-selectin in endothelial cells. 752 84

Three different intercellular adhesion molecules (ICAMs) have been identified acting as ligand for counter-receptor leukocyte-function-associated antigen-1 (LFA-1) (CD11a/CD18). We have recently shown that ICAM-1 (CD54) is present on cultured human epidermal Langerhans cells but not on freshly isolated Langerhans cells, and that this molecule participates in the generation of an antigen-specific T-cell response. ICAM-2 (CD102) was not involved because this molecule is expressed by neither fresh nor cultured Langerhans cells. In this study, the presence of ICAM-3 (CD50) on Langerhans cells was examined. Flow cytofluorometric analysis demonstrated that ICAM-3 is strongly displayed by fresh Langerhans cells, and daily determinations showed that the level of this trypsin-resistant molecule remained nearly unchanged during in vitro culture for up to 4 d, indicating that Langerhans cells constitutively express this molecule. Analysis of RNA extracted from purified cultured Langerhans cells by means of reverse transcriptase-polymerase chain reaction demonstrated the presence of mRNA specific for ICAM-3. Antigen-specific T-cell responses triggered by Langerhans cells were dose-dependently inhibited by anti-ICAM-3 if the antibody was added within the first 16 h of T-cell stimulation. Simultaneous addition of anti-ICAM-1 and anti-ICAM-3 synergistically inhibited T-cell responses, although a total block was never achieved. Pretreatment of Langerhans cells with anti-ICAM-3 resulted in a reduced T-cell response, whereas pretreatment of T cells did not. These results suggest that ICAM-3 on Langerhans cells, like ICAM-1, is functionally involved in the initiation of antigen-specific activation of T cells, but the expression of these two ICAMs on Langerhans cells is differently regulated.
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PMID:Intercellular adhesion molecule-3 (CD50) on human epidermal Langerhans cells participates in T-cell activation. 753 71

We demonstrate that in addition to possessing binding sites for intact factor V (FV), unstimulated peripheral blood monocytes also express activated factor V (FVa) on their surfaces. FVa was identified on the monocyte surface by monoclonal antibody B38 recognizing FVa light chain and by human oligoclonal antibodies H1 (to FVa light chain) and H2 (to FVa heavy chain) using immunofluorescence microscopy and flow cytometry. On Western blots, partially cleaved FV could be identified as a 220 kDa band in lysates of monocytes. In addition to surface expression of FVa, monocytes also contain intracellular FV as detected only after permeabilization by Triton X-100 by monoclonal antibody B10 directed specifically to the Cl domain not present in FVa. We sought to determine whether the presence of FV in peripheral blood monocytes is a result of de novo synthesis. Using in situ hybridization, no FV mRNA could be detected in monocytes, while in parallel control studies, factor V mRNA was detectable in Hep G2 cells and CD18 mRNA in monocytes. In addition, using reverse transcriptase and the polymerase chain reaction, no FV mRNA was detected in mononuclear cells or in U937 cells, but mRNA for factor V was present in Hep G2 cells using the same techniques. These data suggest that FV is present in human monocytes, presumably acquired by binding of plasma FV, and that the presence of this critical coagulation factor is not due to de novo synthesis.
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PMID:Characterization of monocyte-associated factor V. 769 89

Cultured Langerhans' cells (CLC) exhibit enhanced antigen-presenting function compared to freshly isolated LC (FLC), but they are commonly believed to be inefficient at processing intact proteins. In this study, FLC and CLC from normal, human immunodeficiency virus (HIV) seronegative volunteers were compared for their ability to present the HIV-1 envelope glycoprotein gp120 or reverse transcriptase (p66) antigens to autologous, specific CD4+ T cell lines. Epidermal cell suspensions enriched for LC were prepared from suction blister roofs. FLC stimulated T cells at lower antigen concentrations compared to unfractionated peripheral blood mononuclear cells (PBMC). CLC were more potent on a per cell basis than FLC, PBMC or adherent monocytes at presenting native gp120, native p66 or immunogenic peptides. CLC were also more efficient than FLC or PBMC in terms of the amount of antigen required for T-cell activation. Chloroquine and leupeptin inhibited presentation of intact p66, but not of an immunodominant peptide, by FLC or CLC, thus indicating that both cells utilize antigen-processing mechanisms that are based on intracellular acidification and protease activity. Incubation of CLC with monoclonal antibodies against HLA-DR, CD11b, CD18, CD50, CD54, CD58 or CD80, but not anti-major histocompatibility complex class I (MHC-I), inhibited antigen-specific T-cell proliferation to varying degrees. We conclude that human CLC retain the ability to process and present protein antigens potently to CD4+ T cells. Thus, CLC have the capacity to participate actively in the generation and maintenance of T-helper cell immunity to viral antigens during HIV-1 infection.
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PMID:Cultured human Langerhans' cells are superior to fresh cells at presenting native HIV-1 protein antigens to specific CD4+ T-cell lines. 869 96

To form distant metastases, tumour cells must stabilize adhesive interactions that prevent detachment at secondary sites. Primary receptor-ligand interactions alone may not maintain prolonged adhesive contacts without secondary events that lead to adhesion stabilization. Computerized imaging methods enable us to examine various substrates for: (i) the wall shear adhesion threshold (WSAT), a measure of the dynamic adhesive potential of tumour cells; (ii) the number of tumour cells that adhered; and (iii) the adhesion stabilization lag time (ASLT) or length of time required for tumour cells to stabilize adhesive contacts capable of withstanding high wall shear force (up to 100 dynes/cm2). The relative WSAT ratios found were: wheat germ agglutinin (WGA) > laminin > fibronectin > vitronectin > collagen I > collagen IV > von Willebrand factor (vWF) (the greater the shear rate the higher the adhesive potential). The relative stabilization ratios found were as follows: laminin < fibronectin < vitronectin < collagen IV < collagen I < vWF < WGA (shorter times correlate with greater stabilization potential). Stabilization data using fibronectin as a substrate correlated the best with metastatic potential. Using three melanoma lines of different metastatic potential semiquantitative reverse transcriptase-polymerase chain reaction (PCR) showed a two- to four-fold increase in alpha1, alpha3, alpha4, alpha5, alpha6, and ICAM-1 in the highly metastatic 70W cells compared to the MeWo and non-metastatic 3S5 melanoma cells. There were no differences in alphav, beta1 and beta3 levels among the three melanoma lines, and PCR products for alphaIIb, alpha2, CD36, or ICAM-2 were not detected. The 70W cells also had higher levels of alphax and beta2 (CD11/CD18 and p150 leukocyte antigen) than either the MeWo or 3S5 cells. The data indicate that melanoma cells exhibit differences in the adhesion properties under fluid shear and differences in the expression of adhesion components that correlate with their metastatic potential.
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PMID:Human melanoma integrins contribute to arrest and stabilization potential while flowing over extracellular matrix. 871 81

Transcription factors play an important role choreographing lineage commitment and expansion of blood cells. Nuclear factors that are expressed primarily or exclusively in hematopoietic cells are likely candidates for regulating blood cell development. The transcription factor PU.1 is found only in hematopoietic cells, whereas ets-2, a related family member, is ubiquitously expressed. To compare the role of these two transcription factors in macrophage development, embryonic stem (ES) cells with a homozygous disruption of either the PU.1 or the ets-2 gene were generated. The ability of both knockout ES cells to differentiate to macrophages was tested. Normal development of macrophages, as determined by histochemical and immunohistochemical analysis, from PU.1 knockout ES cells was significantly blocked. Furthermore, the expression of known markers associated with macrophages, such as c-fms, CD11b, CD18 and granulocyte-macrophage colony-stimulating factor receptor, were not detected by reverse transcriptase-polymerase chain reaction. In contrast to the PU.1 knockout ES cells, macrophages, development from the ets-2 knockout ES cells was normal. Although both PU.1 and ets-2 are found in macrophages, these data show a distinct role for the lineage-restricted PU.1 transcription factor in macrophage development.
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PMID:PU.1 but not ets-2 is essential for macrophage development from embryonic stem cells. 887 88

Expression of antigens coexpressed on cord blood (CB) CD34+ cells was evaluated by flow cytometry analysis and reverse transcriptase polymerase chain reaction (RT-PCR). Antigen expression was also comparatively analyzed by flow cytometry and limiting dilution (LD) RT-PCR to investigate effects of chymopapain on epitopes of several cell surface markers: LD RT-PCR allows detection of the expression of antigens degraded by chymopapain which are not identified by flow cytometry. Monoclonal antibodies (MoAbs) that recognize chymopapain resistant epitopes on several coexpressed cell surface markers were identified: these included MoAbs directed against CD11a, CD13, CD18, CD38, CD45RO, CD51, HLA-DR, Thy-1, c-kit, flt-3 (STK-1), and mdr-1. Interestingly, chymopapain treatment caused enhanced staining with MoAbs against HLA-DR, Thy-1, flt-3, mdr-1, and CD51. The frequency (LD RT-PCR) of CD18, CD38, Thy-1, and c-kit RT-PCR signals on pure sorted CD34+ CD18-, CD34+ CD38-, CD34+ Thy-1-, and CD34+ c-kit- cells, respectively, was similar in corresponding subsets treated or not with chymopapain. In contrast, the frequency of CD33 RT-PCR signals on sorted CD34+ CD33- cells was higher in chymopapain-treated samples than in untreated samples and thus confirmed at the transcriptional level that the epitope recognized by anti-CD33 is chymopapain sensitive. Our findings extend data on the phenotypic profile of CB CD34+ cells and show that several key cell surface markers of hematopoietic progenitor cells are chymopapain resistant. In addition, the results of the present study demonstrate that the RT-PCR can be applied to the analysis of multiple RNA species in small numbers of hematopoietic progenitor cells and show that LD RT-PCR allows the identification and frequency determination of rare cells which are undetectable by flow cytometry.
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PMID:Surface antigen expression on CD34+ cord blood cells: comparative analysis by flow cytometry and limiting dilution (LD) RT-PCR of chymopapain-treated or untreated cells. 887 54

Associations between hematopoietic cells and their microenvironment are central to the development and maintenance of a functional hematopoietic system. It is important, therefore, to identify the surface receptors that mediate adhesive interactions among hematopoietic cells, stromal cells, and extracellular matrix components. In this study, we examined the expression of mRNA transcripts encoding a number of cell adhesion molecules and surface antigens in primitive hematopoietic cells isolated from murine bone marrow and fetal liver. Using a panel of probes, we hybridized a library of globally amplified cDNA prepared by reverse transcriptase-polymerase chain reaction of poly(A)+ mRNA from individual precursors and mature cell populations, representing precisely defined positions within the hematopoietic developmental hierarchy. The panel included probes specific for the CD45, CD34, P-glycoprotein (mdr1), Ly-6A/E (Sca-1), heat stable antigen (CD24), Fc receptor for IgG FcgammaRII (CD32), CD44, CD22, and ICAM-1 (CD54) genes, as well as alphaL (CD11a), alphaM (CD11b), beta2 (CD18), alpha4 (CD49d), alpha5 (CD49e), beta1 (CD29), and beta7 integrin subunit sequences. The data, which revealed stage- and lineage-specific expression patterns, should prove useful in designing future mechanistic studies aimed at elucidating the role played by adhesion receptors in normal and abnormal hematopoiesis.
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PMID:Expression mapping of adhesion receptor genes during differentiation of individual hematopoietic precursors. 932 54


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