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Biomedical subjects

L A Falk

Publications and source records attributed to L A Falk.

At least 19 recordsLinked to original sources
PubMed1991

Bidirectional effects of transforming growth factor beta (TGF-beta) on colony-stimulating factor-induced human myelopoiesis in vitro: differential effects of distinct TGF-beta isoforms.

Transforming growth factor-beta (TGF-beta) has potent antiproliferative effects on human hematopoietic progenitor cells. We report here that TGF-beta 1 and -beta 2 also exert bimodal dose-dependent stimulation of granulocyte-macrophage colony-stimulating factor (CSF) and granulocyte-CSF-induced day 7 granulocyte-macrophage colony-forming units. This increase in colony formation was restricted to low doses (0.01 to 1.0 ng/mL) of TGF-beta 1 and was due to increased granulopoiesis, showing that TGF-beta can affect the differentiation as well as the proliferation of hematopoietic progenitors. Furthermore, TGF-beta 3 was found to be a more potent inhibitor of hematopoietic progenitor cells than TGF-beta 1 and -beta 2. In contrast to the bidirectional proliferative effects of TGF-beta 1 and -beta 2, the effects of TGF-beta 3 on human hematopoiesis were only inhibitory, showing for the first time that TGF-beta isoforms differ not only in potencies but also with regard to the nature of the response they elicit.

Cell Differentiation↗
PubMed1991

Mechanistic studies of transforming growth factor-beta inhibition of IL-2-dependent activation of CD3- large granular lymphocyte functions. Regulation of IL-2R beta (p75) signal transduction.

CD3- large granular lymphocyte (LGL) express constitutive levels of functional IL-2R beta. TGF-beta inhibited several IL-2R beta-mediated events in LGL, including IL-2-induced NK and lymphokine-activating factor activities, IFN-gamma gene expression and secretion, and IL-2R alpha expression. TGF-beta inhibited these IL-2-induced LGL functions in a dose-dependent and reversible manner. By contrast, TGF-beta had little effect on LGL IL-2R beta expression and TGF-beta receptors were not induced by IL-2. Studies were performed to examine binding and internalization of radiolabeled IL-2. These experiments demonstrated that the rapid binding and internalization of [125I]IL-2 was not altered in CD3- LGL pretreated with TGF-beta. These internalization studies indicated that the TGF-beta inhibition represented postreceptor-binding events in NK cells. Further studies were initiated to examine signaling events in CD3- LGL. When IL-2-induced tyrosine phosphorylation events were examined, significant inhibition was seen of selected phosphoproteins in TGF-beta-pretreated cells. In addition, the ability of TGF-beta to also inhibit IL-2 induction of LGL IL-2R alpha and IFN-gamma mRNA expression was consistent with the hypothesis that posttranscriptional mechanisms were unlikely to be affected by TGF-beta. Collectively, these data indicated that TGF-beta inhibited IL-2-induced CD3- LGL functions and suggested that TGF-beta inhibition occurs either at the level of specific tyrosine phosphorylation and/or IL-2-induced transcriptional control factors.

Antigens, Differentiation, T-Lymphocyte↗
PubMed1991

Differential expression of transforming growth factor-beta 1 (TGF-beta 1) receptors in murine myeloid cell lines transformed with oncogenes. Correlation with differential growth inhibition by TGF-beta 1.

Transforming growth factor-beta 1 (TGF-beta 1) is a pleiotropic polypeptide hormone known to play an important role as a modulator of hematopoietic processes in human and murine cells. One of the characteristics of TGF-beta 1 is the ability to inhibit the growth of several cell types, including cells of the myeloid lineage. To study the mechanism by which TGF-beta 1 inhibits the growth of myeloid cells, we have used three murine myeloid cell lines, the parental interleukin-3-dependent 32D-123 cell line and two retrovirally infected interleukin-3-independent cell lines (32D-abl, 32D-src), all of which are growth inhibited by TGF-beta 1. Each of these oncogene-transfected cells expresses a greater number of TGF-beta 1 receptors than the parental cell line and responds to TGF-beta 1 with increased sensitivity; 32D and 32D-src cells are 2- and 58-fold more sensitive to TGF-beta 1 inhibition than the parental cell line (ED50 = 35 pM). Both 32D-abl- and 32D-src-transformed cell lines expressed higher levels of the 65- and 85-kDa TGF-beta 1 receptor species than did the parental cells. We observed a correlation between the greater sensitivity of 32D-src cells to TGF-beta 1 and the more rapid down-modulation and reappearance of cell surface TGF-beta 1 receptors on 32D-src cells. Thus, the level of TGF-beta 1 receptor expression and rate of reexpression both have a crucial regulatory effect on the functional activity of the TGF-beta 1 ligand.

Animals↗
PubMed1991

Induction of transforming growth factor-beta 1 (TGF-beta 1), receptor expression and TGF-beta 1 protein production in retinoic acid-treated HL-60 cells: possible TGF-beta 1-mediated autocrine inhibition.

Treatment of HL-60 cells, a human promyelocytic leukemia cell line, with the vitamin A derivative retinoic acid (RA) for 7 days resulted in a dose-dependent decrease in proliferation and increase in granulocytic differentiation. The role of transforming growth factor-beta 1 (TGF-beta 1), a protein with pleiotropic effects on the proliferation and differentiation of various cell types, was examined during RA-induced differentiation of HL-60 cells. Although TGF-beta 1 alone had little effect on proliferation or differentiation of HL-60 cells, addition of TGF-beta 1 to HL-60 cells treated with a suboptimum concentration of RA (1.0 nmol/L) resulted in a marked decrease in proliferation with no effect on granulocytic differentiation. Studies of the mechanism of RA-induced TGF-beta sensitivity showed that although untreated HL-60 cells expressed low levels of TGF-beta 1 binding proteins on the cell surface, the levels were increased in a dose-dependent manner after RA treatment. Maximum induction was achieved after treatment with 10 nmol/L RA and consisted predominantly of the 65-Kd TGF-beta 1 receptor type. Moreover, RA treatment also resulted in a dose-dependent increase in both TGF-beta 1 steady-state mRNA expression and production of active TGF-beta with maximum induction at 10 nmol/LRA. RA treatment of HL-60 cells had no effect on TGF-beta 2 and TGF-beta 3 mRNA expression. These data suggest that the effects of RA may be mediated by a TGF-beta 1-mediated autocrine antiproliferative loop during differentiation of HL-60 cells.

Cell Differentiation↗
PubMed1991

In vivo and in vitro effects of TGF-beta 1 on normal and neoplastic haemopoiesis.

TGF-beta 1 and TGF-beta 2 are equipotent selective inhibitors of murine and human haemopoiesis in vitro. Primitive haemopoietic cells such as the high proliferative potential progenitor cell and the colony-forming unit (CFU)-GEMM are directly inhibited by TGF-beta whereas the more differentiated CFU-G, CFU-M and CFU-E are not. Recombinant TGF-beta 1 administered intraperitoneally or intravenously to mice selectively inhibits haemopoietic colony formation in a time- and dose-dependent manner to the same extent as seen in vitro. The progenitors are reversibly prevented from entering the cell cycle. This inhibitory action of TGF-beta functions on at least two levels: (1) down-modulation of the cell surface expression of receptors for growth stimulatory molecules and (2) interference with the intracellular signalling pathways of these molecules. In addition, expression of TGF-beta receptors is regulated during cytokine stimulation of haemopoiesis. Neoplastic B lymphocytes can proliferate by escaping from a TGF-beta-mediated autocrine inhibitory loop. Activation signals (e.g. phorbol esters) inhibit tumour cell growth by stimulating active TGF-beta production and inducing cell surface expression of TGF-beta receptors. These results indicate that TGF-beta may be useful as a bone marrow protective and/or an antitumour agent.

Animals↗
PubMed1990

Inhibition of murine monocyte proliferation by a colony-stimulating factor-1 antisense oligodeoxynucleotide. Evidence for autocrine regulation.

Using a combination of v-myc and v-ras oncogenes, we have established a growth factor-independent monocyte cell line from murine fetal liver (FL-ras/myc). Biologic and molecular characterization demonstrated that the gene for the macrophage growth factor CSF-1 and the c-fms proto-oncogene (CSF-1 receptor) are expressed in this cell line, thus suggesting autocrine regulation as a possible mechanism for the unregulated growth of these cells. To study this possibility, we used 1) mAb, to neutralize the CSF-1 protein produced by the cell line, and 2) antisense oligomers, to inhibit CSF-1 gene products by specific base-pairing of complementary nucleic acids. We report here that both approaches inhibited in vitro cell growth by 60 to 70%, whereas the combination of oligomer and mAb inhibited proliferation by 95%. However, control antisense oligomers (50% bp mismatch with CSF-1 mRNA) did not inhibit FL-ras/myc cell growth. Furthermore, the inhibitory effects of mAb and oligomers were reversible when they were removed from the media. Detection of cell-associated CSF-1 protein by immunofluorescence showed that cells treated with the antisense oligomer expressed significantly less CSF-1 protein. These results indicate that the FL-ras/myc cell line requires CSF-1 for autonomous growth and that oligomers can efficiently block production of autocrine growth factors.

Animals↗
PubMed1990

Transforming growth factor beta is a potent inhibitor of interleukin 1 (IL-1) receptor expression: proposed mechanism of inhibition of IL-1 action.

Transforming growth factor beta (TGF-beta) acts as a potent inhibitor of the growth and functions of lymphoid and hemopoietic progenitor cells. Cell proliferation depends not only on the presence of growth factors, but also on the development of specific receptor-signal transducing complexes. We therefore investigated whether the inhibitory actions of TGF-beta could be mediated by inhibition of growth factor receptors. TGF-beta inhibited the constitutive level of interleukin 1 receptor (IL-1R) expression on several murine lymphoid and myeloid progenitor cell lines, as well as IL-1R expression induced by interleukin 3 (IL-3) on normal murine and human bone marrow cells. Furthermore, treatment of bone marrow progenitor cells with TGF-beta concomitantly inhibited the ability of IL-1 to promote high proliferative potential (HPP) colony formation as well as blocked IL-1-induced IL-2 production by EL-4 6.1 cells. These findings provide the first evidence that the inhibitory action of TGF-beta on the growth and functional activities of hematopoietic and T cells is associated with a reduction in the cell surface receptor expression for IL-1.

Animals↗
PubMed1990

Synergy between transforming growth factor-beta and tumor necrosis factor-alpha in the induction of monocytic differentiation of human leukemic cell lines.

We examined the effect of transforming growth factor-beta (TGF-beta) alone and in combinations with other factors on the growth and differentiation of the human promyelocytic cell line HL60 and the human monoblastic cell line U937. Treatment with TGF-beta alone did not significantly affect growth or differentiation of HL60 cells, while it significantly inhibited proliferation and induced monocytic differentiation of a small percentage of U937 cells. Combinations of TGF-beta and tumor necrosis factor-alpha (TNF-alpha) acted in synergy to inhibit cell proliferation and to induce monocytic differentiation of both HL60 and U937 cells. In contrast, no synergy was observed when HL60 cells were treated with TGF-beta in various combinations with interferon-alpha (IFN-alpha), interferon-gamma (IFN-gamma), and retinoic acid. Examination of TNF-alpha receptor expression on HL60 and U937 cells showed that these cell lines expressed comparable levels of high-affinity TNF-alpha binding sites. Treatment of HL60 and U937 cells with TGF-beta did not induce significant changes in TNF-alpha receptor expression in either cell line. In contrast, HL60 cells expressed much lower levels of TGF-beta receptors than did U937 cells. Treatment of both HL60 and U937 cells with TNF-alpha induced a dose-dependent increase in expression of TGF-beta receptors, suggesting that the synergy between TNF-alpha and TGF-beta may result, at least in part, from upregulation of TGF-beta receptor expression by TNF-alpha.

Cell Differentiation↗
PubMed1990

Differential production of IFN-alpha/beta by CSF-1- and GM-CSF-derived macrophages.

Mature macrophages, derived in vitro from bone marrow progenitors under the influence of either macrophage colony stimulating factor (CSF-1) or granulocyte-macrophage (GM)-CSF, have been shown to differ morphologically and functionally. The data presented in this report demonstrate that macrophages derived from bone marrow progenitors under the influence of CSF-1 are highly resistant to infection with vesicular stomatitis virus (VSV), and that this refractoriness can be reversed by treatment of cells with anti-IFN-alpha/beta antibody. In contrast, macrophages derived from bone marrow progenitors under the influence of GM-CSF are highly susceptible to the cytopathic effects of VSV, but can be protected by very low concentrations of exogenous IFN-alpha/beta. These findings suggest that CSF-1 derived macrophages have a greater capacity for the production and/or utilization of IFN-alpha/beta than GM-CSF-derived macrophages, which may account for many of the differentiative differences reported previously.

Animals↗
PubMed1988

Analysis of Ia antigen expression in macrophages derived from bone marrow cells cultured in granulocyte-macrophage colony-stimulating factor or macrophage colony-stimulating factor.

Bone marrow cells from C3H/HeJ mice were cultured in recombinant granulocyte-macrophage-CSF (rGM-CSF) or recombinant or purified (natural) preparations of macrophage-CSF (CSF-1) for 7 days, the adherent macrophages removed enzymatically, recultured in the absence of growth factor, and examined for their differentiative and functional characteristics. Expression of Ia Ag differed markedly in these two populations. Antibody plus complement-mediated cytotoxicity indicated that the percent of Ia-positive macrophages was low (approximately 15 to 20%) in both populations. Treatment of cultures with rIFN-gamma increased the percentage of Ia-positive cells in both populations; however, more CSF-1-derived macrophages were induced to become Ia positive than rGM-CSF-derived macrophages. In contrast, total Ia expression and Ia density per cell, as measured by ELISA and quantitative immunofluorescence, respectively, showed that medium-treated rGM-CSF-derived macrophages exhibited greater total Ia expression and higher Ia density per cell than CSF-1-derived macrophages. Treatment of CSF-1-derived macrophages with rIFN-gamma increased total Ia expression per culture to the levels exhibited by rGM-CSF-derived cells, although the density of Ia Ag per cell remained lower than in rGM-CSF-derived cells (medium or rIFN-gamma-treated). Northern blot and slot blot analysis of cytoplasmic RNA extracted from freshly harvested rGM-CSF- or CSF-1-derived cells indicated that the differences seen in basal Ia expression were also reflected at the level of steady-state, Ia-specific mRNA. The functional capacity of these two macrophage populations to stimulate Ag-specific T cell proliferation was also assessed. rGM-CSF- or CSF-1-derived macrophages were first cultured in the absence or presence of rIFN-gamma, Ag-pulsed, and irradiated before co-culture with Ag-primed, purified T cells. Ag-induced T cell proliferation was significantly greater in rGM-CSF- than in CSF-1-derived macrophages. Treatment of either population with rIFN-gamma had only a minimal effect on the ability of either macrophage population to stimulate Ag-specific T cell proliferation. These findings suggest that the development of mature macrophages from bone marrow progenitors under the influence of either GM-CSF or CSF-1 may, in part, underlie the functional heterogeneity of different macrophage populations.

Animals↗
PubMed1988

Comparison of bone marrow progenitors responsive to granulocyte-macrophage colony stimulating factor and macrophage colony stimulating factor-1.

The responsiveness of bone marrow progenitors (BMP) from C3H mice to highly purified or recombinant preparations of Macrophage Colony-Stimulating Factor-1 (CSF-1) and Granulocyte-Macrophage Colony-Stimulating Factor (GM-CSF) was compared by counting the number of colonies (greater than or equal to 50 cells) after 10 days in culture with CSF. Cells responsive to CSF-1 or GM-CSF exhibited maximum colony formation over a wide dose range, although GM-CSF supported colony formation at lower concentrations. The response of BMP to optimal concentrations of CSF-1 was greater than or equal to 5 times greater than the response of BMP to GM-CSF. Analysis of the kinetics of colony formation revealed that, at day 5, the number of BMP responsive to GM-CSF or CSF-1 was approximately equal; the number of CSF-1 colonies increased significantly through day 10, while those cultured in GM-CSF did not. The response of BMP to CSF-1 and GM-CSF was also studied in liquid culture; the differences in yield of mature macrophages was consistent with the differences observed in agar culture. Although both cell populations were shown to be 100% mononuclear by day 7, Coulter Channelyzer analysis of these mature macrophages showed marked differences in cell size distribution. By day 7, cells grown in CSF-1 resulted in a homogeneous population of large cells, whereas GM-CSF cultures showed a heterogeneous distribution. Finally, CSF-1-derived cells possessed increased nonspecific and specific phagocytic capabilities when compared to GM-CSF-derived macrophages. These findings indicate that the actions of GM-CSF and CSF-1 upon the bone marrow compartment results in the generation of mature macrophages which differ morphologically and functionally and may account for the heterogeneity in macrophage populations.

Animals↗
PubMed1988

Bone marrow progenitors cultured in the presence of granulocyte-macrophage colony-stimulating factor versus macrophage colony-stimulating factor differentiate into macrophages with distinct tumoricidal capacities.

Bone marrow-derived cells from C3H/HeJ mice were cultured in the presence of recombinant murine granulocyte-macrophage colony-stimulating factor (rGM-CSF) or highly purified murine macrophage colony-stimulating factor (CSF-1) for 7 days. Following this 7-day culture period, mature macrophages were harvested and replated at precise densities in the absence of exogenous rGM-CSF or CSF-1, and assayed in a two-signal tumoricidal assay. Cultures were stimulated with medium only or with combinations of recombinant interferon-gamma (rIFN-gamma) as the "priming" signal, and/or butanol-extracted lipopolysaccharide (But-LPS) as the "triggering" signal for 24 hr. At this time, 51Cr-labeled, P815 tumor target cells were added, and the percent tumor cell cytotoxicity was determined after 16 hr. Macrophages derived under the influence of rGM-CSF exhibited significant tumoricidal capacity with medium alone (16 +/- 5%). The addition of "priming" signal only (i.e., rIFN-gamma, 10.0 U/ml) significantly increased tumoricidal capacity to 31 +/- 9%. Treatment with But-LPS alone did not alter the basal tumoricidal activity of rGM-CSF-derived macrophages. Combinations of rIFN-gamma (10.0 U/ml) and But-LPS (0.5-5.0 micrograms/ml) generated highly tumoricidal macrophages (50-60% tumor cell cytotoxicity). In contrast, medium-treated CSF-1-derived macrophages exhibited a significantly lower basal level of tumor cytotoxicity (6 +/- 3%). Unlike rGM-CSF-derived macrophages, treatment of CSF-1-derived macrophages with high concentrations of rIFN-gamma alone did not increase significantly the level of cytotoxicity above that of medium-treated cultures. However, CSF-1-derived macrophages responded to the highest concentrations of But-LPS (5.0 micrograms/ml) to increase tumoricidal activity from 6 +/- 3% to 17 +/- 5%. Optimal tumoricidal activity (44 +/- 17%) was observed when CSF-1-derived macrophages were treated simultaneously with high concentrations of both rIFN-gamma and But-LPS. Thus, macrophages derived from bone marrow progenitors in either rGM-CSF or CSF-1 exhibited tumoricidal capacities that differed in basal activity as well as in their requirements for and sensitivities to "priming" and "triggering" signals.

Animals↗
PubMed1988

Granulocyte-macrophage colony stimulating factor (GM-CSF) and macrophage colony stimulating factor (CSF-1) synergize to stimulate progenitor cells with high proliferative potential.

The ability to expand a population of bone marrow progenitors capable of forming macrophage colonies of high proliferative potential (HPP-CFC) was achieved using a culture system and signal requirements not previously shown to support the growth of HPP-CFC. Using bone marrow cells from untreated animals (not 5-FU-treated), culture conditions designed primarily for the detection of GM-CFC or M-CFC progenitors, and a more stringent criteria for HPP-CFC colony size (greater than or equal to 2 mm diameter), HPP-CFC progenitor expansion was demonstrated following simultaneous addition of rGM-CSF and CSF-1 to bone marrow cultures. Examination of the sequence and temporal requirements for rGM-CSF and CSF-1 addition necessary for the development of HPP-CFC-like colonies revealed that addition of the second factor could be delayed for up to 5 days and still result in the development of significant numbers of HPP-CFC colonies. Based on a comparison with human spleen cell conditioned medium (HSCM) and interleukin 1 (rIL 1), as sources of "synergistic activity" (SA) for the development of HPP-CFC-like colonies in combination with CSF-1, the combination of GM-CSF and CSF-1 appears to represent a novel pathway for stimulating the expansion of HPP-CFC progenitors with high proliferative potential.

Animals↗
PubMed1988

Human immunodeficiency virus (HIV) antigenemia (p24) in the acquired immunodeficiency syndrome (AIDS) and the effect of treatment with zidovudine (AZT).

Infection with human immunodeficiency virus (HIV) may cause viral antigenemia, detected primarily as p24 viral core protein. Among 16 patients with the acquired immunodeficiency syndrome (AIDS) or AIDS-related complex studied serially, 12 had or developed antigenemia ranging from 16 to 3006 pg/mL in plasma. The level could be categorized as high (greater than 100 pg/mL) or low (15 to 65 pg/mL). Three patients with anti-p24 antibody had no antigenemia. Zidovudine (AZT), 200 or 250 mg every 4 hours, reduced antigenemia by about 90%; other regimens were less effective. Leukocyte cultures were positive for HIV from patients with antigenemia, and in one third of samples in the absence of antigenemia. High levels of antigenemia correlated with symptoms, CD4 cell count, and prognosis. Drug toxicity requiring a lower dose was followed by increased antigenemia, recurrent symptoms, and decreased CD4 cells, suggesting lymphocyte toxicity. Monitoring antigenemia can be useful in evaluating patients with HIV infection and in evaluating the effect of antiviral chemotherapy.

AIDS-Related Complex↗
PubMed1987

Diagnosis of human immunodeficiency virus infection in seronegative homosexuals presenting with an acute viral syndrome.

Early diagnosis of acute human immunodeficiency virus (HIV) infection is difficult because patients may be seronegative for HIV at the time of presentation. We have used a serum HIV antigen (HIV-Ag) enzyme immunoassay (EIA) to diagnose acute HIV infection in four high-risk patients. The clinical syndrome in these four patients was characterized by fever (four), rash (three), myalgias-arthralgias (three), and pharyngitis (two). All patients had spontaneous resolution of their symptoms within eight to 12 days. Serum HIV antibody, as measured by a commercially available screening EIA and by Western blot analysis, was negative in all patients at time of presentation and all seroconverted on subsequent testing. Human immunodeficiency virus was isolated from two of two patients during the acute illness. Initial serum samples from all four patients were positive for HIV-Ag. Serum samples of three of four patients became negative for HIV-Ag and positive for HIV antibody. These data suggest that serum HIV-Ag detection by EIA may be useful in the diagnosis of the acute syndrome caused by HIV infection.

Acquired Immunodeficiency Syndrome↗
PubMed1987

Correlation of serum HIV antigen and antibody with clinical status in HIV-infected patients.

An enzyme immunoassay (EIA) has been developed which detects antigen(s) (Ag) of the human immunodeficiency virus (HIV) in the serum of patients with the acquired immunodeficiency syndrome (AIDS), AIDS-related complex (ARC), and patients at high risk for HIV infection. The test has a sensitivity of approximately 50 pg/ml of HIV protein. The specificity of the assay was determined with various virus infected cell lines, normal human sera/plasma, and serum from patients not known to be at risk for HIV infection. No false-positive HIV-Ag results were seen. Sera from 69% of patients with AIDS were positive for HIV-Ag as were 46% of patients with ARC and 19% of asymptomatic, HIV-antibody-positive individuals. There were significant associations between the stage of HIV infection--ie, AIDS vs ARC vs asymptomatic--and the detection of HIV-Ag in serum (p less than 0.0001) and the lack of detection of antibody to HIV core Ag (p less than 0.0001). HIV-Ag was also found in the serum of two asymptomatic antibody-negative individuals who were at high risk for AIDS and who later developed HIV antibody. The presence of HIV-Ag in sera was confirmed by an inhibition procedure. Thus, HIV-Ag can be detected in the serum of infected individuals prior to antibody production and correlates with the clinical stage of HIV infection.

Acquired Immunodeficiency Syndrome↗