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(2b) Increases the Expression of Apoptosis Receptor CD95 and Chemokine Receptors CCR1 and CCR3 in Monocytoid Cells1
*
Institute of Human Virology, University of Maryland, Baltimore MD 21201;
Laboratory of Basic Science, National Cancer Institute, National Institutes of Health, Bethesda MD 20814; and
Department of Morphology and Embriology, Human Anatomy Section, Ferrara, Italy
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Abstract |
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 Top Abstract IntroductionMaterials and MethodsResultsDiscussionReferences |
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-2b, known as potent immune modulator, can either inhibit or
enhance immune cell activity within the tightly regulated
microenvironment of inflammation, depending upon the concentration of
the cytokine and the activation stage of the cell. Chemokine receptors,
which not only mediate chemotaxis of immune cells to the site of
inflammation but also affect cellular activation by transferring
corresponding signals, represent yet another level of immune
regulation. Here we demonstrate that IFN- increases the expression
of CCR1 and CCR3 in primary mononuclear phagocytes, as well as in the
monocytoid cell line U937. Enhanced receptor mRNA expression correlated
with functional readouts such as increased intracellular calcium
mobilization and cell migration in response to ligands. Expression of
CCR2b, CCR4, CCR5, and CXCR4 was unchanged or decreased after IFN-
treatment. These observations indicate a differentially regulated
cellular signaling relationship of IFN- pathways and chemokine
receptor expression. We also provide evidence that, under these
conditions, IFN- treatment increased the expression of CD95 (Fas,
Apo1), resulting in enhanced susceptibility to apoptosis. Taken
together, these data add important information for the rational
application of IFN- (2b) in immune and cancer
therapies. |
Introduction |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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-2b,
a member of the cytokine family that was first defined by its ability
to establish an antiviral state in cells, was also shown to modulate a
variety of physiologic processes that appear to be divergent. Whether a
cell becomes more activated and will be induced to proliferate and
differentiate or whether antiproliferative, anergic, and apoptotic
processes are mediated instead critically depends upon the
preactivation stage of a cell (e.g., IFN receptor balance,
costimulatory signals) and the concentration of IFN- within a
microenvironment (1). Convergently, IFN- has been shown
to have proinflammatory effects, but has also been used to inhibit
chronic inflammations (2). Whereas in vitro systems can
facilitate dissection of the different cellular pathways involved,
these results might be difficult to interpret with regard to
physiologic relevance.
Although often quite complex, clinical data, for which IFN--2b was
successfully used as a treatment modality in cancer, chronic
inflammation, and viral infection, provide a most interesting source of
information. Opinions vary markedly about the underlying mechanism that
leads to the commonly observed IFN--mediated clinical effects.
Experimental data provide evidence for the support of several
hypotheses. Whether the antitumor effects of IFN- relate to induced
cell differentiation into a stage accessible to immune surveillance or
to the control of cell cycling and therefore cell growth inhibition
remains unresolved. However, there is also experimental evidence that
IFN- enhances the activation of a cell so as to affect apoptosis as
mediated through the CD95 (Fas, Apo1) signaling pathway (3, 4).
It has been shown in some experimental systems that IFN- can induce
the differentiation of cells and enhance the expression of integrin
(ß1) and integrin receptors (5),
thereby facilitating cell adhesion and affecting cell trafficking.
Chemokines and chemokine receptors
(CRs)3 are important
mediators of signals that regulate leukocyte trafficking as well
(6, 7). The level of CR expression on a cell affects
responses to its specific ligands, because resting immune cells with a
low density of appropriate receptors may not be competent to migrate
and adhere even in the presence of high concentrations of chemokines.
We were interested to find out whether IFN--2b is involved in the
process of modulating CR expression and signaling by a cell. Because
the modulation of APCs by IFN- results in a complex alteration of
their Ag-presenting functions (8, 9, 10), we specifically
investigated human monocyte-derived cell subsets as well as the
monocytoid cell line U937 to assess the expression and function of CRs
subsequent to IFN--2b priming. In addition, we investigated whether
changes in CD95 apoptosis receptor expression and changes in
susceptibility to apoptosis as induced through CD95 are linked to these
events.
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Materials and Methods |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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Peripheral blood samples were obtained from healthy volunteers
according to the protocols approved by the Institutional Review Board.
PBMCs were isolated by automated Ficoll/Hypaque density-gradient
centrifugation using a CS-3000 Plus Blood Cell Separator (Fenwal
Division, Baxter Healthcare, Deerfield, IL). Monocytes were isolated
from PBMCs by counterflow-centrifugal elutriation using a Beckman
JE-5.0 rotor and a type A chamber (Beckman Instruments, Palo Alto, CA).
The purity of the separated monocyte fraction was 
98% as determined
by cytomorphology in Pappenheim stain and 96% as determined by the
expression of CD14 Ag (LeuM3; Becton Dickinson, Mountain View, CA) and
measured by flow cytometry. U937 cells were obtained from the American
Type Culture Collection (Manassas, VA). Cells were cultured in complete
medium (RPMI 1640, containing 10% heat-inactivated FCS, low endotoxin
grade; all Life Technologies, Gaithersburg, MD) at a concentration of
0.8 x 106 cells/ml. IFN--2b (Schering,
Kenilworth, NJ) was added to the cultures in varying concentrations so
as to assess dose-dependent effects. A concentration of 300 IU/ml was
determined to be sufficient for mediating effects on CR expression
without toxic side effects and was therefore used in most of the
experiments. Aliquots of differently treated cells were collected for
mRNA analysis, calcium flux assays, cell surface staining, and FACS
analysis or migration assays. In apoptosis experiments, the
anti-CD95 mAb CH11 (Kamyia, San Francisco, CA), an Ab that mimics
the Fas ligand by triggering the CD95 receptor, or mAb ZB4, a CD95
blocking Ab (AMAC, Westbrook, ME), were used at concentrations ranging
from 0.01 µg/ml to 0.5 µg/ml. Cell viability was measured using a
standard trypan blue (Life Technologies) exclusion test. In some
experiments, an automated colorimetric assay based on
tetrazoliumbromide (MTT) reduction was used to determine cell number
and cell metabolic rates. Levels of the chemokine RANTES were
determined in culture supernatants derived from monocyte-derived
mononucleated phagocytes (MDMs) or U937 cells using an ELISA system
(R&D Systems, Minneapolis, MN) according to the manufacturer’s
recommendations. Samples were stored at <80°C until they were
assayed.
Transient calcium flux measurement
A method that has been described previously was applied
(11). Briefly, aliquots of 106 cells
were incubated for 20 min at 37°C with Fluo-3, reconstituted with
Pluronic F-127 (Molecular Probes, Eugene, OR) according to the
manufacturer’s directions. After incubation, the samples were washed
once with RPMI 1640 (without phenol red, without sodium carbonate,
containing 25 mM HEPES) and finally resuspended in 1 ml of the same
medium. Data were acquired with a FACScalibur (Becton Dickinson), with
excitation at 488 nm. Cells were gated by forward and side scatter
properties. Calcium mobilization was determined by a two-parameter
density plot, measuring linear emission at 530 nm in the FL-1 window
for the gated cell population over time. After 20 s of
acquisition, the appropriate chemokine (25 ng/ml of RANTES, macrophage
inflammatory protein-1 (MIP-1), MIP-1ß, or stromal cell-derived
factor-1 (SDF-1); all from R&D Systems) or 100 ng/ml of the
ionophore ionomycin (Sigma, St. Louis, MO) were added.
Cell migration assays
Cell migration assays were performed as described previously
(12). Briefly, 1.5 x 105 U937 cells
in 150 µl of RPMI 1640 medium containing 0.25% human serum albumin
were transmigrated through 5-µm pore size bare filter transwell
inserts (Costar, Cambridge, MA) for 12 h. Migrated cells were
counted by FACS analysis scatter-gating on lymphocytes. Chemotaxis was
conducted in the presence of optimized ligand concentrations (RANTES,
100 ng/ml; MIP-1, 100 ng/ml; eotaxin, 200 ng/ml; MIP-1ß, 250
ng/ml; SDF-1, 250 ng/ml; all R&D Systems). Three independent
experiments were performed in duplicate cultures; mean values (± SD)
were determined as expressed as a percentage as compared with untreated
controls.
Semiquantitative mRNA assays
Semiquantitative mRNA assays were performed using end-point dilution and direct comparison of partner samples as is recommended under circumstances in which no internal control/competitor is available. Aliquots of differently treated cells were collected at days 2 and 5. Total cellular RNA was isolated by TRIzol LS reagent (Life Technologies) according to the manufacturer’s protocol. Samples of RNA were treated by DNase I (amplification grade, Life Technologies). Synthesis of first-strand cDNA was performed in 20 µl of reaction mix (50 mM Tris-HCl (pH 8.3), 75 mM KCl, 3 mM MgCl, 10 mM DTT, 500 µM each of dNTPs, and 2.5 µM of random hexamer primer, Perkin-Elmer Applied Biosystems, Branchburg, NJ), 1.5 µg of RNA, and 200 U of SuperScript II RT (Life Technologies) for 1 h at 42°C, followed by heating for 5 min at 99°C. Amplification was performed with 2 µl of RT mixture in a total volume of 20 µl, using 2 µM dNTPs, 8 pmol of primers, and 2.5 U of AmpliTaq AGold polymerase (Perkin-Elmer Applied Biosystems) for 35 cycles (94°C for 45 s, 60°C for 1.30 min, 72°C for 2 min) after an initial 9-min denaturation at 94°C. The resulting PCR products were separated on 2% SeaKem GTG agarose gel (FMC BioProducts, Rockland, ME). As a control for DNA contamination, equal amounts of RNA extraction products were used for each sample assessed, and PCR amplification was performed without the addition of RT to the first-strand synthesis. The conditions for the semiquantitative mRNA assay were specifically defined so as to exclude the possibility of amplifying contaminating genomic DNA. The sets of primers used have been described previously (13).
Flow cytometry
For a qualitative and quantitative determination of cell surface
molecules, flow cytometry was conducted by incubating cells at 4°C in
PBS containing 1% BSA and 5 mM EDTA for 30 min with Abs at
concentrations recommended by the manufacturer after cells had been
washed and incubated with 10% normal goat serum in PBS to block
unoccupied sites when indicated. Abs to CXCR4 (mouse IgG2a, clone 12G5,
obtained from the AIDS Research and Reference Reagents Program,
Rockville, MD) were developed with anti-IgG2a (goat-anti-mouse,
FITC-labeled, human-adsorbed; Caltag Laboratories, Burlingame, CA). The
mouse IgG2a isotype control Abs were obtained from Coulter (Hialeah,
FL). PE-conjugated mAbs to CD4 and CD14, as well as appropriate isotype
control Abs, were obtained from Becton Dickinson. The FITC-conjugated
anti-CD95 mAb UB2 and appropriate isotype control Abs were obtained
from PharMingen (San Diego, CA). The receptor density for MIP-1 was
determined by flow cytometry using the Fluorokine staining kit (R&D
systems) according to the manufacturer’s recommendations.
Cell cycle analysis and apoptosis assay
DNA analysis of cell cycle status was performed using flow cytometry. After culture, cells were harvested, washed with PBS containing 2% FCS, fixed with ice-cold 70% ethanol, rewashed, and resuspended with 10 µg/ml propidium iodide solution (Boehringer Mannheim, Indianapolis, IN) containing 10 µg/ml bovine RNase (Boehringer Mannheim). After 30 min, DNA content was measured by flow cytometry. Collected data were analyzed using M-Cycle software, version 2.5 (Phoenix Flow Systems, Phoenix, AR). This method allows determination of cell cycle status and quantification of apoptotic cells by measurement of the corresponding peak. A TUNEL assay (Apotag; Oncor, Gaithersburg, MD) also was used to quantitate by flow cytometry the number of cells undergoing apoptosis. In some experiments, apoptosis was also evaluated by using the Cell Death Detection ELISAplus (Boehringer Mannheim), which quantitates cytoplasmic histone-associated DNA fragments.
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Results |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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-2b influences the
expression of RANTES receptors (CCR1, CCR3, CCR4, and CCR5) on primary
MDMs. Elutriated monocytes were primed in the presence of IFN--2b
for 6 days as described in Materials and Methods. Because
CRs are 7-transmembrane, G-coupled proteins that mediate intracellular
calcium mobilization, the adherent cell subpopulations (MDMs) were
analyzed for their ability to respond to the ligand RANTES, using an
intracellular calcium flux assay. Subsequent to IFN stimulation, an
increase in the level of signal (Fig. 1
,
upper right panel) was observed in MDMs when compared with
untreated controls (Fig. 1, upper left panel). The calcium
mobilization response to ionomycin remained unchanged (Fig. 1, compare
lower left panel with lower right panel),
indicating a specific regulation of RANTES receptors by the treatment.
Simultaneously, we observed IFN--induced changes in cell morphology
as determined by size and granularity using flow cytometry (FACS) (Fig. 2, compare A and
B). A distinct subpopulation of larger cells with a
comparatively high granularity (Fig. 2B, defined as R1) was
detected only in IFN--treated monocyte cultures.
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, produced as a primary
response to inflammation/infection, modifies CR-mediated signals in
MDMs, a subset of monocyte-derived APCs. To extend these observations,
we used an in vitro model in which the majority of the conditions are
standardized and the data can be reproduced, without the variability
associated with primary cells. Thus, we analyzed the monocytoid
(CD14+, CD4+,
HLA-DR+) cell line U937 to determine whether the
observed changes in transient calcium flux responses to RANTES were
comparable with those observed in primary cells. Only a small
proportion (5%) of unprimed U937 cells responded minimally to
RANTES and MIP-1 (ligands to CCR1, CCR3, CCR4, and CCR5), whereas no
response was observed with MIP-1ß (ligand to CCR5). After IFN-
priming, an increase in transient intracellular calcium flux response
was observed to both RANTES (Fig. 3A) and MIP-1, but not to
MIP-1ß (data not shown). IFN- treatment caused >30% of the cells
to respond to RANTES, as determined by transient calcium flux. This
effect was dose-dependent (Fig. 3, compare A, B,
and C in the upper panel) and was reduced to
baseline levels by neutralizing (polyclonal) anti-IFN- Abs (data
not shown). Untreated and IFN-treated cells responded in a similar
manner to the Ca2+ ionophore ionomycin (Fig. 3, lower panel, compare A, B, and
C). This confirmed the receptor/ligand-specific modulation
of calcium mobilization by IFN-.
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-induced changes in CR
expression and to possibly distinguish responses to different ligands,
cell migration assays were used to determine whether treatment with
IFN- enhances chemotaxis in response to the chemokines RANTES,
MIP-1, eotaxin, MIP-1ß, and SDF-1. In this assay, the ability
of U937 cells to migrate in culture through a membrane in response to
different stimuli is determined by enumerating the cells in both sides
of the culture chamber after 12 h. IFN--2b pretreatment (300
IU/ml, for 4 days) induced an increase in cell migration to 300% in
response to RANTES (100 ng/ml), to 200% in response to MIP-1
(100 ng/ml), and to 150% in response to eotaxin (200 ng/ml) when
compared with untreated controls that were exposed to the same
chemokine. No significant changes in cell migration in response to
MIP-1ß (250 ng/ml) or to SDF-1 (250 ng/ml) were observed (Fig. 4).
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-2b. The cytokine induced a marked increase in CCR1 and CCR3
expression as determined at 2 days after the initiation of treatment.
The level of CXCR4 and CCR5 expression remained unchanged (Fig. 5A). Similar results were
obtained in experiments using U937 cells. The expression of CCR1 and
CCR3 was increased, whereas the expression of CCR5 and CXCR4 remained
unchanged under IFN--2b treatment (Fig. 5B). No specific
messages for CCR2b and CCR4 were detectable by means of RT-PCR
amplification, independent from treatments with IFN- (data not
shown).
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(specific ligand to CCR1 and CCR5) and compared these samples with
untreated cells by flow cytometry. A marked increase in fluorescence
intensity was observed in cell populations that had been treated with
IFN--2b (Fig. 6, left
panel), indicating a higher cell surface density of CCR1 and/or
CCR5. Unchanged surface staining with MIP-1ß (ligand to CCR5)
indicated that the difference in the labeling with MIP-1 is due to
an increase in CCR1 (data not shown). To assess the effects of IFN-
treatment on the surface receptor density of CXCR4, a receptor-specific
Ab stain was used. FACS analyses revealed a slight decrease in CXCR4
expression in IFN- treated cells (Fig. 6, right
panel).
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-2b treatment (when compared with
untreated cultures) that were not able to be explained by toxicity, the
cell numbers (using trypan blue exclusion) as well as cell metabolic
rates (using the MTT assay (14)) were determined. After 5
days, cultures that were treated with 300 IU/ml IFN- contained
29 ± 4% fewer cells than the controls. However, when the
metabolic rates as determined by MTT assays were compared, only a 17 +
6% reduction was observed in IFN--treated cultures (data not
shown). To determine whether the lower cell number in primed U937
cultures was due to apoptosis-related cell death, we applied a TUNEL
assay and found no significant difference in the percentage of
apoptotic cells in the two differently treated groups under the
described culture conditions (p > 0.5,
determined in two independent experiments). Application of the Cell
Death Detection ELISAplus (Boehringer Mannheim)
to cell culture supernatants and to cell lysates confirmed that lower
cell density in IFN--treated U937 cell cultures was not caused by
induction of cell death.
The cell viability data and the metabolic assays indicated that
IFN--2b decreases cell proliferation rates. Therefore, we performed
cell cycle analysis using flow cytometry. Propidium iodide staining of
the cells allowed assessment of DNA content during the cell cycle,
distinguishing G0/G1-phase,
S-phase, and G2/M-phase peaks. Patterns of DNA
content of cells (identified as viable by gating) were compared between
treatment groups, and the relative amount of cells within the different
peaks was calculated. IFN- treatment of U937 cells for 3 days (300
IU/ml IFN-) resulted in a 13 ± 3% increase of cells that were
at G0/G1 phase (data not
shown).
We were also interested in evaluating whether expression of the
activation marker CD95, a receptor known to mediate signals that can
lead to apoptosis, was modulated by IFN--2b in our system,
especially because different researchers reported distinct outcomes in
various experimental systems (3, 4). Flow cytometry
analysis revealed a slight increase in CD95 expression on U937 cells
that were treated with IFN- (300 IU/ml, for 4 days; Fig. 7A). In comparison, however,
this was a far less intense increase in CD95 receptor density than that
induced by IFN-
(30 ng/ml, 3 days of treatment) (Fig. 7B). When both IFN- and IFN- were combined at similar
concentrations, a further increase in CD95 expression was noted (Fig. 7C). Changes in CD95 expression as induced by IFN--2b or
IFN- were dose-dependent and were not detectable by means of FACS
analysis when IFN- was used as single treatment at
concentrations of <10 IU/ml (1 ng/ml for IFN-, data not shown).
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-2b-pretreated U937 cells (500 IU/ml, for 4 days) when compared
with untreated controls. When cells were primed with both IFN- and
IFN- (50 ng/ml) under these culture conditions, only 8 ± 2%
of cells remained viable. Titration experiments in which IFN-,
IFN-, and CH11 were evaluated separately and in combination revealed
that IFN- and IFN- have at least additive effects on
CD95-mediated apoptosis induction in U937 cells (data not shown).
Because inflammatory responses are regulated by "pro and contra"
signals and concepts of autocrine loops as well as negative feed backs
have been described for a variety of cellular receptors upon
interaction with their ligands, we investigated the effect of
IFN--2b on chemokine production. Theoretically, the RANTES receptor
CCR1 and CCR3 expression and signaling (that we found to be increased)
could be modulated by RANTES production as induced by IFN-. We
measured RANTES in cell culture supernatants after 6 days of IFN-
treatment and found levels that were reduced to 74 ± 15% of
levels in untreated controls (37 ± 8 ng
RANTES/106cells).
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Discussion |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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include the
enhancement of cellular adhesion molecule expression (15).
It was not known, however, that the modulation of cell adhesion by
IFN- as observed in monocytoid cells involves the differential
regulation of CR expression. We have now demonstrated that IFN--2b
can enhance CCR1 and CCR3 expression on APC subsets. These events
appear to be specifically related to the pathways involved in IFN-
signal transduction. Alternatively, CR modulation could be the result
of a feedback regulation to the IFN--induced reduction of chemokine
production. Although our experimental setting did not allow for the
exclusion of one or the other possibility, our results illustrate that
CR expression and signaling can be differentially regulated by IFN-,
because receptors such as CCR2b, CCR4, CCR5, or CXCR4 were not affected
or found to be decreased.
Our study supports a paradigm in which locally produced cytokines can
regulate the quantity and the quality of leukocytes trafficking to the
site of action as mediated by both the chemokines and their receptors
(16). Moreover, increased systemic levels of cytokines
such as IFN- may change the overall activation of leukocytes by
priming more cells into a stage of enhanced susceptibility to
chemokines that are produced at defined anatomic sites. Our data
provide evidence that the recruitment and maturation of APC precursors
is regulated in a similar manner, in that increased levels of IFN-
act by differentially increasing CR subset expression. This priming
effect, in turn, may also contribute to some differentiation steps of
monocytes in the development toward mature APCs. In support of our
hypothesis, involvement of IFN- in the maturation of monocytes that
includes modulation of CCR5 has recently been demonstrated (13, 17). Thus, morphological changes in primary monocyte-derived
cells treated with IFN-, which we detected by flow cytometry, may
indicate comparable processes. A better functional and phenotypic
characterization of these cell subsets remains an issue of future
investigations.
A number of cytokines and growth factors (including IL-2, IL-4, IL-10,
IL-12, and IL-13, as well as GM-CSF and IFN- (13, 18, 19, 20, 21, 22, 23, 24)) were found to have CR-modulating properties. The
experimental systems that were used to detect changes in CR expression
and signaling, however, vary. Effects on the regulation of gene
transcription, the CR mRNA stability, or the cell surface receptor
expression and the rate of internalization were reported to take place
within minutes but can require up to several days. In our experimental
system, the maximal effect of IFN- on enhanced CCR1 and CCR3
expression was detected between days 2 and 5 posttreatment. This time
interval necessary for response may indicate an indirect modulation,
possibly as a feedback mechanism, especially because levels of newly
produced RANTES, a ligand for CCR1, CCR3, and CCR5 were found to be
slightly decreased compared with cultures that were not treated with
IFN--2b. Consequently, further studies are required to define the
direct connection between intracellular pathways of IFN--induced
signals and CR expression.
We also provide evidence that IFN- may be involved in the process of
cell survival-regulation by mediating susceptibility to apoptosis in
activated immune cells of monocytoid origin. This was demonstrated by
the enhanced CD95 expression and increased susceptibility of U937 cells
to CD95-triggered apoptosis. A further increase of CD95 expression and
response to related signaling was observed by a combination of
IFN--2b and IFN- treatment, perhaps an indication of partially
overlapping signal transduction for both type I and type II IFN
(25, 26). A relationship of IFN--induced signals and
CD95 expression is well established (27, 28). We have now
demonstrated such an interaction for IFN--2b and the CD95 system in
monocytoid cells in vitro, supporting the rational of using the
augmenting effects of both type I and type II IFN for developing new
combination treatment approaches to cancer.
It has been proposed that IFN--induced apoptosis may occur in cells
during all cell cycle stages; therefore, apoptosis and cell cycle
arrest would represent independent responses to IFN- (29, 30). The high degree of cell death that was inducible through
CD95 receptor triggering in our experimental system supports the
previously observed independence of some apoptosis pathways from cell
cycle stages. In addition to confirming that IFN- affects cell
cycling, our results also indicate that these events are related to the
APC differentiation and maturation process by involving changes in CR
expression and function. Although further studies are necessary to
elucidate the mechanisms that control the differential regulation of CR
expression in greater detail, the newly identified immunoregulatory
effect of IFN--2b on APCs as related to CR expression and function
may help in understanding the complex pathophysiologic role of this
cytokine and may contribute to the development of alternative
immune-modulating therapeutic strategies in malignancies.
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Footnotes |
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2 Address correspondence and reprint requests to Dr. Frank F. Weichold, Institute of Human Virology, University of Maryland Biotechnology Institute, 725 West Lombard Street, Baltimore, MD 21201. E-mail address:
3 Abbreviations used in this paper: CR, chemokine receptor; MDM, monocyte-derived mononucleated phagocyte; MIP, macrophage inflammatory protein; SDF, stromal cell-derived factor.
Received for publication December 23, 1998. Accepted for publication July 8, 1999.
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References |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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-interferons: 40th anniversary of the discovery of interferons. Cancer Res. 58:2489. and its effects on the cytokine cascade: a pro- and anti-inflammatory cytokine. Leuk. Lymphoma 23:55.[Medline]
in chronic myelogenous leukemia. Blood 89:957.2. Eur. J. Immunol. 26:3119.[Medline]
restores normal ß1 integrin-mediated inhibition of hematopoietic progenitor proliferation by the marrow microenvironment in chronic myelogenous leukemia. Blood 87:3883.
B and RXR ß-like proteins in interferon-induced HLA class I and ß globin gene transcription in K562 erythroleukaemia cells. Mol. Cell. Biochem. 178:103.[Medline]
and - on some in vitro immune functions of bovine intraepithelial and lamina propria leukocytes. J. Interferon Res. 8:495.[Medline]
increases expression of chemokine receptors CCR1, CCR3, and CCR5, but not CXCR4 in monocytoid U937 cells. Blood 91:4444.-interferons on immune function. Semin. Oncol. 24:S9.
. J. Immunol. 160:3869. priming up-regulates IFN-stimulated gene factor 3 (ISGF3) components, augmenting responsiveness of IFN-resistant melanoma cells to type I IFNs. J. Immunol. 160:5475. induces Ice gene expression and enhances cellular susceptibility to apoptosis in the U937 leukemia cell line. Biochem. Biophys. Res. Commun. 229:21.[Medline]
in hematopoietic cell lines. Cell Growth Differ. 8:343.[Abstract]
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