| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
|
|
|
|||||||
|
|||||||||
Departments of Medicine and Microbiology/Immunology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599
 |
Abstract |
|---|
 Top Abstract IntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
|
Introduction |
|---|
|
TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
APO-1/Fas (CD95) is a type I transmembrane glycoprotein belonging to the nerve growth factor/TNF receptor superfamily (7). Fas is expressed on activated T and B cells (7), thymocytes (8), malignant T and B cells (9), and in a variety of tissues outside the immune system such as liver, lung, and kidney (10). The interaction of Fas and its ligand has been shown to play an important role in the regulation of programmed cell death of T and B lymphocytes (11). The Fas/Fas ligand (FasL)3 pathway serves at least two functions in the immune system: first, to limit the expansion of an immune response by eliminating lymphocytes that are no longer needed, and second, to eliminate autoreactive T cells that have escaped thymic selection (12).
Recently, we have observed that cells from Fas-deficient lpr mice were resistant to the apoptosis induced by ionizing radiation, providing evidence that the Fas/FasL system may also be involved in surveillance of injured cells (13). Therefore, we wondered whether the apoptosis known to occur after UV-B irradiation might involve the Fas/FasL signaling pathway. We have found that UV-B irradiation increased Fas and FasL expression in human lymphocytes, and that a lymphocyte cell line released functional soluble FasL (sFasL) after UV-B irradiation.
These data suggest that UV-B-induced apoptosis is at least in part mediated by Fas in human lymphocytes and monocytes. Therefore we propose a third function for the Fas/FasL pathway in the immune system: to facilitate the apoptosis and elimination of cells undergoing UV light exposure and other forms of environmental trauma.
|
Materials and Methods |
|---|
|
TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
Peripheral blood from 10 healthy donors (age 25–35) was separated by density centrifugation, the mononuclear cell interface was collected over Histopaque 1077 (Sigma, St. Louis, MO) after centrifugation at 2000 rpm for 30 min, and it was then washed two times in RPMI 1640. The mononuclear cells were resuspended at a concentration of 1 x 106/ml in RPMI 1640, 100 U/ml penicillin, 100 µg/ml streptomycin, 2 mM L-glutamine, 1 mM sodium pyruvate, 10% FBS, and nonessential amino acids (University of North Carolina Cancer Center Tissue Culture Facility, Chapel Hill, NC). These cells were transferred to 24-well plates at 37°C for 1 h to allow monocytes to adhere. Nonadherent cells were removed, washed, resuspended under the same conditions, irradiated, and cultured at 37°C in a 5% CO2/95% air-humidified atmosphere in 24-well plates at a concentration of 1 x 106cells/ml. In some experiments ZnCl2 (1 mM) or cycloheximide (CHX) (30 µg/ml) (Sigma) was added 5 min after irradiation.
Cell lines
The U937 human histiocytic lymphoma and the Jurkat human T cell leukemia clone E6-1, both constitutively expressing Fas receptor and sensitive to killing by anti-Fas, were obtained from the American Type Culture Collection (Rockville, MD). The E6-1R, an anti-Fas-resistant variant of E6-1S, was generated by continuous culture in medium containing anti-Fas (clone 7C11, 1:1000) (a generous gift from Dr. M. Robertson, Indiana University, Indianapolis, IN) for 3 mo. The E6-1R2, a FasL-resistant variant of E6-1S, was selected from continuous coculture for 3 mo with a National Institutes of Health 3T3 cell line transfected with FasL (a generous gift from Dr. I. N. Crispe, Yale Medical School, New Haven, CT) (14).
Irradiation of cells
UV-B irradiation was delivered using two FS-20 sun lamps, which emit most of their energy within the UV-B range (290–320 nm) with an emission peak at 310 nm. Preliminary experiments showed equivalent UV effects on cells irradiated in complete medium compared with PBS. In subsequent studies, therefore, cells were irradiated in complete media with different doses of UV-B (0.1, 0.5, 1, 10, and 20 mJ/cm2) as determined with an IL-1700 research radiometer (International Light, Newburyport, MA). Mock UV-B-irradiated control cells were treated in an identical manner except that the UV-B lamps were turned off.
Cell staining for surface markers and apoptosis
Fluoresceinated anti-Fas (clone DX2, isotype: mouse IgG1
,
anti-CD4 (clone HIT3a, isotype: mouse IgG2a, and isotype-matched
FITC-labeled mouse Ab controls were obtained from PharMingen (San
Diego, CA). For staining, samples were washed twice with HBSS
containing 15 mM HEPES, 0.5% L-glutamine, and 3% FBS
(HBSS complete) (University of North Carolina Cancer Center Tissue
Culture Facility, Chapel Hill, NC), and fluoresceinated Abs were added
to 1 x 106 cells for 30 min at 4°C in 96-well
microtiter plates. The cells were washed once with complete HBSS
followed by two washes in PBS containing 0.1% NaN3. To
permeabilize cell membranes for DNA staining, 1 x 106
cells were added to 3 ml of 70% ethanol, incubated for 45 min at
4°C, and washed twice. For DNA staining, 0.1 ml of 1 mg/ml RNase A
(Sigma) was added per sample, followed by 0.2 ml of 100 µg/ml
propidium iodide (PI) (Sigma). Cells were incubated for 20 min in the
dark at 4°C and were analyzed with a FACScan (Becton Dickinson,
Mountain View, CA) with Cytomation data acquisition and software (Fort
Collins, CO) for green and red fluorescence.
Analysis of apoptotic cells
Apoptotic cells appeared in the <2 N DNA peak identified by PI immunofluorescence. They could also be distinguished from necrotic cells by analyzing the light scatter profile. Cell death by necrosis resulted in a large decrease in forward-angle light scatter (FSC) and side scatter (SSC), while apoptotic cells were a discrete population showing a smaller decline in FSC and an increase in SSC (13, 15, 16, 17). Samples were collected in list mode, so that when cell surface markers were used, the percentage of cells undergoing apoptosis could be determined by gating on FITC-stained cells and subsequently analyzing DNA staining. At least 30,000 events were collected per sample in all experiments.
Apoptosis detection with the JAM test
To screen a large number of samples, DNA fragmentation and cell death were measured using a modified standard assay for cell proliferation, involving vacuum aspiration of labeled cells through fiberglass filters. Since high m.w. DNA is trapped in these filters, small pieces of fragmented DNA are washed through, leaving only intact DNA from living cells (18). E6-1S cells (5 x 105/well in 96-well plates) were labeled for 16 h with 2.5 µCi/ml of [3H]thymidine (9.25 x 104 Bq/ml). The supernatant was then removed, and fresh medium and anti-FasL (PharMingen) at different concentrations were added. After 5 h of incubation of 37°C in a 5% CO2 incubator, cells were harvested and counted in a liquid scintillation counter. The percentage of specific DNA fragmentation was calculated as: 100 x (spontaneous cpm - experimental cpm)/spontaneous cpm. Experimental cpm is defined as cpm of retained DNA in the presence of anti-FasL, and spontaneous cpm is cpm of retained DNA in the absence of anti-FasL. Experiments were performed in triplicate.
Western blotting for FasL
A total of 4 x 106 per sample of PBLs were washed in PBS and lysed for 20 min on ice in 50 mM HEPES, 150 mM NaCl, 1% Triton X-100, 10% glycerol, 10 mM NaF, 1 mM EDTA, 2 mM sodium orthovanadate, 1 mM DTT, and 1 mM PMSF. After centrifugation for 15 min at 14,000 rpm, the amount of proteins in the supernatant was determined by BCA Protein Assay Reagent (Pierce, Rockford, IL) and BSA standards. Then 30 µg of lysate in Laemmli buffer were separated per lane on 12% SDS-PAGE. Western blots were probed with mouse anti-human FasL obtained from Transduction Laboratories (Lexington, KY). Bound Abs were detected with goat anti-mouse-horseradish peroxidase conjugate. An enhanced chemiluminescence system (Renaissance, NEN Life Science Product, Boston, MA) was used for detection.
Detection of sFasL
To analyze the production of sFasL by E6-1 cells in response to UV-B irradiation, cells (1 x 106/ml) were irradiated (1 mJ/cm2), resuspended in complete medium, and cultured at 37°C for 2 h. Cells were recovered after brief centrifugation and aliquots of supernatant (500 µl) assayed for their cytotoxic activity using nonirradiated E6-1S susceptible to anti-Fas killing, E6-1R2 cells resistant to FasL, or anti-Fas-mediated killing as targets (1 x 105). Supernatants from nonirradiated cells were used as additional controls. Target cells were suspended in aliquoted supernatant (500 µl) and were harvested after 5-h culture. Apoptosis was measured by PI staining as described above.
Statistical analysis
Student’s t test was used to determine the statistical significance of differences between groups. Statistical significance was defined as p < 0.05.
|
Results |
|---|
|
TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
To test their sensitivity to UV-B irradiation, lymphocytes from
healthy donors were cultured for 24 and 48 h after mock UV
exposure or after 20, 10, and 1 mJ/cm2 of UV-B irradiation.
Apoptosis was detected according to the FSC vs SSC profile (13, 15, 16, 17). At the lowest UV-B dose (1 mJ/cm2), it was
possible to detect a clear apoptotic population but minimal necrosis.
In contrast, with the highest dose (20 mJ/cm2), after 24
and 48 h most of the cells were necrotic (Fig. 1
A). The 10
mJ/cm2-dose yielded a mixed population of necrotic and
apoptotic cells. The UV-B response thus differed qualitatively
depending on the irradiation dose. To test if the E6-1S
clone responded to UV injury in a similar fashion, these cells were
also exposed to graded UV-B doses. For detecting the apoptotic
population in these cells the PI staining was used, although FSC vs SSC
analysis (not shown) yielded much the same results. As with normal
lymphocytes, we found a remarkable difference in the outcome depending
on the UV-B dose (Fig. 1B). This suggests that apoptosis can
occur alone or with necrosis and that this mechanism is preserved in
this cell line. Moreover, as indicated by their sensitivity to small
UV-B doses (1, 0.5, 0.1, 0.05 mJ/cm2), E6-12
cells are extremely sensitive to UV-B-induced apoptosis compared with
normal lymphocytes (Fig. 1B).
|
To test whether the Fas/FasL system might mediate UV-B-induced
apoptosis, lymphocytes from healthy donors were cultured for different
intervals after UV-B irradiation at different doses and Fas expression
was assessed. Figure 2A shows
data from a representative experiment. We found a significant increase
in Fas+ cells compared with nonirradiated cells at both 10
and 1 mJ/cm2 of UV irradiation. We found no significant
increase in anti-CD4+ staining, even at the highest
UV-B dose, suggesting that the increase of Fas+ cells was
not due to nonspecific increased staining following UV-B exposure (Fig. 2B). We found a similar increase in Fas expression even at
very low doses of UV-B, which correspond to possible in vivo UV
exposure. Lymphocytes from 10 healthy donors were cultured and stained
for Fas-FITC at T0 (0 h), T1 (24 h) and T2 (48 h) in vitro with and
without exposure to UV-B irradiation (10 mJ/cm2). Figure 3 shows the mean percentage of
Fas+ cells at different time points. The difference between
the UV-B-irradiated and untreated groups was significant at both 24 and
48 h (p < 0.01).
|
|
To test if the Fas increase was affected by inhibiting
UV-B-induced apoptosis or by inhibiting protein synthesis,
ZnCl2 or CHX was added to cultured human lymphocytes
immediately after UV-B irradiation (10 mJ/cm2). Zn (1 mM)
inhibited apoptosis (data not shown) as expected (19),
accompanied by a marked increase in the intensity of Fas expression,
probably due to the accumulation of Fas+ cells unable to
undergo apoptosis (Fig. 4). No
substantial difference in apoptosis percentage (data not shown) or in
Fas expression was noticed in cultures containing CHX (30 µg/ml),
suggesting that increased Fas expression does not require protein
synthesis. Histograms shown are representative of three different
experiments (Fig. 4).
|
The U937 and E6-1 cell lines, which express Fas constitutively and
are sensitive to UV-B (Fig. 5), were
irradiated and, after 5 h of culture, were stained with
fluoresceinated monoclonal anti-Fas. After UV-B irradiation, Fas
expression was greatly increased on U937 cells. The E6-1 cells showed
enhanced Fas+ expression after UV-B irradiation (Fig. 5).
|
We wondered if the Fas expression noted after UV-B irradiation
differed between live and apoptotic cells. Two-color staining (Fas-FITC
and PI) was performed to assess Fas expression in both populations. The
apoptotic lymphocyte population could be distinguished both with PI
staining and by FSC vs SSC profile. After UV-B irradiation (10
mJ/cm2), Fas expression on live cells increased, but it was
striking that the vast majority of the cells undergoing apoptosis were
Fas+, as shown in Figure 6.
Few apoptotic cells were detectable without UV-B irradiation. The
increased Fas expression on apoptotic cells after UV-B irradiation is
consistent with a functional role for the Fas molecule in bringing
about their death. Histograms shown in Figure 6 are representative of
eight different experiments.
|
To test whether FasL was also increased after UV-B irradiation,
PBLs from healthy donors were irradiated with different doses (1, 10,
and 20 mJ/cm2), and after 18 h of culture, FasL expression
was measured by Western blot. Results are shown in Figure 7. Nonirradiated cells showed no or
little FasL expression; yet, after 1 and 10 mJ/cm2 of UV-B
irradiation, there was a clear FasL increase. Surprisingly, after 20
mJ/cm2, FasL did not increase, implying that the highest
dose was inducing necrosis more than apoptosis, or at least that the
mechanism involved was not the Fas/FasL system.
|
The increased expression of Fas after UV-B exposure raised the
question of whether FasL was also increased after UV-B irradiation. To
approach this issue, we generated E6-1 cell lines resistant to
anti-Fas or to FasL (E6-1R and E6-1R2)
(Fig. 8). These cell lines served as
valuable reagents to assess the FasL activity of cell supernatants,
because they did not undergo apoptosis when incubated with anti-Fas
or FasL, respectively, and could thus be compared with wild-type E6-1
cells. Both cell lines were stained with PI after UV-B irradiation to
determine the fraction undergoing apoptosis. The E6-1R line
showed a moderate decrease in the apoptotic population compared with
the E6-1S (Fig. 9). In
contrast, the E6-1R2 line showed a nearly complete
resistance to UV-B-induced apoptosis (Fig. 9). These results are
consistent with a role for the Fas/FasL system in UV-B-induced
apoptosis. The difference in UV-B sensitivity between the
E6-1R and E6-1R2 cell lines is probably due to
the fact that, despite the resistance to anti-Fas,
E6-1R was still sensitive to FasL killing (Fig. 8).
|
|
We wondered if UV-B irradiation induced the release of sFasL.
E6-1S cells were irradiated (1 mJ/cm2), washed,
and cultured for 2 h. Supernatants from irradiated cells were
collected and their cytotoxicity tested on nonirradiated
E6-1S and E6-1R2 cells by detecting apoptosis
with PI staining. There was no difference in the percentage of cells
undergoing apoptosis in both clones after adding supernatants from
nonirradiated E6-1S (1.9% vs 2.5%). In contrast, the
supernatant from the irradiated cells induced apoptosis in the
E6-1S and not in the E6-1R2 clone (17.6% vs
3.5%) (Fig. 10), suggesting that sFasL
was released upon irradiation.
|
To test the functional role of the Fas/FasL system after UV-B
irradiation, we tested the effect of blocking Fas/FasL interactions
with an anti-FasL Ab. E6-1S cells were labeled with
[3H]thymidine. After 16 h, cells were UV-B
irradiated (1 mJ/cm2) and cultured with anti-FasL
(clone NOK-1, PharMingen) or the isotype control at different
concentrations for 5 h. Apoptosis was detected using the JAM test.
We found significant inhibition of apoptosis dependent on the
concentration of anti-FasL, confirming that UV-B-induced apoptosis
was, in part, Fas mediated (Fig. 11).
|
|
Discussion |
|---|
|
TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
The cellular response to UV irradiation is dependent upon the induced
expression of many genes, the so called "UV response"
(22), which includes the immediate early genes
c-fos (23, 24) and c-jun (23, 25) and transcription factors SAP-1 and nuclear factor B
(26). UV irradiation also suppresses lymphocyte
proliferative, cytotoxic, and accessory functions (27).
The mechanism is not entirely clear, but may involve alteration of
cytokine production and secretion (27), calcium
homeostasis (28), MHC class II Ag expression
(28) and, depending upon wavelength and duration of
exposure, direct effects on DNA integrity (29).
Circulating human T lymphocytes are exquisitively sensitive to the
DNA-damaging and lethal effects of UV-B irradiation, raising the
possibility that UV-B may contribute to immune suppression via a direct
effect on extracapillary T lymphocytes (20, 21). Finally
UV-B irradiation is a strong inducer of apoptosis (21, 28), but this occurs via incompletely understood pathways.
Our results confirmed the susceptibility of human lymphocytes, human T (E6-1), and histiocytic (U937) cell lines to UV-B irradiation-induced apoptosis. Unexpectedly, we noticed a remarkable difference in the nature of the UV-B response depending on the dose. In normal lymphocytes, a dose of 20 mJ/cm2 induced mainly necrosis, yet exposure to 10 and 1 mJ/cm2 yielded a clear apoptotic population. The results were even more marked with the E6-1 cell line using 1 and 0.1 mJ/cm2. These results are in agreement with previous observations in which a very low UV-B dose was able to induce apoptosis in PBMC (21). One explanation for the response to different UV-B doses is that lymphocytes are physiologically protected against UV irradiation by the skin tissue layers. It is possible that in our experiments, with the lowest UV-B dose, which corresponds to a possible in vivo UV exposure, the apoptotic machinery was exhibiting the normal cellular UV-B response. In contrast, the direct lymphocyte irradiation at the highest UV dose may have induced diffuse cellular damage, resulting mainly in necrosis instead of apoptosis. UV-B stress may thus involve the apoptotic machinery only below certain doses.
An important finding in the present work was the markedly increased Fas expression following UV-B. Recently it has been shown that exposure to UV-B light induced clustering and internalization of cell surface receptors for epidermal growth factor, TNF and IL-1, and UV-B-induced activation of these receptors (30). An analogous mechanism could only in part explain the increases of Fas expression in our experiments since CHX-treated cells, despite protein synthesis inhibition, showed increased Fas expression after UV-B irradiation. Another explanation could be the expression of an intracellular pool of preformed Fas receptor, although this remains to be established. The increased Fas expression very likely renders the UV exposed cells sensitive to FasL, which is also induced by UV-B. Whether Fas-mediated killing occurs via an autocrine or paracrine pathway remains to be established.
Since completion of this work, a report has appeared showing that UV exposure of MCF7 and BJAB cells induced apoptosis apparently via a Fas-dependent mechanism (31). Our data, using freshly isolated PBL as well as cell lines, are consistent with these findings, but the increase in fluorescence intensity by flow cytometry in our studies is in contrast to the receptor aggregation reported in this study. The differences in UV exposure and in the cell lines used in this report may account for these differences.
Another important finding in the present work was the increased expression of FasL in PBLs after a low dose of UV-B, but not with the highest dose (20 mJ/cm2). The results are in contrast with a recent report (32) in which UV light induced apoptosis by activating directly the Fas receptor, independently of its ligand. Once again differences in UV exposure may account for discrepancies, especially because in our experiments only low doses of UV-B involved the Fas/FasL pathway. Our results imply, depending on the UV-B dose, a more complex scenario with multiple features for the so-called UV response, and not just a simple gradient of dose/response.
It has been recently reported that Jurkat T cells constitutively express intracellular FasL, which is rapidly secreted as functional sFasL after stimulation with anti-CD3 or phytohemagglutinin; moreover, Jurkat supernatants induce apoptosis in Fas-expressing cells (33). In our experiments, the supernatant from UV-B-irradiated Jurkat cells was able to induce apoptosis only in the E6-1 clone sensitive to Fas killing, indicating that UV-B also triggers FasL release by Jurkat cells. The role of the Fas/FasL system in UV-B induced apoptosis was also confirmed by the blocking with anti-FasL Ab of the induction of apoptosis.
To investigate CD95-signaling requirements, several groups have created mutant cell lines incapable of transmitting apoptotic signals through CD95 by continuous culture in medium containing anti-Fas (34, 35, 36). In most cases the phenotypic differences between the wild-type and the mutant cell line were minor (9, 35, 36). Because we have shown that the anti-Fas-resistant cell line was still sensitive to FasL, these findings could explain why previously reported differences between wild-type and mutant cell lines were difficult to detect.
Recently, we have observed that cells from Fas-deficient lpr mice were resistant to the apoptosis induced by ionizing radiation. Because the lpr mice differed from controls only in their lack of Fas expression, these observations raised the possibility that Fas itself participated in the apoptosis induced by ionizing radiation (13). Furthermore, two different groups (37, 38) have shown that the Fas system contributes to keratinocyte apoptosis in both type A and B UV-irradiated human skin. These findings are consistent with the important role for Fas/FasL interactions in the present work.
The Fas/FasL system can be added to the list of the mechanisms involved in the UV response. Since UV-B damaged lymphocytes are no longer needed and since they could become dangerous, activation of the Fas/FasL system may facilitate the apoptosis and elimination of cells undergoing this and other forms of environmental trauma. Its malfunction could be involved in the pathogenesis of autoimmune or neoplastic disorders. Exposure to sunlight has long been associated with exacerbation of systemic lupus erythematosus, the prototype of the autoimmune diseases (39, 40). It is possible that inadequate UV response due to lesions in the Fas/FasL system might contribute to systemic lupus erythematosus photosensitivity.
|
Acknowledgments |
|---|
|
Footnotes |
|---|
2 Address correspondence and reprint requests to Dr. Philip L. Cohen, Department of Medicine, Division of Rheumatology & Immunology, CB 7280, Chapel Hill, North Carolina 27599-7280. E-mail address:
3 Abbreviations used in this paper: FasL, Fas ligand; sFasL, soluble FasL; CHX, cycloheximide; PI, propidium iodide; FSC, forward-angle scatter; SSC, side scatter; MFI, mean fluorescence intensity.
Received for publication November 5, 1997. Accepted for publication March 6, 1998.
|
References |
|---|
|
TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
in the formation of sunburn cells. J. Invest. Dermatol. 104:922.[Medline]
B and HIV-1 LTR activity in mouse L cells by ultraviolet radiation: LTR trans-activation in a nonirradiated genome in heterokaryons. Exp. Cell Res. 230:9.[Medline]
This article has been cited by other articles:
|
|
 |
|
  J. Narbutt, B. Cebula, A. Lesiak, A. Sysa-Jedrzejowska, M. Norval, T. Robak, and P. Smolewski The Effect of Repeated Exposures to Low-Dose UV Radiation on the Apoptosis of Peripheral Blood Mononuclear Cells Arch Dermatol, February 1, 2009; 145(2): 133 - 138. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 W.-H. Zhou, L. Dong, M.-R. Du, X.-Y. Zhu, and D.-J. Li Cyclosporin A improves murine pregnancy outcome in abortion-prone matings: involvement of CD80/86 and CD28/CTLA-4 Reproduction, March 1, 2008; 135(3): 385 - 395. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 J.P. Buyon and R.M. Clancy Dying right to live longer: positing apoptosis as a link between maternal autoantibodies and congenital heart block Lupus, February 1, 2008; 17(2): 86 - 90. [Abstract] [PDF]
|
|
|
|
 |
|
 L. Frisoni, L. McPhie, S.-A. Kang, M. Monestier, M. Madaio, M. Satoh, and R. Caricchio Lack of Chromatin and Nuclear Fragmentation In Vivo Impairs the Production of Lupus Anti-Nuclear Antibodies J. Immunol., December 1, 2007; 179(11): 7959 - 7966. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
N. Calvani, R. Caricchio, M. Tucci, E. S. Sobel, F. Silvestris, P. Tartaglia, and H. B. Richards Induction of Apoptosis by the Hydrocarbon Oil Pristane: Implications for Pristane-Induced Lupus J. Immunol., October 1, 2005; 175(7): 4777 - 4782. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
L. Frisoni, L. Mcphie, L. Colonna, U. Sriram, M. Monestier, S. Gallucci, and R. Caricchio Nuclear Autoantigen Translocation and Autoantibody Opsonization Lead to Increased Dendritic Cell Phagocytosis and Presentation of Nuclear Antigens: A Novel Pathogenic Pathway for Autoimmunity? J. Immunol., August 15, 2005; 175(4): 2692 - 2701. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
R. Caricchio, L. McPhie, and P. L. Cohen Ultraviolet B Radiation-Induced Cell Death: Critical Role of Ultraviolet Dose in Inflammation and Lupus Autoantigen Redistribution J. Immunol., December 1, 2003; 171(11): 5778 - 5786. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 H. Q. Wang, T. Quan, T. He, T. F. Franke, J. J. Voorhees, and G. J. Fisher Epidermal Growth Factor Receptor-dependent, NF-{kappa}B-independent Activation of the Phosphatidylinositol 3-Kinase/Akt Pathway Inhibits Ultraviolet Irradiation-induced Caspases-3, -8, and -9 in Human Keratinocytes J. Biol. Chem., November 14, 2003; 278(46): 45737 - 45745. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
M. B. M. Teunissen, G. Piskin, S. d. Nuzzo, R. M. R. Sylva-Steenland, M. A. de Rie, and J. D. Bos Ultraviolet B Radiation Induces a Transient Appearance of IL-4+ Neutrophils, Which Support the Development of Th2 Responses J. Immunol., April 15, 2002; 168(8): 3732 - 3739. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 T. Jackle, C. Hasel, I. Melzner, S. Bruderlein, P. M. Jehle, and P. Moller Sustained hyposmotic stress induces cell death: apoptosis by defeat Am J Physiol Cell Physiol, November 1, 2001; 281(5): C1716 - C1726. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 I. Herr and K.-M. Debatin Cellular stress response and apoptosis in cancer therapy Blood, November 1, 2001; 98(9): 2603 - 2614. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
J.-H. Lai, L.-J. Ho, K.-C. Lu, D.-M. Chang, M.-F. Shaio, and S.-H. Han Western and Chinese Antirheumatic Drug-Induced T Cell Apoptotic DNA Damage Uses Different Caspase Cascades and Is Independent of Fas/Fas Ligand Interaction J. Immunol., June 1, 2001; 166(11): 6914 - 6924. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
C. Nicolo, B. Tomassini, M. R. Rippo, and R. Testi UVB-induced apoptosis of human dendritic cells: contribution by caspase-dependent and caspase-independent pathways Blood, March 15, 2001; 97(6): 1803 - 1808. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 G. De Panfilis, A. Caruso, P. Sansoni, G. Pasolini, D. Semenza, and C. Torresani Identification of Fas-L-Expressing Apoptotic T Lymphocytes in Normal Human Peripheral Blood : In Vivo Suicide Am. J. Pathol., February 1, 2001; 158(2): 387 - 391. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 S. T. Eichhorst, M. Müller, M. Li-Weber, H. Schulze-Bergkamen, P. Angel, and P. H. Krammer A Novel AP-1 Element in the CD95 Ligand Promoter Is Required for Induction of Apoptosis in Hepatocellular Carcinoma Cells upon Treatment with Anticancer Drugs Mol. Cell. Biol., October 15, 2000; 20(20): 7826 - 7837. [Abstract] [Full Text]
|
|
|
|
 |
|
 W Liu, M Kato, A. Akhand, A Hayakawa, H Suzuki, T Miyata, K Kurokawa, Y Hotta, N Ishikawa, and I Nakashima 4-hydroxynonenal induces a cellular redox status-related activation of the caspase cascade for apoptotic cell death J. Cell Sci., January 2, 2000; 113(4): 635 - 641. [Abstract] [PDF]
|
|
|
|
|
|
S. Nakagawa, C. W. Koomen, J. D. Bos, and M. B. M. Teunissen Differential Modulation of Human Epidermal Langerhans Cell Maturation by Ultraviolet B Radiation J. Immunol., November 15, 1999; 163(10): 5192 - 5200. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
C. Ruiz-Ruiz, G. Robledo, J. Font, M. Izquierdo, and A. Lopez-Rivas Protein Kinase C Inhibits CD95 (Fas/APO-1)-Mediated Apoptosis by at Least Two Different Mechanisms in Jurkat T Cells J. Immunol., November 1, 1999; 163(9): 4737 - 4746. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
V. N. Ivanov and Z.'e. Ronai Down-regulation of Tumor Necrosis Factor alpha Expression by Activating Transcription Factor 2 Increases UVC-induced Apoptosis of Late-stage Melanoma Cells J. Biol. Chem., May 14, 1999; 274(20): 14079 - 14089. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
M. Li, T. Kondo, Q.-L. Zhao, F.-J. Li, K. Tanabe, Y. Arai, Z.-C. Zhou, and M. Kasuya Apoptosis Induced by Cadmium in Human Lymphoma U937 Cells through Ca2+-calpain and Caspase-Mitochondria- dependent Pathways J. Biol. Chem., December 8, 2000; 275(50): 39702 - 39709. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
C. C. Q. Vu, C. D. Bortner, and J. A. Cidlowski Differential Involvement of Initiator Caspases in Apoptotic Volume Decrease and Potassium Efflux during Fas- and UV-induced Cell Death J. Biol. Chem., September 28, 2001; 276(40): 37602 - 37611. [Abstract] [Full Text] [PDF]
|
|
| |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
