Amelioration of systemic autoimmune disease by the stimulation of apoptosis-promoting receptor Fas with anti-Fas mAb

Fas antigen (Fas) is a cell surface receptor molecule that mediates apoptosis-inducing signals into activated and/or autoreactive peripheral T and B cells by stimulation with Fas ligand or agonistic anti-Fas mAb. The i.p. administration of the hamster anti-mouse Fas mAb RK-8, which induced apoptosis both in vivo and in vitro, did not kill adult mice, whereas those given another hamster anti-mouse Fas mAb Jo2 rapidly die of fulminant hepatitis with hemorrhage. Here, we report that MRL-gld/gld mice thoroughly recovered and/or were prevented from glomerulonephritis, arthritis, sialadenitis, vasculitis and lymphoadenopathy after receiving a single administration of the agonistic anti-mouse Fas mAb RK-8. The serum levels of autoantibodies were decreased after the administration. All the therapeutic effects of RK-8 persisted for >6 months. These findings suggest that the systemic administration of agonistic anti-Fas mAb without fulminant hepatitis-inducing activity is a useful therapeutic strategy for treating systemic autoimmune disease.

Resistance to fas-mediated apoptosis of peripheral T cells in human T lymphocyte virus type I (HTLV-I) transgenic mice with autoimmune arthropathy

Transgenic mice carrying the env-pX region of human T lymphocyte virus type I (HTLV-I) develop autoimmune arthropathy in high incidence. Adopting the approach that Fas-mediated apoptosis has a critical function in the elimination of self-reactive T cells, we examined the involvement of this apoptosis in the induction of autoimmunity in HTLV-I transgenic mice. Splenic T cells derived from the transgenic mice were more resistant to apoptosis induced by anti-Fas mAb than those of the nontransgenic mice, whereas no appreciable difference in apoptosis was detected for thymocytes from either mouse's type. The resistance of transgenic T cells may be due to Tax coded in the pX region, since Tax mediates the inhibition of anti-Fas- induced apoptosis in mature T cell line, Jurkat. Among the transgenic mice, the extent of the resistance to Fas-mediated apoptosis was further enhanced in transgenic T cells with disease. These results suggest that the escape of self-reactive T cells from Fas-mediated apoptosis in the periphery, is critical for the development of autoimmune arthropathy in HTLV-I transgenic mice.

Affinity labeling displays the stepwise activation of ICE-related proteases by Fas, staurosporine, and CrmA-sensitive caspase-8

The activation of multiple interleukin-1beta converting enzyme-related proteases (caspases) in apoptotic mammalian cells raises questions as to whether the multiple active caspases have distinct roles in apoptotic execution as well as how these proteases are organized in apoptotic signaling pathways. Here we used an affinity-labeling agent, YV(bio)KD-aomk, to investigate the caspases activated during apoptotic cell death. YV(bio)KD-aomk identified six distinct polypeptides corresponding to active caspases in Fas-stimulated Jurkat T cells. On staurosporine treatment, four polypeptides were detected. Competition experiments showed that the labeled caspases have distinct substrate preferences. Stepwise appearance of the labeled caspases in each cell death event was consistent with the view that the activated caspases are organized into protease cascades. Moreover, we found that stepwise activation of caspases similar to that induced by Fas ligation is triggered by exposing non-apoptotic Jurkat cell extracts to caspase-8 (MACH/FLICE/Mch5). Conversely, CrmA protein, a viral suppressor of Fas-induced apoptosis, inhibited the protease activity of caspase-8. Overall, these findings provide evidence that caspase-8, a CrmA-sensitive protease, is responsible for initiating the stepwise activation of multiple caspases in Fas-stimulated cells.

Rheumatic diseases in an MRL strain of mice with a deficit in the functional Fas ligand

OBJECTIVE

To characterize Fas antigen expression on the cell surface, and to determine the effect of this expression in rheumatic diseases using a newly established gld-congenic MRL strain of mice (MRL/gld), which is defective in its functional Fas ligand (Fas-L).

METHODS

Flow cytometric analyses of lymphoid cells and macrophages were performed using anti-Fas and other cell surface markers. Histopathologic manifestations were examined using immunochemistry and light and electron microscopy. Serum levels of IgG and anti-DNA antibodies were measured by single radial immunodiffusion and enzyme-linked immunosorbent assay, respectively.

RESULTS

MRL/gld mice developed systemic lymphadenopathy with an accumulation of Thy1.2+, B220+ and CD4-, CD8- T cells, which both express the Fas antigen. Splenic B cells positive for surface IgM and/or surface IgD, and resident peritoneal macrophages exhibited up-regulated expression of the Fas antigen, at much higher levels than those observed in MRL/MpJ-+/+ (MRL/+) mice. Forms of rheumatic disease were observed in these mice, although not in C3H/HeJ-gld/gld mice. These forms included diffuse glomerulonephritis, granulomatous arteritis, and arthritis, and were associated with the infiltration of mononuclear cells expressing the Fas antigen. Serum levels of IgG and anti-DNA antibodies were significantly increased in MRL/gld mice compared with MRL/+ mice.

CONCLUSION

Rheumatic disease was generated by the gld gene in mice with an MRL background, as it is by the lpr gene, which is a Fas deletion mutant, associated with autoimmune traits. Rheumatic disease in this MRL strain was initiated by an incapacity for Fas/Fas-L-induced apoptosis, resulting in the development of autoimmunity and allowing for a persistent immune response in the affected lesions.

Involvement of Fas antigen in ovarian follicular atresia and luteolysis

The Fas antigen (Fas) is a cell-surface receptor protein that mediates apoptosis-inducing signals and plays an important role in the immune system. Significant amounts of Fas mRNA can be detected not only in lymphoid organs but also in the liver, heart, and ovary. In the ovary, apoptosis is thought to cause follicular atresia and luteolysis. We have investigated the involvement of Fas in these events. Here we report that Fas protein is expressed on granulosa and luteal cells but not on oocytes in the ovary. An injection of anti-Fas monoclonal antibody with apoptosis-inducing activity into adult mice enhanced follicular atresia and luteolysis. After the injection, the corpora lutea disappeared and the number of follicles containing pyknotic granulosa cells increased. There were also fewer ovulated ova and lower levels of luteal cell-produced progesterone. Furthermore, as the result of a non-functional Fas/Fas ligand system, mature ovaries from the mouse mutant/pr (lymphoproliferation) were histologically abnormal in terms of follicular development, in that the number of secondary follicles significantly increased. These results suggested that Fas plays an important role in follicular atresia and luteolysis in the ovarian physiology of adult mice.

In vivo analysis of Fas antigen-mediated apoptosis: effects of agonistic anti-mouse Fas mAb on thymus, spleen and liver

Fas antigen (Fas/CD95) is a cell surface receptor protein that mediates apoptosis-inducing signals. To analyze the function of Fas in vivo, we examined the effects of agonistic anti-Fas antibodies in mice. The i.p. administration of the hamster anti-mouse Fas mAb, RK-8, which induced apoptosis both in vivo and in vitro, did not kill adult mice, whereas those given the another hamster anti-mouse Fas mAb, Jo2, rapidly died of fulminant hepatitis with hemorrhage. Histological analyses of mice given RK-8 indicated severe damage of the thymus, and moderate damage of the spleen and liver. Most of the thymocytes and some hepatocytes underwent apoptosis within 1 day of administration. Flow cytometry revealed that CD4+ T cells were more sensitive to Fas-mediated apoptosis than CD8+ T cells. At day 7 after administration, the thymus was atrophied. These in vivo effects of RK-8 were transient; the thymus was regenerated, and the liver and spleen were apparently normal 1 month after injection. The administration of RK-8 into newborn mice caused severe damage of the liver and thymus. Most of the hepatocytes died and jaundice was induced. The newborn mice died within 1 week. Most hepatocytes of newborn mice may be more sensitive to apoptosis-inducing signals through Fas than those of adult mice. These results indicated that functional Fas, which introduces the death signal in vivo, is expressed on thymocytes, CD4+ splenocytes, and some adult and most newborn mouse hepatocytes.

Anti-Fas IgG1 antibodies recognizing the same epitope of Fas/APO-1 mediate different biological effects in vitro

Fas/APO-1 is a cell surface glycoprotein that mediates programmed cell death or apoptosis when cross-linked with agonistic anti-Fas or anti-APO-1 mAb or the endogenous Fas/APO-1 ligand. In this report, we examined the in vitro biological properties of a panel of anti-human Fas mAb of IgG1 subclass (ZB4, VB3, WB3 and CBE). We found that anti-Fas clone VB3 induced marked apoptotic cell death in Fas/APO-1-expressing Jurkat cells, although this cell killing was delayed when compared to the cytolytic effect mediated by the prototypic anti-Fas antibody of IgM subclass (clone CH-11). The ZB4 antibody, on the other hand, efficiently blocked apoptosis induced by CH-11. The WB3 and CBE clones neither induced or inhibited apoptosis. These antibodies were all found to recognize one and the same linear site on the Fas/APO-1 molecule, despite their different biological effects. The ability of these anti-Fas mAb to induce or inhibit apoptosis appeared to correlate with their relative affinity for the Fas/APO-1 molecule. These results provide further evidence for the potential of anti-Fas antibodies of the IgG1 subclass to elicit signals via the Fas/APO-1 molecule.

Gene transfection of mouse primordial germ cells in vitro and analysis of their survival and growth control

We evaluated electroporation, liposome-mediated transfection, and the calcium phosphate (CaPO4) coprecipitation method for gene transfection of mouse primordial germ cells (PGCs) in culture as a prelude to the investigation of molecular mechanisms of the germ cell development. We found that electroporation severely damaged PGCs, and the efficiency of liposome-mediated transfection was very low. In contrast, using the CaPO4 coprecipitation method, 18% of PGCs transfected with plasmid pSV-LT expressed simian virus 40 large tumor antigen (SV 40 T-Ag) transiently. However, we did not detect any effects on the proliferation and survival of PGCs obtained from the embryonic gonads at 11.5 days postcoitum (d.p.c.) during 2 days of culture after the transfection. PGCs isolated from the 11.5-d.p.c. gonads change from spread- to round-shape and exhibit growth arrest during a few days of culture, and these rounded PGCs quickly disappear from the culture. We found that the transfection and expression of Bcl-XL or adenovirus type 2 E1B 19,000-molecular-weight protein (E1B 19K) significantly promoted the survival of PGCs and retarded the disappearance of rounded PGCs from the culture system. These results suggest that the Bcl-XL or E1B 19K can prevent the apoptosis of PGCs and inhibit the cell death of the rounded PGCs in culture.

Accumulation of somatic hypermutation and antigen-driven selection in rapidly cycling surface Ig+ germinal center (GC) B cells which occupy GC at a high frequency during the primary anti-hapten response in mice

Well-developed germinal centers (GC) contain rapidly dividing surface immunoglobulin-negative (sIg-) B cells (centroblasts), and most of their progeny are sIg+ B cells (centrocytes) in a resting state. It has been predicted that somatic hypermutation occurs in centroblasts, whereas antigen-driven selection takes place in centrocytes. The present analysis indicates that murine GC B cells bearing sIg with specificity for an immunizing antigen are in a rapidly cycling state and increase exponentially in number to occupy spleen GC at high frequency during the 1st week after primary immunization; however, the number of these cells is significantly reduced in the 2nd week of immunization. During that period, these proliferating sIg+ GC B cells accumulate somatic hypermutations with nucleotide exchanges indicative of affinity maturation. These sIg+ GC B cells co-express B7-2, ICAM-1, and LFA-1, and have potent antigen-presenting activity which results in T cell activation in vitro. These observations indicate that the sIg+ GC B cells accumulate somatic hypermutations and undergo antigen-driven selection through proliferation, probably upon activation by T cells. This sIg+ GC B cell population may represent cell cycling centrocytes; however, the possibility that these may represent centroblasts undergoing re-expression of sIg could not be excluded.

Infection with Mycobacterium avium-intracellulare with abscess, ulceration and fistula formation

Infections caused by Mycobacterium avium-intracellulare complex are generally manifested as pulmonary disease, osteomyelitis or lymphadenitis, and cutaneous infection is rare. We describe a case of M. intracellulare infection of the skin in a 79-year-old man without apparent immunologically disabling disease or therapy. He had cutaneous infection of the right hand over 10 years, developing a fistula and, finally, an ulcer and abscess, 2 months before his death from heart failure. Mycobacterium intracellulare was identified by both microbiological characteristics and DNA-DNA hybridization.

Role of macrophages in the development of arteritis in MRL strains of mice with a deficit in Fas-mediated apoptosis

The lpr and gld genes have been shown to encode the Fas antigen deletion mutant and the Fas ligand (FasL) mutant, respectively. An MRL strain of mice bearing the gld gene was observed to spontaneously develop granulomatous arteritis, similar to that in mice bearing the lpr gene, indicating that arteritis in this strain is due to an inefficient Fas-FasL interaction resulting in an incapacity for Fas-mediated apoptosis. The arterial lesions in both strains were characterized by a remarkable perivascular accumulation of activated macrophages bearing Mac-2 antigen, following the infiltration of CD4+ cells, and this resulted in the destruction of the arterial wall. Almost all of these infiltrating cells were Fas-positive, as determined in MRL/gld mice. Macrophage colony-stimulating factor (M-CSF), which is present at increased levels in MRL/lpr mice, but not in MRL/Mp- +/+ (MRL/+) mice, induced the expression of Mac-2 antigen and Fas antigen on spleen adherent cells of MRL/+ mice. Moreover, continuous infusion of M-CSF into the peritoneal cavity of subcutis of MRL/+ mice induced the release of oxygen radicals of peritoneal macrophages or granuloma formation associated with the massive accumulation of Mac-2+ cells, respectively. These findings suggest that macrophages in these mice, which may be activated by M-CSF and may avoid Fas-mediated apoptosis, play a critical role as effector cells in the destruction of arterial wall.

A possible involvement of Fas-Fas ligand signaling in the pathogenesis of murine autoimmune gastritis

BACKGROUND & AIMS

A Th1 clone, II-6, established from an autoimmune gastritis BALB/c mouse that underwent thymectomy 3 days after birth, recognized a 15 mer peptide constructing the alpha subunit of H+, K(+)-adenosine triphosphatase as antigen and induced gastritis in nu/nu mice by adoptive transfer. The aim of this study was to examine the molecular mechanism of target (parietal cells) destruction in either thymectomized or II-6 cell-transferred nu/nu mice.

METHODS

Expression of Fas, major histocompatibility complex class II, and intercellular adhesion molecule 1 molecules on the gastric mucosa of these mice were immunohistochemically examined. In situ DNA fragmentation in these thymectomized or nu/nu mice was tested by the terminal deoxynucleotidyl transferase-mediated digoxigenin-deoxyuridine triphosphate nick end label (TUNEL) method. Moreover, activity of II-6 cells to induce apoptosis was tested by using the 15 mer peptide-pulsed B lymphoma cells, A20.2J, as the target.

RESULTS

A portion of parietal cells in gastritis-bearing thymectomized or nu/nu mice at an early stage expressed Fas, major histocompatibility complex class II, and intercellular adhesion molecule 1 molecules and was TUNEL positive. Fas-ligand message was induced on activated II-6 cells and caused DNA fragmentation of the antigen-pulsed A20.2J cells.

CONCLUSIONS

Cognate interaction between Fas antigen on the target and Fas ligand on the effector seems to be one possible mechanism for the target cell destruction in organ-specific autoimmune gastritis.

Induction of Fas-dependent apoptosis in synovial infiltrating cells in rheumatoid arthritis

Apoptosis is a feature of the synovium of rheumatoid arthritis (RA). We have recently shown that RA synoviocytes were susceptible to anti-Fas mAb and undergo apoptosis in vitro. To investigate whether infiltrating mononuclear cells also undergo Fas-dependent apoptosis, double-labeling techniques combined with immunohistochemical examination with anti-CD3 mAb and the TdT-mediated dUTP-blotin nick end labeling (TUNEL) method to detect apoptotic cells, or in situ RT assay to detect Fas mRNA, were performed using frozen tissue sections. We also examined the in vitro induction of Fas-dependent apoptosis in freshly isolated synovium infiltrating mononuclear cells (SIM), synovial stromal cells (SSC) and peripheral blood lymphocytes (PBL) using tissues from nine patients with RA and three with osteoarthritis (OA). The results showed expression of Fas antigen and apoptotic cells in a number of CD3-bearing cells in RA synovial tissues. In vitro treatment with anti-Fas mAb produced a significant apoptosis of RA SIM and SSC, while none of PBL, and neither SIM nor SSC from OA exhibited apoptosis. Moreover, approximately 50% of CD4+, CD3+ and CD45RO+ cells, and > 90% of Fas-expressing cells of RA SIM underwent apoptosis in response to anti-Fas mAb, as detected by flow cytometry. Our results suggest that RA synovial infiltrating lymphocytes acquire high susceptibility to anti-Fas mAb and undergo apoptosis. Such a phenomenon of infiltrating T cells in RA synovium may play an important pathophysiological role and suggest a possible therapeutic effect for anti-Fas mAb in RA.

Therapeutic effect of the anti-Fas antibody on arthritis in HTLV-1 tax transgenic mice

We have recently demonstrated Fas-mediated apoptosis in the synovium, of patients with rheumatoid arthritis (RA) and suggested that it may be one factor responsible for the regression of RA. To examine whether the induction of apoptosis caused by anti-Fas mAb may play a potential role as a new therapeutic strategy for RA, we investigated the effect of anti-Fas mAb (RK-8) on synovitis in an animal model of RA, the human T cell leukemia virus type I (HTLV-1) tax transgenic mice. We report here that administration of anti-Fas mAb into mice intra-articularly improved the paw swelling and arthritis within 48 h. Immunohistochemical study and in vitro culture studies showed that 35% of synovial fibroblasts, 75% of mononuclear cells, and some of polymorphonuclear leukocytes infiltrating in synovium underwent apoptosis by anti-Fas mAb. In situ nick end labeling analysis and electron microscope analysis clearly showed that many cells in synovium were induced apoptosis by anti-Fas mAb administration. However, local administration of anti-Fas mAb did not produce systemic side effects. Results demonstrated that administration of anti-Fas mAb in arthritic joints of the HTLV-1 tax transgenic mice produced improvement of arthritis. These findings suggest that local administration of anti-Fas mAb may represent a useful therapeutic strategy for proliferative synovitis such as RA.

Chromosome 22 complements apoptosis in Fas-and TNF-resistant mutant UK110 cells

Fas and p55 tumor necrosis factor receptor (TNFR) transfer an apoptosis signal when they are crosstinked with their ligands or agonistic antibodies. However, the signal transduction mechanism of apoptosis via Fas and p55 TNFR has not yet been elucidated. We previously described a recessive mutant UK110 from the human monocytic leukemia U937 cell line, that showed resistance against Fas- and p55 TNFR-mediated apoptosis. By cytogenetic analysis and microcell-fusion method, we demonstrate here that introduction of chromosome 22 can specifically restore the sensitivity to Fas- and TNF-mediated apoptosis in UK110 cells. Moreover, introduction of chromosome 22 into UK110 can complement the processing of interleukin-1 beta converting enzyme (ICE)-like proteases, such as CPP32/Yama/Apopain and ICH-1L, after treatment with anti-Fas and anti-p55 TNFR antibodies. These results suggest that the product of a gene located on chromosome 22 participates in the Fas-and p55 TNFR-mediated apoptosis at a point upstream of ICE-like proteases.

Concanamycin A, a powerful tool for characterization and estimation of contribution of perforin- and Fas-based lytic pathways in cell-mediated cytotoxicity

Perforin- and Fas-based cytolytic pathways are two major mechanisms of cell-mediated cytotoxicity. Recently, we have shown that an inhibitor of vacuolar type H+-ATPase, concanamycin A (CMA), inhibits perforin-based cytotoxic activity, mostly due to accelerated degradation of perforin by an increase in the pH of lytic granules. Here we show that CMA failed to inhibit the cytolytic activity of CD4+ CTL clone and perforin-deficient CD8+ CTL clone, which exclusively mediate Fas-based cytotoxicity, although CMA inhibited acidification and induced drastic vacuolation of cytoplasmic granules in these clones. In a wide range of alloantigen-specific CTL, a significant amount of the lysis of Con A blasts from normal mice and of Fas-positive tumor cells remained unaffected even in excess concentrations of CMA. However, CMA almost completely inhibited the lysis of Con A blasts from lpr mice and of Fas low expressing or negative tumor cells. Cytolysis by alloantigen-specific CD8+ CTL derived from gld mice was completely prevented by CMA. Furthermore, CMA-insensitive cytolysis exerted by CD8+ CTL clone was completely inhibitable by soluble Fas molecules. Thus, these data clearly indicate not only that CMA-insensitive cytolysis mediated by alloantigen-specific CTL is Fas dependent, but also that CMA is a selective inhibitor to block only the perforin-based killing pathway. In contrast, brefeldin A blocked the Fas-based cytotoxicity, but only marginally reduced the perforin-based cytotoxicity. Moreover, CMA and brefeldin A in combination completely abrogated all cytolytic activity of alloantigen-specific CTL. Taken together, these results reveal that CTL mainly exert perforin-based cytotoxicity and complementary Fas-based cytotoxicity, and that CMA is a powerful tool to clarify the contributions of the two distinct cytolytic pathways.

Concanamycin A, a powerful tool for characterization and estimation of contribution of perforin- and Fas-based lytic pathways in cell-mediated cytotoxicity

Perforin- and Fas-based cytolytic pathways are two major mechanisms of cell-mediated cytotoxicity. Recently, we have shown that an inhibitor of vacuolar type H+-ATPase, concanamycin A (CMA), inhibits perforin-based cytotoxic activity, mostly due to accelerated degradation of perforin by an increase in the pH of lytic granules. Here we show that CMA failed to inhibit the cytolytic activity of CD4+ CTL clone and perforin-deficient CD8+ CTL clone, which exclusively mediate Fas-based cytotoxicity, although CMA inhibited acidification and induced drastic vacuolation of cytoplasmic granules in these clones. In a wide range of alloantigen-specific CTL, a significant amount of the lysis of Con A blasts from normal mice and of Fas-positive tumor cells remained unaffected even in excess concentrations of CMA. However, CMA almost completely inhibited the lysis of Con A blasts from lpr mice and of Fas low expressing or negative tumor cells. Cytolysis by alloantigen-specific CD8+ CTL derived from gld mice was completely prevented by CMA. Furthermore, CMA-insensitive cytolysis exerted by CD8+ CTL clone was completely inhibitable by soluble Fas molecules. Thus, these data clearly indicate not only that CMA-insensitive cytolysis mediated by alloantigen-specific CTL is Fas dependent, but also that CMA is a selective inhibitor to block only the perforin-based killing pathway. In contrast, brefeldin A blocked the Fas-based cytotoxicity, but only marginally reduced the perforin-based cytotoxicity. Moreover, CMA and brefeldin A in combination completely abrogated all cytolytic activity of alloantigen-specific CTL. Taken together, these results reveal that CTL mainly exert perforin-based cytotoxicity and complementary Fas-based cytotoxicity, and that CMA is a powerful tool to clarify the contributions of the two distinct cytolytic pathways.

IL-4 and anti-CD40 protect against Fas-mediated B cell apoptosis and induce B cell growth and differentiation

Most Th2 clones, when activated, produce IL-4 and express CD40 ligand (CD40L) on their cell surface. Therefore, they can induce growth and differentiation of B cells by cognate help. In contrast, activated Th1 clones, which produce IFN-gamma and express both CD40L and Fas ligand (FasL) on their cell surface, often induce B cell apoptotic cell death. To understand the mechanism by which Th2 cells can induce B cell growth and differentiation in the presence of FasL-positive cells, we stimulated B cells with IL-4, anti-IgM and/or anti-CD40 in the presence of anti-Fas. We report here that addition of anti-Fas strongly inhibited anti-CD40-induced B cell proliferation without affecting anti-IgM-induced B cell proliferation. Furthermore we showed that stimulation of B cells with anti-CD40 induced the expression of Fas molecules on the B cells (approximately 30%) and rendered them highly sensitive to anti-Fas-mediated apoptotic cell death. Indeed, over 23% of anti-CD40-stimulated B cells showed hypodiploid DNA after being incubated with anti-Fas, while h2 cells could dominate over FasL-positive Th1 cells by production of CD40L and IL-4, which in combination induce antibody production and inhibit the Th1 cell-mediated immune response.

Functional significance of the Fas molecule in naive lymphocytes

The Fas molecule mediates apoptotic signal in many cell types. Mouse mutations (lpr, lprcg, gld), which impair the function of Fas, cause spontaneous autoimmune disease. We generated Fas-deficient (Fas-/-) mice by homologous recombination. In embryonic stem cells Fas-/- mice developed lpr-like disease, confirming that the abnormality of Fas is causal in the lpr phenotype. We also made Fas-/- chimeric mice composed of a mixture of Fas+/+ and Fas-/- cells. The chimeric mice also showed the lpr phenotype. In Fas-/-, chimeric mice, the Fas-deficient population expanded progressively among mature T and B lymphocytes. The expansion of Fas-deficient lymphocytes occurred at the naive, pre-primed, lymphocyte stage. These results suggest that the Fas molecule functions not only after antigenic stimulation, as previously hypothesized, but also at the naive lymphocyte stage.

Pure autonomic failure with motor neuron disease: report of a clinical study and postmortem examination of a patient

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Sarcoidosis after interferon therapy for chronic active hepatitis C

Sarcoidosis is characterized by multisystemic granulomatous lesions of unknown etiology. A 62-year-old woman developed sarcoidosis after treatment with alpha-2a interferon (IFN) for 24 weeks (total dose: 522 million units) for chronic hepatitis C. She developed complete atrioventricular block and multiple noncaseating granulomatous lesions in the lung. IFN therapy, which may disturb cellular immune activation in some patients, may have contributed to the onset and progression of sarcoidosis.

Fas antigen expression in brains of patients with Alzheimer-type dementia

Fas antigen (CD95) is a cell surface protein that mediates apoptosis. We have investigated the immunohistochemical localization of Fas antigen in postmortem brain tissue from control subjects, patients with Alzheimer-type dementia (ATD), and from a few patients with diffuse Lewy body disease, progressive supranuclear palsy and adrenoleukodystrophy. In all brains, including controls, vascular endothelial cells and residual blood plasma were weakly stained. In ATD brains, senile plaques and a small number of star-like cells were brains of patients with neurological diseases other than ATD. In double immunostaining for Fas and glial fibrillary acidic protein (GFAP), a small number of cells were positive for both antigens. The majority of Fas-positive astrocytes were, however, negative for GFAP. This implies the downregulation of GFAP production in these cells. Doubly labeled astrocytes were also found around senile plaques, suggesting that the Fas immunoreactivity in senile plaques was derived from astrocytic membranes. The results of this study indicate that Fas antigen is expressed by a subset of reactive astrocytes in degenerative neurological diseases. Such astrocytes may undergo the Fas-mediated apoptotic process.

A recessive mutant of the U937 cell line acquired resistance to anti-Fas and anti-p55 tumor necrosis factor receptor antibody-induced apoptosis

Human monocytic leukemia U937 cells readily undergo apoptosis when cells are treated with various stimuli including antitumor agents, tumor necrosis factor (TNF)-alpha and anti-Fas antibody. However, the signal transduction mechanism resulting in apoptosis is unclear. To study the mechanism of apoptosis, we isolated and characterized a mutant, UK110, from U937 cells, which was resistant to TNF-alpha and anti-Fas antibody-induced apoptosis but was less resistant to etoposide-induced apoptosis. TNF-alpha induced signals are mediated by two types of TNF receptors (TNFR), p55- and p75-TNFR, and p55-TNFR is homologous to the Fas antigen. Interestingly, UK110 cells showed resistance to apoptosis by agonistic anti-p55-TNFR antibody, indicating that UK110 cells were resistant to Fas- and p55-TNFR-mediated apoptosis. Because expression of apoptosis-associated molecules, such as c-Myc, Bcl-2, and Bax, was similar between U937 and UK110 cells an undetermined pathway for apoptosis through Fas and p55-TNFR could be mutated in UK110 cells. To clarify the genetic phenotype of UK110 cells, we performed somatic cell hybridization with parental U937 and the UK110 cells. All of the hybrid clones were as sensitive as the parental U937 cells to apoptosis by both anti-Fas and anti-p55-TNFR antibodies, indicating that the apoptosis resistance in UK110 cells resulted from recessive genotype.

Role of point mutation of the K-ras gene in tumorigenesis of B6C3F1 mouse lung lesions induced by urethane

In order to elucidate the role of point mutation of the K-ras gene in the tumorigenetic process of lung tumors, an experimental model of lung lesions in mice induced by the administration of urethane was used. A total of 135 B6C3F1 male mice, 6 weeks old, were given urethane in the drinking water at 0, 6, 60, 600 or 1200 ppm, and were then killed after varying periods of time. The lung lesions were histologically characterized as hyperplasia, adenoma and adenocarcinoma. Point mutations in codons 12 and 61 of the K-ras gene were detected by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) and confirmed by using dideoxy sequencing analysis. K-ras gene mutation was identified in 9 (23.7%) of 38 lesions classified as hyperplasia, 31 (46.3%) of 67 adenomas, and 3 (50%) of 6 adenocarcinomas. The most frequent mutation was an AT-to-TA transversion at the second base of codon 61 and this pattern accounted for 65% of the three mutant forms observed. These results suggest that the point mutation of K-ras gene is involved in all stages of mouse lung tumorigenesis, i.e., activation of this gene can also influence the later stages of lung lesions.

Normal clonal expansion but impaired Fas-mediated cell death and anergy induction in interleukin-2-deficient mice

Despite a normal development of all major lymphoid subsets, with time, interleukin-2 (IL-2)-deficient mice develop a fatal immunopathology. The disease phenotype is characterized by lymphoadenopathy, splenomegaly, T cell infiltration of various organs, overproduction of a number of cytokines and autoantibody formation. Phenotypically, CD4+ and CD8+ T cells exhibit features characteristic of antigenically experienced cells. The accumulation of cells with a memory phenotype together with the previous suggestion of an involvement of IL-2 in the termination phase of immune responses prompted us to study the fate of superantigen-reactive T cells in IL-2-deficient mice in comparison to their IL-2-producing littermates. We show that expansion in vivo of CD4+ and, to a lesser extent, CD8+ T cells reactive to the superantigens staphylococcal enterotoxin A and B (SEA and SEB) proceeds normally in the absence of IL-2, but that fewer CD4+ cells are subsequently deleted. The residual superantigen-reactive cells fail to become anergic as measured by proliferation in vitro in response to the same superantigen. T cell blasts generated in vitro from lymph node cells of IL-2-deficient mice by superantigen stimulation in the absence of exogenous IL-2 also fail to become anergic. In contrast to cells from IL-2-producing littermates, they do not exhibit Fas-induced apoptosis when cultured on anti-Fas antibody-coated plates, although Fas expression by IL-2-deficient cells is normal or even elevated compared to the IL-2-producing control cells. The data suggest that activation of T cells in the absence of IL-2 fails to generate a signal which is necessary to activate the apoptotic pathway and thus leads to an accumulation of antigen-experienced cells and the chronic inflammatory responses observed in IL-2-deficient mice.

Role for ceramide as an endogenous mediator of Fas-induced cytotoxicity

Triggering of the Fas/APO-1 cell-surface receptor induces apoptosis through an uncharacterized chain of events. Exposure of Fas-sensitive cells to an agonist monoclonal antibody induced cell death and a 200-300% elevation in endogenous levels of the sphingolipid ceramide, a proposed intracellular mediator of apoptosis. In contrast, similar treatment of Fas-resistant cells caused insignificant changes in ceramide levels. Because resistant cell lines expressed the Fas antigen, these results indicate that these cells have a defect in the proximal signaling events leading to ceramide generation. Exposure of the resistant cell lines to a synthetic analog of ceramide induced apoptosis, thus bypassing Fas resistance and indicating that the signaling pathways downstream of ceramide were intact. Furthermore, activation of protein kinase C with the diacylglycerol analog phorbol 12-myristate 13-acetate significantly reduced Fas-induced cytotoxicity, suggesting opposing roles for ceramide and protein kinase C in regulation of apoptosis. These results provide evidence for ceramide as a necessary and sufficient lipid mediator of Fas-mediated apoptosis and suggest this process may be modulated via activation of additional signal-transduction pathways.

Expression and function of mouse Fas antigen on immature and mature T cells

We prepared mAbs specific for the mouse Fas Ag (CD95) and used them to analyze the expression and apoptosis-inducing activity of the Fas Ag on murine immunocytes. Cytofluorometry of mouse bone marrow, thymus, and splenocytes using the mAbs indicated that cells of the T lineage, except for bone marrow cells, expressed Fas Ag on the surface. CD4-CD8- undifferentiated thymocytes expressed low levels of Fas Ag. Immature CD4+CD8+ thymocytes and mature CD4+CD8- and CD4-CD8+ thymocytes were highly positive for Fas Ag. CD4+CD8+ thymocytes were specifically sensitive to the apoptosis-inducing activity of anti-Fas, although CD4-CD8-, CD4+CD8-, and CD4-CD8+ thymocytes were resistant. Spleen T cells were resistant to anti-Fas, whereas they expressed Fas Ag. The superantigen, staphylococcal enterotoxin B (SEB) administered to BALB/c mice, induced clonal expansion and successive clonal deletion of spleen T cells bearing the V beta 8 TCR, which specifically reacts to SEB. Such clonal deletion of V beta 8 T cells was highly suppressed in lpr mice, which have defects in the Fas Ag gene. In SEB-administrated BALB/c mice, expression of Fas Ag was significantly enhanced on V beta 8, but not on V beta 6 T cells, which cannot react to SEB. Moreover, V beta 8 T cells in SEB-primed mice were sensitive to the cell-killing activity of anti-Fas, although V beta 6 T cells were resistant. These findings show that the expression level and apoptosis-inducing activity of Fas Ag on peripheral T cells are directly up-regulated by stimulation through the TCR in vivo.

Expression and function of mouse Fas antigen on immature and mature T cells

We prepared mAbs specific for the mouse Fas Ag (CD95) and used them to analyze the expression and apoptosis-inducing activity of the Fas Ag on murine immunocytes. Cytofluorometry of mouse bone marrow, thymus, and splenocytes using the mAbs indicated that cells of the T lineage, except for bone marrow cells, expressed Fas Ag on the surface. CD4-CD8- undifferentiated thymocytes expressed low levels of Fas Ag. Immature CD4+CD8+ thymocytes and mature CD4+CD8- and CD4-CD8+ thymocytes were highly positive for Fas Ag. CD4+CD8+ thymocytes were specifically sensitive to the apoptosis-inducing activity of anti-Fas, although CD4-CD8-, CD4+CD8-, and CD4-CD8+ thymocytes were resistant. Spleen T cells were resistant to anti-Fas, whereas they expressed Fas Ag. The superantigen, staphylococcal enterotoxin B (SEB) administered to BALB/c mice, induced clonal expansion and successive clonal deletion of spleen T cells bearing the V beta 8 TCR, which specifically reacts to SEB. Such clonal deletion of V beta 8 T cells was highly suppressed in lpr mice, which have defects in the Fas Ag gene. In SEB-administrated BALB/c mice, expression of Fas Ag was significantly enhanced on V beta 8, but not on V beta 6 T cells, which cannot react to SEB. Moreover, V beta 8 T cells in SEB-primed mice were sensitive to the cell-killing activity of anti-Fas, although V beta 6 T cells were resistant. These findings show that the expression level and apoptosis-inducing activity of Fas Ag on peripheral T cells are directly up-regulated by stimulation through the TCR in vivo.

Expression of the Fas antigen on primary human leukemia cells

The antigen defined by the monoclonal antibody anti-Fas can mediate apoptosis, is associated with the receptor for tumor necrosis factor, and is expressed on a limited number of human tissues. In this study we analyzed the expression of Fas on primary human leukemic cells and on mononuclear cells from other hematologic disorders. A total of 95 samples of blood or bone marrow were studied by indirect immunofluorescence. These samples included the normal controls, 47 cases of acute myelogenous leukemia (AML), 11 cases of acute lymphoblastic leukemia (ALL), 21 cases of leukemic lymphoma, seven cases of chronic myelogenous leukemia (CML), five cases of plasma cell leukemia or multiple myeloma, and five cases of myelodysplastic or myeloproliferative syndromes. Normal controls were negative without exception. Among AML, 13/47 cases (28%) were positive; among ALL, 1/11 cases (9%) was positive; among leukemic lymphomas, 3/21 cases (14%) were positive. In a case of plasma cell leukemia which strongly expressed the Fas antigen, we demonstrated that the antibody mediates cell lysis, which was synergistically enhanced by the addition of rabbit complement. In patients with AML, Fas positivity had no obvious clinical relevance. Taken together, our results show that approximately 30% of cases of AML and occasionally other leukemias express the Fas antigens, whereas normal controls are negative in our test system. These findings may be useful in the treatment of refractory leukemias or may permit the purging of autologous transplants.

Involvement of apoptosis antigen Fas in clonal deletion of human thymocytes

Apoptosis appears to play a major role in the differentiation and selection of T and B lymphocytes, but the mechanisms of clonal deletion of T cells in thymus are not well understood. We have prepared an anti-human Fas IgM mAb with associated apoptosis-inducing activity in Fas antigen-positive target cells including human T cells. We analyzed the expression of apoptosis antigen Fas on human thymocytes by cytofluorometry showing low, but significant amounts of Fas antigen on double-negative and double-positive undifferentiated thymocytes. On the contrary, most of the differentiated thymocytes (single-positive or CD3-brightest) expressed undetectable levels of Fas antigen. About 1-2% of thymocytes expressed high amounts of Fas antigen, and these cells, which were CD3-bright, were CD4-bright and CD8-low at the stage of late double-positive lineage. Immunohistological analysis shows these Fas-bright cells on the edge of the medulla. Stimulation through the TCR complex was shown to induce the expression of Fas antigen on thymocytes at the late double-positive stage and prolonged stimulation through the TCR complex rendered the Fas-bright thymocytes sensitive to apoptosis-inducing activity of anti-Fas. To show the involvement of the Fas system in the negative selection/clonal deletion of thymocytes, we organ-cultured human thymus in the presence of the superantigen, staphylococcus enterotoxin B (SEB), and new antagonistic anti-Fas mAb, which can inhibit the apoptosis-inducing activity of the original anti-Fas mAb. The SEB-reactive TCR complex on thymocytes was at first down-regulated by SEB, then the SEB-reactive clone was deleted by apoptosis, which was inhibited by an antagonistic anti-Fas mAb. Thus, Fas antigen is shown to be involved in the negative selection/clonal deletion of superantigen-reactive thymocytes.

IL-5 receptor-mediated tyrosine phosphorylation of SH2/SH3-containing proteins and activation of Bruton's tyrosine and Janus 2 kinases

Interleukin 5 (IL-5) induces proliferation and differentiation of B cells and eosinophils by interacting with its receptor (IL-5R) which consists of two distinct polypeptide chains, alpha and beta (beta c). Although both IL-5R alpha and beta c lack a kinase catalytic domain, IL-5 is capable of inducing tyrosine phosphorylation of cellular proteins. We investigated the role of IL-5R alpha in tyrosine phosphorylation of molecules involved in IL-5 signal transduction, using an IL-5-dependent early B cell line, Y16 and transfectants expressing intact or mutant IL-5R alpha together with intact beta c. The results revealed that the transfectants expressing truncated IL-5R alpha, which entirely lacks a cytoplasmic domain, together with beta c, showed neither protein-tyrosine phosphorylation nor proliferation in response to IL-5. This confirms that IL-5R alpha plays a critical role in protein-tyrosine phosphorylation which triggers cell growth. IL-5 stimulation results in rapid tyrosine phosphorylation of beta c and proteins containing Src homology 2 (SH2) and/or SH3 domains such as phosphatidyl-inositol-3 kinase, Shc, Vav, and HS1, suggesting their involvement in IL-5-mediated signal transduction. IL-5 stimulation significantly enhanced activities of Janus 2 and B cell-specific Bruton's tyrosine kinases (JAK2 and Btk) and increased the tyrosine phosphorylation of JAK2 kinase. These results and recent data on signaling of growth factors taken together, multiple biochemical pathways driven by tyrosine kinases such as JAK2 and Btk are involved in IL-5 signal transduction.

Serum alleviates the requirement of the granulocyte-macrophage colony-stimulating factor (GM-CSF)-induced Ras activation for proliferation of BaF3 cells

Deletion analysis of the beta subunit of the human granulocyte-macrophage colony-stimulating factor (GM-CSF) receptor previously defined two cytoplasmic regions required for distinct signaling. The membrane-proximal region is responsible for induction of c-myc and pim-1, and is indispensable for GM-CSF-dependent proliferation of mouse BaF3 transfectants. The distal region is required for activation of Ras, Raf-1, MAP kinase and p70 S6 kinase as well as induction of c-fos and c-jun, but is dispensable for GM-CSF-dependent proliferation of transfectants under normal culture conditions containing serum. Here we show that signals induced by the distal region of the beta subunit are also required for proliferation. GM-CSF supported proliferation of BaF3 transfectants expressing the normal beta subunit, even in serum-free medium. However, in the absence of seru, GM-CSF did not support proliferation of BaF3 transfectants that have the beta deletion mutants lacking the distal region. Serum-induced activation of Ras, phosphorylation of MAP kinase and expression of c-fos in parental BaF3 cells and antisense oligonucleotide against c-raf blocked DNA synthesis of BaF3 cells. These results indicate that proliferation of BaF3 cells requires signals induced by the proximal as well as the distal region of the beta subunit of the GM-CSF receptor, and that serum alleviates the requirement of signals induced by the distal region.

p53 mutations in lung cancers from Japanese mustard gas workers

Mustard gas (MG) is a mutagenic and carcinogenic alkylating agent, and is a known risk factor for occupational lung cancer. Our hypothesis is that lung cancers from MG workers contain mutations (G:C to A:T transitions) as the result of MG-produced DNA promutagenic adducts in the p53 tumor suppressor gene. We analyzed 12 primary lung cancers from Japanese MG factory workers and 12 lung cancers from non-exposed individuals. Genomic DNA was isolated from archival paraffin-embedded tissues. Exons 5-8 were amplified by polymerase chain reaction using p53-specific primers, and sequenced by dideoxy termination methods. Six out of 12 lung cancers from MG workers contained a total of eight somatic point mutations: two cases had double G:C to A:T transitions; one had a G:C to T:A transversion; one case had an A:T to G:C transition; and two cases had single base deletions. Four of the six mutated purines occurred on the non-transcribed, DNA-coding strand. Out of 12 unexposed cases, there were six single base mutations in six cancers, and no double mutations. The p53 mutational frequency in the MG-exposed cases is similar to the non-exposed controls and the usual smoking-related lung cancers reported previously. However, the distinctive double mutations (G:C to A:T transition) observed in two cases are unusual and may be related to MG exposure.

Expression of Fas antigen on keratinocytes in vivo and induction of apoptosis in cultured keratinocytes

Fas antigen, which belongs to a nerve growth factor/tumor necrosis factor receptor superfamily, is a membrane protein that induces apoptosis. In humans, distribution of Fas antigen has been reported on cell lines and lymphocytes. Immunohistochemical studies revealed Fas antigen on the keratinocytes of lesional epidermis in lichenoid drug eruption, erythema multiforme, contact dermatitis, bullous pemphigoid, pemphigus vulgaris, and herpes zoster; it is co-expressed with intercellular adhesion molecule-1. Cultured keratinocytes expressing Fas antigen increased from 8.4% to 34.6% after stimulation with interferon gamma for 24 h. Treatment of interferon-gamma-stimulated keratinocytes with anti-Fas for 48 h resulted in DNA fragmentation and death of 32% of cells, suggesting that Fas antigen may mediate apoptosis. The expression of Fas antigen on keratinocytes in lesional skin suggests that death via Fas antigen may play an important role in the pathogenesis of keratinocyte cytotoxicity.

Cytotoxicity of fresh NK1.1+ T cell receptor alpha/beta+ thymocytes against a CD4+8+ thymocyte population associated with intact Fas antigen expression on the target

Recent studies have revealed that 10-20% of CD4+8- or CD4-8- thymocyte populations contain NK1.1+ T cell receptor (TCR)-alpha/beta+ cells. This subpopulation shows characteristics that are different from NK1.1- CD4+ or NK1.1- CD8+ T cells and seems to have developed in a manner different from NK1.1- T cells. Although extensive studies have been performed on the NK1.1+ TCR-alpha/beta+ thymocytes, the physiological role of the NK1.1+ TCR-alpha/beta+ thymocytes has been totally unclear. In the present study, we found that freshly isolated NK1.1+ TCR-alpha/beta+ thymocytes, but neither whole thymocytes nor lymph node T cells, directly killed CD4+8+ thymocytes from normal syngeneic or allogeneic mice by using a long-term cytotoxic assay in which flow cytometry was used to detect the cytotoxicity. However, only weak cytotoxicity was detected against thymocytes from lpr mice on which the Fas antigen that transduces signals for apoptosis into the cells is not expressed. Furthermore, the NK1.1+ TCR-alpha/beta+ thymocytes exhibited high cytotoxicity against T lymphoma targets transfected with fas genes as compared with the parental T lymphoma targets or target cells transfected with mutated fas genes, which lack the function of transducing signals. On the other hand, NK1.1+ effector thymocytes from gld mice that carry a point mutation in Fas ligand did not kill thymocyte targets from normal mice. The present findings, thus, consistently suggest that the NK1.1+ TCR-alpha/beta+ thymocytes kill a subpopulation among CD4+8+ thymocytes via Fas antigen and in this way regulate generation of T lineage cells in the thymus.

Alteration in length of telomeric repeats in lung cancer

We investigated the relationship between telomere length and various characteristics of tumor cells in 46 lung cancer specimens (40 primary lesions and six metastatic lesions). Three variant patterns of telomere length were observed in 16 cases (34.8%): reduction in 13 cases, elongation in two cases, and convergence in one case. These variant patterns were frequently observed in small cell carcinomas, in metastatic lesions, and in cases which possessed the S-type allele of the L-myc gene. All three cases with telomere elongation or convergence were associated with a poor prognosis. This is compatible with the previous report suggesting that telomerase activity may be an indicator of immortality in vitro. In adenocarcinoma, telomere reduction or elongation was also observed in the early stages with a low percentage of cells in the S-phase, while in cases with other histologic types, these changes were observed only in late stage, in metastatic lesions, or in cancerous tissues with a high percentage of cells in the S-phase. Although the reduction of telomere length in these tissues may be a result of many cell divisions, it may represent another stage of carcinogenesis in early-stage adenocarcinoma.

Further experimental evidence of selective nerve regeneration in aortic Y-chambers

To explain the discrepancy between Weiss and Taylor's results and our recent findings about axonal growth patterns in a fresh aortic chamber, we examined whether regenerating axons show preferential growth toward a nerve piece in an aortic Y-chamber. In our previous studies, we could not reproduce their results, which showed that regenerating nerve fibres from the proximal stump of a severed peripheral nerve grew randomly in the two channels with and without a nerve segment; our results showed preferential regeneration toward a nerve segment channel. In the present study, we retraced the steps of Weiss and Taylor using white rats, the longitudinal section of the specimen, and silver staining. Despite using the same methods we were still unable to show that the growth pattern was random, but we did find preferential axonal growth into the nerve segment channel of a fresh aortic Y-chamber. The evidence of selective nerve regeneration was unequivocal and we cannot support the findings of Weiss and Taylor reported in 1944.

Tumorigenicity study of ferric citrate administered orally to mice

Ferric citrate (FC) was orally administered at concentrations of 0.12 (maximum tolerated dose) or 0.06% in the drinking water to male and female B6C3F1 mice. Treatment was continued for 96 wk and the experiment was terminated at wk 100. There was no significant difference between treated and control groups in the tumour incidence or in the distribution of different types of tumour. Thus the long-term oral administration of FC to mice did not yield any evidence of chronic toxicity or tumorigenicity.

Fas and its ligand in a general mechanism of T-cell-mediated cytotoxicity

To investigate the mechanisms of T-cell-mediated cytotoxicity, we estimated the involvement of apoptosis-inducing Fas molecule on the target cells and its ligand on the effector cells. When redirected by ConA or anti-CD3 monoclonal antibody, a CD4+ T-cell clone, BK1, could lyse the target cells expressing wild-type Fas molecule but not those expressing death signaling-deficient mutants. This indicates the involvement of Fas-mediated signal transduction in the target cell lysis by BK1. Anti-CD3-activated but not resting BK1 expressed Fas ligand as detected by binding of a soluble Fas-Ig fusion protein, and the BK1-mediated cytotoxicity was blocked by the addition of Fas-Ig, implicating the inducible Fas ligand in the BK1 cytotoxicity. Ability to exert the Fas-mediated cytotoxicity was not confined to BK1, but splenic CD4+ T cells and, to a lesser extent, CD8+ T cells could also exert the Fas-dependent target cell lysis. This indicates that the Fas-mediated target cell lytic pathway can be generally involved in the T-cell-mediated cytotoxicity. Interestingly, CD4+ T cells prepared from gld/gld mice did not mediate the Fas-mediated cytotoxicity, indicating defective expression of functional Fas ligand in gld mice.

Anti-Fas on nonhematopoietic tumors: levels of Fas/APO-1 and bcl-2 are not predictive of biological responsiveness

Fas/APO-1 is a cell surface protein known to trigger apoptosis in a variety of cell types upon specific antibody binding. Although extensively studied on normal and malignant hematopoietic cells, little is known about Fas/APO-1 on nonhematopoietic cells. In the study presented here, we have examined Fas/APO-1 expression and function on 11 human tumors of nonhematopoietic origin. By flow cytometric analysis, Fas/APO-1 was expressed on 10 of the 11 tumors at levels comparable to those previously reported for lymphoid cells sensitive to the cytolytic effects of anti-Fas. Despite abundant cell surface expression, only 4 of the 10 Fas-positive tumors were sensitive to the cell-killing effects of anti-Fas. Moreover, anti-Fas enhanced the growth of 2 of 10 Fas-positive tumors. Additional studies using cycloheximide demonstrated that de novo protein synthesis was required for anti-Fas-triggered growth stimulation and, at least in one case, was responsible for the resistance to antibody-induced apoptosis. The biological effects initiated by anti-Fas engagement, however, were not correlated with endogenous bcl-2 expression. This report documents that: (a) Fas/APO-1 is widely expressed on cultured nonhematopoietic tumors; (b) the inherent susceptibility to anti-Fas-induced apoptosis is not correlated with expression of the Fas/APO-1 protein; (c) Fas/APO-1 engagement can result in growth enhancement; and (d) protective/growth-promoting proteins other than bcl-2 may contribute to the diverse spectrum of biological effects induced by anti-Fas engagement of the Fas/APO-1 protein.

Anti-Fas antibody induces different types of cell death in the human histiocytic cell line, U937, and the human B cell line, B104: the role of single-strand DNA breaks and poly (ADP-ribosyl)ation in cell death

We investigated the anti-Fas antibody-induced cell death in two different types of human cell lines, U937 and B104. IFN-gamma increased the surface expression of Fas antigen and susceptibility to anti-Fas Ab-induced cell death of B104 and U937 cells. Anti-Fas Ab-induced death of U937 and B104 cells required neither a Ca2+ influx nor macromolecular synthesis. U937 cells treated with anti-Fas Ab represented apoptosis with DNA fragmentation, whereas anti-Fas Ab-treated B104 cells did not. Single-strand DNA breaks, however, appeared in the B104 cells. Zinc ions prevented DNA fragmentation and the morphological features of apoptosis in anti-Fas Ab-treated U937 cells, but did not inhibit cell death. However, zinc ions, when used in combination with the poly(ADP-ribosyl)ation inhibitors, inhibited anti-Fas Ab-induced U937 cell death. The inhibitors by themselves did not inhibit anti-Fas Ab-induced U937 cell death, but did inhibit anti-Fas Ab-induced B104 cell death. A substantial decrease in NAD pools was observed in anti-Fas Ab-treated B104 and U937 cells in parallel with the increase of DNA strand breaks before cell death became apparent. These results suggest the involvement of single-strand DNA breaks and poly(ADP-ribosyl)ation in the mechanisms of anti-Fas Ab-induced U937 and B104 cell death.

Unidirectional cross-phosphorylation between the granulocyte colony-stimulating factor and interleukin 3 receptors

The mouse interleukin-3 (IL-3)-dependent hemopoietic precursor cell line 32DC13 responds to granulocyte colony-stimulating factor (G-CSF) for proliferation and differentiation. We established a subline (32D-FH) of the 32DC13 cells which has lost the ability to respond to G-CSF. When murine G-CSF receptor cDNA was introduced into the 32D-FH cell line, the transformants responded to G-CSF as well as to IL-3 for proliferation. Adding G-CSF to the transformants rapidly induced tyrosine phosphorylation not only of the G-CSF receptor but also of both subtypes of the IL-3 receptor beta-chain (AIC2A and AIC2B molecules). On the other hand, stimulation of the transformants with IL-3 induced tyrosine phosphorylation of the AIC2A and AIC2B but not of the G-CSF receptor. These results indicate that the tyrosine kinase activated through the G-CSF receptor interacts with the IL-3 receptor beta-chains but not vice versa. This unidirectional cross-phosphorylation between the G-CSF and IL-3 receptors may play a role in granulopoiesis induced by G-CSF.

IL-5 receptor positive B cells, but not eosinophils, are functionally and numerically influenced in mice carrying the X-linked immune defect

Mouse IL-5 (mIL-5) acts on B cells and eosinophils to induce growth and differentiation through the mIL-5 specific receptor (mIL-5R). The functional high-affinity mIL-5R is a heterodimer composed of alpha and beta chains. We investigated the expression of mIL-5R and the responsiveness of B cells and eosinophils to mIL-5 in X-linked immunodeficient (xid) mice. mIL-5R expression analyzed by using mAbs specific for alpha and beta chains revealed that xid B cells had fewer mIL-5R alpha +mIL-5R beta + than BALB/c B cells. In particular, a decrease in the number of peritoneal mIL-5R+ B cells among Ly-1 B cells (known as B-1 cells) was remarkable. Furthermore, the frequency of precursors of mIL-5 responsive B cells in xid mice was approximately 100-fold lower than that of BALB/c mice. Interestingly, sorted mIL-5R+ peritoneal B cells from xid mice displayed a low response to mIL-5. Intraperitoneal injection of mIL-5 into BALB/c mice induced polyclonal IgM production and an increase in the number of eosinophils. The same regimen failed to induce an increase in the same parameters in xid mice. However, xid mice showed mIL-5-induced eosinophilia in peripheral blood to a similar extent as BALB/c mice. Eosinophils from mIL-5-injected xid mice expressed both alpha and beta chains of mIL-5, and responded to mIL-5 with prolonged in vitro survival.

Thymic metastasis from prostatic carcinoma: report of a case

The thymus is an important organ involved in cell-mediated immunological function, and to our knowledge, there has never been a case of thymic metastasis reported. We recently examined a 65-year-old man who presented at our department with a cough and shortness of breath on exertion. He had a history of prostatic carcinoma for which he had undergone an orchiectomy 11 years previously. Investigations disclosed a mediastinal tumor, 14 x 9 cm in size, and histological examination of the resected tumor confirmed a diagnosis of thymic metastasis from prostatic carcinoma.

Rapid acceleration of neutrophil apoptosis by tumor necrosis factor-alpha

We demonstrate here that human necrosis factor-alpha, a potent neutrophil activator, induces rapid (within 3 h) apoptosis of these cells, i.e. neutrophils treated with this cytokine exhibit (i) light and electron microscopic changes characteristic to apoptotic cells, (ii) reduced propidium iodide binding to DNA, and (iii) the ladder form of DNA, as shown by agarose gel electrophoresis. These results suggest that apoptosis acceleration may be involved in processes by which neutrophils are prevented from damaging tissues.

Overcoming tumor necrosis factor and drug resistance of human tumor cell lines by combination treatment with anti-Fas antibody and drugs or toxins

Monoclonal mouse anti-Fas antibody is directed against Fas antigen, a M(r) 36,000 encoded polypeptide that belongs to the family of cell surface proteins which includes nerve growth factor receptor, tumor necrosis factor (TNF) receptors, B-cell antigen CD40, and T-cell antigens OX40. Anti-Fas antibody mimics TNF-alpha in its cytolytic activity but not in other TNF-alpha-mediated activities. Thus, we examined if anti-Fas antibody synergizes in cytotoxicity with toxins and drugs. The present studies demonstrate that anti-Fas antibody in combination with diphtheria toxin (DTX), Adriamycin, or cis-platinum results in enhanced cytotoxicity and synergy and also overrides resistance to TNF, drugs, or toxins when tested against a battery of human tumor cell lines. Synergy with anti-Fas and DTX requires that DTX is enzymatically active, since inhibitors of DTX-mediated protein synthesis inhibition resulted in loss of synergy. When the plant toxin ricin was used, there was no synergy with anti-Fas antibody but rather an additive effect. The synergy was not obtained in a TNF receptor-negative line but was achieved with other anti-Fas-resistant lines. Cell lines resistant to either Adriamycin or cis-platinum were rendered sensitive by the combination of drug and anti-Fas antibody. Further, combination treatment of anti-Fas and Adriamycin overcame resistance of the gp 170-expressing, multidrug-resistant MDR ovarian line. In all cases, cytotoxicity was augmented by pretreatment of target cells with gamma-interferon which upregulates Fas antigen expression. These results show that anti-Fas antibody can synergize in cytotoxicity with toxins and chemotherapeutic drugs, and combination treatment can reverse resistance to TNF, toxins, and/or drugs.

Differential expression of apoptosis-related Fas antigen on lymphocyte subpopulations in human peripheral blood

The Fas Ag is a newly defined cell-surface molecule that may mediate apoptosis. The antibody against Fas Ag can induce the apoptotic cell death in cell lines expressing this Ag. PBL subpopulations at various ages were here examined for Fas expression by two-or three-color flow-cytometric analyses using anti-Fas mAb. It was found that Fas Ag was appreciably detected on a proportion of T and B cells, whereas its expression was absent for NK cells. For CD4+ and CD8+ T cells, Fas Ag was expressed preferentially on CD45RO+ (memory or previously activated) populations, but not on CD45RO- naive ones. TCR-gamma/delta+ T cells, especially their CD45RO+ subsets, also expressed Fas Ag. Expectably, neonatal T cell subpopulations, most of which had the naive (CD45RO-) phenotype, expressed little Fas Ag. Fas-expressing B cells dominated in surface(s) IgD- populations, but neonatal B cells as well as adult sIgD+ B cells had little Fas Ag. The Fas Ag was inducible after in vitro mitogenic stimulation of naive T and B cells from neonatal blood. These observations suggested that expression of Fas Ag on T and B cells in the peripheral blood might reflect their in vivo Ag-activated status. In contrast to Fas-expressing cultured cell lines, however, viability of in vitro stimulated T and B cells as well as freshly isolated CD45RO+ T cells was not significantly changed after the treatment with anti-Fas mAb, indicating that additional cellular conditions to Fas expression might be required for anti-Fas-induced cell death.