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.