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Biomedical subjects

K Frei

Publications and source records attributed to K Frei.

At least 91 records · Page 5Linked to original sources
PubMed1992

Production of macrophage colony-stimulating factor by astrocytes and brain macrophages.

Morphological hallmarks of inflammatory and degenerative diseases of the brain are hypertrophy of astrocytes and accumulation of macrophages recruited from circulating blood monocytes and/or from resident macrophages, the so-called microglial cells. Recently, production of granulocyte-macrophage colony-stimulating factor (GM-CSF) by astrocytes has been suggested to contribute to the macrophage response. Here we report that in addition to GM-CSF, murine astrocytes also produce macrophage (M)-CSF upon stimulation with tumor necrosis factor alpha, interleukin-1 and lipopolysaccharides. The bioactivity detected in supernatant of astrocytes was characterized using the M-CSF-dependent cell line M-NFS-60 and neutralizing anti-M-CSF antibodies. RNase protection analysis showed M-CSF mRNA already in unstimulated astrocytes without striking up-regulation by the stimuli. Thus, in astrocytes the expression of the M-CSF gene is predominantly regulated at the posttranscriptional level.

Animals↗
PubMed1992

The cerebroside sulfate activator from pig kidney: purification and molecular structure.

The activator protein for hydrolysis of cerebroside sulfate by arylsulfatase A was purified from pig kidney in high yield. This protein, also known as sphingolipid activator protein-1 and saposin-B, was particularly rich in pig kidney. Purification was achieved by a simple procedure involving homogenation and heat treatment followed by affinity, ion exchange, and gel filtration chromatographies. The final product was better than 90% pure by gel electrophoresis and HPLC. It was possible to sequence more than 60 amino acids from the N-terminus with only a few uncertain residues. The sequence differed from that predicted for the human protein by about 10%, with most amino acid variations being conservative. There appeared to be a residual glycosyl substituent on asparagine 21, but the sugar content was low and the protein failed to bind to concanavalin A. The cerebroside sulfate activator proved to be exceptionally resistant to denaturation or protease digestion. The apparent molecular mass was approximately 20,000 Da on preparative gel-filtration columns, but was variable when estimated by HPLC gel filtration. Values ranging from 30,000 to over 100,000 Da were observed in neutral buffers, while values around 15,000-16,000 Da were seen in acidic buffers such as those used for assay of the biological activity. This was further decreased to a putative subunit of 7000-8000 Da under severe denaturing conditions. Pig kidney is a convenient source for the large-scale preparation of this interesting protein which has heretofore been obtained from human sources.

Amino Acid Sequence↗
PubMed1992

Modulation of the immune response by transforming growth factor beta.

For the past several years immunologists have been fascinated by a series of experiments showing that transforming growth factor beta (TGF beta) suppresses T- and B-lymphocyte growth as well as IgM and IgG production by B cells. Moreover, while exerting chemotactic activity on monocytes and inducing expression of interleukin-1 and interleukin-6 by these cells, TGF beta interferes with bacterially induced tumor necrosis factor alpha production, oxygen radical formation and the adhesiveness of granulocytes to endothelial cells. These mechanisms may provide the basis for the effect of TGF beta to prevent the microvascular changes associated with brain edema formation in bacterial meningitis. Given the potential of lymphocytes as well as macrophages to produce TGF beta 1, this cytokine may exert negative feedback signals on the immune response, provided the cytokine is processed from its latent form to the bioactive homodimer. Potent effects of TGF beta have been observed in experimental animals including the inhibition of the generation of virus-specific cytotoxic T cells and antiviral antibodies as well as the diminution of cellular infiltrates with decreased major histocompatibility complex class-II expression and CD8+ T cells in the tissue of virally infected animals. TGF beta may also be of importance in tumor immunology. By the production of bioactive TGF beta as detected in glioblastoma and acute T-cell leukemia, tumor cells may induce an immunodeficiency state and escape immune surveillance. In inflammation, monitoring of TGF beta in the tissue will bring light on the immune regulation in acute and chronic inflammatory diseases.

Animals↗
PubMed1991

Murine brain macrophages induced NMDA receptor mediated neurotoxicity in vitro by secreting glutamate.

Supernatants (SN) of brain macrophages in culture induce death of cerebellar granule cells in vitro, while those of astrocytes and endothelial cells do not. This toxicity can be prevented by N-methyl-D-aspartate (NMDA) receptor antagonists. Macrophage SN contain high concentrations of glutamate. Reducing the glutamate level of macrophage SN, either by exposure to astrocytes or by enzymatic degradation abolished the toxic effect. Thus, macrophage neurotoxicity is mediated by glutamate acting on NMDA receptors, and might play a role in vivo in traumatic and cerebrovascular brain lesions.

2-Amino-5-phosphonovalerate↗
PubMed1991

Transforming growth factor-beta modulates T cell-mediated encephalitis caused by Borna disease virus. Pathogenic importance of CD8+ cells and suppression of antibody formation.

Borna disease is a virus-induced, immune-mediated encephalomyelitis based on a delayed-type hypersensitivity reaction. The severity of clinical symptoms after intracerebral infection of rats with Borna disease virus was reduced after treatment with transforming growth factor (TGF-beta 2). Intraperitoneal injection of the recombinant molecule, rTGF-beta 2, started on the day of infection at a dose of either 1 micrograms given every day or every other day for 8 consecutive days or 2 micrograms every third day, was found to result in the absence of typical Borna disease symptoms at 14 days after infection in most of the TGF-beta-treated rats, a time point at which all infected control animals not treated with rTGF-beta 2 showed distinct signs of Borna disease. The inhibition of the disease was paralleled by a significant reduction of the inflammatory reaction in the brain. However, the efficacy of treatment with rTGF-beta 2 was transient, because after day 21 only a slight or no reduction of the inflammatory reaction and, consequently, symptoms of Borna disease could be observed. Immunohistologic investigations revealed reduced CD4+ T cell numbers and no changes in macrophage counts in encephalitic lesions of rTG-beta treated rats. However, CD8+ cells were markedly decreased in the encephalitic lesions. Furthermore, the expression of MHC class II Ag was significantly reduced in the brain of rTGF-beta 2 treated Borna disease virus-infected rats, whereas MHC class I Ag expression was not. Most treated animals showed a reduction of Borna disease virus-specific serum antibodies, the result of an inhibition of the IgG response. The results presented here suggest a distinct influence of rTGF-beta 2 on T cell-mediated immune functions during the early phase of Borna disease virus-induced encephalomyelitis.

Animals↗
PubMed1991

Expression of TGF-beta 2 in human glioblastoma: a role in resistance to immune rejection?

Glioblastomas are among the most malignant tumours for which no curative treatment exists. A dysfunction of cellular immunity with decreased skin reactivity and lymphocyte blastogenesis has been described in patients with glioblastomas. In culture human glioblastoma cells release a factor termed glioblastoma-derived T cell suppressor factor (G-TsF) which inhibits the antigen-dependent growth of both helper and cytotoxic T cells. Purification and cloning indicated that G-TsF is a novel member of the TGF-beta family with a well-conserved mature sequence but less homology in the precursor segments. The factor was renamed TGF-beta 2. The two glioblastoma cell lines investigated expressed mRNAs for both G-TsF/TGF-beta 2 and TGF-beta 1 but only G-TsF/TGF-beta 2 protein was secreted. Neuroblastoma cells express only the mRNA for TGF-beta 1 but not the protein, nor the mRNA for G-TsF/TGF-beta 2. Recombinant G-TsF/TGF-beta 2 inhibits the generation of virus-specific cytotoxic T cells when injected into mice infected with lymphocytic choriomeningitis virus. Thus G-TsF/TGF-beta 2 might contribute to the impairment of tumour immune surveillance. Some T cell clones may escape the immunosuppressive effects of TGF-beta: ovalbumin-specific T helper cell lines that showed different degrees of susceptibility to TGF-beta contained clones which had lost receptor(s) for TGF-beta.

Animals↗
PubMed1991

Interleukin-6 is elevated in plasma in multiple sclerosis.

Levels of interleukin-6 (IL-6)--a cytokine which induces immunoglobulin production of activated B cells--were measured in cerebrospinal fluid (CSF) and plasma of patients with multiple sclerosis (MS), acute meningo-encephalitis (AM) and muscular tension headache (TH). MS patients had in repeated samples higher levels of IL-6 in plasma compared to patients with AM and TH. IL-6 concentrations in MS plasma were about 17 times higher than MS CSF, while in AM 20-fold higher levels were found in CSF compared to plasma during the acute stage. IL-6 in AM CSF decreased rapidly during clinical recovery. No correlation was found between IL-6 in MS patients' plasma or CSF and disease activity. The functional significance of elevated IL-6 concentrations in MS plasma is unknown, although the findings support the hypothesis of a systemic B cell response in MS.

Acute Disease↗
PubMed1991

Production of random classes of immunoglobulins in brain tissue during persistent viral infection paralleled by secretion of interleukin-6 (IL-6) but not IL-4, IL-5, and gamma interferon.

The activities of cytokines were determined in cerebrospinal fluid (CSF) and serum of mice persistently or intracerebrally acutely infected with lymphocytic choriomeningitis (LCM) virus (LCMV). In contrast to CBA/J (LCMV carrier) mice that responded with low levels of LCMV-specific antibody, high-responder NMRI (carrier) mice showed antibody production by B cells outside of lymphoid organs. The B cells that had infiltrated the brains of LCMV carrier mice exhibited no preferential immunoglobulin isotype or subtype virus-specific antibody production. Phenotypic analysis of the brain infiltrates in virus carrier mice revealed dominance of CD4+ T cells in contrast to virtual absence of CD4+ and dominance of CD8+ in mice with acute LCM. In NMRI but not in CBA/J carrier mice, significant concentrations of interleukin-6 (IL-6) were detected in CSF and serum; IL-2, IL-4, IL-5, granulocyte-macrophage CSF (GM-CSF), and gamma interferon (IFN-gamma) were not elevated. In contrast, during acute, lethal LCM, IL-6 and IFN-gamma were found at high concentrations, and IL-4, IL-5, and GM-CSF were detectable in CSF and serum, but virus-specific antibody-producing cells were not (yet) detectable in the brain. Thus, distinct cytokine patterns are found in acute versus chronic LCMV infection of the brain: in LCM carrier mice, local random-class immunoglobulin production correlated with the absence of IL-2, IL-4, IL-5, and IFN-gamma but active secretion of IL-6.

Animals↗
PubMed1990

Interleukin 6 production in experimental cerebral malaria: modulation by anticytokine antibodies and possible role in hypergammaglobulinemia.

The production of Interleukin 6 (IL-6) was studied during experimental cerebral malaria (ECM) induced by Plasmodium berghei ANKA (PbA) infection. IL-6 is present in the serum of mice with ECM, the highest concentrations being observed in mice with full-blown neurological syndrome. High IL-6 levels were also observed, however, in the absence of pathology in nonlethal malaria infection. These data suggest that IL-6 is produced in large amounts during malaria infection, but does not play a major role in the pathogenesis of ECM. A modulation of IL-6 production in ECM was achieved by in vivo treatment with other anticytokine antibodies: antibodies to interferon (IFN-gamma) or to tumor necrosis factor (TNF) abolished the rise of IL-6, while anti-IL-3 and anti-granulocyte/macrophage colony-stimulating factor antibodies only partially prevented this rise, suggesting that the two cytokines IFN-gamma and TNF are important intermediates in IL-6 production. Passive immunization against IL-6 did not prevent ECM, but significantly reduced serum IgG levels in malaria-infected mice. Thus, by its effects on B cells, IL-6 may be involved in hypergammaglobulinemia and immune-complex diseases, e.g., glomerulonephritis observed during malaria infection.

Animals↗
PubMed1990

Increased secretion of tumor necrosis factors alpha, interleukin 1, and interleukin 6 by human mononuclear cells exposed to beta-galactoside-specific lectin from clinically applied mistletoe extract.

A beta-galactoside-specific lectin from proprietary mistletoe extract, recently reported to exhibit immunomodulatory potency in vivo (T. Hajto, K. Hostanska, and H J. Gabius, Cancer Res. 49: 4803-4808, 1989), induced increased secretion of tumor necrosis factor alpha, interleukin 1, and interleukin 6 in cultures of human peripheral blood mononuclear cells. The enhancement of secretion, determined independently by bioassays and enzyme-linked immunosorbent assay-based quantitation, was caused by selective protein-carbohydrate interaction, as revealed by the strict dependence on the presence of the carbohydrate-binding subunit of the specific lectin-binding sugar as well as anti-lectin antibodies. Increased cytokine levels in serum of patients after injection of optimal lectin doses corroborated the in vitro results. Thus, these data provide an explanation for the increases in cellular parameters of the host defense system in vivo, which presents a further step toward their potentially beneficial clinical exploitation in standardized regimens.

Animals↗
PubMed1990

Production of hemopoietic colony-stimulating factors by astrocytes.

Astrocytes may play a central role in regulation of immune mediated processes in the central nervous system. By their inducible expression of MHC class II Ag and secretion of cytokines they may propagate expansion and activation of T and B lymphocytes invading the brain tissue. Here we report that astrocytes may also contribute to the macrophage response observed in inflammatory and degenerative diseases of the brain. Murine astrocytes secrete granulocyte-macrophage CSF (GM-CSF) as evidenced by induction of colony formation in bone marrow cells and growth of FDC-P1 cells. Both effects are neutralized with anti-GM-CSF- but not with anti-IL-3-antibodies. Some residual activity detected in the bone marrow assay after antibody treatment can be explained by concomitant production of granulocyte CSF (G-CSF). The mRNA of both G- and GM-CSF are identified by Northern blots in astrocytes. Furthermore, mRNA for IL-1 alpha and IL-1 beta are detected in comparable amounts in astrocytes and brain macrophages, the latter, however, comprising much more potent sources of TNF-alpha.

Animals↗
PubMed1990

Lymphokines and bacteria, that induce tumoricidal activity, trigger a different secretory response in macrophages.

The abilities of various macrophage-activating agents to trigger tumoricidal activity and/or the secretion of prostaglandin E2 (PGE2), interleukin 6 (IL 6) and transforming growth factor beta (TGF beta) in bone marrow-derived mononuclear phagocytes (BMM phi) in vitro were comparatively assessed. Induction of tumoricidal activity by lymphokines, that is only short-lived, was not associated with enhanced secretion of these activities by BMM phi; in contrast, incubation with heat-killed facultative intracellular bacteria resulted in persisting tumoricidal activity and in marked enhancement of the secretion of IL 6 and PGE2, but not of TGF beta activity. These findings support the concept that the pattern of the secretory response induced in macrophages by lymphokines differs from that triggered by bacteria and that the rapid decay of lymphokine-induced tumoricidal activity is not due to autocrine macrophage deactivation mediated by one of these agents alone.

Animals↗
PubMed1990

Role of tumor necrosis factor in Listeria resistance of nude mice.

The effects of sheep anti-murine recombinant tumor necrosis factor-alpha (TNF-alpha) on resistance to Listeria monocytogenes infection were studied in T cell-deficient nu/nu mice. The sheep anti-TNF-alpha antibody preparation was specific for TNF since it neutralized 300 U of recombinant murine TNF-alpha in vitro at a dilution of up to 1/1,000 but did not neutralize 32 U of interferon (IFN)-alpha, -beta or 32 U of IFN-gamma in vitro at a 1/20 dilution. When tested in vivo in sublethally Listeria-infected nu/nu or T cell-competent C57BL/6 or ICR mice, a single treatment of 0.2 ml anti-TNF-alpha given intraperitoneally on either day -1,0 or +1 resulted in the death of mice by day 5-7 due to the uncontrolled growth of Listeria; bacterial counts in spleen and liver were increased on days 3-5 by a factor of 10-1,000 in these organs. When examined histologically, organs from mice with the anti-TNF-alpha treatment contained more, and considerably bigger, lesions that exhibited central necrosis. The enhancing effect of anti-TNF-alpha on Listeria infection seemed greater early during Listeria infection on days 1-6 when compared to later phases of the infection around days 6-10. From the data presented we conclude that in addition to other lymphokines, such as IFN-gamma, TNF-alpha is of importance during the entire course of a Listeria infection in nu/nu mice.

Animals↗
PubMed1989

Immunosuppression and transforming growth factor-beta in glioblastoma. Preferential production of transforming growth factor-beta 2.

Transforming growth factor (TGF)-beta 1 is a polypeptide that is assumed to play a fundamental role in the growth of both normal and neoplastic cells. TGF-beta 2 is a closely related polypeptide, originally described as glioblastoma cell-derived T cell suppressor factor (G-TsF) due to its immunosuppressive activity. Expression of the genes for TGF-beta 1 and G-TsF/TGF-beta 2 was examined in tumor cells and was found to be different in several cell lines and tissues that were tested. Whereas two glioblastoma cell lines expressed both TGF-beta 1 and G-TsF/TGF-beta 2 mRNA, one melanoma and neuroblastoma cell lines showed only TGF-beta 1 mRNA which in the case of the neuroblastoma required cycloheximide treatment for its detection. The coordinate expression of the genes for TGF-beta 1 and G-TsF/TGF-beta 2 in glioblastoma was not paralleled by secretion of both polypeptides as only G-TsF/TGF-beta 2 but not TGF-beta 1 was identified in supernatants of glioblastoma cells. These data provide evidence for a post-transcriptional level of regulation for production of the two forms of TGF-beta. As mRNA for G-TsF/TGF-beta 2 was also identified in fresh surgically removed human glioblastoma tissue, G-TsF/TGF-beta 2 may also be secreted within the tumor in vivo. Unlike glioblastoma, human fetal brain tissues or adult brain specimens studied did not express detectable levels of TGF-beta mRNA. Impaired cell-mediated immunity is an established finding in patients with glioblastoma. Secretion of G-TsF/TGF-beta 2 by tumor cells in vivo may contribute to decreased immune surveillance for tumor development, as well as neovascularization of the tumor tissue.

Adult↗
PubMed1989

Transforming growth factor-beta inhibits the generation of cytotoxic T cells in virus-infected mice.

The immunoregulatory effects of human recombinant transforming growth factor (rTGF) beta 1 and human recombinant glioblastoma-derived T cell suppressor factor (rG-TsF)/TGF beta 2 was investigated in mice infected with lymphocytic choriomeningitis virus (LCMV) or vaccinia virus. Starting on the day of infection, i.p. injections of 1 microgram/day or rTGF-beta 1 or rG-TsF/TGF-beta 2 suppressed the generation of virus specific CTL. The effect of TGF-beta on CTL (day 8) was less pronounced when TGF-beta treatment was delayed for 3 days after LCMV infection. rG-TsF/TGF-beta 2 also has an inhibiting effect on CTL-mediated disease in LCMV-infected mice: it prolonged the survival time of mice infected with LCMV and reduced the local swelling reaction after infection into the footpad. These results indicate that rTGF-beta 1 and rG-TsF/TGF-beta 2 influence T cell immune reactivity in vivo.

Animals↗
PubMed1989

On the cellular source and function of interleukin 6 produced in the central nervous system in viral diseases.

Interleukin 6 (IL6) was found to be produced in the central nervous system (CNS) of ICR+/+ mice infected with lymphocytic choriomeningitis virus (LCMV) or with vesicular stomatitis virus (VSV). When infecting athymic ICR nu/nu mice which cannot develop T cell-mediated meningitis after LCMV infection, no significant synthesis of IL6 was detected in the CNS. IL6 was found, however, to be produced intrathecally in ICR nu/nu mice infected with VSV, which causes a T cell-independent acute encephalitis. This suggested that IL6 may also originate from cells not belonging to the T cell compartment. Indeed, in vitro assays showed that both virus-infected microglial cells and astrocytes secreted IL6. In astrocytes, the infection resulted in the induction of the 1.3-kb messenger RNA IL6. Besides its effect on the development of B cell immunity in the brain, IL6 may be involved in repair mechanisms initiated in the course of viral-induced tissue damage. As shown here, IL6 induced an increase of the secretion of a neurotrophic factor, nerve growth factor by astrocytes. Thus, the intrathecal synthesis of IL6 may be part of the host response to infection favoring immune-mediated elimination of the infectious agent as well as trophic support for neurons.

Animals↗