Your browser doesn't support javascript.
loading
Show: 20 | 50 | 100
Results 1 - 20 de 96
Filter
Add more filters










Publication year range
2.
Am J Trop Med Hyg ; 56(1): 66-70, 1997 Jan.
Article in English | MEDLINE | ID: mdl-9063364

ABSTRACT

The molecular pathogenesis of schistosomal liver fibrosis has been studied in a murine model of Schistosoma mansoni. A novel fibroblast growth factor, fibrosin, was identified as a product of a subpopulation of CD4+ lymphocytes resident in the hepatic egg granulomas. We describe a sensitive, quantitative, antigen-capture enzyme-linked immunosorbent assay that can detect fibrosin in mouse serum and plasma at concentrations > 0.05 pg/ml. Using this assay, we detected in infected mice circulating fibrosin levels that were several-fold increased above those detected in uninfected controls. Circulating fibrosin levels increased after week 4 of infection, reached a peak at week 8, and normalized by week 12. We propose that circulating fibrosin might be a useful marker of hepatic fibrogenesis in schistosomiasis.


Subject(s)
Liver Cirrhosis/etiology , Lymphokines/blood , Schistosomiasis mansoni/complications , Animals , Antibodies, Helminth/immunology , Antibodies, Monoclonal/immunology , Antibody Specificity , Blotting, Western , Chromatography, Affinity , Enzyme-Linked Immunosorbent Assay , Female , Hybridomas , Immunoglobulin G/immunology , Lymphokines/immunology , Mice , Mice, Inbred C57BL , Rats , Rats, Inbred Lew , Sensitivity and Specificity
3.
Int Arch Allergy Immunol ; 111(4): 326-9, 1996 Dec.
Article in English | MEDLINE | ID: mdl-8957104

ABSTRACT

Tissue fibrosis accounts for considerable chronic morbidity in certain connective tissue diseases. Knowledge of the pathobiology of this complication, particularly the identification of fibrogenic proteins, is now sufficiently advanced to consider novel therapeutic strategies to interfere with pathological fibrogenesis. Studies in a murine model of the helminthic infection, schistosomiasis mansoni, led to the discovery of a novel fibrogenic protein, fibrosin. Molecular analysis suggests that the domain of cloned fibrosin cDNA that encodes the fibrogenically active moiety of the protein is highly conserved in mice and humans, but lacks significant sequence homology with other known cDNAs. Native fibrosin, as well as a synthetic fibrosin peptide, stimulate a variety of relevant responses in fibroblasts. Several cell types can produce fibrosin, including CD4+ lymphocytes and fibroblasts themselves. Observations in experimental schistosomiasis and in scleroderma reveal two possible mechanisms by which fibrosin might be involved in fibrosis. These observations could have implications for diagnosis and novel therapeutic strategies for fibrosis that complicates connective tissue diseases.


Subject(s)
Fibroblasts/metabolism , Lymphokines , Animals , Cloning, Molecular , Connective Tissue Diseases/complications , Fibrosis/etiology , Granuloma/metabolism , Humans , Liver/pathology , Lymphokines/genetics , Lymphokines/physiology , Lymphokines/therapeutic use , Mice , Schistosomiasis mansoni/metabolism
4.
Proc Natl Acad Sci U S A ; 92(6): 2154-8, 1995 Mar 14.
Article in English | MEDLINE | ID: mdl-7892239

ABSTRACT

Tissue fibrosis that complicates chronic inflammation can be a cause of serious morbidity. The molecular links between inflammation and fibrosis appear to be a variety of proteins produced by activated chronic inflammatory cells. Collectively, these fibrogenic cytokines promote the growth of fibroblasts and the production of extracellular matrix that are the characteristic features of fibrotic tissue. In an attempt to clone cDNA for a fibrogenic lymphokine that we had isolated, we transfected COS-7 cells with a cDNA library derived from concanavalin A-stimulated lymphocyte line CDC25. Conditioned medium from the transfected COS-7 cells but not from sham-transfected cells stimulates fibroblast proliferation in vitro. We used heterologous expression in COS-7 cells of pools of CDC25 cDNA and screening for biological activity in conditioned medium to enrich for the cDNA clone(s) that encodes this activity. With this strategy of sib selection we isolated clone 2B3. The culture supernatants of 2B3-transfected COS-7 cells exert maximum growth-stimulating effects on fibroblasts at a dilution of 1:20,000. The isolated cDNA has one open reading frame (216 nucleotides) that has no significant homology with nucleotide sequences that encode other proteins. A synthetic peptide constructed from the deduced amino acid sequence is biologically active in picomolar concentrations, even though it may represent only a portion of the native fibrosin. This lymphokine, which we designate fibrosin, may play a role in regulating fibrogenesis in certain chronic inflammatory diseases.


Subject(s)
CD4-Positive T-Lymphocytes/immunology , Lymphokines/biosynthesis , Amino Acid Sequence , Animals , Antibodies , Base Sequence , Cell Division/drug effects , Cell Line , Cells, Cultured , Chlorocebus aethiops , Cloning, Molecular , Codon , DNA, Complementary/analysis , Fibroblasts/cytology , Fibroblasts/drug effects , Fibrosis , Humans , Infant, Newborn , Kidney , Kinetics , Lymphocyte Activation/drug effects , Lymphokines/isolation & purification , Lymphokines/pharmacology , Male , Molecular Sequence Data , Peptides/chemical synthesis , Phosphoprotein Phosphatases/biosynthesis , Phosphoprotein Phosphatases/chemistry , Protein Biosynthesis , Proteins/chemistry , Recombinant Proteins/biosynthesis , Recombinant Proteins/isolation & purification , Recombinant Proteins/pharmacology , Skin/cytology , T-Lymphocytes, Helper-Inducer/immunology , Thymidine/metabolism , Transfection
5.
Infect Immun ; 61(9): 3901-6, 1993 Sep.
Article in English | MEDLINE | ID: mdl-8359912

ABSTRACT

We compared the abilities of gamma interferon (IFN-gamma), tumor necrosis factor alpha (TNF-alpha), and sensitized murine lymph node lymphocytes to activate syngeneic murine peritoneal macrophages to inhibit the growth of intracellular Mycobacterium bovis BCG in vitro. IFN-gamma could activate antimycobacterial defense only when added to macrophage cultures prior to their infection with BCG. TNF-alpha was without any effect. In contrast, BCG-sensitized lymphocytes could induce antimycobacterial defenses when added after macrophages had been infected with BCG. The cell-mediated effect required direct contact between effector lymphocytes and the targets (BCG-infected macrophages), as revealed in studies in which these cell populations were separated by a semipermeable membrane. Cyclosporin A, which inhibits the production of relevant macrophage-activating lymphokines, did not abrogate the ability of sensitized lymphocytes to activate antimycobacterial effects in infected macrophages. Furthermore, only BCG-sensitized lymphocytes, and not Listeria-sensitized lymphocytes, could activate the antimycobacterial effects. These lymphocytes were not cytotoxic to the infected macrophages. The presence of anti-TNF-alpha antibody in cocultures reduced the antimicrobial effects. We propose that the activation of antimycobacterial defense in macrophages can occur by direct physical contact with sensitized lymphocytes. This process may be due to lymphocyte membrane-associated TNF-alpha, as we previously demonstrated in our studies of antileishmanial defense.


Subject(s)
Cell Communication , Interferon-gamma/pharmacology , Macrophage Activation , Macrophages/immunology , Mycobacterium bovis/immunology , Tumor Necrosis Factor-alpha/pharmacology , Animals , Cells, Cultured , Female , Listeria/immunology , Lymphocytes/immunology , Macrophage Activation/drug effects , Macrophages/microbiology , Mice , Mice, Inbred C57BL , Mycobacterium bovis/growth & development , Recombinant Proteins
6.
Infect Immun ; 61(9): 3985-7, 1993 Sep.
Article in English | MEDLINE | ID: mdl-8359921

ABSTRACT

We report that the novel lymphokine fibroblast-stimulating factor 1, produced within hepatic schistosomal egg granulomas, stimulates liver fat-storing cells (FSC) in vitro to proliferate and express fibronectin genes. Because FSC are critical in hepatic fibrogenesis generally, we propose that in vivo stimulation of FSC by fibroblast-stimulating factor 1 may be an important step in schistosomal liver fibrosis.


Subject(s)
Adipose Tissue/drug effects , Fibroblasts/drug effects , Granuloma/metabolism , Lymphokines/pharmacology , Schistosoma/metabolism , Schistosomiasis/metabolism , Adipose Tissue/cytology , Adipose Tissue/metabolism , Animals , Cell Division/drug effects , Cells, Cultured , Fibronectins/genetics , Liver/cytology , Liver/drug effects , Mice , Mice, Inbred C57BL , Ovum , Procollagen/genetics
11.
Parasitol Today ; 8(8): 277-9, 1992 Aug.
Article in English | MEDLINE | ID: mdl-15463639

ABSTRACT

Schistosomiasis is one of the most prevalent of several chronic inflammatory diseases in which morbidity results primarily from tissue scarring. New concepts regarding the molecular pathogenesis of scar formation are being applied in research efforts to define the basis of liver fibrosis in schistosomiasis. Such investigations have led to the identification of an apparently novel lymphokine, fibroblast stimulating factor-I (FsF-I), produced in the egg granulomas. FsF-1 and other granulomo-derived fibrogenic cytokines may represent the molecular links between periovular granulomotous inflammation and hepatic fibrosis. Here, David Wyler postulates that the unmodified production of these f brogenic signals may be responsible for the development of severe hepatic fibrosis in the subpopulotion of infected individuals who develop this complication.

12.
J Immunol ; 148(11): 3583-7, 1992 Jun 01.
Article in English | MEDLINE | ID: mdl-1350293

ABSTRACT

Granulomas that form around Schistosoma mansoni eggs deposited in the liver secrete a variety of fibrogenic factors that may provide a molecular link between chronic inflammation and hepatic fibrogenesis in schistosomiasis. We recently isolated from conditioned medium of egg granuloma cultures a approximately equal to 60-kDa heparin-binding growth factor for fibroblasts. Because this protein is distinct from other defined heparin-binding growth factors, we designated it "fibroblast stimulating factor-1" (FsF-1). We now report that FsF-1 is a lymphokine. We prepared IgG antibody against purified FsF-1 and determined that it did not cross-react with a variety of growth factors or recombinant interleukins. Using two-color flow cytometry of dissociated granuloma cell suspensions, we observed that approximately 20% to 25% of granuloma CD4+ lymphocytes express surface FsF-1. We isolated CD4+ granuloma lymphocytes by FACS and observed that these cells spontaneously secrete into culture supernatant a fibroblast mitogen that is neutralized by anti-FsF-1 antibody. Furthermore, anti-FsF-1 can specifically immunoprecipitate a metabolically labeled protein produced by the granuloma CD4+ lymphocytes. The labeled protein has the same apparent molecular mass (approximately equal to 60 kDa) as FsF-1 purified from granuloma culture supernatants. These findings define CD4+ lymphocytes as a source of FsF-1. Because FsF-1 has biologic and chemical features distinct from most other defined lymphokines and from other heparin-binding growth factors, FsF-1 appears to be a novel lymphokine.


Subject(s)
CD4-Positive T-Lymphocytes/physiology , Fibroblast Growth Factors/metabolism , Fibroblasts/pathology , Schistosomiasis mansoni/physiopathology , Animals , Female , Fibroblast Growth Factors/immunology , Flow Cytometry , Granuloma/pathology , Granuloma/physiopathology , Mice , Mice, Inbred C57BL , Schistosomiasis mansoni/pathology
13.
J Leukoc Biol ; 51(3): 296-9, 1992 Mar.
Article in English | MEDLINE | ID: mdl-1347312

ABSTRACT

In our studies of host defense against the intracellular parasite Leishmania major, we obtained evidence for a novel mechanism of macrophage activation for antimicrobial defense that involves direct cell contact between CD4+ T lymphocytes and Leishmania-infected macrophages. The mechanism is distinctive as it does not involve secretion of lymphokines but is apparently mediated by the membrane-anchored form of tumor necrosis factor (mTNF; approximately 50-60 kd) present on the surface of the effector T lymphocytes. Furthermore, it is not cytotoxic to the host cell and its expression is antigen specific and genetically restricted. We prepared a Leishmania-specific cloned T-T cell hybridoma line 1B6 (CD4+, TH1) that expresses membrane-bound TNF but does not secrete TNF or other macrophage activators. We now report that 1B6 cells can activate antileishmanial defense in inflammatory macrophages, whereas soluble recombinant murine TNF (sTNF) alone is unable to do so. On the other hand, both 1B6 cells and sTNF can act synergistically with recombinant murine interferon-gamma (IFN-gamma, a known soluble macrophage-activating factor) in activating antimicrobial defense and NO2- release. The effects of 1B6 alone and the synergistic effects of 1B6 and IFN-gamma or sTNF and IFN-gamma are arginine dependent. These results suggest that mTNF may be more efficient than sTNF in macrophage activation and that contact with effector CD4+ lymphocytes that express mTNF may be an important mechanism of host defense.


Subject(s)
CD4-Positive T-Lymphocytes/chemistry , Leishmania/immunology , Leishmaniasis/immunology , Macrophage Activation/drug effects , Membrane Proteins/chemistry , Tumor Necrosis Factor-alpha/analysis , Animals , CD4-Positive T-Lymphocytes/physiology , Cell Communication , Female , Immunity, Innate/drug effects , Macrophages/immunology , Macrophages/parasitology , Mice
15.
Mem Inst Oswaldo Cruz ; 87 Suppl 4: 117-25, 1992.
Article in English | MEDLINE | ID: mdl-1343881

ABSTRACT

Morbidity in schistosomiasis mansoni occurs primarily as a result of the complications of hepatic fibrosis. Yet, the pathogenesis of schistosomal hepatic fibrosis is poorly understood. The fact that the hepatic egg granuloma is the hallmark of this infection suggests a potential role for granulomatous inflammation in hepatic fibrogenesis. Our studies in a murine schistosomiasis model indicate that hepatic granuloma cells secrete a variety of fibrogenic cytokines that may initiate the scarring process. Among these cytokines, we identified a novel protein that we designated fibroblast stimulating factor-1 (FsF-1). FsF-1 is a lymphokine that can stimulate fibroblast growth and matrix synthesis. A notable feature of hepatic fibrosis in this model is that production of FsF-1 and other granuloma-derived fibrogenic cytokines is down-regulated in chronic infection, an event that may be under immunological control. The spontaneous reduction of FsF-1 secretion presumably accounts for reduced scar formation late in infection of mice. In the context of relevant clinical studies, our findings engender the hypothesis that Symmer's fibrosis may develop in a small subpopulation of individuals as a result of immunogenetically-determined dysregulation of fibrogenic cytokine production.


Subject(s)
Granuloma/pathology , Liver Cirrhosis/pathology , Liver Diseases/pathology , Lymphokines/physiology , Schistosomiasis mansoni/pathology , Animals , Cells, Cultured , Cytokines/biosynthesis , Fibroblasts/metabolism , Granuloma/metabolism , Granuloma/parasitology , Liver Cirrhosis/metabolism , Liver Cirrhosis/parasitology , Liver Diseases/metabolism , Liver Diseases/parasitology , Mice , Models, Biological , Ovum/immunology , T-Lymphocytes, Helper-Inducer/immunology
16.
J Exp Med ; 174(4): 755-9, 1991 Oct 01.
Article in English | MEDLINE | ID: mdl-1680956

ABSTRACT

In our studies of host defense to the intracellular protozoan Leishmania major, we uncovered a novel mechanism of antileishmanial defense that involves direct cell contact between effector CD4+ lymphocytes and Leishmania-infected macrophages. The mechanism is distinctive because it does not involve lymphokine secretion and induces no cytotoxic effects in the host cells; its expression is antigen-specific and genetically restricted. We now demonstrate that these effector CD4+ cells display tumor necrosis factor (TNF) on their surface and provide evidence that the membrane-associated TNF is involved in the activation of the antileishmanial defense. Using a Leishmania-specific cloned T-T cell hybridoma line (1B6; CD4+, T helper type 1) that activates antileishmanial defense in macrophages through cell contact and does not secrete TNF, we noted that only cells bearing surface TNF (TNF+), but not ones lacking surface TNF (TNF-), exerted these effects. Moreover, the antileishmanial effects excreted by TNF+ 1B6 cells as well as by lymph node CD4+ TNF+ lymphocytes could be blocked with anti-TNF antibody. We propose that membrane-associated TNF on CD4+ T cells may provide a mechanism of targeting activation signals to macrophages in an antigen-specific and genetically restricted manner.


Subject(s)
CD4-Positive T-Lymphocytes/immunology , Leishmania tropica/immunology , Leishmaniasis, Cutaneous/immunology , Macrophage Activation , Macrophages/immunology , Tumor Necrosis Factor-alpha/physiology , Animals , Antibodies, Protozoan/immunology , Blotting, Western , CD4 Antigens/immunology , Cell Membrane/immunology , Female , Mice , Mice, Inbred BALB C , Mice, Inbred C57BL , Mice, Inbred Strains , Tumor Necrosis Factor-alpha/analysis
17.
New Biol ; 3(8): 734-40, 1991 Aug.
Article in English | MEDLINE | ID: mdl-1931818

ABSTRACT

The traditional concept of tissue scarring as a static pathological endpoint has been replaced by the modern perspective of a potentially reversible process comprising a sequence of discrete biological events (cell recruitment and hyperplasia, excessive matrix production, and matrix degradation). Cytokines, including several produced by inflammatory cells, have been identified that specifically regulate these events. Research into the cellular and molecular biology of scar formation is motivated by clinical and basic scientific considerations. One model of fibrogenesis that is being studied in detail is the liver fibrosis associated with schistosomiasis. In this helminthic infection, the host's granulomatous inflammatory response to the parasite eggs apparently lead to scar formation. A novel lymphokine that is mitogenic for fibroblasts and is produced by CD4+ lymphocytes in the granuloma has been found in infected livers. Preliminary evidence for the existence of immunoregulatory mechanisms of fibrogenesis in this disease also has been obtained. The potential role of genetic determinants that may influence this process needs to be further studied.


Subject(s)
Fibroblasts/parasitology , Liver Cirrhosis/parasitology , Liver Diseases, Parasitic/pathology , Schistosomiasis/pathology , Animals , Humans , Liver Cirrhosis/pathology
18.
Hepatology ; 13(5): 970-6, 1991 May.
Article in English | MEDLINE | ID: mdl-1903125

ABSTRACT

Schistosomiasis is the main cause of hepatic fibrosis worldwide, yet its pathogenesis remains unknown. We previously reported that conditioned medium from cultures of hepatic egg granulomas (isolated from mice acutely infected with Schistosoma mansoni) can stimulate fibroblast proliferation and matrix production in vitro. We have proposed that initiation of hepatic fibrosis in this infection might be under the control of granuloma-derived cytokines. We now report that conditioned medium from cultures of schistosomal egg granulomas isolated from liver of chronically infected mice has reduced fibrogenic activity compared with medium from cultures of granulomas obtained from more acutely infected mice. In related studies, we adoptively transferred splenocytes from infected mice and examined the fibrogenic activity in culture supernatants of hepatic egg granulomas isolated from the recipients. Those prepared from recipients of splenocytes from chronically infected mice contained substantially less fibrogenic activity than did those from recipients of splenocytes of acutely infected mice. These findings suggest that the fibrogenic influence of schistosomal egg granuloma products decreases during the course of chronic murine S. mansoni infection. Furthermore, our preliminary findings suggest that immunoregulatory cells may be responsible for the down-regulation of this influence. Previous observations indicating that in murine schistosomiasis hepatic collagen and hyaluronate synthesis and deposition are elevated in acute but not chronic infection might be explained on the basis of our observations.


Subject(s)
Cytokines/physiology , Granuloma/complications , Liver Cirrhosis/etiology , Schistosomiasis mansoni/complications , Animals , Cells, Cultured , Cytokines/immunology , Dose-Response Relationship, Immunologic , Female , Fibroblasts/cytology , Granuloma/immunology , Mice , Mice, Inbred C57BL , Schistosomiasis mansoni/immunology , Spleen/cytology , Spleen/immunology
19.
J Immunol ; 146(5): 1679-84, 1991 Mar 01.
Article in English | MEDLINE | ID: mdl-1704403

ABSTRACT

Liver fibrosis is the most serious complication of infection with Schistosoma mansoni and Schistosoma japonicum and is responsible for severe morbidity and mortality in hundreds of thousands of patients in many Third World nations. The pathogenesis of this condition remains to be elucidated. We proposed that certain cytokines produced by cells that comprise the chronic granulomas that surround the helminth eggs within the liver initiate hepatic fibrogenesis. We now report our successful purification to apparent homogeneity of the egg granuloma-derived fibroblast mitogen. The high affinity of this factor for heparin (elutes from heparin-Sepharose with 1.5 M NaCl) facilitates its purification by a two-step procedure, and identifies the cytokine as a heparin-binding growth factor (HBGF). Furthermore, because it has an isoelectric point approximately equal to 6.2, it has one of the characteristics of a class 1 (acidic) HBGF. We immunized rabbits with the purified factor and observed that the resulting antibodies (IgG) detected the factor but not acidic fibroblast growth factor (the prototypic class 1 HBGF) either by dot-blot ELISA or neutralization of biologic activity. The granuloma product and fibroblast growth factor also differ in target-cell specificity and amino acid composition. On the basis of these distinctions, we have designated the granuloma-derived mitogen fibroblast-stimulating factor-1. With the availability of purified fibroblast-stimulating factor-1 and the future analysis of its amino acid sequence, its structural relationship to other mesenchymal growth factors can be determined.


Subject(s)
Fibroblasts/cytology , Growth Substances/isolation & purification , Schistosomiasis mansoni/metabolism , Animals , Female , Fibroblast Growth Factor 1/analysis , Granuloma/metabolism , Granuloma/parasitology , Growth Substances/metabolism , Heparin/metabolism , Liver Diseases, Parasitic/metabolism , Mice , Mice, Inbred C57BL
20.
Cell Immunol ; 133(1): 178-86, 1991 Mar.
Article in English | MEDLINE | ID: mdl-1825032

ABSTRACT

Antileishmanial defense has been ascribed to the antimicrobial effects induced by soluble macrophage-activating lymphokines (MAFs), such as interferon-gamma and granulocyte-macrophage colony-stimulating factor. Recently, we identified an additional mechanism of T cell-mediated macrophage activation of defense against Leishmania that is apparently lymphokine independent, requires cell-cell contact, and is not cytotoxic to host cells. By employing antigen-specific murine T cell hybridoma lines, we observed that this property was associated with CD4+ subpopulations possessing the characteristics of the Th1 subset. In the present study, we address the question of whether contact-mediated macrophage activation can also be induced by Th2 lymphocytes. We employed as T effector cells in antileishmanial defense assays the Th2 cell line D10.G1.4 (D10) which is specific for conalbumin. We observed that D10 cells were able to induce activation of Leishmania-infected macrophages only when the macrophages were also primed with conalbumin, and that this activation apparently occurred by a mechanism without the secretion of MAF. Moreover, when mice infected with L. major were injected into footpad lesions with conalbumin and D10 cells, in situ parasite replication was partially inhibited. The expression of this antimicrobial mechanism by Th1 as well as Th2 clones suggests that the property of contact-mediated (lymphokine-independent) activation may be shared by certain lymphocytes in both Th1 and Th2 subpopulations. We hypothesize that this activation mechanism may involve the interaction of a lymphocyte membrane-associated MAF (such as tumor necrosis factor) and its receptor on the infected macrophage, resulting in the induction of antimicrobial effects but not cytotoxicity to the host cell.


Subject(s)
Leishmania tropica/immunology , Leishmaniasis/immunology , Macrophage Activation , Macrophages/immunology , T-Lymphocytes, Helper-Inducer/immunology , Animals , Cell Communication , Clone Cells , Colony-Forming Units Assay , Granulocyte-Macrophage Colony-Stimulating Factor/pharmacology , Leishmaniasis/parasitology , Macrophages/cytology , Mice , Mice, Inbred BALB C , Mice, Inbred C3H , T-Lymphocytes, Helper-Inducer/cytology , Tumor Necrosis Factor-alpha/physiology
SELECTION OF CITATIONS
SEARCH DETAIL
...