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G Milon

Publications and source records attributed to G Milon.

At least 19 recordsLinked to original sources
PubMed1996

Trafficking of Plasmodium chabaudi adami-infected erythrocytes within the mouse spleen.

Plasmodium chabaudi adami causes a nonlethal infection in mice. We found that crisis, the time of rapidly dropping parasitemia, was abrogated by splenectomy, indicating the role of spleen in parasite killing. The factors that mediate spleen-dependent immunity are not known. An earlier study in Plasmodium berghei-infected rats showed an association between increased clearance of heat-treated erythrocytes and the onset of crisis [Wyler, D. J., Quinn, T. C. & Chen, L.-T. (1982) J. Clin. Invest. 67, 1400-1404]. To determine the potential effects of different vascular beds in parasite killing, we studied the distribution of parasitized erythrocytes and bacteria in the spleens of P. chabaudi adami-infected mice during precrisis (a period of rising parasitemia) and during crisis. After intravenous injection, bacteria were localized predominantly in the marginal zone. In contrast, parasitized erythrocytes were found in the red pulp. We also found that during precrisis, a time of no immunity, the uptake of radiolabeled infected erythrocytes by the spleen was increased, not decreased. These data imply that no change occurs in the flow of parasitized erythrocytes through the spleen during the transition to an immune state (crisis). Our observations suggest that immune effector mechanisms, not circulatory changes, account for spleen-dependent parasite killing during a P. chabaudi adami infection in mice.

Animals↗
PubMed1996

Activated mast cells release biological activities able to support eosinophil production from mouse hemopoietic precursors.

Mouse bone marrow cells cultured for 6 days in the presence of recombinant murine IL-3 and granulocyte-macrophage colony-stimulating factor (GM-CSF) were used as a source of precursors responsive to eosinopoietins. They were further cultured for 7 days in the presence of either a combination of recombinant cytokines or supernatants of bone marrow-derived mast cells (BMMC) activated with either immunological or nonimmunological stimuli. Cytosmears of collected cells were analyzed for eosinophil contents and allowed to demonstrate that supernatants of passively sensitized BMMC support both total cell proliferation and eosinophil production, after various periods of incubation with monoclonal rat anti-mouse IgE antibodies (the 6HD5 mAbs). In contrast, a stimulation with 100 ng/ml dinitrophenylated bovine serum albumin (DNP-BSA) did not generate supernatants displaying such bioactivities. Low doses of methyl ester of L (but not D)-leucine or of the calcium ionophore A23187 also allowed the release of eosinopoietic bioactivities. In addition, immunoreactive IL-5, GM-CSF, and IL-3 were quantified in the BMMC supernatants. These results demonstrate that activated BMMC are able to effect eosinophil production.

Animals↗
PubMed1996

Molecular characterisation of ninein, a new coiled-coil protein of the centrosome.

We describe the cDNA cloning of ninein, a novel component of centrosomes. In the mouse, ninein is predicted to be an acidic protein (calculated pI of 4.8) with alternatively spliced forms of 245 kDa and 249 kDa that contain extensive regions of coiled-coil structure flanked by non-coiled ends. Other interesting features of this protein include an EF-hand-like domain, a potential GTP binding site and four leucine zipper domains. Specific polyclonal antisera were raised to two non-overlapping recombinant fragments of the protein and used to characterise the cellular distribution of ninein. Immunofluorescence and immunoelectron microscopy experiments with macrophage-like cells, Mm1, showed that ninein is localised specifically in the pericentriolar matrix of the centrosome. Studies with NIH3T3 fibroblasts demonstrated that ninein is associated with the centrosome throughout the cell cycle and can also be detected within nuclei at interphase. At mitosis ninein was also observed in association with the mitotic spindle. Immunocytochemical staining of mouse tissues showed that ninein was expressed in a heterogeneous fashion. Staining, if present, was always consistent with a centrosomal localisation and was never associated with nuclei. Ninein provides a new molecular tool for analysing the structure and function of the centrosome.

3T3 Cells↗
PubMed1995

Normal development and function of natural killer cells in CD3 epsilon delta 5/delta 5 mutant mice.

The CD3 epsilon polypeptide contributes to the cell surface display as well as to the signal transduction properties of the T-cell antigen receptor complex. Intriguingly, the distribution of CD3 epsilon is not restricted to T cells, since activated mouse, human, and avian natural killer (NK) cells do express intracytoplasmic CD3 epsilon polypeptides. CD3 epsilon is also present in the cytoplasm of fetal thymic T/NK bipotential progenitor cells, suggesting that it constitutes a component of the NK differentiation program. We report here that the genetic disruption of CD3 epsilon exon 5 alters neither NK cell development nor in vitro and in vivo NK functions, although it profoundly blocked T-cell development. These results support the notion that CD3 epsilon is dispensable for mouse NK cell ontogeny and function and further suggest that the common NK/T-cell progenitor cell utilizes CD3 epsilon as a mandatory component only when differentiating toward the T-cell lineage.

Amino Acid Sequence↗
PubMed1995

Transgenic mice expressing high levels of soluble TNF-R1 fusion protein are protected from lethal septic shock and cerebral malaria, and are highly sensitive to Listeria monocytogenes and Leishmania major infections.

Mice bearing a transgene coding for a soluble tumor necrosis factor receptor type 1 (TNFR1)-FcIgG3 fusion protein and placed under the control of the alpha-1-antitrypsin gene promoter were generated. Depending on the mouse line, blood levels of the protein ranged from 25 ng/ml to over 100 micrograms/ml; this level of expression was most often transmitted to the transgene-bearing progeny as a relatively stable feature. High-expressor mice were completely resistant to lipopolysaccharide-induced shock and lethality, including after D-galactosamine sensitization, and mice expressing about 1 microgram of the fusion protein/ml were partially (60%) protected. In contrast, mice expressing less than 0.1 microgram of the protein/ml were more sensitive than controls with respect to incidence and time of death, even though the biological activity of serum tumor necrosis factor (TNF) was partially neutralized. High-expressor mice of the adequate genetic background were markedly, although not completely, protected from death by cerebral malaria after injection with Plasmodium berghei. They were highly susceptible to Listeria monocytogenes, dying from bacterial dissemination after sublethal infection, and to Leishmania major, displaying severe, non-healing lesions after local infection. Under the same conditions, mice expressing about 1 microgram protein/ml were only partially sensitive to these last agents, compared to non-transgenic littermate mice which were fully resistant. These transgenic mice represent a model of permanent, complete or partial, impairment of TNF use, which compares favorably, for ease of breeding and for the range of effects, to mice bearing gene disruptions.

Animals↗
PubMed1995

Listeria monocytogenes: a live vector able to deliver heterologous protein within the cytosol and to drive a CD8 dependent T cell response.

After an introduction on the entry and lifestyle of Listeria monocytogenes within mammalian eucaryotic cells, this chapter gives a brief overview of murine experimental listeriosis. Among the main characteristics of this murine model of infectious/pathogenic processes initiated by a facultative intracellular bacteria, we point out two main recent advances. One relates to Listeria monocytogenes-induced production of cytokines as local, and transient signals able to direct the immune responses along a type 1 pathway of CD4/CD8 T cell differentiation. The other relates (a) to the recognition of L. monocytogenes-reactive CD8+ T lymphocytes as effectors able, once recruited within infected loci, to critically contribute to the complete clearance of the bacteria, and (b) to the recently recognized specificity of some of these CD8 lymphocytes in BALB/c mice. In this paper, we also briefly review (a) the readout assays presently used to monitor the outcome of the infectious/pathogenic processes and the related development and expression of immune responses induced by intravenous inoculation of wild-type virulent or attenuated L. Monocytogenes, (b) why all this information allows us to consider the use of L monocytogenes of attenuated virulence as relevant live recombinant vectors in order to deliver heterologous proteins to the class I processing and presentation pathway, and to induce CD8 T cells along the type 1 pathway.

Animals↗
PubMed1995

Parasite-host relationships: in-situ study of Leishmania spp. in resistant and susceptible mice.

The host's skin is a critical tissue in the natural life cycle of the Leishmania spp. known to cause an 'asymptomatic' infectious process or cutaneous or visceral leishmaniasis in mammals. The dermis, once disturbed by the inoculation of infective parasites, becomes a site of dynamic events, the progression of which depends upon both host and parasite characteristics. Whatever the final site of the morbidity caused by the parasites, whether it be cutaneous, visceral or muco-cutanous, this site reflects the parasite and host's ability to create a pro- or anti-parasite micro-environment. The characteristics of this environment are now amenable to analysis in situ, as illustrated by the study of the cutaneous processes initiated by inoculation of Leishmania major in laboratory mice.

Animals↗
PubMed1995

Experimental models for leishmaniasis and for testing anti-leishmanial vaccines.

In public health terms, leishmaniases are diseases of humans and dogs, whereas, in epidemiological terms, Leishmania spp. are considered to represent infections of a wide variety of animals, which represent the natural reservoirs of the various parasite species involved. Humans and dogs (which may be considered secondary or 'accidental' hosts in the leishmanial life-cycle) often exhibit severe clinical signs and symptoms when infected, whereas reservoir hosts generally show a few, minor or no signs. This situation makes the definition of a suitable laboratory model a difficult one, since the various experimental hosts may behave either like a reservoir or an accidental host. This review discusses the concept of animal models for leishmaniases and provides a critical evaluation of the most common experimental models and their respective advantages and disadvantages. In this state-of-the-art review, particular emphasis is given to the value of using mouse, hamster, cotton-rat, dog and primate models, especially in the context of testing potential anti-leishmanial vaccines.

Animals↗
PubMed1995

Attenuated Listeria monocytogenes as a live vector for induction of CD8+ T cells in vivo: a study with the nucleoprotein of the lymphocytic choriomeningitis virus.

Listeria monocytogenes spends most of its intracellular life cycle in the cytosol of the infected eucaryotic cells. Within this cellular compartment originates the endogenous pathway of antigen processing and presentation. We thus assumed that recombinant L. monocytogenes expressing an heterologous protein, the nucleoprotein of the lymphocytic choriomeningitis virus (LCMV), should be able to induce antigen-specific CD8+ T cells in vivo. The LCMV nucleoprotein gene was inserted in phase with the sequence coding for the putative signal sequence of the hemolysin of L. monocytogenes in order to target its secretion into the cytosol of the infected cell. The ability of this recombinant bacterium to induce LCMV-reactive CD8+ T cells was then monitored in BALB/c mice. The immune status of the immunized BALB/c mice was studied on the seventh day after a single i.v. injection of a sublethal dose of the recombinant bacteria: (i) cytotoxic CD8+ T cells were detected in liver; (ii) using in vitro re-stimulation with PMA and ionomycin, secondary cytotoxic CD8+ T cells were detected in spleen; (iii) an early inflammatory reaction dependent on the presence of CD8+ T cells occurred in the footpad after intraplantar inoculation of live LCMV; and (iv) mice were protected against an otherwise lethal intracerebral LCMV challenge; the protection was accompanied by elimination of the virus. When the immune status of the immunized hosts was monitored for a longer period post-immunization, the balance between immune protection and immunopathology described for the anti-LCMV immune responses was observed; two phases of protection were detected, flanking a transitory phase of exacerbation of the lymphocytic choriomeningitis disease (weeks 2-5).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

Sialoadhesin, a macrophage sialic acid binding receptor for haemopoietic cells with 17 immunoglobulin-like domains.

Sialoadhesin is a macrophage-restricted adhesion molecule of 185 kDa that mediates sialic acid-dependent binding to cells. It is expressed strongly by macrophages in lymphoid and haemopoietic tissues where it is likely to mediate cell-cell interactions. Here we report the molecular cloning of murine sialoadhesin and show that it is a new member of the immunoglobulin (Ig) superfamily with 17 Ig-like domains. COS cells transfected with a cDNA encoding full-length sialoadhesin bound mouse bone marrow cells in a sialic acid-dependent manner. Alternatively spliced cDNAs, predicting soluble forms of sialoadhesin containing the first three or 16 Ig-like domains of sialoadhesin, were expressed in COS cells and the respective proteins purified. When immobilized on plastic, the 16-domain form bound cells in a sialic acid-dependent manner, suggesting that sialoadhesin can function in both secreted and membrane-bound forms. The most similar proteins in the database were CD22, myelin-associated glycoprotein, Schwann cell myelin protein and CD33. Like sialoadhesin, CD22 mediates sialic acid-dependent cell adhesion. The sequence similarity of sialoadhesin to CD22 and related members of the Ig superfamily indicates the existence of a novel family of sialic acid binding proteins involved in cell-cell interactions.

Amino Acid Sequence↗
PubMed1994

Malaria pathogenesis.

Malaria is a disease caused by repeated cycles of growth of the parasite Plasmodium in the erythrocyte. Various cellular and molecular strategies allow the parasite to evade the human immune response for many cycles of parasite multiplication. Under certain circumstances Plasmodium infection causes severe anemia or cerebral malaria; the expression of disease is influenced by both parasite and host factors, as exemplified by the exacerbation of disease during pregnancy. This article provides an overview of malaria pathogenesis, synthesizing the recent field, laboratory, and epidemiological data that will lead to the development of strategies to reduce mortality and morbidity.

Anemia↗
PubMed1994

Transient inducible events in different tissues: in situ studies in the context of the development and expression of the immune responses to intracellular pathogens.

Intracellular pathogens whether facultative like Mycobacterium sp., e.g. Bacillus Calmette Guérin, Listeria monocytogenes or strictly intracellular like Leishmania sp. initiate either asymptomatic infectious processes or disease depending both on factors of the host (genetic as well as environmental ones) and the infectious/pathogenic agents. In this contribution, we first summarized informations which justify to develop in situ analysis to decipher the sequential events that result in different modes/classes of immune responses. How the mode of the immune response is determined remains a main question to address. Although it has recently become clear, in vitro, that immunocompetent cells and their cytokines are critical to set on a stable mode of immune response, acting on naive T cells, this area deserves more in vivo studies. Indeed, peripheral T cells, at different stages of differentiation, may exist in vivo (a) naive/virgin, (b) experienced, (c) effector T cells, depending on the level of stimulation of the immune system by either endogenous or exogenous (e.g. gut flora) signals. The three chosen examples illustrate our contributions in this field focusing on three different non-lymphoid tissues which may become infected: bone marrow (Bacille de Calmette Guérin), liver (Listeria monocytogenes), skin (Leishmania major). These three illustrations also allow to attract attention on the interest of using mice of genetically different strains the immune response of which is set up under different modes.

Animals↗
PubMed1994

Expansion of gamma interferon-producing CD8+ T cells following secondary infection of mice immune to Leishmania major.

Reinfection of immune mice with Leishmania major elicits a secondary gamma interferon (IFN-gamma) response to which specific CD8+ T cells are essential. We have shown previously that specific CD8+ T cells from reinfected immune mice release substantially higher levels of IFN-gamma, a cytokine essential for the efficient activation of parasitized macrophages to kill intracellular L. major. By using an ELISPOT assay, which allows the detection of IFN-gamma production by individual cells, it is shown here that this elevated IFN-gamma response is the result of an increase of up to 50-fold in the frequency of parasite-specific CD8+ T lymphocytes in the spleens and draining lymph nodes of both immune reinfected CBA and BALB/c mice. This observation is additional evidence of the role that CD8+ T cells play in immunity to reinfection with L. major.

Animals↗
PubMed1993

Regulation of interleukin-1 receptor expression in mouse brain and pituitary by lipopolysaccharide and glucocorticoids.

Interleukin-1 (IL-1) receptors have been characterized in mouse pituitary and brain. Previous studies have demonstrated that IL-1 receptor density is high in the dentate gyrus in the hippocampus and that lipopolysaccharide (LPS) injection caused an 80% decrease in the number of hippocampal IL-1 receptors, while pituitary receptors in the anterior pituitary were unaffected. In order to investigate on the role of glucocorticoids (GC) in the control of IL-1 receptor expression in the brain and pituitary, the effect of stress, exogenous GC administration or adrenalectomy (ADX) on IL-1 receptor density was determined. Assays were achieved under basal and LPS-stimulated conditions by in situ quantitative autoradiography technique using human recombinant 125I-IL-1 alpha as a tracer. An increase of GC concentration in serum, following immobilization stress or dexamethasone (DEX) treatment (short and long term), did not modify, in the hippocampus, the density of IL-1 receptors under basal conditions or after peripheral LPS injection. On the contrary, ADX significantly decreased IL-1 receptor density in LPS-treated animals. In the anterior pituitary, a significant increase in the density of basal IL-1 receptors was observed 6 h following immobilization stress or after 7 days of DEX treatment while short-term DEX treatments are ineffective. In contrast to what was observed in the hippocampus, no changes in pituitary receptor densities were observed in ADX mice. These results indicate that hippocampal and pituitary IL-1 receptor expressions are differentially regulated by GC. Therefore, this report constitutes the first demonstration of an in vivo regulation of IL-2 receptors in the pituitary.

Adrenalectomy↗
PubMed1992

Induction of protective CD8+ T lymphocytes by an attenuated Listeria monocytogenes actA mutant.

We tested the ability of an attenuated actA mutant of Listeria monocytogenes to induce protective immunity in mice. This mutant can enter and multiply in the cytosol of the infected host cell, but is deficient in actin-dependent cell-to-cell spread. It was found to be of attenuated virulence for inbred C3H mice: the LD50 after i.v. injection was 1000-fold higher than that of the wild-type strain. Mutant bacteria multiplied up to the fourth day in the liver, but only for 1 day in the spleen. A single infection with the maximum sublethal dose of the actA mutant induced long-lasting immunity; the LD50 of virulent wild-type L. monocytogenes increased 100-fold and growth of wild-type L. monocytogenes was controlled in liver and spleen of these mice. The presence of Listeria-reactive T cells in spleen of C3H mice infected 7 days previously with the actA mutant was monitored, through their ability to protect naive syngeneic recipients against wild-type L. monocytogenes. Protection was mainly conferred by Thy-1+ CD8+ T lymphocytes; depletion of CD4+ T cells had no significant effect on the level of transferred protection. Such attenuated mutants may be used to develop live vector vaccines for delivery of heterologous proteins into the cytosol, thereby favoring the induction of a CD8+ T cell response.

Animals↗
PubMed1992

Transfer of both protection and delayed-type hypersensitivity against live Listeria is mediated by the CD8+ T cell subset: a study with Listeria-specific T lymphocytes recovered from murine infected liver.

The recruitment of specific T lymphocytes in murine liver is thought to be a key event in the ultimate control of Listeria monocytogenes growth during primary infection. However, there has been little functional characterization of the cell populations recruited in this non-lymphoid organ. Therefore in this study, the recruited lymphomyeloid cells were isolated from the liver of C57BL/6 mice at the peak of the immune response (day 7) triggered by a non-lethal L.monocytogenes infection. The anti-Listeria T lymphocytes were detected in vivo by their ability to transfer protection and delayed-type hypersensitivity (DTH) to live L.monocytogenes in naive recipients: protection was measured not only by the effect on reduction of the bacterial load in liver and spleen, but also on survival after the lethal challenge, and DTH was detected using as eliciting antigen, either live L.monocytogenes or heat-killed L.monocytogenes. When live pathogens were used, both functions were found to be mediated by T lymphocytes belonging to the CD8+ subset. However, when heat-killed L.monocytogenes were used as eliciting antigen in the DTH assay, Listeria-specific CD8+ T lymphocytes could not be restimulated in immune lymphoid cell populations recovered either from liver or spleen of Listeria-infected mice. Both populations were thus found to share the same qualitative properties in the DTH assay. The importance of the use of live pathogens versus heat-killed pathogens for detection of DTH and protection functions is discussed in the light of current concepts on processing and presentation pathways of Listeria-derived peptides.

Animals↗
PubMed1991

Dynamics of lymphocytes and inflammatory cells recruited in liver during murine listeriosis. A cytofluorimetric study.

During primary infection of mice by Listeria monocytogenes, bacterial elimination is dependent on the recruitment of myelomonocytic cells in the infectious foci and the activation of their bactericidal mechanisms through cytokines secreted by Listeria-specific T lymphocytes. The immune events occurring in the liver, one of the main infected organs, have not yet been studied in detail. In the present quantitative study, we describe the dynamics of recruitment of cells belonging to the lymphoid or myelomonocytic lineages in the liver. The different cell populations mobilized into the liver were isolated each day during the course of a sublethal L. monocytogenes infection and their phenotype was characterized by flow cytometry. Three distinct phases of recruitment were observed. 1) During the first day of infection, 17 x 10(6) lymphomyeloid cells were recruited in the liver with a predominance of myelomonocytic cells; 51% of the incoming cells were M1/70+; the NK cell population (detected by the 4D11 antibody) also increased transiently at this period. 2) From day 3 to 5, a high number of myelomonocytic cells infiltrated the liver (13 x 10(6) M1/70+ cells); most of these cells were macrophages (as detected with the macrophage-restricted antibody FA/11 or observed after May-Grünwald Giemsa staining); the antigranulocytic antibodies 7/4 and RB6.8C5 were found to label these mononuclear phagocytes at this period of infection. A subpopulation of Thy-1+ cells (16%) was found to be labeled by the RB6.8C5 antibody in normal liver and, at day 5 and 6, all Thy-1+ cells also bound the RB6.8C5 mAb.3) From day 5 onward, two waves of phenotypically distinct T lymphocytes were observed; the number of CD8+ T lymphocytes (15 x 10(6) cells) increased first at day 5 and peaked on day 7; CD4+ T lymphocytes (6.2 x 10(6) cells) were then recruited with a 2-day delay (on day 7) in the liver.

Animals↗