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G Milon

Publications and source records attributed to G Milon.

At least 55 records · Page 3Linked to original sources
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

Drugs or vaccines?

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Journal Article↗
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↗
PubMed1991

Lysozyme is an inducible marker of macrophage activation in murine tissues as demonstrated by in situ hybridization.

This study demonstrates the induction of lysozyme mRNA expression in situ in tissue macrophages (M phi) of mice following in vivo stimulation. The resting resident tissue M phi of most tissues do not contain enough lysozyme mRNA to be detected by in situ hybridization using 35S-labeled RNA probes. Following Bacille Calmette Guerin or Plasmodium yoelli infection, however, M phi recruited to liver and spleen hybridize strongly to the lysozyme probe. Within 24 h of infection, cells found in the marginal zone of the spleen begin to produce lysozyme mRNA. This response is also evoked by a noninfectious agent (intravenously injected sheep erythrocytes), and is possibly the result of an early phagocytic interaction. Later in the infection, other cells in the red and white pulp of the spleen, and cells in granulomas in the liver, become lysozyme-positive. Kupffer cells are rarely lysozyme-positive. Lysozyme mRNA levels in liver granulomas remain relatively constant during the infection, and lysozyme is produced by most granuloma cells. This contrasts with tumor necrosis factor alpha (TNF alpha) mRNA, which is produced by fewer cells in the granuloma, and which can be massively induced by lipopolysaccharide administration. The production of lysozyme, previously considered a constitutive function of M phi, is therefore an indicator of M phi activation in vivo, where immunologically specific and nonspecific stimuli both stimulate lysozyme production at high levels in subpopulations of cells occupying discrete anatomical locations.

Animals↗
PubMed1991

Receptors for interleukin-1 (alpha and beta) in mouse brain: mapping and neuronal localization in hippocampus.

Interleukin-I receptors were mapped and characterized in mouse brain by quantitative autoradiography using human recombinant [125I]interleukin-I alpha and [125I]interleukin-1 beta as ligands. Both ligands provide identical receptor mapping. In terms of specificity, interleukin-1 alpha and interleukin-1 beta were equally potent in binding competitions assays with either [125I]interleukin-1 alpha or [125I]interleukin-1 beta (EC50 11 pM). These receptors were shown to be highly concentrated in the dentate gyrus, in the choroid plexus at various levels of the brain, in the pituitary and in the meninges. They were also present at low concentrations in the cortex but undetectable in other brain structures. In the dentate gyrus, interleukin-1 receptors were localized on the granular and molecular layers (granule cells) when visualized on slides dipped in nuclear emulsion. Cellular localization of interleukin-1 receptors was assessed using selective lesion by colchicine. The complete loss of [125I]interleukin-1 binding in hippocampal areas where neurons were destroyed by colchicine demonstrates that interleukin-1 receptors are located on granule cells. Following lesion, sparse undestroyed cells, with glial cell morphology, also showed significant labelling. In conclusion, interleukin-1 receptors are located on the granule cells in the mouse dentate gyrus. These neurons may therefore be targets for neuromodulation by interleukin-1 and they may play a key role in the central effect of interleukin-1 as well as in the control of the immune response by the brain.

Animals↗
PubMed1991

Establishment of resistance to Leishmania major infection in susceptible BALB/c mice requires parasite-specific CD8+ T cells.

Although CD4+ T cells are generally accepted to be responsible for the determination of resistance to infection in experimental murine cutaneous leishmaniasis, a contribution of CD8+ lymphocytes to immunity can be demonstrated under certain well-defined conditions. Normally highly susceptible BALB/c mice can be rendered resistant to infection with Leishmania major promastigotes by a single injection of monoclonal anti-CD4 antibodies at the beginning of infection. Mice treated in such a way can heal their primary cutaneous lesions and acquire immunity to subsequent challenge infection. Both the resolution of the primary infection and the induced state of immunity to reinfection in these mice is shown to be dependent upon the anti-leishmanial effector functions of CD8+ T cells. Furthermore, in contrast to control infected BALB/c mice, which are unable to mount a delayed-type hypersensitivity (DTH) response to viable parasites, mice cured as a result of treatment with anti-CD4 antibodies in vivo exhibit a strong DTH response, which can be significantly reduced by injection of either anti-CD4 or anti-CD8 monoclonal antibodies prior to antigenic challenge with viable promastigotes. Moreover, increased numbers of specific CD8+ T cells, able to transfer Leishmania-specific DTH responses, were found in lymphoid organs of BALB/c mice rendered resistant to infection by immunointervention with anti-CD4 monoclonal antibodies at the beginning of infection. Neutralization in vivo of interleukin 4 during the course of infection in BALB/c mice also enables these otherwise susceptible mice to resolve their cutaneous lesions and to decrease the parasite burden in infected tissues. CD8+ T cells are required for both of these beneficial effects. Taken together, these results indicate that in the immune BALB/c mouse, as in the normally resistant CBA mouse, CD8+ lymphocytes are involved in the elimination of L. major and in the establishment and maintenance of immunity against infection with this parasite.

Animals↗
PubMed1991

Pleiotropic control of Listeria monocytogenes virulence factors by a gene that is autoregulated.

Evidence for pleiotropic activation of virulence genes in Listeria monocytogenes is presented. A complementation study of a spontaneous prfA-deletion mutant and analysis of cassette and transposon insertion mutants showed that the gene prfA activates the transcription of four independent genes which code for a phosphatidyl-inositol-specific phospholipase C (gene plcA), listeriolysin O (gene hlyA), a metallo-protease (gene prtA) and a lecithinase (gene prtC). Transcription of prfA is not constitutive. During the growth phase, two peaks of prfA transcript accumulation were observed: the first was during exponential growth, and the second was at the beginning of the stationary phase. In addition, two prfA-specific transcripts of 2.2 kb and 1 kb are detected. Early in exponential growth, prfA is co-transcribed with plcA which lies upstream prfA, giving rise to the 2.2 kb plcA-prfA transcript. In late-exponential growth and at the beginning of the stationary phase, prfA transcripts of 1 kb are predominantly detected. Our results demonstrate that since prfA controls plcA transcription, it also regulates its own synthesis.

Amino Acid Sequence↗
PubMed1990

Isolation and flow cytometric analysis of the free lymphomyeloid cells present in murine liver.

Recruitment of circulating lymphomyeloid cells in the liver during infection often plays a critical role, mediating control or exacerbation of the pathogen growth. This paper describes a simple and rapid technique to recover these lymphomyeloid cells from a normal or an infected liver. After portal perfusion with saline buffer, the liver is gently dissociated on steel screens and the resulting cell population spun in 35% Percoll in 100 IU/ml Calciparine to remove all nuclei and cell debris: the recovery of a pure liver lymphomyeloid cell population is usually achieved in 40-60 min. Phenotypic and functional analysis could then be easily carried out on this cell population. This methodology was applied to normal mouse liver: flow cytometric analysis of the purified free lymphomyeloid cells showed the presence of T lymphocytes (46% +/- 3 with a CD4/CD8 ratio of 2.8), B lymphocytes (20% +/- 2 IgG and 30% IgM positive) and myelomonocytic cells (14% +/- 2 complement receptor type III positive).

Animals↗
PubMed1990

A CD4+ TH2 cell line isolated from mice chronically infected with Trypanosoma cruzi induces IgG2 polyclonal response in vivo.

In our study we describe further characteristics of a CD4+ T cell line (G-05) isolated from lymph nodes of C3H/HeJ mice chronically infected with Trypanosoma cruzi. This T cell line secreted lymphokines such as interleukin (IL) 4 and IL 5 and could be defined as a TH2 type of helper T cells. By passive transfer into naive mice, the G-05 line was able to induce a polyclonal B cell activation in the spleen. This splenic B cell activation was quite similar to that seen in chronically T. cruzi-infected animals, where the isotypic pattern presents a large increase of IgG2a and IgG2b isotypes. Moreover, it was possible to reproduce this kind of polyclonal B cell activation in vivo, with the supernatant of G-05 T cells cultured in the presence of T. cruzi extract, accessory cells and exogenous IL 2. Analysis of this supernatant showed the presence of large amounts of IL 4, IL 5, IL 3 and IL 6 but not of interferon-gamma, and residual IL 2 activity was not significant. These results suggest that the G-05 T cells considered as TH2 cells on the basis of their lymphokine production are involved in the development of the in vivo polyclonal B cell activation in T. cruzi infection.

Animals↗
PubMed1989

Antibody to the murine type 3 complement receptor inhibits T lymphocyte-dependent recruitment of myelomonocytic cells in vivo.

We have used the delayed-type hypersensitivity (DTH) response to SRBC or tuberculin to examine the role of the murine type 3 complement receptor in T lymphocyte-dependent inflammatory recruitment. Intravenous injection of 5C6, a CR3-specific rat mAb known to impair myelomonocytic adhesion, divided the DTH to SRBC in actively immunized mice into two phases. The early phase, which lasted 24 h, was characterized by maximal oedema and maximal inflammatory recruitment and was 5C6 inhibitable. The later phase was 5C6 resistant and reached a peak 48 h after antigenic challenge and was superimposable on the declining peak seen in control mice. Passive transfer of reactive T cells mixed with antigen was used to examine the myelomonocytic effector arm of the DTH alone. Both passive transfer of cutaneous DTH to SRBC and passive transfer of the largely monocytic T cell-dependent recruitment to tuberculin in the peritoneal cavity were completely abolished by systemic 5C6 treatment. Injection of 5C6-treated donor leukocytes at the site of passive transfer had no effect. Treatment of donor mice with 5C6 at the time of active immunization did not alter their ability to provide reactive T cells for passive transfer. The myelomonocyte-restricted rat mAb 7/4 and the rapidly cleared F(ab')2 fragment of 5C6 showed no inhibition of the DTH. In all cases, inhibition of footpad swelling correlated with histological evidence of inhibition of myelomonocytic cell recruitment. Peritoneal cell counts after local DTH to tuberculin showed complete inhibition of monocyte recruitment. We conclude that CR3 plays a quantitatively important role in T cell-dependent inflammatory recruitment. This is absolute in passive transfer experiments, but only partial after active immunization. Leukocyte CR3 plays a common role in both immunologically specific and nonspecific inflammatory recruitment and provides a target that could possibly be manipulated to therapeutic advantage.

Animals↗