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M Lenfant

Publications and source records attributed to M Lenfant.

At least 55 records · Page 3Linked to original sources
PubMed1985

[Presence of a peripheral type benzodiazepine binding site on the macrophage; its possible role in immunomodulation].

Saturable binding site for 3H-flunitrazepam (KD = 43 +/- 7 nM, Bmax = 391 +/- 58 fmoles/cell, i.e. 250,000 sites/cell) is characterized on Mouse peritoneal inflammatory macrophages. The affinity for different ligands (PK 11195 greater than Ro 5-4864 greater than diazepam greater than flunitrazepam greater than clonazepam greater than Ro 15-1788) shows that this site is of peripheral type. In vivo the humoral response in Mice to Sheep red blood cells was stimulated by administration of 1 mg/kg of PK 11195 (+85%), Ro 5-4864 (+80%) and diazepam (+58%). Clonazepam and Ro 15-1788 are devoid of activity. This suggests that molecules which show affinity for the "peripheral type" benzodiazepine binding site might modulate the immune response.

Animals↗
PubMed1984

Interaction of benzodiazepines with mouse macrophages.

Mouse peritoneal inflammatory macrophages have a saturable binding site for [3H]flunitrazepam with a KD of 43 +/- 7 nM and Bmax of 391 +/- 58 fmol per 10(6) cells, which corresponds to 250 000 sites per cell. The IC50 values for PK 11195, Ro 5-4864, diazepam, flunitrazepam, clonazepam, ethyl-beta carboline 3-carboxylate and Ro 15-1788 were 5.6, 6.5, 21, 40, 3 000, 12 000 and 80 000 nM respectively; gamma-aminobutyric acid did not displace [3H]flunitrazepam. These results indicate that the benzodiazepine binding site on the macrophage is of the peripheral type. In vivo experiments show that, at 1 mg/kg, peripheral and mixed type molecules stimulate the humoral response to sheep red blood cells while central type benzodiazepines are inactive. The hypothesis that this effect is mediated through the binding on the macrophage may be considered.

Animals↗
PubMed1984

A convenient source of CFU-s inhibitors: the fetal calf liver.

The presence of a bone-marrow stem-cell inhibitor able to prevent CFU-s entry into DNA synthesis after cytosine arabinoside (Ara-C) treatment has been detected in 7-month-old fetal calf liver. The inhibitory fraction was obtained through ultrafiltration of a delipidated tissue extract powder and purified by BioGel-P-2 chromatography. The elution pattern on Sephadex G10 is similar to that of the bone-marrow inhibitory extract previously obtained from fetal calf bone marrow. It corresponds to a low-molecular-weight molecule (MW less than 2000), devoid of species specificity and having no inhibitory effect on GM-CFC proliferation.

Animals↗
PubMed1983

Prevention of graft-versus-host mortality in mice by preincubation of the graft with highly purified spleen-derived immunosuppressive peptides.

Two non-species-specific spleen-derived immunosuppressive peptides (SDIP) have been highly purified from bovine spleen and are referred to as SDIPe and SDIPHP with reference to the last step of the purification procedure (electrophoresis or high pressure liquid chromatography, respectively). Preincubation of lymphoid cells with very dilute preparations of both SDIPs significantly reduced their capacity to induce a lethal graft-versus-host reaction (GVHR), but did not diminish their capacity to form hematopoietic colonies in the spleens of lethally irradiated syngeneic hosts (CFUs). Therefore, such pretreatment of bone marrow grafts by SDIP could be useful candidate for GVHR prevention. In contrast, preincubation with thymulin (serum thymic factor (FTS) plus ZnCl2), which shares several physicochemical properties with SDIP, significantly improved the ability of lymphoid cells to induce lethal GVHR. The opposite immunomodulatory effects of these highly similar peptides are discussed.

Animals↗
PubMed1983

The stimulatory effect of serum thymic factor (FTS) on spontaneous DNA synthesis of mouse thymocytes.

Synthetic serum thymic factor (FTS), a T-cell differentiating factor, was studied for its ability to modify the spontaneous DNA synthetic activity of immature or immunocompetent T cells in vitro. In serum free RPMI 1640 medium, FTS stimulated [3H]thymidine incorporation into the DNA of young adult mouse thymocytes in a time and concentration dependent manner. One to 100 pg/ml FTS were the effective concentrations, and the stimulation appeared 3 h after the treatment. A comparable stimulation was noticed, but to a lesser extent, on cultured bone marrow cells. In contrast, no effect could be detected on spleen cells whatever time or concentrations were studied. Neither thymocytes treated in vitro with hydroxyurea nor the medullary, cortisol-resistant thymocytes were sensitive to FTS treatment. In contrast, thymocytes bearing receptor to peanut agglutinin (PNA+) were significantly stimulated with FTS, which suggested that the target population of FTS belongs to the maturing, non-immunocompetent thymocyte compartment.

Aging↗
PubMed1983

Relationship between a spleen-derived immunosuppressive peptide 'SDIP' and the 'Facteur thymique sérique' (FTS): biochemical and biological comparison of the two factors.

A spleen-derived immunosuppressive peptide (SDIP) has been purified to homogeneity. Its physicochemical properties (electrophoretic mobility, u.v. spectra, absence of dansyl derivative) and its enzymatic susceptibilities (proteolytic enzymes, RNase, and DNase) were similar to those of the thymic hormone 'FTS'. SDIP and FTS were eluted with identical retention times in high performance liquid chromatography analysis in three different systems. When tested in sheep cell rosettes, and in the FTS radioimmunoassay in J.F. Bach's laboratory, SDIP presented an activity similar to FTS. In order to compare the thymic hormone to SDIP the biological activity of FTS was determined in in vivo and in in vitro humoral immunity reactions to a T-dependent antigen. As SDIP, FTS inhibited in vivo and in vitro the 19S-bearing cell formation during the last step of the differentiation of the lymphocytes, in the same range of concentration. The two factors appeared to stimulate the incorporation of [3H]-thymidine into the DNA of short-term cultures of thymocytes. The similarity of biological properties of SDIP and FTS together with the similarity observed in the physico-chemical and biochemical properties led to the conclusion that bovine spleen contains a factor similar to FTS.

Animals↗
PubMed1983

Further purification of a CFU-S inhibitor: in vivo effects after cytosine arabinoside treatment.

This paper describes a large scale extraction procedure which allows the preparation of a stable CFU-S inhibitor from fetal calf bone marrow. The use of BioGel P-2 gels results in an increase of the specific activity of the inhibitor as well as in the yield of the preparation. When injected into mice, the inhibitory fraction (Ve/Vo 1.17-1.8) prevent CFU-S entry into cycle after cytosine arabinoside at a dose of 4 micrograms per mouse. When administered during lethal protocols of Ara-C treatment, it significantly increases the percentage of surviving animals. Thus, this low molecular weight factor (below 2,000 D), devoid of species-specificity, enhances the tolerance of animals to high doses of chemotherapy and might be of interest in cancer treatment.

Animals↗
PubMed1982

New insight into lymphocytic chalone research. The 'facteur thymique Sérique' might be responsible for part of the immunosuppressive activity detected in the 'chalone fraction'.

Immunosuppressive activities have been detected in bovine spleen extracts and attributed to the presence of a 'lymphocytic chalone'. Following the immunosuppression of a T cell-dependent humoral response in mice as assay, we purified a peptide to homogeneity present at a concentration of 10-50 ng/kg of spleen whose properties were identical to those of the serum thymic factor. This factor appeared to be a regulator of the humoral immune response in the splenic extract and as such might be responsible for part of the immunosuppressive activities detected in the splenic 'chalone' fraction.

Animals↗
PubMed1981

Influence of a bovine spleen extract on immunological responses in mice.

The presence of immunological stimulatory and inhibitory activities has been detected in a bovine spleen extract F prepared by acetic extraction of an acetonic powder. F was fractioned after water dilution, by ultrafiltration on an Amicon PM-10 membrane. Two successive ultrafiltrates (mol. wt. less than 10,000) are obtained: U1 which contained the largest pool of the low molecular weight substances, and U2 which was shown previously to be enriched in an immunosuppressive peptide. The biological activities of U1 have been studied compared to those of U2: 1. Added to mouse spleen cells culture, U1, at low dose, stimulated 3H-thymidine incorporation into the DNA of the cells, but inhibited it when large dose was added. In this test, U2 was devoid of stimulatory action. 2. When injected into mice sensitized with sheep red blood cells, three distinct activities were detected: U1 was inhibitory at the sensitization period; at the last step of differentiation of the lymphocyte, U1 was stimulatory at low dose and inhibitory at large dose. As assessed by Biogel P-2 chromatography, this last activity was attributed to the presence in fraction U1 of the immunosuppressive peptide previously characterized in U2.

Animals↗
PubMed1981

Further study on the humoral response of a highly-purified spleen-derived immunosuppressive peptide (SDIP).

Some biological properties of a highly-purified non-cytotoxic spleen-derived immunosuppressive peptide (SDIP) have been investigated. SDIP was shown to inhibit the primary anti-sheep red blood cell (SRBC) response at the last step of differentiation of the lymphocyte. In the present study we demonstrated that this response seemed to be T- and adherent spleen-cell dependent as no inhibition was noticed either in the response to TNP-LPS, a T-independent antigen, or in the response to SRBC in adherent spleen cell-depleted cultures. SDIP activity did not occur through an inhibition of splenocytes DNA synthesis since [3H]-thymidine ([3H]-TdR) incorporation was not modified in mitogen or allogenic stimulated cultures. Conversely, SDIP could act through a stimulation of a T-cell subset as a low specific increase of [3H]-TdR was noticed in cultured thymocytes.

Animals↗
PubMed1979

Immunosuppressive activity of a purified spleen extract (lymphocytic chalone?) is not due to polyamines spermine and spermidine.

Spermine, spermidine and a purified spleen extract (PSE) have been compared in vivo in these three tests: hemolytic plaque forming capacity in sensitized mice, delayed hypersensitivity reaction and 3H-thymidine incorporation into various tissue cells. The results obtained demonstrated that the immunosuppressive activity of PSE cannot be attributed to those polyamines. Ion exchange analysis of PSE before and after acid hydrolysis confirmed the absence of free and/or bound polyamines in the studied extract.

Animals↗