Biomedical subjects

F Loor

Publications and source records attributed to F Loor.

At least 73 records · Page 4Linked to original sources

PubMed1989

Serum concentrations of IgM, IgG1, IgG2b, IgG3 and IgA in C57BL/6 mice and their congenics at the lpr (lymphoproliferation) locus.

The serum concentrations of IgM, IgG1, IgG2b, IgG3 and IgA were determined in mice of C57BL/6 background, from weaning to one year of age, by quantitative isotype-specific, indirect double sandwich enzyme-linked immunosorbent assays (ELISAs). Only limited data could be obtained for the IgG2a isotype in the present study. The mean serum Ig levels found for 6-month-old B6 mice were 0.22 mg/ml for IgM, 0.28 mg/ml for IgG1, 1.22 mg/ml for IgG2b, 0.18 mg/ml for IgG3, 0.075 mg/ml for IgA and about 0.7 mg/ml for IgG2a. In comparison with mice of the wild strain, C57BL/6 mice homozygous at the lpr (lymphoproliferation) locus showed very high increases in serum Ig levels when older than 20 weeks. With 6-month-old B6 lpr mice, increases in concentration were found for all tested heavy chain isotypes: 6 to 6.5-fold for IgA (0.45 mg/ml) and IgG1 (1.82 mg/ml), 9-fold for IgG3 (1.6 mg/ml), 11 to 11.5-fold for IgM (2.44 mg/ml) and IgG2b (13.8 mg/ml) and about 8-fold for IgG2a (5.5 mg/ml). Therefore homozygosity at the lpr locus provides the conditions for generalized, poly-isotypic rather than isotype-specific restricted Ig enhancement. This observation may be more compatible with hyperinducibility of all B-cell subclasses than with excessive production of T-cell-derived factors whose activity would be expected to be restricted to some T-dependent subclasses, and at least to affect IgM-committed B cells to a lesser extent than other B-cell classes.

Animals↗

PubMed1989

Overcoming multidrug resistance in Chinese hamster ovary cells in vitro by cyclosporin A (Sandimmune) and non-immunosuppressive derivatives.

Cyclosporin A (Sandimmune) increased the in vitro susceptibility of 'parental' and 'multidrug-resistant' (MDR) chinese hamster ovary (CHO) cell lines to three anti-tumour drugs: colchicine, daunomycin, and vincristine. Several immunosuppressive or non-immunosuppressive derivatives of cyclosporin (Cs) were compared for their ability to sensitise both parental and MDR cells to chemotherapeutic agents. Although 5-10-fold increases of sensitivity to anti-tumour drugs could be obtained for cells of the parental line with several Cs-derivatives, the largest 'gains' of sensitivity (chemosensitisation) were obtained for the cells of the MDR line and with only some of the Cs derivatives. The MDR cells employed displayed the typical MDR phenotype. However, we found no correlation between the immunosuppressive activity of Cs derivatives and their capacity to reverse MDR and all four possible combinations of these two activities could indeed be shown among the tested Cs derivatives. This study demonstrates for the first time that some immunosuppressive Cs can be devoid of chemosensitising activity.

Animals↗

PubMed1989

Proliferation of interleukin 2 dependent cytotoxic T cell line cells. Different protein kinase C activators achieve the same maximal promotion, but with distinct dose-response profiles.

Protein kinase C activators of the teleocidin family are claimed to be able to replace interleukin 2 for inducing short-term proliferation of the interleukin 2 dependent murine cytotoxic T cell line. While teleocidin B4 was found to be much more active than 12-O-tetradecanoyl-phorbol-13-acetate, a related molecule showing a substitution of a single OH by OCH3, olivoretin A, lacked detectable activity in this assay. However, the maximal proliferation achievable by protein kinase C activators did not exceed one third of the one given by recombinant interleukin 2.

Cell Line↗

PubMed1989

Lymphoid cell transfers between adult C57BL/6 mice differing at the lpr and/or nu locus. Humoral immunity phenotype of the chimeras.

Congenic C57BL/6 mice (B6) homozygous only at the nu (nude, athymic) locus (B6 nu) or also at the lpr (lympho-proliferation) locus (B6 nu, lpr) were used as recipients for the transfer of spleen and/or lymph node cells from either normal B6 mice (B6+) or lpr-homozygous B6 mice (B6 lpr). Highly increased survival was obtained for [B6 lpr----B6 nu, lpr] chimeras, but not for [B6+----B6 nu, lpr] and [B6 nu----B6 nu, lpr] chimeras. All long-term survivors that were killed showed an increased responsiveness to the T-cell mitogen concanavalin A (Con A) but no change of responsiveness to the B-cell mitogen lipopolysaccharide (LPS). Some enlargement of spleen and lymph nodes was observed only in some specific [B6----B6 nu, lpr] chimeras (female recipients of spleen cells). Within a few weeks after cell grafting, all but [B6 nu----B6 nu, lpr] chimeras developed highly increased levels of serum immunoglobulins, as well as a higher occurrence of anti-single-stranded (ss) DNA containing sera. These chimeras had been constructed in order to dissect the components of the lpr phenotype etiopathology (primordial involvement of B and/or T lineage cells, lymphoid and/or environmental influences). Though the evolution of serological parameters showed some chimera type-specific features, it seems difficult to reconstitute the entire expression of the lpr phenotype.

Animals↗

PubMed1988

Establishment and characterization of long-term cultured cell lines of murine resident macrophages.

Murine resident macrophages can proliferate in vitro when they are grown in coculture on a layer of mesothelial or endothelial type feeder cells. Resident macrophages were obtained from lung explants of C57Bl/6 lpr/lpr mice and from spleen explants or peritoneal washing of Balb/c mice; the cells were seeded without further washing. After 3-4 weeks of culture, the macrophages began to proliferate on a confluent layer of feeder cells. The macrophages then could be collected in the fluid phase and reseeded for permanent culture after generation of a new feeder layer. These cells were characterized as macrophages by the following criteria: 1) their morphology, ultrastructure, and adherence properties; 2) more than 90% of the macrophages phagocytized yeasts compared with less than 1% of the feeder cells; 3) the presence of functional Fc and mannose receptors, nonspecific cytoplasmic esterases, and membrane ectoenzymes such as nicotinamide adenine dinucleotide (NAD) glycohydrolase and nucleotide pyrophosphatase; 4) by cytofluorographic phenotype analysis with monoclonal antibodies, characterizing a normal macrophage population (MAC1+, Fcrec+, H-2K+, THY1-, LYT2-, L3T4-). 5) by functional studies proving that the expanded macrophages could function as accessory cells in the induction of lymphocyte proliferation in response to concanavalin A (Con A), that they generated reactive oxygen radicals and that they were cytotoxic for tumor cells. During coculture, growth or activating factors such as macrophage colony-stimulating factor or gamma-interferon were released in the medium. Long-term cultured macrophages had chromosomal abnormalities. Our study suggests that tissue macrophages can proliferate in vitro and hence that it is possible to establish long-term cultured cell lines of macrophages of defined and reproducible characteristics.

Animals↗

PubMed1988

Radiation therapy of spontaneous autoimmunity: a review of mouse models.

The classical types of generalized autoimmune disease in man are systemic lupus erythematosus (SLE) and rheumatoid arthritis (RA). Several murine strains which develop SLE and sometimes RA-like diseases are now available. They should help in the understanding of the etiopathology of SLE and RA. Basically two main therapeutic strategies which use solely irradiation have been tried; one being sublethal whole-body irradiation (WBI) and the other fractionated total lymphoid irradiation (TLI). Other protocols which combine lethal WBI and stem cell transplantation have often been attempted. It was regularly found that the bone marrow transplant (BMT) dictates the immune status of the recipient. This paper reviews the data published about NZB, NZB/W, BXSB and MRL mice in this context.

Animals↗

PubMed1988

Protein kinase C activators of the teleocidin family decrease the IgE-binding capacity of rat basophilic leukemia cells.

The tumor promoters 12-O-tetradecanoylphorbol-13-acetate (TPA) and the teleocidins (TCDs) had similar inhibitory effects on IgE binding onto the membrane of rat basophilic leukemia (RBL)-2H3 cells. The level of expression of the functional IgE Fc receptor (Fc epsilon R), as measured by CELISA, was decreased up to a maximum of 60% within 5 min-1 h of treatment. This inhibition was obtained at concentrations of 0.1 microgram/ml for most TCDs, of 1 microgram/ml for TPA and of 20 micrograms/ml for one TCD (olivoretin A). These molecules also decreased the amount of cell-bound IgE detectable by CELISA on cells that had been coated with IgE prior to TCD treatment. When incubated with RBL-2H3 cells for 30 min-2 h, the TCDs and TPA stimulated serotonin release. Depending on their concentration, they had various effects on IgE-plus antigen-induced serotonin release. It is suggested that the down-regulation of IgE receptor expression by these tumor promoters is mediated through protein kinase C activation and phosphorylation of the Fc epsilon R.

Animals↗

PubMed1988

Lymphoid cell transfers between adult C57BL/6 mice differing at the LPR locus. Lack of lymphadenopathy transfer and effects on host survival.

"1 pr" is an autosomal recessive locus which determines the lymphoproliferation of an abnormal T cell subset ("T lpr" cell subset). Though a thymus is necessary for the initiation of the lymphadenopathy, adult thymectomy does not interfere with the development of disease. C57BL/6 (B6) mice (either treated with cyclophosphamide or not), lpr heterozygous at the lpr locus, or not), and nu homozygous B6 mice (either homozygous at the lpr locus, or not) are refractory to the growth and massive proliferation of grafted cells of the aberrant T lpr cell subset, which polyclonally expands in lpr homozygous B6 mice. Their lack of expansion in B6 nu, lpr mice is surprising, since such animals may develop the lymphadenopathy under certain circumstances (thymus grafting). While the injection of normal B6 lymphoid cells does not improve the health of the B6 nu, lpr mice, but may even accelerate their wasting, the injection of B6 lpr lymphoid cells into B6 nu, lpr mice causes, after a transient wasting, a remarkable prolongation of survival. B6 nu recipients of B6 lpr lymphoid cells show no sign of wasting and survive like recipients of normal B6 (B6+) cells. Thus the "lpr type" lymphoproliferative potential is neither simply carried by the T lpr subset cells themselves, nor simply determined by the lpr environment of athymic, lpr homozygous mice, and it is also not readily reconstituted by grafting T lpr cells in athymic lpr mice.

Animals↗

PubMed1988

Partial expression of the lpr locus in the heterozygous state: presence of autoantibodies.

B6 mice heterozygous at the lpr locus (B6 +/lpr and B6 lpr/+) were compared with lpr homozygous mice (B6 lpr/lpr) and control mice (B6 +/+) for levels of serum immunoglobulin (Ig), presence of autoantibodies and rate of B-cell membrane immunoglobulin (mIg) capping. The total serum Ig levels in B6 +/lpr and B6 lpr/+ mice remained much below the high titres found in B6 lpr/lpr mice, and were close to the titres found in B6 +/+ mice. However, the presence of anti-single-stranded (ss) DNA antibodies and of anti-nuclear antibodies (ANA) was detected in most B6 +/lpr and B6 lpr/+ mice, although less frequently and in lower titres than in B6 lpr/lpr mice. The rate of mIg capping was higher in B6 +/lpr and B6 lpr/+ mice than in B6 +/+ mice, but the acceleration of the capping process remained inferior to the one found in B6 lpr/lpr mice. Therefore, the lpr locus is not totally recessive: some B-cell hyperactivity is expressed in the heterozygous state. This is in contrast with its lack of expression at the level of lympho-proliferation of the lpr-characteristic T-cell subset: none of the lpr heterozygous B6 mice displayed detectable lymphadenopathy.

Aging↗

PubMed1987

An enzyme-linked lectin-binding assay on cells (CELLBA) for the comparison of lectin receptor expression on cell surfaces.

Lectins can be used to specifically detect some cell surface glycans. Their expression on different cells or on cells of a given lineage throughout differentiation or following treatment with drugs can be compared using lectins labelled with radioactive, fluorescent or enzymatic probes. We describe a new method which, by analogy with CELISA (ELISA on cells), is called CELLBA (or ELLBA on cells) for cellular, enzyme-linked lectin-binding assay. It permits the comparison of the expression of specific glycans in a large number of different cell samples. As an example, it was able to detect alterations of cell surface glycan expression caused by inhibitors of N-linked oligosaccharide trimming.

Agglutination↗

PubMed1987

Detection of mouse IgE by CELISA.

The detection and quantitation of mouse IgE is usually impaired by the difficulty to obtain reliable antibody reagents which are fully specific for the epsilon chain - and reactive enough - to be used in an enzyme-linked immunosorbent assay (ELISA). An ELISA on cells (CELISA) was developed for the detection of mouse IgE, using rat basophilic leukemia (RBL) cells. It is based on the high affinity of the receptors for the Fc of IgE (Fc epsilon R) displayed on the surface of the RBL cells. Since the epsilon chain specific recognition is achieved by the biological receptor of IgE, the detection of cell-bound IgE does not need the use of epsilon chain specific antibodies. Instead, one can use any enzyme-coupled antibody capable to recognize the IgE through its light-chain epitopes. Interestingly, when the IgE bound to the RBL cells has a known specificity, it can be detected through its paratopes using the cognate antigen coupled to an enzyme.

Animals↗

PubMed1987

Effect of glycoprotein-processing inhibitors on the mouse IgE binding capacity of rat basophilic leukemia cells.

The basophile surface high affinity receptors for IgE (Fc epsilon R) are heavily glycosylated glycoproteins like the IgE Fc itself. Their functional expression in their physiological environment can be studied with the help of a recently developed CELISA (ELISA on cell) methodology. The relevance of the IgE and Fc epsilon R glycans for their interaction in situ has been probed using inhibitors of discrete trimming steps of N-linked carbohydrate processing. The IgE produced by mouse hybridoma cells in the presence of deoxynojirimycin (dNM), a glucosidase I inhibitor, keeps intact both its antigen and Fc epsilon R-binding capacities. Rat basophilic leukemia (RBL) cells cultured in presence of dNM or of another glucosidase I inhibitor, castanospermine (Cs), show marked decreases in their capacity to bind mouse monoclonal IgE. In contrast, their culture in the presence of either deoxymannojirimycin (dMM) or swainsonine (Sw) either does not affect or even slightly increases the membranous expression of Fc epsilon R capable to bind mouse IgE.

1-Deoxynojirimycin↗

PubMed1987

Bone marrow transfers in X-irradiated mice congenic at the lpr locus: some paradoxical effects.

MRL/l mice, which are homozygous at the lpr locus, can be inhibited in lpr phenotype expression (lymphadenopathy, accelerated death) by a transfer of MRL/n bone marrow cells following X-irradiation of the recipients (MRL/n bone marrow----X-irradiated MRL/l chimeras). Female MRL/l bone marrow----X-irradiated MRL/l chimeras express the lpr phenotype with a delay corresponding to the age at the time of cell transfer. However, the equivalent male chimeras resemble MRL/n bone marrow----X-irradiated MRL/l chimeras. When the reverse MRL/l bone marrow----X-irradiated MRL/n chimeras are constructed, one finds that whichever the sex is, the chimeras undergo a wasting disease looking like a graft-versus-host disease, with particularly a marked atrophy of the spleen. A similar GVH like disease is observed with C57Bl/6 lpr bone marrow----X-irradiated C57Bl/6 normal mice. These animals survive at least 5 months but manifest a spleen aplasia. When reconstituted with MRL/n bone marrow, MRL/l recipients develop higher levels of antinuclear and anti-ds/ss DNA antibodies than MRL/n recipients. This suggests that the 'lpr environment' of the host may have an influence on the development of B cell hyperactivity.

Animals↗

PubMed1986

A comparison of five different methods for the detection of TNP specific mouse IgE: ELISA, ELISA on cells, rosetting, granule enzyme release assay and passive cutaneous anaphylaxis.

Using the same anti-TNP hybridoma supernatant pool as IgE antibody source (2 micrograms/ml), several methods were compared for their sensitivity in IgE detection and convenience for screening purposes. Using rat basophilic leukemia (RBL) cells as specific receptor cells, one out of two rosetting methods with TNP-sheep red blood cells allowed the detection of 0.5 ng IgE/ml (50 pg/assay) while the other was much less sensitive (60 ng/ml). More convenient for screening was an ELISA method performed on cells, in which the IgE bound to the RBL cell surface could be detected either by enzyme-anti-Ig or by enzyme-antigen conjugates with a similar, albeit low, sensitivity of 10 ng IgE/ml (500 pg/assay). Using the same antibody and cell sources, a very convenient and more sensitive method for screening purposes was found to be the measurement of antigen-induced basophil granule beta-N-acetylglucosaminidase release by IgE sensitized RBL cells: 0.5 ng IgE/ml and 50 pg/assay. For the same anti-TNP IgE source, this compares with a detection limit by ELISA of 0.2 ng IgE/ml (10 pg/assay) and by passive cutaneous anaphylaxis in rats of 2 ng IgE/ml (100 pg/assay).

Acetylglucosaminidase↗

PubMed1986

Increased membrane immunoglobulin capping of B cells from C57Bl/6 lpr/lpr and C57Bl/6 nu/nu mice.

When the capping of membrane immunoglobulin on spleen B cells from normal C57Bl/6 mice (B6) is taken as reference, a faster capping rate is found for cells of age-matched B6 mice which are congenic at the lymphoproliferation (lpr) or nude (nu) loci. Though both congenic strains can be characterized by an abnormal T-lineage cell content, the nature of the abnormality itself is very different since B6 nudes lack thymus-processed/influenced lymphocytes whereas B6 mice with the lpr phenotype suffer from an invasion of all lymphoid organs with cells of a particular T-cell subset. Moreover, the more "normal" capping rate of B cells from the double congenic B6 mice (nu/nu, lpr/lpr) is intriguing. Since other mice homozygous at the lpr locus (MRL-1) or at the nu locus (BALB/c nude) also cap faster than their congenic controls (MRL-n and BALB/c, respectively), the observed effects do not appear to depend on a peculiarity of the B6 genetic background. If the faster capping of B cells of nu congenic and of lpr congenic mice had a common origin, it might be that T cells would control in some way the mobility of B-cell membrane immunoglobulins: both congenic mice have in their spleen a very low proportion of mature T cells together with a very high proportion of prethymic/thymic immature T-cell types, either of which might affect B-cell behavioral responses to membrane immunoglobulin clustering.

Animals↗

PubMed1986

The C57B1/6 nu/nu, lpr/lpr mouse. III. Autoimmunity status.

C57B1/6 mice homozygous at the lpr (lymphoproliferation) locus display evident lymphadenopathy (in our B6 colony, primordially cervical lymph node enlargement) and autoimmunity (various autoantibodies). Four groups of mice corresponding to the diverse combinations of the lpr gene and the nu (nude, athymic) gene on the B6 genetic background have been compared for signs of lymphadenopathy. It occurred in all tested B6 +/+, lpr/lpr mice and none of the other groups (B6 nu/nu, +/+; B6 nu/nu, lpr/lpr and B6 +/+, +/+). B cell hyperactivity/autoimmunity was also evaluated by serum antibody analyses: higher serum immunoglobulin levels, anti-nuclear antibodies, anti-native DNA, anti-single stranded DNA, rheumatoid-like factors (anti-rabbit IgG), and natural antibodies against dinitrophenol and trinitrophenol haptens and their non cross reactive carriers: bovine serum albumin, hen egg albumin and keyhole limpet haemocyanin. Interestingly the levels of serum immunoglobulins and of some specific antibodies were somewhat higher in B6 nu/nu, lpr/lpr than in 'normal' B6 nu/nu, +/+, though they remained much lower than in B6 +/+, lpr/lpr animals. This suggests that the lpr gene may express its influence on the level of B cell activity in the absence of T lineage cells that would have normally matured in a thymus and that this effect of the lpr gene does not require the massive proliferation of T lineage cells observed in B6 +/+, lpr/lpr mice.

Aging↗

PubMed1986

Cyclosporine facilitates B-cell membrane immunoglobulin capping.

The immunomodulatory molecule cyclosporine was found to cause an early acceleration of the capping of mouse B-cell membrane immunoglobulin. This was most marked when the capping process was slightly retarded by keeping the cells at 32 degrees. This is a sign that the drug can cause B-cell membrane alterations. At lower drug doses they might not be as easily detected, but are nevertheless sufficient to inhibit the activation of some B cells by membrane immunoglobulin clustering.

Animals↗

PubMed1985

Interference of cyclosporin with lymphocyte proliferation: effects on mitochondria and lysosomes of cyclosporin-sensitive or -resistant cell clones.

Cyclosporin was previously shown to interfere with--but not to abolish--the increased activities of lysosomes and mitochondria consequent to a mitogenic activation of normal mouse lymphocytes. This was evident from the fluorescence profiles of cell populations after vital staining with euchrysine (giving a lysosomal-specific red fluorescence) and rhodamine-123 (giving a mitochondrial-specific green fluorescence). Fluorescence profiles of the population of cells not exposed to a mitogen were also altered by cyclosporin, with lower lysosomal and mitochondrial fluorescence of these cell populations. In order to find out more precisely what could be the direct effects of cyclosporin on those cellular organelles, our cyclosporin-sensitive (BE7) and cyclosporin-resistant (LB7) lymphoblastoid cell lines were tested and showed clear-cut differences. Only minor effects could be detected for the lysosomal and mitochondrial activities of the resistant cells. On the contrary, cyclosporin caused, in the cells of the sensitive clone BE7, a clear decrease of mitochondrial activity together with an unexpected increase of the red fluorescence of euchrysine. The latter might not correspond to a real increase of the lysosomal activity of such cells. Indeed electron microscopy studies do not show higher numbers of lysosomes; rather they show that numerous vacuoles appear in the cytoplasm of the cyclosporin-treated BE7 cells (but not in the cells of the resistant clone and not in untreated cells of either types).

Animals↗