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Biomedical subjects

J F Nicolas

Publications and source records attributed to J F Nicolas.

At least 145 records · Page 8Linked to original sources
PubMed1990

[Adhesion molecules: their potential implication for dermatology].

Many biological events involve an initial stage of adhesion. The molecules that are responsible for the process of adhesion have been studied extensively in recent years. The most widespread receptors taking part in cell-external matrix and cell-cell reactions are from the families of integrins and immunogloblins. In normal skin, the keratinocytes and fibroblasts essentially express beta 1 (VLA) receptors and the cells of Langerhans the beta 2 receptors of the integrin family. Their pathological modification is under study. In contrast, involvement of the ICAM-1 molecule (ligand of receptor LFA-1) in pathology seems to be considerable. ICAM-1 is expressed by keratinocytes in many benign and malignant skin diseases and this makes possible interaction with LFA-1 lymphocytes. The passage of lymphocytes towards the epidermis is the basis of all inflammatory and immune reactions and is dependent on adhesion molecules. It will doubtless, in the future, be possible to explain the physiopathology of inflammatory skin reactions in terms of excessive expression or insufficient ICAM-1 by pathological keratinocytes.

Antigens, Differentiation↗
PubMed1989

Visualizing interleukin 2 gene expression at the single cell level.

To analyze the expression of the interleukin (IL)2 gene at the single cell level, we have constructed a chimeric gene in which the regulatory sequences from the mouse IL2 gene were fused 5' proximal to the coding region of the Escherichia coli beta-galactosidase (lacZ) gene. Once stably introduced into a T cell hybridoma, the IL 2-lacZ reporter gene was shown to display a pattern of induction similar to the one observed for the resident IL 2 gene. Two points emerged from monitoring IL 2 expression for the resident IL2 gene. Two points emerged from monitoring IL 2 expression at the single cell level. First, upon activation the expression of the IL2-lacZ gene appears asynchronous. Second, at the peak of induction the percentage of beta-galactosidase+ cells never reached 100% and the level of beta-galactosidase reached among positive cells was highly heterogeneous within a cloned population of T cells. In combination with the possibility to sort viable lymphocytes according to lacZ expression, the IL2-lacZ reporter gene described herein should provide a way to isolate somatic cell mutants deficient in signal transduction by the T cell antigen receptor complex.

Animals↗
PubMed1989

Epithelial cell heterogeneity in mammalian thymus: monoclonal antibody to high molecular weight keratins exclusively binds to Hassall's corpuscles.

Hassall's corpuscles represent a subset of medullary thymic epithelial cells whose origin and function within the thymus still remain largely unknown. The present study shows that Hassall's corpuscles can be defined by their intracellular content in specific keratin subunits. Two monoclonal anti-keratin antibodies were used: KL1, directed to high molecular weight keratins, and KL4, specific for high and medium molecular weight polypeptides. In vivo, KL1 exclusively binds to Hassall's corpuscles of five mammalian species including mouse, rat, guinea-pig, rabbit and pig. Thus KL1 appears as an exclusive marker of Hassall's corpuscles in a large number of mammals. In vitro, thymic epithelial cells gave rise in certain species to Hassall's corpuscles. In contrast to its in vivo reactivity, KL1 never labelled Hassall's corpuscles developed in vitro. These data strongly support the following conclusions: (1) Hassall's corpuscles derive from medullary epithelial cells; (2) they represent advanced stages of thymic epithelial maturation; (3) thymic epithelial cell differentiation is impaired in vitro. Furthermore, this study provides additional evidence that thymic epithelium heterogeneity reflects different stages in epithelial maturation.

Animals↗
PubMed1989

A novel system for screening antiretroviral agents.

We propose a new screening system of drugs capable of inactivating retroviruses by interfering with the binding, entry into the cell, uncoating, reverse transcription, migration into the nucleus or integration of the retrovirus. It is based on the utilization of recombinant retroviruses which can be detected in single cells by the expression of a LacZ reporter gene. It allows simple and rapid quantification of the number of infectious viral particles. The screening system can then be used to precisely define the period sensitive to the drug.

Animals↗
PubMed1989

Treatment of cutaneous T cell lymphoma with intermediate doses of interferon alpha 2a.

In this study we treated 6 patients with epidermotropic cutaneous T cell lymphoma (CTCL) with intermediate doses of recombinant alpha 2a interferon (18-100 x 10(6) IU/week) for 2-6 months. One patient experienced complete clinical remission in spite of a persistent dense lymphocytic skin infiltrate. One patient was markedly improved and 2 patients were moderately improved. The clinical condition of the 2 remaining patients was unchanged by interferon treatment. In all cases lesions relapsed a few weeks after treatment was discontinued. This study shows that interferon can be used to treat epidermotropic CTCL. However, a 2- to 6-month treatment using moderate doses did not lead to the high percentage of remission previously reported by others with high doses of recombinant alpha 2a interferon, for longer periods. This result suggests that interferon should be used at high doses and/or for long time periods for clinical improvement of CTCL patients.

Adult↗
PubMed1989

Bullous pemphigoid and cicatricial pemphigoid: immunoblotting detection of involved autoantigens.

Bullous pemphigoid (BP) and cicatricial pemphigoid (CP) are subepidermal bullous autoimmune diseases which have distinct clinical features but identical immunological status. In order to determine whether these diseases could be dissociated on the basis of qualitative differences in serum antibodies to basement membrane zone (BMZ) antigens, the reactivity of sera from 7 CP and 29 BP patients with proteins extracted from normal human epidermal sheets (containing most of the lamina lucida components) was analysed using immunoblotting and compared to that of 10 normal sera. 20 out of the 29 BP sera contained antibodies recognizing one or several protein(s) of 240, 200, 180 and 165 kD molecular weight (MW). Antibodies in 4 out 7 CP sera specifically reacted with one or two polypeptides of 240 and 120 kD MW. These data confirm the heterogeneity of BP antigens and show the presence in CP of a novel 120 kD MW polypeptide which is found only in CP but not in BP. Taken together these findings demonstrate that in BP and CP, autoantibodies are directed to both common and specific BMZ antigens, their physiopathological significance need to be understood.

Adult↗
PubMed1989

[Keratinocyte-fibroblast interactions: I. Production by the keratinocytes of soluble factors stimulating the proliferation of normal human skin fibroblasts].

Epidermal cells produce IL-1 and contra IL-1 which respectively stimulate and decrease fibroblast proliferation. In order to get better insight into the nature of keratinocyte-fibroblast interactions, we have analyzed the effect of soluble factors produced by unstimulated normal human keratinocytes and keratinocyte cell lines on the proliferation of normal human dermal fibroblasts. The results were compared to these obtained with human recombinant IL-1 and IL-2. We observed that: 1) normal keratinocytes (monolayers or stratified) released in the culture medium a factor stimulating fibroblast proliferation by 45 to 160%; 2) supernatants of unstimulated PAM 212 keratinocyte cell line also contained the stimulatory activity; 3) addition of IL-1 beta to the culture medium at concentration ranging from 0.1 to 1.000 U/ml induced a dose-dependent increase in fibroblast proliferation, whereas IL-2 was ineffective; 4) gel filtration analysis (ACA 54) of serum-free supernatant showed that the activity could be eluted from 3 peaks (Mw ranging from 10 to 20 kD). The present data show that unstimulated normal human keratinocytes produce soluble factor(s) (maybe related to IL-1) which stimulate human dermal fibroblast proliferation and which could be of major importance in the modulation of fibroblast metabolism, in vivo.

Adult↗
PubMed1989

[The role of the T-lymphocyte in atopic dermatitis].

Atopic dermatitis (AD) comprises a wide spectrum of clinical symptoms, among which dermatitis is the most prominent feature. Recent finding that Langerhans cells bind IgE molecules via Fc receptors brought new insight into the pathogenesis of dermatitis lesions in AD. Langerhans cells from AD patients can present environmental allergens to T cells, both in vivo and in vitro, because they can bind allergens through IgE. Alternatively, Langerhans cells from normal individuals do not bind IgE molecules and are ineffective in stimulation of allergen specific T cells. Thus, the dermatitis lesion in AD seem to be due to an IgE-mediated delayed type hypersensitivity mechanism.

Dermatitis, Atopic↗
PubMed1988

Retroviral vectors.

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Cloning, Molecular↗
PubMed1988

An indicator gene to demonstrate intracellular transposition of defective retroviruses.

An indicator gene for detection and quantitation of RNA-mediated transposition was constructed (neoRT). It was inserted into a Moloney murine leukemia provirus (Mo-MLV) deleted for the envelope gene to test for intracellular transposition of defective retroviruses [Mo-MLV(neo)RT]. NeoRT contains the selectable neo gene (which confers resistance to the drug G418), inactivated by a polyadenylylation sequence inserted between the neo promotor and coding sequence. The polyadenylylation sequence is flanked (on the antisense strand of the DNA) by a donor and an acceptor splice site so as to be removed upon passage of the provirus through an RNA intermediate. 3T3 cells transfected with the defective Mo-MLV(neo)RT provirus are sensitive to G418. After trans-complementation with Mo-MLV, viral transcripts confer resistance to G418 upon infection of test cells. In the resistant cells, the polyadenylylation sequence has been removed, as a result in most cases of precise splicing of the intronic domain. Retrotransposition of the defective Mo-MLV(neo)RT provirus was demonstrated by submitting transfected G418-sensitive clones to selection. Between 1 and 10 G418-resistant clones were obtained per 10(7) cells. Several possess additional copies, with evidence for precise removal of the intronic domain. By using target test cells in coculture experiments, extracellular intermediates of retrotransposition could not be detected.

DNA Transposable Elements↗
PubMed1988

Fluorescence-activated cell analysis and sorting of viable mammalian cells based on beta-D-galactosidase activity after transduction of Escherichia coli lacZ.

We demonstrate that individual cells infected with and expressing a recombinant retrovirus carrying the Escherichia coli beta-galactosidase gene (lacZ) can be viably stained, analyzed, sorted, and cloned by fluorescence-activated cell sorting based on the levels of lacZ expressed. To accomplish this we have devised a method to enzymatically generate and maintain fluorescence in live mammalian cells. Accumulation of fluorescent products in cells is linear with time, with a direct correlation of fluorescence to enzymatic activity. This technology for beta-galactosidase detection is more sensitive than other available cytochemical or biochemical methods. We have used this procedure to show that the expression of psi-2-MMuLVSVnlsLacZ in the T-cell lymphoma BW5147 and the B-cell hybridoma SP2/0 is not completely stable and that subclones selected by the fluorescence-activated cell sorter for low lacZ activity demonstrate distinctly lower average expression of LacZ. These findings indicate the utility of beta-galactosidase as a reporter molecule at the single-cell level for studies of gene regulation, including studies of promoter efficacy, enhancer activity, trans-acting factors, and other regulatory elements.

Animals↗